Employment conditions have drastically changed in recent years due to socioeconomic recessions and transformations in the industrial and services sectors (Ahonen et al., 2018; Kalleberg, 2016). Thus, employment quality (i.e., a set of employment characteristics established by the terms and conditions of the employee-employer relationship; Eisenberg-Guyot et al., 2020; Julià et al., 2017) has caught the attention of researchers and policy makers around the world (Kalleberg, 2018). Researchers have suggested that a Standard Employment Relationship (SER) characterized by a full-time, permanent contract and a high salary is the gold criterion for employment quality (Vanroelen et al., 2021). However, the significant decline in SER (high-quality employment) and the increase in non-SER (low-quality employment) in Western countries highlights the urgent need to investigate their consequences (Kalleberg, 2018), including employees’ health (Benach et al., 2014). This is especially important given the great burden of poor health conditions and sick leave for organizations and societies (Organization for Economic Co-operation and Development [OECD], 2015). Moreover, continuous investigation about the consequences of employment quality is strongly encouraged in order to guide evidence-based policy making (Eurofound & International Labour Organization [ILO], 2019).

The research conducted so far shows that employment quality is positively related to employee health (Benach et al., 2014; Donnelly, 2021; Peckham et al., 2019; Van Aerden et al., 2016; Vives et al., 2011). In this line, research on separate employment characteristics has highlighted that SER characteristics are positively related to health, whereas non-SER characteristics, such as temporary, part-time, and low paying jobs, contribute to worse employee health (Gevaert et al., 2021; Quinlan & Bohle, 2015). Similarly, a recent systematic review highlighted that salary is positively related to mental health (Utzet et al., 2020).

Nonetheless, as some scholars pointed out (Ahonen et al., 2018; Findlay et al., 2017), there is a scarcity of studies that have examined the mechanisms underlying the relationship between employment quality and employee health. Recently, Peckham et al. (2019) investigated whether the relationship between employment quality and employee health was mediated by three mediators: material deprivation, employee stressors, and occupational risk factors. This research, however, implemented a typological approach to operationalize employment quality, where eight classes or types of employment were identified by means of latent class analysis based on combinations of specific employment indicators (e.g., salary, type of contract, employment relationship type, work shift). Thus, this study did not show which specific indicators of employment quality were related to employee health via the considered mechanisms. Moreover, they tested mediation with Baron and Kenny’s (1986) procedure, a method that is currently not recommended due to its conceptual and statistical problems (see MacKinnon et al., 2002; Rucker et al., 2011; Zhao et al., 2010). Therefore, our knowledge about the mechanisms underlying the relationships between specific indicators of employment quality and employee health is still quite limited (Ahonen et al., 2018).

This omission is worrisome for both theoretical and practical reasons. Theoretically, it shows that we do not fully understand why employment quality is related to employee health. To remedy this problem, we need to uncover the underlying mechanisms (i.e., mediators) that intervene in this relationship. In fact, scholars have called for research that elucidates pathways and mechanisms linking employment quality and health in order to provide a more nuanced view of this relationship (Ahonen et al., 2018). The identification of the mediators through which a predictor is related to an outcome often represents “an increase in knowledge and an important refinement of the theory” (Spencer et al., 2005, p. 846). From a practical perspective, identifying the mechanisms involved can help policy makers and employers design occupational health interventions aimed at improving employee health.

In the present study, we focus on two mediating psychological mechanisms. Specifically, we tested a mediation model that posits that three employment quality indicators: type of job contract (0. temporary vs. 1. permanent), employment relationship (0. part-time vs. 1. full-time job), and salary, are related to employee health complaints via two mediators: work engagement (i.e., “a positive, fulfilling, work-related state of mind that is characterized by vigor, dedication, and absorption”; Schaufeli et al., 2002, p. 74) and affective job insecurity (i.e., employees’ emotional reactions, such as concern, worry, or anxiety, to the perceived possibility of total job loss or job feature losses; Huang et al., 2012; Lee et al., 2018). We draw on the Job Demands-Resources (JD-R) theory (Demerouti et al., 2001; Bakker & Demerouti, 2017) to frame our study. This theory posits that job features can be classified in two categories: job resources (“aspects of the job that are functional in achieving work goals, reduce job demands and the associated physiological and psychological costs, or stimulate personal growth, learning, and development”; Bakker & Demerouti, 2017, p. 274) and job demands (aspects that hinder goal attainment and require sustained effort) (Bakker & Demerouti, 2017). The JD-R theory argues that job resources and job demands trigger two processes that impact employee health: (1) a motivational process, through which job resources are positively related to motivational states (i.e., work engagement), which in turn are positively related to employee health; and (2) a health-impairment process, through which job demands are positively related to employee strains (i.e., affective job insecurity), which in turn are negatively related to employee health (Bakker & Demerouti, 2017). Initially, these processes were considered independent (Demerouti et al., 2001). However, several meta-analyses and empirical studies have also shown cross-links between the two processes, so that resources are also negatively related to employee strains, and demands are also negatively related to motivational states (Alarcon, 2011; Crawford et al., 2010; González-Romá et al., 2020; Lesener et al., 2019; Schaufeli & Taris, 2014).

We argue that employment quality is an important resource for employees (Vahle-Hinz et al., 2013). High-quality employment reflects the possession of employment resources (i.e., higher salary, full-time employment, and a permanent job contract). Based on the JD-R theory (Bakker & Demerouti, 2017) and the aforementioned cross-links, we posit that the three employment quality indicators are related to employee health complaints via two parallel mediators: work engagement and affective job insecurity (see Fig. 1). We chose work engagement as a mediator because it is a positive psychological state that is promoted by job resources (Bakker et al., 2008) and considered a key antecedent of employee health (Salanova, 2021). We focused on affective job insecurity as a mediator because it is associated with non-standard employment arrangements (i.e., temporary and part-time jobs) (Kalleberg, 2018), and a recent meta-analysis showed that it is associated with negative health outcomes (more strongly than cognitive job insecurity; Jiang & Lavaysse, 2018). Finally, we focused on employee psychosomatic health complaints as an indicator of employee health because they encompass both psychological and somatic aspects and, therefore, provide a more comprehensive view of employee health. In fact, psychosomatic health complaints are crucial in occupational health research, given that they are very common reasons for visits to general practitioners, and they are associated with high sick-leave costs and lack of productivity (Brosschot & Van Der Doef, 2006). Figure 1 presents our research model.

Fig. 1
figure 1

The hypothesized research model

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This study aims to make several contributions. First, we contribute to the occupational health literature by identifying two psychological mediators (work engagement and affective job insecurity) in the relationship between employment quality indicators and employee health, specifically employee health complaints. This knowledge improves our understanding about why employment quality indicators are related to employee health. Our study responds to the call for better theoretical understanding of how and why employment quality is related to employee health (Ahonen et al., 2018; Benach et al., 2016). Second, by simultaneously investigating and comparing the magnitude of the indirect effects of three traditional employment quality indicators we provide a more nuanced and detailed view of the employment quality-employee health relationship. Third, our results contribute to extending the JD-R theory in two directions: (1) by highlighting the existence of cross-links between the motivational and health-impairment processes; and (2) by showing that this theory can be used as a theoretical framework to examine the relationships between employment quality and its hypothetical consequences. Finally, from a practical perspective, we provide implications for organizations and policy makers that can be useful for improving employee health.

Employment Quality Indicators

In this study, we consider three indicators of employment characteristics: type of job contract (temporary vs. permanent contract), employment relationship (part-time vs. full-time), and salary. We chose these indicators for the following reasons. First, the segmented labor market theory (Doeringer & Piore, 1971) posits that the labor market is divided into two segments: a primary segment that includes the established core of the labor market and a secondary segment that consists of peripheral jobs. On the one hand, the primary segment is represented by jobs with Standard Employment Relationships (SER), which are characterized by permanent contracts and full-time, higher salary jobs. These characteristics are indicators of high-quality employment situations. On the other hand, the peripheral segment of the labor market consists of non-standard jobs, which are characterized by temporary contracts and part-time, lower salary jobs. These characteristics are indicators of low-quality employment situations. Second, scholars have suggested that the SER-type is deeply embedded in employees’ mindsets as the gold standard for employment quality (Vanroelen et al., 2021), and previous studies have highlighted the health benefits of SER compared to non-standard employment arrangements (Gevaert et al., 2021; Van Aerden et al., 2016). Third, employment quality has to be operationalized by using objective indicators because they facilitate measurement and comparison across studies (Hofmans et al., 2020). In fact, occupational health researchers have suggested that employment conditions should be characterized as objectively as possible (Peckham & Seixas, 2021). Thus, in this study, we assume that high employment quality is indicated by SER-like objectifiable characteristics (full-time jobs, permanent contracts, and higher salaries), whereas low employment quality is indicated by non-SER-like characteristics (temporary contracts, part-time arrangements, and lower salaries).

From Employment Quality to Employee Health Complaints: The Mediator Role of Work Engagement

We posit that the three employment quality indicators investigated in this study are positively related to work engagement. According to the JD-R theory (Bakker & Demerouti, 2007), job resources are positively related to work engagement. High employment quality means that employees have access to important resources. Organizations and employers provide more resources to employees in SER than in non-SER jobs (Ahonen et al., 2018; O’Connor et al., 2020). For instance, research has shown that permanent employees receive more training and information about how to perform their jobs than temporary employees (Macmillan & Shanahan, 2021). Moreover, research has shown that supervisor and coworker support are other resources that are more present in employees in full-time and permanent jobs than in employees in part-time and temporary jobs (Menéndez et al., 2007; Saloniemi et al., 2004). Salary is also considered an important resource for employees because it can facilitate the attainment of employment and personal goals and help to meet their basic psychological needs (Farndale & Murrer, 2015; Kulikowski & Sedlak, 2020).

Because full-time jobs, permanent contracts, and high salaries are important resources for employees, they should be positively related to work engagement. High-quality employment arrangements generally offer employees more autonomy in performing their tasks (Standing, 2011), a broader network of social contacts at work (Spreitzer et al., 2017), and more challenging tasks to complete (Gevaert et al., 2021). Thus, high-quality employment helps employees to meet their basic psychological needs of autonomy, relatedness, and competence, triggering intrinsic motivation and work engagement (Ryan & Deci, 2000). The positive relationship between employment quality indicators and work engagement is also congruent with the Job Characteristics Model (Hackman & Oldham, 1976), which posits that some of the aforementioned characteristics associated with high-quality employment (e.g., autonomy) are positively related to critical psychological states and work motivation.

We also posit that work engagement is negatively related to employee health complaints. The association between work engagement and employee health seems to be mediated by the autonomic nervous system. This system has two different components: the sympathetic nervous system (which activates the body to respond to environmental demands) and the parasympathetic nervous system (which facilitates restorative and regulation functions) (Seppälä et al., 2012). Work engagement increases the activity of the parasympathetic nervous system, thus promoting healthy and adaptable responses that contribute to employee health (Seppälä et al., 2012).

In addition to the physiological rationale underlying the relationship between work engagement and employee health complaints, research in psychology has suggested that work engagement can have a positive spillover influence on employee health behaviors (Amano et al., 2020). For instance, engaged workers are more inclined to participate in healthy activities that foster relaxation and psychological detachment from work, such as sports and exercise (Bakker et al., 2014). As a positive psychological state, work engagement can motivate individuals to adopt healthier behaviors through goal setting, self-efficacy, and self-regulation (DeSteno et al., 2013). Moreover, drawing on the Broaden-and-Build Theory (Fredrickson, 2004), we propose that work engagement, as a positive psychological state, can trigger a positive spiral of personal resources that can help individuals to cope better with work stress and, consequently, improve employee health (Fredrickson, 2013; Salanova et al., 2010).

Therefore, employees who are engaged in their work are less likely to experience health complaints. Results from a recent meta-analysis support this association (Mazzetti et al., 2021); they showed that work engagement is positively related to physical health and negatively related to psychological distress. Considering the arguments and empirical evidence mentioned above, we hypothesize the following:

Hypothesis 1

There is a negative indirect effect of type of contract (0. temporary vs. 1. permanent; Hypothesis 1a), employment relationship (0. part-time vs. 1. full-time; Hypothesis 1b), and salary (Hypothesis 1c) on employee health complaints via work engagement. Having a permanent job (H1a), a full-time job (H1b), and a higher salary (H1c) leads to higher work engagement, which in turn is negatively related to employee health complaints.

From Employment Quality to Employee Health Complaints: The Mediator Role of Affective Job Insecurity

We posit that the three indicators of employment quality investigated are negatively related to affective job insecurity. Low-quality employment involves objective characteristics that reflect some instability (Urbanaviciute et al., 2021), which triggers affective job insecurity. The latter is a “subjective translation” of the employee’s labor market position (De Witte et al., 2015). This position is indicated by various objective characteristics, such as the type of job contract (temporary vs. permanent contract), the employment relationship (part-time vs. full-time), and the salary. Employees with low-quality employment arrangements (temporary contract, a part-time job, and a lower salary) have objectively weaker labor market positions because they are part of the secondary labor market (Doeringer & Piore, 1971; Urbanaviciute et al., 2021). Thus, employees in low-quality employment situations should experience higher affective job insecurity than employees in high-quality employment situations. There is empirical evidence supporting this relationship (Chung, 2019; Keim et al., 2014; van Wijk et al., 2021).

We also posit that affective job insecurity is positively related to employee health complaints. Experiencing affective job insecurity means that the employment situation is perceived as threatening (because there is fear of losing the job). If, in addition, employees cannot change the employment arrangement (as occurs with employees with low-quality employment), the threatening situation will trigger a stress response that may have negative consequences for employee health (Lazarus & Folkman, 1984). In fact, previous studies have viewed job insecurity as a severe work stressor that is detrimental to employee health (De Cuyper et al., 2010; De Witte et al., 2016; Shoss et al., 2020). Empirical evidence from longitudinal studies supports this relationship. In their review of 30 years of longitudinal studies on the association between job insecurity and health, De Witte et al. (2016) found support for the influence of job insecurity on self-perceived health and psychosomatic complaints. A meta-analysis by Llosa et al. (2017) found a positive relationship between job insecurity, on the one hand, and depression and anxiety, on the other. In general, employees with more job insecurity have worse mental and physical health than employees with less job insecurity (De Witte et al., 2015; Henares-Montiel et al., 2021; Högnäs et al., 2022; Jiang & Lavaysse, 2018; Llosa et al., 2017; Thomson & Hünefeld, 2021). The overall empirical evidence suggests that job insecurity is positively related to employee health impairment (De Witte & Van Hootegem, 2021). Given the theoretical and empirical arguments presented above, we hypothesize the following:

Hypothesis 2

There is a negative indirect effect of type of contract (0. temporary vs. 1. permanent; Hypothesis 2a), employment relationship (0. part-time vs. 1. full-time; Hypothesis 2b), and salary (Hypothesis 2c) on employee health complaints via affective job insecurity. Having a permanent job (H2a), a full-time job (H2b), and a higher salary (H2c) leads to lower affective job insecurity, which in turn is positively related to employee health complaints.

Method

Procedure and Sample

The data analyzed in this manuscript were collected within the framework of a broader research project (Davcheva et al., 2020). However, none of the focal variables analyzed in the present study have been used in previous publications based on data from the same research project (see Appendix). The aforementioned research project was approved by the corresponding Committee of Research Ethics. To collect the data, we used the services of a market research company that managed a respondent panel. Panel members who were invited to participate in the study had to be over 17 years old and could not be self-employed. Those who agreed to participate received a link to the online questionnaire. On the first part of the questionnaire, they provided their informed consent.

We implemented a time-lagged design with data collection at three time points separated by three months starting in July 2020. We used a three-month lag between subsequent time points because time lags should be long enough to mitigate common method biases, but not long enough to hide a relationship that actually exists (Podsakoff et al., 2003, 2012). Moreover, previous studies using this time lag reported significant relationships involving some of the investigated variables (e.g., De Cuyper et al., 2022; Jiang & Lavaysse, 2018; Topa & Aranda-Carmena, 2022).

The initial sample (Time 1, T1) was composed of 611 participants. At Time 2 (T2), 578 participants responded (response rate: 94.6%). At Time 3 (T3), 540 of the 578 participants who responded at T1 and T2 also answered the questionnaire (response rate based on the T1 sample: 88.4%). Thus, the initial longitudinal sample was composed of 540 participants.

Respondents who were unemployed at T1 (74), at T2 (21), and at T3 (16) were eliminated from the longitudinal sample, yielding N = 429 participants. Moreover, participants who changed jobs between time points (T1-T2: 26 participants, and T2-T3: 12 participants) were also removed from the sample (yielding N = 391). To ensure data quality, we identified inattentive participants by using three instructed response items (e.g., ’Please choose response option 4 now’) throughout the questionnaire at each measurement point. We eliminated subjects who responded incorrectly to any of these items. Based on this criterion, 68 participants at T1, 39 participants at T2, and 31 participants at T3 were removed, resulting in 253 participants. Additionally, 6 participants had missing values on the employment relationship variable. Therefore, our final sample was composed of 247 employees (51% men; mean age = 37 years, SD = 10) who held the same job throughout the study period. The participants had a variety of jobs across different industrial sectors (health and social services: 11%; education: 8.9%; construction: 8.5%; information and communication: 8.1%; administrative services: 6.3%; among others).

Additionally, given that our sample showed high attrition across time, we conducted a response-nonresponse analysis. We compared three groups of subjects: (1) those who only responded at T1 (N1); (2) those who only responded at T1 and T2 (N2); and (3) those who responded at all three time points (T1, T2, and T3; N3 = 253Footnote 1). First, we filtered participants at each time point according to the aforementioned criteria, eliminating the participants who were unemployed, those who changed jobs between adjacent time points, and those who had attention errors. At T1, of the 611 initial participants, we eliminated 86 unemployed subjects and 92 who had attention errors at T1, yielding a sample of 433 respondents at T1. To identify the sample of participants who (at the least) responded at T1 and T2 from this sample of 433 respondents, we further eliminated the unemployed participants at T2 (38), those who changed their jobs between T1 and T2 (26), and those who had attention errors (41) at T2. This yielded a sample of 328 participants who (at the least) responded at T1 and T2. The difference 433–328 = 105 represented the group of participants who responded only at T1 (N1 = 105). To identify the sample of participants who only responded at T1 and T2 (N2) from the group of 328 subjects who (at the least) responded at T1 and T2, we subtracted the group of participants who responded at all three time points (N3 = 253), yielding N2 = 328–253 = 75.

We compared the group of participants who responded at all three time points (N3 = 253) with the other two groups (N1 = 105 and N2 = 75) on the variables measured at Time 1: type of job contract and employment relationship (using several chi-square tests) and salary (with an ANOVA). We found no significant relationship between the distribution of the participants in these three groups, on the one hand, and the type of job contract and employment relationship, on the other. Likewise, we found no significant differences in salary among the three groups.

We also compared the final sample of participants who responded at all three times (N3 = 253) with the participants who only responded at T1 and T2 (N2 = 75). This comparison focused on the variables measured at Time 2: work engagement and affective job insecurity (using independent sample t-tests), and the results showed no significant differences between the two groups on these variables. Thus, attrition seemed to have no relevant effect on the study variables.

Measures

Employment Quality Indicators (T1). We measured three objective employment quality indicators: type of job contract, employment relationship, and salary. Type of Job Contract was measured by directly asking individuals “What type of job contract do you have?” (0 = temporary and 1 = permanent). Employment Relationship was measured by directly asking participants “Do you work part-time or full-time?” (0 = part-time and 1 = full-time). Salary was measured by asking participants to indicate their average monthly net earnings on a graded scale from 0 (less than 450 euros) to 6 (more than 2100 euros). Lower values on these indicators indicate low employment quality, whereas higher values indicate high employment quality.

Work Engagement (T2) was measured with the 3-item version of the Utrecht Work Engagement Scale, proposed and validated by Schaufeli et al. (2019). The scale includes one item for each of the three work engagement dimensions: vigor (i.e., “At my work, I feel bursting with energy”), dedication (i.e., “I am enthusiastic about my job”), and absorption (i.e., “I am immersed in my work”). Respondents answered using a 6-point frequency rating scale ranging from 1 (never) to 6 (always). Cronbach’s alpha was 0.86.

Affective Job Insecurity (T2) was measured with a 4-item scale (Llosa et al., 2017) (i.e., “I fear that I might lose my job”). Participants answered using a 6-point Likert scale ranging from 1 (strongly disagree) to 6 (strongly agree). Cronbach’s alpha was 0.88.

Employee Health Complaints (T3) were measured with an 8-item psychosomatic symptoms scale (Hagquist, 2008). The participants were asked to report how many days in the past week they had experienced giddiness, headache, stomachache, sleep difficulties, concentration difficulties, low appetite, feelings of tension, or sadness. Participants answered using an 8-point scale ranging from 0 (0 days) to 7 (all 7 days). Cronbach’s alpha was 0.86.

To gather evidence about the validity of the study measures in our sample, we conducted a confirmatory factor analysis (CFA). We compared the fit of the hypothesized three-factor measurement model (work engagement, affective job insecurity, and health complaints) with the fit of a one-factor model. The three-factor model showed a better fit to data (χ2 (87) = 139.84, p < .001; CFI = 0.97; RMSEA = 0.05; SRMR = 0.05)Footnote 2 than the one-factor solution, which did not show an acceptable fit (χ2 (90) = 1028.61, p < .001; CFI = 0.51; RMSEA = 0.20; SRMR = 0.15). For the three-factor model, which showed satisfactory goodness-of-fit, all the items’ standardized factor loadings were statistically significant (p < .01) and ranged between 0.51 and 0.94. Regarding the correlations among the three factors, as expected, work engagement was negatively correlated with affective job insecurity (r = − .32, p < .001) and employee health complaints (r = − .33, p < .001). Finally, affective job insecurity was positively correlated with employee health complaints (r = .29, p < .001).

Analysis

To fit our research model and obtain the parameter estimates, we used Structural Equation Modeling (SEM) with Robust Maximum Likelihood estimation, as implemented in Mplus 8 (Muthén & Muthén, 1998–2017). The exogenous variables in our model (type of job contract, employment relationship, and salary) were modeled as observed variables. The mediators (work engagement and job insecurity) and the outcome (health complaints) were modeled as latent variables whose indicators were the items included in each measurement scale (3 for work engagement, 4 for job insecurity, and 8 for employee health complaints). Because indirect effects do not follow a normal distribution (MacKinnon et al., 2002), the hypothesized indirect effects were tested by means of bootstrapping methods with 1000 replications and 95% Confidence Intervals (CI).

Results

Descriptive statistics and correlations among the study variables are displayed in Table 1.

Table 1 Descriptive statistics and correlations among the study variables
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The hypothesized research model showed a good fit to data (χ2 (126) = 190.42, p < .001; CFI = 0.96; RMSEA = 0.04; SRMR = 0.05). Although salary was negatively correlated with employee health complaints, when we included the direct relationship between these variables in the model, controlling for the mediators, it was not statistically significant (b = − 0.08, p = .23). Thus, the most parsimonious model (that is, the proposed research model) was retained.

The standardized parameter estimatesFootnote 3 obtained for the examined bivariate relationships are shown in Fig. 2. Type of job contract was not related to work engagement (b = 0.06, p = .34), but, as expected, it was negatively related to affective job insecurity (b = − 0.22, p = .001). Employment relationship was not related to work engagement (b = 0.004, p = .97) or affective job insecurity (b = 0.007, p = .93). Salary was positively related to work engagement (b = 0.19, p = .014) and negatively related to affective job insecurity (b = − 0.15, p = .014). Work engagement was negatively related to employee health complaints (b = − 0.26, p = .001), and affective job insecurity was positively related to employee health complaints (b = 0.20, p < .001).

Fig. 2
figure 2

Parameter estimates for the hypothesized research model. Note. Coefficients are standardized. Standard errors are in brackets. INS: Affective job insecurity item; EHC: Employee health complaints item. Type of job contract: 0 = temporary; 1 = permanent. Employment relationship: 0 = part-time, 1 = full-time. * p < .05;** p < .01 (two-tailed)

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Regarding the hypothesized indirect effects via work engagement, the results were the following (see Table 2). Contrary to our expectations, the unstandardized indirect effect (IE) of type of job contract on employee health complaints via work engagement was not statistically significant, given that the confidence interval included 0 (IE = -0.05, 95% CI [ -0.168, 0.043]). Thus, Hypothesis 1a was not supported. Moreover, the unstandardized indirect effect of employment relationship on employee health complaints via work engagement was not statistically significant because the confidence interval included 0 (IE = -0.01, [-0.151, 0.116]). Thus, Hypothesis 1b was not supported. As expected, the unstandardized indirect effect of salary on employee health complaints via work engagement was negative and statistically significant (IE = -0.04, [-0.099, -0.011]). Thus, Hypothesis 1c was supported.

Table 2 Estimates for the hypothesized indirect effects and effect sizes
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To facilitate the interpretation of the observed significant indirect effects, we computed appropriate measures of effect size: partially and completely standardized indirect effects (abps and abcs, respectively; see Preacher & Kelley, 2011). Partially standardized indirect effects were computed when the predictor involved was a dichotomous variable (type of job contract: temporary vs. permanent, and employment relationship: part-time vs. full-time job). Completely standardized indirect effects were computed when the predictor involved was salary (see Table 2). For the indirect effect of salary on employee health complaints via work engagement, abcs = 0.05. Thus, employee health complaints decreased by 0.05 standard deviations (SD) for every one-SD increase in salary via work engagement.

Regarding the hypothesized indirect effects via affective job insecurity, we obtained the following results (see Table 2). The unstandardized indirect effect of type of job contract (0 = temporary and 1 = permanent) on employee health complaints via affective job insecurity was negative and statistically significant (IE = -0.13, 95% CI [-0.301, -0.027]). Thus, Hypothesis 2a was supported. The corresponding partially standardized indirect effect (abps) equaled 0.09. Thus, employee health complaints decreased by 0.09 standard deviations for employees with permanent contracts compared to employees with temporary ones via affective job insecurity. The unstandardized indirect effect of employment relationship on employee health complaints via affective job insecurity was not statistically significant (IE = 0.01, [ -0.079, 0.111]). Thus, Hypothesis 2b was not supported. Finally, the unstandardized indirect effect of salary on employee health complaints via affective job insecurity was negative and statistically significant (IE = -0.03, [ -0.068, -0.001]), supporting Hypothesis 2c. In this case, abcs = 0.03. Thus, employee health complaints decreased by 0.03 SDs for every one-SD increase in salary via affective job insecurity.

The total standardized indirect effect of salary on employee health complaints via the two mediators was − 0.08. This means that employee health complaints decreased by 0.08 SDs for every one-SD increase in salary via the two mediators, work engagement and affective job insecurity.

Moreover, we compared the two hypothesized indirect effects from salary to employee health complaints via the two investigated mediators to ascertain whether their magnitudes were different. We used the “model test” command in Mplus and the corresponding Wald test. This test was not statistically significant (W(1) = 0.42, p = .51), which means that the two indirect effects were not statistically different from each other, and both mediators contributed equally to explaining the relationship between salary and employee health complaints. We also compared the two significant indirect effects via affective job insecurity: type of job contract → affective job insecurity → employee health complaints and salary → affective job insecurity → employee health complaints. The Wald test was not statistically significant (W(1) = 3.34, p = .07), indicating that both salary and type of contract had a similar negative indirect effect on employee health complaints via affective job insecurity.

Discussion

The main aim of this study was to ascertain whether the relationships between three employment characteristics (type of job contract, employment relationship, and salary) and employee health complaints were mediated by work engagement and affective job insecurity. As hypothesized, our results showed that salary had a negative indirect effect on employee health complaints via the two mediators considered. Moreover, we found that type of contract (0. temporary vs. 1. permanent) had a negative indirect effect on employee health complaints via affective job insecurity, but not via work engagement. We did not find any indirect effects from employment relationship (0. part-time vs. 1. full-time) to employee health complaints. The significant indirect effects did not differ in their magnitude. These results have theoretical and practical implications that we discuss below.

Theoretical Implications

First, our findings uncover two of the mechanisms (work engagement and affective job insecurity) that help to understand why some indicators of employment quality are negatively related to employee health complaints. According to the first mechanism (work engagement) and the JD-R theory, employment quality indicators are resources that initiate a motivational process by fostering work engagement, which in turn decreases employee health complaints. In line with previous literature, our findings indicate that salary functions as a job resource that can trigger employee motivation. Specifically, the results indicate that a higher salary resulted in higher work engagement and fewer health complaints (consistent with Hypothesis 1c). The explanation underlying this indirect effect is that salary can help to meet employees’ basic psychological needs of competence and autonomy, which in turn fosters intrinsic motivation and work engagement (Ryan & Deci, 2000). Salary can be interpreted by employees as a recognition of their competence at work (Fall & Roussel, 2014; Kuvaas, 2006). Moreover, higher salaries may signal that employees are trusted to perform their jobs without being externally regulated, which can strengthen employee perceptions of autonomy (Gagné & Deci, 2005). Finally, higher salaries can foster work engagement by facilitating easier access to opportunities for learning and professional and personal growth (e.g., investing in one’s professional career by registering in training seminars), which are important levers for work engagement (Hu & Schaufeli, 2011). Then, work engagement stimulates the activity of the parasympathetic nervous system, which facilitates restorative and regulation functions that help employees to enact healthy and adaptable responses that decrease their health complaints (Seppälä et al., 2012). Moreover, work engagement facilitates the adoption of healthier behaviors via goal setting and self-regulation, and it can trigger a positive spiral of personal resources that can help individuals to cope better with stress and, therefore, improve their health (Fredrickson, 2013; Salanova et al., 2010).

Contrary to our expectations, we did not find a negative indirect effect of type of contract (0. temporary vs. 1. permanent) on health complaints via work engagement because the relationship between contract type and work engagement was nonsignificant. In other words, having a permanent (vs. temporary) job did not lead to higher work engagement and, indirectly, fewer health complaints (contrary to Hypothesis 1a). From the perspective of the JD-R theory, this result suggests that the type of contract did not function as a resource. However, a literature review on temporary employment suggests that the lack of relationship between contract type and work engagement may be related to differences in employment quality among different types of temporary employees and the associated work experiences (De Cuyper et al., 2008). Among temporary workers, agency workers (hired by an external agency to perform work at a user organization) and on-call workers (who fill short-term vacancies for a limited number of hours or days) are the subgroups with the worst employment conditions (Bernhard-Oettel et al., 2005; De Cuyper et al., 2008).The subgroup of fixed-term contract workers (directly hired by the organization for a specific time period) generally has longer contracts and more stability than temporary agency and on-call workers (De Cuyper et al., 2009). Fixed-term employees have been found to experience similar levels of work outcomes (e.g., job satisfaction and commitment) to those of permanent workers (De Cuyper et al., 2008). Thus, it is possible that the contract type-work engagement relationship only emerges when all the subgroups of temporary workers are represented in the study sample. Otherwise, the sample will present some restriction of range that can affect the magnitude of the observed relationships between contract type and work engagement. One potential explanation for the lack of association between contract type and work engagement in our study might be that the subgroup of temporary workers we surveyed was too homogeneous. Unfortunately, we did not collect data to discriminate among different types of temporary employees.

Focusing on the second mediating mechanism (affective job insecurity), two of the employment quality indicators we considered (contract type and salary) were negatively related to health complaints via affective job insecurity. Having a permanent position led to lower affective job insecurity and fewer health complaints (as proposed in Hypothesis 2a), and a higher salary also led to lower affective job insecurity and fewer health complaints (consistent with Hypothesis 2c). These results are congruent with the cross-links between the motivational and health-impairment processes embedded within the JD-R theory (Alarcon, 2011; Crawford et al., 2010; González-Romá et al., 2020; Lesener et al., 2019; Schaufeli & Taris, 2014). Employees with temporary contracts and lower salaries have objectively worse labor conditions (Urbanaviciute et al., 2021) that lead them to experience their employment situation as insecure (De Witte et al., 2015). This increased affective insecurity represents a real threat to employees because they fear they will lose their jobs. The threat experienced triggers a stress response that impacts employee health and is observed in an increase in self-reported health complaints (Lazarus & Folkman, 1984). Interestingly, permanent workers had fewer health complaints via lower job insecurity, but not via engagement. This indicates that permanent workers were not more engaged, but rather less insecure about their jobs, and so they reported fewer health complaints. The fact that the contract type was indirectly related to health complaints only via affective job insecurity is in line with previous literature on nonstandard employment (De Witte et al., 2015). This literature shows that temporary work is intrinsically insecure, which triggers the affective job insecurity mechanism towards employee health.

We did not find support for the hypothesized indirect effects of the employment relationship (part-time vs. full-time) on employee health complaints via work engagement and affective job insecurity. Having a full-time (vs. part-time) job did not lead to higher work engagement and fewer health complaints (contrary to Hypothesis 1b); nor did it lead to lower affective job insecurity and fewer health complaints (contrary to Hypothesis 2b). From the perspective of the JD-R theory and the cross-links between the motivational and health-impairment processes, these results suggest that the employment relationship does not function as a resource that fosters motivational states and reduces employee strain. One possible explanation is that the relationship between the employment relationship and the two mediators may depend on employees’ preferences for the type of employment relationship. Some employees have a part-time job because they prefer it (voluntary part-timers), whereas other employees work part-time because they could not find a full-time job (involuntary part-timers). Research has shown that there may be important differences in the work experience of these two groups of part-time employees. Overall, involuntary part-timers have more negative work experiences (Spreitzer et al., 2017). Compared to voluntary part-timers, involuntary ones face an undesired employment situation that poses an important threat to their professional career and personal project. This may explain why they are more likely to suffer from job insecurity than voluntary part-timers (Veliziotis et al., 2015). Moreover, voluntarily accepted part-time jobs can help employees to meet their needs (e.g., work-family conciliation) and increase their perceived autonomy to structure their schedules. These benefits associated with a preferred part-time job can increase their work engagement and (indirectly) their health (Beham et al., 2012; Donnelly & Schoenbachler, 2021). Based on the previous arguments, it is possible that the involuntary part-timers would show the expected effects (lower engagement and higher job insecurity), but those who choose and prefer part-time work would not. However, in our study we did not collect information to identify voluntary vs. involuntary part-timers. Future research should investigate whether the association between the employment relationship (part-time vs. full-time) and the two mediators considered depends on employees’ preferences for the type of employment relationship.

Despite the lack of significance of some of the hypothesized indirect effects, the identification of two mediating mechanisms (work engagement and affective job insecurity) in the relationship between contract type and salary, on the one hand, and health complaints, on the other, represents a valuable increase in knowledge and an important refinement of the theory involved (Spencer et al., 2005). We are now better able to understand and explain the relationships between the aforementioned employment quality indicators and employee health complaints. Uncovering intervening variables contributes to moving our discipline forward (Mathieu et al., 2008).

Second, the indirect effects of salary identified here (salary → work engagement → health complaints; salary → affective job insecurity → health complaints) were of similar magnitudes (that is, the difference between them was not statistically significant). This result is important because previous research has focused on the relationship between employment quality and health via dysfunctional mediators (e.g., job insecurity; Peckham et al., 2019) while disregarding the potential relationship between employment quality indicators and work motivation states and its associated health consequences. Our findings highlight that the influence of salary on employee health complaints via functional motivational states (i.e., work engagement) may be as strong as its influence via dysfunctional threatening states (i.e., affective job insecurity). Future studies and theoretical models should include both types of mediators and pathways in order to improve our understanding of the mechanisms through which employment quality influences employee criteria. By considering one of the mediators investigated here (work engagement) and its associated consequences (e.g., job performance, Christian et al., 2011; Mazzetti et al., 2021; turnover intention, Mazzetti et al., 2021), future studies could examine the indirect effects of employment quality indicators via work engagement on a variety of important employee criteria.

Third, our findings also have implications for the JD-R theory. We showed that one of the employment quality indicators we investigated (salary) can start the motivational process for resources expected from the JD-R theory via key motivational states (e.g., work engagement). However, we also showed that salary can negatively impact health complaints through its influence on affective job insecurity. This last result is congruent with the idea that cross-links exist between the motivation and health-impairment processes embedded within the JD-R theory. Based on these cross-links, resources may also have an impact on strain variables (e.g., affective job insecurity, emotional exhaustion), and demands may also have an impact on motivational states. These cross-links have been reported by previous empirical studies and meta-analyses (Alarcon, 2011; Crawford et al., 2010; González-Romá et al., 2020; Lesener et al., 2019; Schaufeli & Taris, 2014). Thus, future studies using the JD-R theory as their theoretical framework should consider including cross-links between the two aforementioned processes.

Finally, researchers have frequently used the JD-R theory to investigate the influence of job resources (e.g., autonomy, variety, feedback from the job; Crawford et al., 2010; Morgeson et al., 2013; Schaufeli et al., 2009) that are characteristic of high-quality jobs when job quality is based on job content (i.e., job tasks). Our results and theoretical framework show that the JD-R theory can also be used to examine the influence of employment quality indicators on employees’ health complaints. These findings contribute to extending the applicability of the JD-R theory in occupational health research.

Practical Implications

Our study shows that some employment characteristics contribute to employee health. Thus, policy makers should approve norms, regulations, and programs that promote and incentivize high-quality employment arrangements among employers. For instance, at the end of 2021, the Spanish government passed a law reforming the labor market regulations (Royal Decree-Law 32/2021, December 28). One of the goals of this reform was to prioritize permanent contracts over temporary ones. Before this reform, the ratio of temporary contracts vs. permanent ones was 90%:10%. Nine months after the reform, the ratio was 65%:35%. Based on our results and the indirect effect of type of contact (temporary vs. permanent) on employee health complaints via affective job insecurity, this labor reform should have contributed to improving employee health.

Policy makers could also launch evidence-based communication campaigns that show the benefits of high-quality employment, not only for employees, but also for employers. For instance, the European Union’s policy has tried to foster quality employment by stressing the importance of “promoting job creation on permanent contracts, ensuring that temporary contracts represent steppingstones and not dead-ends…” (European Commission, 2018, p. 7). All of this can help to make employers aware of the importance of offering high-quality conditions to their employees and the impact this may have on their organizations.

For example, based on the association between employee health complaints and absenteeism (Roelen et al., 2010), offering high-quality employment can help to reduce absenteeism in organizations and its associated economic costs. Moreover, based on the positive relationship we observed between salary and work engagement, on the one hand, and the positive relationship between the latter and job performance documented in the literature (Mazzetti et al., 2021), on the other, we suggest that by offering affordable salary increases, employers can foster employee job performance, which in turn, may contribute to improving organizational performance. Furthermore, based on the negative relationship we found between some employment characteristics (type of contract and salary) and affective job insecurity, on the one hand, and the negative relationship between the latter and employee wellbeing reported in the literature (De Witte et al., 2015; Jiang & Lavaysse, 2018), on the other, we suggest that by offering high-quality employment, employers can improve employee wellbeing.

We are aware that many factors can influence companies’ employment decisions (e.g., market demand, economic crisis, growth expectations), and that under certain circumstances companies cannot afford the economic resources associated with salary increases and the transformation of temporary contracts into permanent ones. However, the practical implications we suggest based on our findings (regulations, programs, and evidence-based communication campaigns) should contribute to promoting and incentivizing high-quality employment arrangements among employers by making it clear that these arrangements can be useful for their organizations.

Limitations and Strengths

Our study has several limitations. First, data were collected from a single source using self-reported questionnaires, which might have inflated the relationships between the study variables. However, the implementation of a time-lagged design with a temporal separation between the study variables should have reduced this potential problem (Podsakoff et al., 2003). The fact that some of the observed correlations between the study variables were close to zero (see Table 1) suggests that common-method variance was not a serious problem in our study (Spector, 2006). Second, we operationalized employment quality using three indicators (type of job contract, employment relationship, and salary). We chose these indicators based on the segmented labor market theory (Doeringer & Piore, 1971) and because they are more objective than other indicators employed in the literature (e.g., whether employees feel easily replaceable, Vives et al., 2010). However, some scholars have suggested other indicators, such as work time arrangements and interpersonal power relations, among others (Kalleberg, 2018; Padrosa et al., 2021). Future research should examine whether the relationships and the mediating mechanisms observed here are found when other indicators of employment quality are used. Third, we implemented a variable-centric approach to estimate the relationships between each indicator of employment quality and the study mediator and outcome variables. However, we note that a person-centric approach could complement our results by showing which specific combinations of the investigated variables’ values (e.g., employees with permanent contracts, full-time jobs, and high salaries) yield lower levels of health complaints. Future studies should consider this perspective.

Fourth, the data analyzed in this study were collected after the lockdown established by the Spanish government in response to the COVID-19 pandemic. The lockdown lasted from March 14, 2020 to June 21, 2020. We collected data in July (Time 1), October, (Time 2), and December (Time 3) of 2020. Thus, the data collection took place once the lockdown had been lifted and people had returned to their jobs under the “new normal” situation. However, there is evidence that suggests that the COVID-19 pandemic increased job insecurity perceptions and health complaints in the Spanish adult population (Centre for Sociological Research [CIS], 2021; Peiró et al., 2023). Thus, it is reasonable to think that, right after the lockdown, subjects were more sensitive to these issues, and this might have affected the relationships involving these variables. Future studies should replicate our findings to determine the degree to which our findings were affected by the COVID-19 pandemic.

Our study also shows several strengths. First, by implementing a time-lagged research design, we more rigorously test the study relationships, and we overcome the limitations of a cross-sectional research design, which has been the most frequent way of testing the relationship between employment quality and health indicators (Matilla-Santander et al., 2020; Steffgen et al., 2020; Vanroelen et al., 2021). Second, by simultaneously estimating the indirect relationships between three objective employment quality indicators, on the one hand, and employee health complaints, on the other, we provide a more nuanced view of the importance of each of these indicators for employee health.

Conclusion

Our study helps to explain why some employment quality indicators are negatively related to employees’ health complaints. We identified work engagement and affective job insecurity as important mediators in the salary-employee health complaints relationship. We also found that having a permanent job contract has a negative indirect effect on employee health complaints via affective job insecurity. By identifying these two mediators, we hope to provide a better theoretical understanding of a research topic that is highly relevant to policy makers, employers, and employees.