The twenty-first century is witnessing one of the most relevant social changes, which Portugal is also related to. According to the National Statistical Institute [1], the Portuguese demographic pyramid reflects a marked population aging (the fifth-highest value and the third lowest value of the Renewal Index of Population at the European level). An aging population has a marked propensity for developing states of multi-morbidity, which projects functional disabilities with direct effects on the consumption of resources [2]. Although the health of the Portuguese population has improved in the recent decades, this has not been accompanied by policies that reflect the need for improvement and investment in the health care of the elderly, recognizing that the phenomenon may mirror an increase in the demand for health care services [3].

Rodrigues et al. [4] in their study, confirmed a high prevalence of multimorbidity (78.3%), increasing across age strata (72.8% for 65—69 years to 83.4% for ≥ 80 years). Hospitalization was reported by 25.8% of the individuals, concluding that the high prevalence of multimorbidity, associated with unhealthy lifestyles, of which diet stands out, is a predictor of vulnerability in the elderly, requiring dedicated intervention. This fact represents an enormous challenge to the health sector. There’s a high expectation on the Primary Health Care Services (PHCS) – seen as a privileged and first-line access route for anyone to the National Health Systems, given their mission. Thus, implementing and improving effective and rapid community intervention strategies that mobilize responses capable of satisfying the specific needs of this population is a demand for the health sector to address [5].

In Portugal, considering the overall effects of aging, the Ministry of Health [6] has approved the National Programme for the Health of the Elderly, recommending special attention to the elderly, and the intervention of health professionals in the case of elderly with malnutrition.

Nutrition is a key component in the health of the elderly population, capable of determining the quality of aging conditions. In this sense, the adequate nutritional status is the reflection of the balance between the elder's body food intake and the body's nutritional needs [7, 8]. The concept of malnutrition refers to a state resulting from a lack of nutrient absorption or intake that leads to changes in the body composition (decreased fat-free mass) and the body cell mass, with a consequent decrease in physical and mental function, associated with a more reserved clinical prognosis [9].

According to the National Programme for the Promotion of Healthy Eating [10], the population's inadequate eating habits are the fourth modifiable risk factor that most contributed to the loss of healthy life years (11.4% of the total number of deaths), especially malnutrition, particularly in the elderly population.

To be noted that malnutrition in the elderly is a current phenomenon often underdiagnosed that has not, yet, received its deserved attention. It is easily assumed as a natural and expected sign of aging, and therefore its early recognition becomes essential for appropriate and timely correction [11]. To highlight that across any of the different authors referenced for systematic reviews, the most common and cross-cutting thematic interest was the relationship between malnourished elderly and their hospitalization and institutionalization [12,13,14,15,16,17]. So, it is important to recognize the importance of re-conducting a new research study capable of validating the terms of analysis for the context of the potential PHC intervention. The study will be based on a methodology that structures a scoping review and simultaneously substantiates the following objectives:

  1. I.

    To identify the screening instruments in the diagnosis of elderly´s malnutrition;

  2. II.

    To identify the health outcomes (morbidity, mortality, functional capacity, and quality of life) associated with under-diagnosis and under-intervention of Family Health Teams (Doctors and Nurses) regarding the phenomenon of malnutrition in the elderly;

Method

Eligibility criteria

The selected studies complied with the following PICOS strategy. Only studies are written in English, Spanish and Portuguese languages were considered. We included data sources on observational, qualitative, quantitative, or mixed indexed studies, published between 2011–2021, addressed to the adults aged 65 years and over, describing the use of screening/intervention tools or the identification of health outcomes (morbidity, mortality, functional capacity and quality of life) associated with under-diagnosis and under-intervention of the Family Health Teams in face of the malnutrition phenomenon. We have published a protocol for a scoping review that can be retrieved from osf.io/sw3aj. https://doi.org/10.17605/OSF.IO/SW3AJ.s health.

Information sources and search strategy

In July of 2021, the literature search was carried out by two reviewers (AT, BS) in PubMed, Web of Science, Scopus & EMBASE. The literature was selected from the year 2011 onwards. We opted to define this as the temporal interval to conduct our research, based on the systematic publication of reviews, in the recent years, regarding the theme of malnutrition in the elderly population [12,13,14,15,16,17]. Snowball citations were retrospectively and prospectively screened to ensure literature saturation. Review articles (i.e. systematic, scoping, narrative reviews), expert opinion excerpts, protocol articles, and trial registers were excluded. The search strategy is presented in Table 1.

Table 1 Search strategy
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Study selection

Studies founded by database analysis were exported to the Rayyan Management Software. Reviewers AT, AM selected the eligible studies for this review. An inclusion/exclusion algorithm was created to facilitate the data screening phases (three in total). In the first data screening phase, the duplicates identified by the software were reviewed and removed by AT, BS. In the second phase, two reviewers AT, AM independently identified assessed the titles and abstracts of the studies for inclusion. Each reviewer decided on the inclusion or exclusion of each paper based on the inclusion/exclusion criteria stated above. During the third phase, two reviewers AT, AM independently reviewed the papers approved during the second phase data review for inclusion. Possible disagreements were resolved by consensus. The reason for exclusion was identified for all excluded studies and a PRISMA flowchart was drawn to summarise the study and selection process (Fig. 1).

Fig. 1
figure 1

Adaptation of PRISMA flow chart

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Data extraction

The selected data was migrated to an Excel document format, and the information was organized according to studies that point out (1) the procedure (screening/intervention tools) that identified the malnutrition in the elderly; (2) and/or data from studies that identify health outcomes associated with under-diagnosis and under-intervention by Family Health Teams.

In addition, when possible, data were extracted on: 1) study characteristics (study design, country of origin, year of publication, and sample size); 2) participant characteristics (socio-economic and educational variables, clinical conditions, living arrangement, mean age, gender, and race); 3) screening instrument used in the diagnosis of malnutrition; 4) elderly´s health outcomes (morbidity, mortality, functional capacity and quality of life); 5) main screening instruments´ characteristics in the diagnosis of elderly´s malnutrition referred in the different studies; 6) main conclusions. The descriptions of the studies are presented in Tables 2, 3, and 4.

Table 2 Description of main sample characteristics, study design, and procedures
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Table 3 Description of main screening instruments´ characteristics in the diagnosis of elderly´s malnutrition referred in the different studies
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Table 4 Description of elderly´s health outcomes (morbidity, mortality, functional capacity, and quality of life), and main conclusions of the eligible studies
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Data synthesis

The included articles were submitted to a qualitative synthesis. The main results were organized into different categories in a discrete and non-overlapping manner. In each category, the results were summarised, highlighting their meaning.

Results

Initially, 483 studies were identified through an electronic database search. After removing duplicates (n = 54), the titles and abstracts were screened, and 391 studies were excluded. The main reasons for the exclusion of the studies were: i) did not consider the research scope (n = 335); ii) study contexts were exclusively hospital/nursing homes /inpatient (n = 32); iii) followed systematic review and meta-analysis methodology (n = 21); iv) include articles published in excluded languages (n = 1); v) opinion articles (n = 1); vi) book chapters (n = 1). Of the 38 full-text articles assessed for eligibility, 13 met the inclusion criteria, and the other 25 were excluded because they presented unclear data regarding the report of our main objectives. References of these studies were manually analyzed, resulting in 3 additional studies. In total, 16 studies were identified for this scoping review (Fig. 1).

Characteristics of included studies

Country of origin, year of publication, and sample sizes

The last ten years (between 2011 and 2021) evoke research interest in the topic across a broad geographical context, most notably in Belgium (18.75%) [21, 22, 32] and the USA (12.5%) [18, 33], followed by, Saudi Arabia [19], Spain [20], Slovenia [23], India [24], Italy [25], Denmark [26], Australia [27], Mexico [28], the Netherlands [29], Sweden [30] and Lithuania (respectively with 0.06%) [31]. Sample sizes of the included studies ranged from a minimum of n = 57 [20] to, a maximum of n = 15 121 31 [18] (Table 2).

Sample characteristics

The sample characteristics of the included studies reveal that the age of the participants ranged between 60 [23, 24, 30] and 99 years [23]. Most of the malnourished elderly were female [18,19,20,21,22,23,24, 26,27,28,29, 31], lived with another person [19, 27, 28, 31], and had associated comorbidities [18, 23, 24, 26,27,28, 30, 32, 33]. It should be noted that given the other terms that we previously established in the analysis of the sample characteristics, only two studies considered the assessment of the socio-economic level of the participants [19, 24] five studies reveal the educational level [19, 24, 28, 30, 33] and two consider race [18, 33] (Table 2).

Design

The research design was mostly observational, and cross-sectional descriptive studies (75%) [18,19,20, 22,23,24,25, 28, 30,31,32,33], followed by quantitative studies (18.7%) [21, 26, 29], and mixed (0.06%) [27]. The dissemination of the articles was essentially from the health area (56.2%) [18, 21, 22, 24, 27, 29, 31,32,33], and from the nutrition scope (43.8%) [19, 20, 23, 25, 26, 28, 30] (Table 2).

Procedures

Fifteen samples of malnourished elderly were obtained based on validated screening instruments [19,20,21,22,23,24,25,26,27,28,29,30,31,32,33] and only one study [18] based on the clinical diagnosis made by the physician, reported in the elderly patient's clinical file (Table 2).

Measures/malnutrion screening instruments

Twelve studies used the Mini Nutritional Assessment (MNA) to diagnose malnutrition in the elderly [19, 20, 22, 24,25,26,27,28, 30,31,32,33]. To highlight that nine of those twelve studies used MNA exclusively for the sample selection [20, 24,25,26, 28, 30,31,32,33]. Hegendörfer et al. [22] used it combined with pre-albumin levels, and Preston et al. [27] used it in association with three other screening instruments (namely, Australian Nutritional Screening Initiative – ANSI; Malnutrition Universal Screening Tool – MUST and Malnutrition Screening Tool—MST). Schilp et al. [29] appealed to Short Nutritional Assessment Questionnaire 65 + (SNAQ 65 +). Galiot et al. [20] and Klemenc-Ketis et al. [23] just used MUST. Ahmed et al. [18] does not consider the screening instrument. The study selected malnourished participants based on the clinical diagnosis in the medical record (ICD-9 and 10). The description of main screening instruments´ characteristics in the diagnosis of elderly´s malnutrition reveals that fourteen studies [19,20,21,22,23,24,25,26, 28,29,30,31,32,33], in their methods sections, explained the nutritional profiles categories (baseline) associated with the choice of their instruments, except for Preston et al. [27] that did not reported any information. Also, only three studies [21, 28, 33] have tried to sustain their instrument's options considering its psychometric characterístics and the recommendation of the Nutrition Group (the European Society for Enteric and Parental Nutrition, the American Society for Parenteral and Enteral Nutrition, and the National Institute for Health and Care Excellence). In all studies, the instrument´s application was assumed by the research/health professional assessment (Tables 2 and 3).

Elderly´s health outcomes

Concerning health outcomes in the elderly at risk of malnutrition, the analysis of the articles reveals a greater interest in studying the phenomenon associated with morbidity (37.5%) [20, 23, 25, 27, 28, 31], followed by mortality (31.25%) [18, 22, 25, 30, 33], activities day living (ADL) (25%) [19, 26, 28, 32], hospitalization (25%) [22, 25, 26, 33], social risk (18.75%) [20, 27, 28], and lastly, health costs and functional capacity (12.5%). In terms of the results, the study of Krishnamoorthy et al. [24] only carried out the characterization of the sample (highlighting the prevalence of malnutrition in the elderly, without its correlation with the variables under analysis). However, we opted for its inclusion considering the relationship between the diagnosis phase and the value of PHC intervention. Only Schilp et al. [29] have established the relationship between malnutrition and the quality of life.

Moreover, based on the description of the elderly´s health outcomes, and main conclusions of the eligible studies (Table 4), it allows us to state that the effects of malnutrition in the elderly, in terms of associated health outcomes, tend to be severe, especially when related to other comorbidities. Ahmed et al. [18] concluded that mortality in an elderly person with diabetes and malnutrition increases by 69%, including ischaemic heart disease; chronic obstructive pulmonary disease; stroke, or transient ischaemic stroke; chronic renal failure, and acute myocardial infarction. In addition, the total annual expenditure on health care for the undernourished individual was significantly higher. However at this point, to Schilp et al. [29], no statistically significant differences were found between the introduction of dietary treatment VS usual care in total costs.

Shakersain et al. [30], found that malnutrition and malnutrition risk was significantly associated with all-cause mortality and shortened survival by 3 and 1.5 years respectively. They also found that being elderly, living alone, and institutionalized directly correlated with poor nutritional status. However, the pure effect of malnutrition on mortality may not be perceived. In the present study, the relationship between poor nutritional status and mortality appears to be independent of chronic diseases suggesting that subclinical changes may play a role in the association between poor nutritional status and mortality. But then, Yang et al. [33], supports the previous analyses by robustly stating by their study that malnutrition in the elderly is assumed to be a risk factor for increased health service utilization and mortality [22, 25, 26].

The risk of malnutrition is identically related to lower physical and cognitive performance, greater functional disability (in terms of autonomy in ADL), and even entails an increased risk of depression and isolation [19,20,21,22, 27, 28, 31, 32]. In this connection, Yang et al. [33], and Mastronuzzi et al. [25], affirm that malnourished participants were more likely to experience sequential under-hospitalization, emergency room visits, use of home health aides, and mortality. This confirms the idea of Rodrigues et al. [28], when verifying that the high prevalence of multimorbidity, associated with unhealthy lifestyles, of which diet and its effects stand out, is a predictor of vulnerability, of increased hospitalization in the elderly.

Schilp et al. [29] assume that the improvement in quality of life occurs after body weight gain, which confirms the hypothesis of an association between body weight change and quality of life. Their study found that one-fifth of the participants were determined to have nutritional risk, identifying as promoting factors: poverty, poor oral health, medication use (P = 0.042), and social isolation. Inherent to this perspective, for Preston et al. [27], frailty itself is statistically significant in increasing their nutritional risk (P = 0.004), which is why it is possible to argue that the relationship between both is reciprocal and dependent.

Discussion

Summary of evidence

The study of elderly´s malnutrition in the community setting has been largely examined in the literature, however, no scoping review is currently available regarding the health processes and outcomes in PHC. In this context, it should be noted that PHC represents a key vector for intervention in promoting healthy eating habits and the prevention of malnutrition [34]. A commitment to differentiated intervention assumes a guide by the synergy of efforts of multidisciplinary teams. This means that the absence of a scoping review about this topic reveals to be a major gap in the literature.

To fill this gap, the present review was conducted (including 16 articles for analysis) with the purpose of synthesizing the data regarding the following objectives: i) to identify the screening instruments in the diagnosis of elderly´s malnutrition; ii) to identify the health outcomes (morbidity, mortality, functional capacity, and quality of life) associated with under-diagnosis and under-intervention of FHT regarding the phenomenon of malnutrition in the elderly.

Reading the articles allows us to state that the study of malnutrition´s association and morbidity had a wide range of interest (37.5%), compared to the other health outcomes (mortality, ADL, hospitalization, social risk, health systems costs, and quality of life, those latter, the least studied). However, overall, and as suggested by previous corroborating [7,8,9], it gets reinforced that the presence of malnutrition tends to accelerate the transformation of frailty into disability and worsen the elderly´s health (prognosis of other diseases, ADL, social risk, and quality of life), increasing the service utilization, but with some reservations for the mortality correlation. In some articles, this aspect may not be perceived, but in others, it is assumed to be a risk factor for increased mortality. At this point, we keep having some doubts about the pure effect of malnutrition on mortality.

Concerning the assessment´s process of risk/ malnutrition in the elderly, from the perspective of diagnosis and subsequent health intervention, it was observed that, although different screening instruments are available, the MNA, recommended by the European Society for Enteric and Parental Nutrition, showed a higher criterion of choice by researchers (75%). Still, two studies have justified it by its adequate predictive validity and specificity of analysis regarding the frail elderly population, (12,5%).

On the other hand, we could see that being elderly, living alone, or institutionalized is directly correlated with poor nutritional status, which sustains some properly, and special health policies recommendations [6], in attempting to reconduct the clinical good practices to the elderly being cared for. Whereas this fact, it seems to have results that confirm the hypothesis of an association between body weight gain and health outcomes improvement. Nevertheless, underlining some studies' recommendations, the dietary treatment should probably be prolonged (at least one year) and thus it will influence the individual's homeostasis positively.

It seems important to highlight that the combination of different results indicates that health professionals' timely and continuous action, especially in PHC, can positively influence the functional outcomes and dietary patterns of the elderly.

Implications for the practice

In the qualitative synthesis analysis of different studies, we also identified some problems to the FHT/health System concerning their interventions profile related to the elderly´s malnutrition and some potential solutions to those obstacles, which we consider relevant to summarize below.

In PHC practices, health professionals do not: a) demonstrate standardized practices in the use of screening instruments [11, 25]; b) underestimate malnutrition in the elderly (assuming it a natural part of aging) [25, 32]; c) elderly´s malnutrition is not routinely checked and reported in the patient's electronic file [25]; d) revealed low awareness, low knowledge capacity, and poor communication between stakeholders [21]. However, some recommendations are addressed: a) to use scientifically validated assessment tools (it standardize clinical diagnoses of malnutrition, ensure identification and the early intervention) [23, 24, 26, 27]; b) to use a simple, quick, and easy-to-fill screening tool such as the MNA makes it possible to identify better than BMI [25]; c) encouraged to adopt a routine of good practices intrinsic to the overall assessment/intervention of the elderly, always from a perspective of care integration (Hospital – PHC) [19, 23]; d) to develop training programs in nutrition education and the use of simple tools to identify nutritional risk in PHC [20, 21]; e) to improve the communication between stakeholders; f) to strength PHC to address and prevent this health issue through balanced dietary practices [24]; and, g) to educate community elders about healthy nutrition and provide them with specific updated guidelines [31].

Strengths and limitations

To the best of our knowledge, this is the first scoping review that synthesizes the range of knowledge available on PHC processes and health outcomes associated with malnutrition in elderly people. This reveals the greatest strength of the current study. The inclusion of peer-reviewed scientific articles published in English, Portuguese and Spanish, with a timeframe that includes the last 10 years of research on the current and growing phenomenon of vulnerability in the elderly, is another possible strength of the scoping review. However, we know that it may have limited the analysis by exclusion.

Given the interest of the current systematic reviews, it contrasts the need for scientific investment in this area of intervention, the PHC. Efforts were made to capture all relevant articles, assumed by the decision and interest to consult the references of eligible studies; however, articles could be overlooked. Including studies with different sampling methods reveals another possible strength of scoping review (as it is advisable to present papers that support and reinforce the results, overcoming the limitation of those with a less representative number of participants). However, the same condition may represent a possible associated limitation. Studies with different sampling representativity are included and compared, limiting the extrapolation of results.

Conclusion

This scoping review has fulfilled the objectives settled, identifying important malnutrition screening instruments (in terms of frequency of use, baseline, and psychometric characteristics), and the impactful health outcomes associated with under-diagnosis and under-intervention of FHT in PHC (revealing understudied content areas). At this point, it is important to say that, in this scoping review, reporting the main screening instruments´ characteristics in the diagnosis of elderly´s malnutrition referred among the different studies (Table 3), with various methodologies designs may be useful for future research in the area, providing information for assessing their applicability, recommendation, and validity.

Regarding the phenomenon of malnutrition in the elderly, and among all articles analyzed, the study also summarises some of the problems that the FHT/health systems are facing, which should be considered and valued in the particular PHC setting. The scientific process is expected to support the definition of quality interventions/clinical governance that facilitate and promote decision-making in FHT.

The current socio-economic situation, aggravated by a pandemic, has led countries, like Portugal, to an unprecedented economic crisis. Associated with this macro context, an increase in the phenomenon of malnutrition is foreseeable, given that people may lose income and see their purchasing power reduced, aspects that will influence the acquisition of foodstuffs. Thus, the possible consequences arising from this new reality should be a call to researchers to invest time in analysis and intervention on the phenomenon of malnutrition in the elderly.