Life satisfaction 18 months and 10 years following spinal cord injury: results from a New Zealand prospective cohort study

Purpose To examine the life satisfaction outcomes after spinal cord injury (SCI) and to identify the factors associated with life satisfaction at 18 months and 10 years post-SCI in New Zealand (NZ). Methods Adults (16–64 years) were recruited between 2007 and 2009 from NZ’s two spinal units following first admission for SCI. Interviews at 6 months, 18 months, and 10 years post-SCI examined demographic, physical, psychosocial, economic, and environmental characteristics. Multivariable regression models were used to identify predictors of life satisfaction at each timepoint. Results Overall, 118 people participated at 6 months, 103 at 18 months, and 63 at 10 years post-SCI. Pre-SCI, 90% of participants were satisfied with life, 67% were satisfied at 18 months, and 78% at 10 years. At 18 months post-SCI, participants who reported: never or sometimes using a wheelchair, no problems with self-care, no problems with anxiety or depression, no/lesser disability, or fewer secondary health conditions (SHCs) at 6 months post-SCI were more likely to be satisfied (p < 0.05), compared to those without these characteristics. Participants who experienced considerable disability at 6 months post-SCI were 22% less likely to be satisfied 10 years post-SCI compared to those experiencing no/lesser disability (p = 0.028). Conclusions A higher proportion of participants were satisfied at both 18 months and 10 years post-SCI than not satisfied. To improve the likelihood of satisfaction with life, increased focus on reducing disability and providing supports for those using wheelchairs, experiencing anxiety/depression or problems with self-care, and effects of SHCs are promising for future potential interventions.


Introduction
Spinal cord injuries (SCI) result from neurological damage to the spinal cord causing temporary or permanent change in function [1]. This can result in partial or complete loss of function below the site of the SCI [1,2]. SCI can result from traumatic (injury) or non-traumatic causes (e.g. haemorrhage or cancer) [2].
The World Health Organization estimates the annual global incidence of SCI to be 40-80 million [3]. In New Zealand (NZ), the incidence is approximately 160 people per year [4]. In NZ, rates differ by ethnicity, with higher rates among Māori and Pacific people (46 and 70 per million, respectively) compared to European and other ethnicities (29 and 16 per million, respectively) [5,6].
NZ has a unique no-fault injury insurance scheme, the Accident Compensation Corporation (ACC), which provides Martin Sullivan-Retired. rehabilitation and financial support (up to 80% of their income) to people experiencing traumatic SCI (and other injuries) [7][8][9]. Non-traumatic SCI are covered by the general public health system with access to limited means-tested financial support [7,8]. These different systems can lead to differences in treatment and experiences between those with traumatic and non-traumatic SCI [8].
SCIs can have large impacts on people's lives, including on levels of life satisfaction [7,10,11]. Life satisfaction has been described as the degree to which people positively perceive their overall quality of life, state of mind, and contentment with the life they lead [12].
Previous research internationally found life satisfaction to be generally positive among people with SCI, although not as satisfied as the general population [13][14][15][16]. A longitudinal study from the United States followed 2183 people from one to 20 years post-SCI and found life satisfaction increased as time post-SCI increased [17]. Post-SCI life satisfaction has been associated with a range of factors including sociodemographic and SCI-related characteristics, physical and mental health, and social and environmental characteristics [18][19][20][21]. However, none of these relationships appear to have been explored in NZ where the health and ACC system is unique. It is important to identify the opportunities for interventions to improve life satisfaction for people after SCI in NZ. Therefore, the overall aim of this paper is to examine the post-SCI life satisfaction outcomes over time and to identify the factors associated with life satisfaction at 18 months and 10 years post-SCI in NZ.

Study design and participants
This research analyses the data previously collected by the 'Longitudinal study of the life histories of people with spinal cord injury' [7]. The study was led by a researcher with lived experience of SCI (MS), interviewers had lived experience (including CB), and questionnaires were developed in consultation with others with lived experience of SCI. Details of this study have been previously published [7,22], but are briefly outlined below.
Individuals were recruited between 2007 and 2009 from NZ's two spinal units following first admission for SCI. Participants were NZ citizens or permanent residents aged 16-64 years who had sustained traumatic or non-traumatic SCI. Eligible participants had an American Spinal Injury Association Impairment Scale (AIS) grade of A, B, C, or D [23]. AIS A is the most severe (and complete) grade SCI, followed by AIS B, C, and D [23]. People with AIS grade E, those with significant cognitive injury or communication impairment, or a life expectancy of less than six months at the time of their SCI were ineligible. All participants provided informed consent at the beginning of the study, and before each follow-up interview, and received a copy of the consent form for their records. Ethical approval was granted by the New Zealand Multi-region Ethics Committee (MEC07/09/117).

Data collection
Data were collected from structured interviews undertaken approximately 6 months, 18 months, and 10 years post-SCI. Clinical information was collected by research nurses in each spinal unit. Interviews collected information about a range of demographic, physical, psychosocial, economic, and environmental characteristics. The first interview asked about pre-SCI characteristics as well as characteristics at 6 months post-SCI; subsequent interviews explored outcomes at later timepoints (the outcome of interest is life satisfaction).

Outcome measure
Life satisfaction outcomes at 18 months and 10 years were assessed by asking participants "Overall, how would you rate your life as a whole" on a 5-item scale [24,25]. Responses were categorised as 'Satisfied' ("Completely satisfied" or "Mostly satisfied") or 'Not satisfied' ("Neither satisfied nor dissatisfied", "Mostly dissatisfied" or "Completely dissatisfied").

Potential predictors of life satisfaction
Potential predictors of post-SCI life satisfaction were identified from previous literature and categorised as pre-SCI, SCI-related, and 6-month post-SCI characteristics.
SCI-related characteristics included the following: AIS grade (A, B, C, or D) [23], SCI aetiology (injury or illness), wheelchair usage (always, sometimes, or never), and ACC support (yes or no).
Life satisfaction was not assessed (as a potential predictor) at 6 months because there was concern (from people with lived experience) that this was too sensitive a question early post-SCI.

Measures
HRQoL was measured using the EQ-5D-3L dimensions of mobility, self-care, usual activities, pain or discomfort, and anxiety or depression [33]. Each dimension has three response options (e.g. no, some or extreme problems), categorised as 'No' or 'Any' problems. Participants also rated their own health state on the EQ-5D-3L Visual Analog Scale (VAS), where 0 is the worst health and 100 is the best health [33]. VAS scores were reported as a continuous variable. Disability was measured by the 12-item World Health Organization Disability Assessment Schedule (WHODAS 2.0 12-item) [35]. Each item was allocated a score between 0 (none) and 4 (extreme/cannot do) to provide a total score between 0 (no disability) and 48 (maximum disability) [37]. Scores were dichotomised ('No/lesser disability' WHODAS score < 10; 'Considerable disability' WHODAS ≥ 10) [37].
Participants self-reported whether they had "any problems" with SHCs from a list: leg swelling, leg spasms, shortness of breath, difficulty coughing, bowel constipation, diarrhoea, indigestion, urinary tract infection, urinary incontinence, problems with bladder programme, headaches, back pain, shoulder pain, pain below the level of SCI, and 'other' problems [26,38]. The number of SHCs with "any problems" for each participant was summed.
Satisfaction with social support was measured using five questions from the Social Support Survey Instrument [36]. Questions asked: "Is there someone available to you whom you can count on to listen when you need to talk?", "Is there someone available to you to give you good advice about a problem?", "Is there someone available to you who shows you love and affection?", "Can you count on anyone to provide you with emotional support (talking over problems or helping you make a difficult decision)?", and "Do you have as much contact as you would like with someone you feel close to, someone in whom you can trust and confide?" [36]. Responses ranged from "None of the time" (1) to "All of the time" (5). A summed score ranged between 5 and 25 and was treated as a continuous variable.

Data analysis
Descriptive statistics [n, % for categorical variables; mean ± standard deviation (SD) for continuous variables] were calculated for pre-SCI, SCI-related, and 6-month post-SCI characteristics. Univariable analyses assessed associations between potential predictors and life satisfaction outcomes at 18 months and 10 years post-SCI. Chi-squared tests (or Fisher's exact tests where appropriate) were used to assess the association between categorical variables and life satisfaction; unpaired t-tests were used for continuous variables.
A multivariable modified Poisson regression model [39] was developed to identify the potential predictor variables associated with life satisfaction outcomes at 18 months and 10 years post-SCI separately. The variables used for these models were those with evidence of univariable association based on p values < 0.15, and variables deemed important based on prior knowledge and research. The aim was to produce separate 'final multivariable models' at 18 months and 10 years post-SCI. Due to the relatively small sample size, which can cause model over-fitting resulting in potentially missed influential variables from the two 'final models', we first created four 'mini-models': (1) demographic and pre-SCI characteristics, (2) SCI-related characteristics, (3) 6-month post-SCI EQ-5D-3L characteristics, and (4) other 6-month post-SCI characteristics. Backwards stepwise selection, with a p value < 0.15, was used for variable retention in the mini-models. Variables retained in these mini-models were used for building the final model. The backwards stepwise selection process was repeated in the final model; a p value < 0.30 was used considering the sample size and the number of parameters to be estimated. Stata version 16.1 was used for all analyses [40]. Table 1 describes the study participants at each of the three timepoints according to their pre-SCI, SCI-related, and 6-month post-SCI characteristics.
For the SCI-related characteristics, most participants (53%) had injuries of the least severe grade (AIS D), followed by 31% with the most severe grade (AIS A). Most SCIs were traumatic (77%); 50% of participants always used a wheelchair, while 12% only sometimes and 38% never used a wheelchair. Support from ACC was received by 79% of participants.

Life satisfaction at 18 months and 10 years post-SCI
Of the 103 participants at 18 months, 68 (67%) were satisfied with life and 34 (33%) were not satisfied. One participant did not respond to the life satisfaction question so was excluded from analyses. Of the 63 participants at 10 years, 49 (78%) were satisfied with life and 14 (22%) were not. Thirtysix participants (57%) were satisfied at both timepoints (18 months and 10 years post-SCI). Overall, a greater proportion of participants were satisfied at 10 years (78%) compared to 18 months (67%). However, the percentage of participants not satisfied with life 10 years post-SCI (22%) was still higher than pre-SCI (10%).

Univariable results at 18 months and 10 years post-SCI
Results from the univariable analyses assessing associations between potential predictors and life satisfaction outcomes at 18 months and 10 years are presented in Table 2.

Univariable associations with life satisfaction at 18 months post-SCI
There were no statistically significant differences (p > 0.05) for pre-SCI characteristics between those satisfied and not satisfied at 18 months post-SCI (Table 2).
Of the SCI-related characteristics, AIS grade and wheelchair usage were associated with life satisfaction (p < 0.05). The association with AIS grade indicates that greater proportion of those with a lesser SCI severity (AIS D) were satisfied with life at 18 months post-SCI compared to those with a greater SCI severity (AIS A). A greater proportion of people who never or only sometimes used a wheelchair were satisfied at 18 months post-SCI compared to those who always used a wheelchair.
Many 6-month post-SCI characteristics were associated with life satisfaction at 18 months post-SCI (p < 0.05). Higher proportions of participants were satisfied at 18 months if they had no problems with EQ-5D-3L selfcare, usual activities, or anxiety or depression, had a higher self-rating of EQ-5D-3L VAS health, were experiencing no or lesser disability, had fewer SHCs, and had greater satisfaction with social support, and sexual activity was not reduced.

Univariable associations with life satisfaction at 10 years post-SCI
Of the pre-SCI characteristics, at 10 years post-SCI significant associations with life satisfaction were found for ethnicity and prior chronic conditions ( Table 2). Greater proportions of those of European ethnicity were satisfied compared to Māori, Pacific or Asian participants (p = 0.046). Also, greater proportions of participants were satisfied at 10 years post-SCI if they experienced a pre-SCI chronic condition compared to those without a prior chronic condition (p = 0.049). However, the very small number of participants in some cells in Table 2 may have influenced the true significance of these 10-year findings.
For SCI-related characteristics, only ACC support was associated with life satisfaction at 10 years post-SCI. Greater proportions of people receiving ACC support were satisfied compared to those not receiving ACC support (p = 0.020).  No statistically significant associations were found between 6-month post-SCI characteristics and life satisfaction 10 years post-SCI.

Variables associated with satisfaction at 18 months and 10 years post-SCI as identified by multivariable modelling
Multivariable mini-models for assessing associations between four groups of variables and life satisfaction at 18 months and 10 years post-SCI are shown in Table 3. p value-based variable selection was not undertaken for the characteristics in Mini-Model 1 (age, sex, ethnicity, and pre-SCI life satisfaction) due to their importance and relevance to the outcome of interest.

Multivariable mini-model associations with life satisfaction at 18 months post-SCI
Māori participants were 1.31 times as likely to be satisfied at 18 months post-SCI than non-Māori. However, the 95% confidence interval (CI) indicates that this finding could be due to chance (95% CI: 0.99-1.73).   After considering other SCI-related variables, those who never or only sometimes used a wheelchair were 1.62 (95% CI: 1.20-2.18) times as likely to be satisfied at 18 months post-SCI than those who always used a wheelchair.
According to 6-month post-SCI characteristics, participants who reported any problems with EQ-5D-3L self-care were less likely (RR = 0.72; 95% CI: 0.56-0.92) to be satisfied at 18 months post-SCI than those with no problems. Similarly, participants who reported any problems with anxiety or depression were less likely (RR = 0.68; 95% CI: 0.50-0.93) to be satisfied at 18 months post-SCI than those with no problems.
Participants experiencing greater disability were less likely (RR = 0.74; 95% CI: 0.60-0.91) to be satisfied with life at 18 months post-SCI compared to those with no/lesser disability. Each additional SHC reported was associated with a 6% reduction in satisfaction with life at 18 months post-SCI (RR = 0.94; 95% CI: 0.90-0.98).

Multivariable mini-model associations with life satisfaction at 10 years post-SCI
Participants who were older at SCI onset (35-64 years) were more likely (RR = 1.32; 95% CI: 0.95-1.84) to be satisfied 10 years post-SCI than younger participants (16-34 years). However, chance could also be an explanation for this finding.
Considering SCI-related characteristics, the association with wheelchair usage suggests that there is an increased likelihood of satisfaction at 10 years post-SCI for participants who never or only sometimes used a wheelchair (RR = 1.30; 95% CI: 0.96-1.76) compared to those who always used a wheelchair.
None of the 6-month EQ-5D-3L characteristics were retained due to all variables producing p values above the threshold (p > 0.15).
Participants who reported experiencing considerable disability were less likely (RR = 0.78; 95% CI: 0.63-0.97) to be satisfied at 10 years post-SCI compared to participants experiencing no/lesser disability. Table 4 presents the final multivariable model for life satisfaction at 18 months post-SCI. Sex was considered but then dropped from the final model due to its high p value in the mini-models and to avoid the possibility of over-fitting the data due to the small sample size. A 10-year model was unable to be developed due to the small sample size.

Multivariable final-model associations with life satisfaction at 18 months post-SCI
While adjusting for age, ethnicity, pre-SCI life satisfaction, and other explanatory variables, only SCIrelated SHCs showed an association with 18-month life satisfaction. This indicated that participants experienced a 5% reduction in satisfaction at 18 months post-SCI with each additional SHC that they experienced (RR = 0.95; 95% CI: 0.90-0.99).
There is also a suggestion that participants with any problems with anxiety or depression at 6 months post-SCI were less likely to be satisfied at 18 months post-SCI than participants with no problems (RR = 0.75; 95% CI: 0.54-1.03); however, this finding could be due to chance.

Discussion
Life satisfaction improved with time since SCI; a higher percentage of participants were satisfied with life 10 years post-SCI (78%) compared to 18 months (67%). This aligns with a Canadian 45-year longitudinal study that reported the years spent non-satisfactorily was a relatively small proportion of time compared to the years spent satisfactorily [41]. At 18 months post-SCI, participants who never or sometimes used a wheelchair, had no problems with selfcare or anxiety or depression, experienced no or lesser disability, or had fewer SHCs were more likely to be satisfied with life. Strongest associations with life satisfaction at 18 months were found for anxiety or depression and SHCs. At 10 years post-SCI, only participants who experienced no or lesser disability were more likely to be satisfied with life. The univariable association between ACC support and life satisfaction at 10 years was not found in the minimultivariable model at 10 years. It seems likely our study was underpowered to detect a relationship. Previous research with this cohort identified differences in socioeconomic outcome according to provision of ACC support [42]. Further research investigating ACC support and longer-term life satisfaction seems warranted.
Wheelchair usage does not appear to have been explicitly analysed in relation to post-SCI life satisfaction previously. The association found here is worth considering in the future research, particularly as the disabling effects of having to use a wheelchair are likely to exacerbate the issues of isolation and exclusion [43].
While no previous published research appears to have specifically examined the relationship between self-care and life satisfaction post-SCI, studies have investigated the related concept of functional independence. Crosssectional and longitudinal studies from the Netherlands and the United States have found an increase in life satisfaction with increasing functional status and ability to do things independently [19,44,45]. These challenges with selfcare and functional independence were also identified in a NZ study after the transition from spinal unit to the 'real world' [46]. These participants felt like the rehabilitation centre did not appropriately prepare them for their return to the community post-SCI and hence struggled with their reintegration and ability to cope [46]. This aligns with our finding of the higher likelihood of being satisfied when experiencing no problems with self-care.
Findings, similar to ours, between anxiety or depression and life satisfaction were identified in a Swedish study where problems with anxiety or depression were associated with lower life satisfaction [47]. Similarly, three other cross-sectional studies from Canada, the Netherlands and the United Kingdom found having fewer problems with psychological functioning was associated with higher life satisfaction [13,48,49]. Future research using specific measures of mental health outcomes seems warranted.
Disability was found to be significantly associated with life satisfaction at both 18 months and 10 years post-SCI in the mini-model analyses. This indicates its long-term importance among this cohort, with other studies showing similar associations between disability and life satisfaction post-SCI [44,45]. These include a cross-sectional study of 190 people in the United States [44], and a five-year prospective cohort study from the Netherlands [45], which found that increased physical disability was associated with decreased life satisfaction.
Our study provides further evidence to support the association between the presence of SHCs and lower life satisfaction, as identified in studies from the Netherlands and Sweden [50][51][52]. Additionally, our study also found that the greater the number of SHCs experienced, the lower the level of life satisfaction [50][51][52]. Previous research with this cohort has explored SHCs post-SCI [26]; however, further in-depth research is needed to investigate SHCs in relation to life satisfaction-particularly as many SHCs are preventable.
Our study contributes important findings about life satisfaction outcomes 10 years post-SCI and the areas where interventions and support are needed to improve life satisfaction. This is particularly important as it is the first study to examine life satisfaction among those with a SCI in NZ. While the majority of participants expressed being satisfied with life post-SCI, it is still important to address and support those who are at risk of lower life satisfaction.
The large number of variables included in the study means that life satisfaction was able to be assessed against a wide range of aspects from all areas of life. The inclusion of a 10-year follow-up period is a strength of this research as there have been few studies on this topic longitudinally following up the same participants from the onset of SCI to 10 years post-SCI and beyond [17,20,41,[53][54][55]. The considerable work and input from people with lived experience of SCIs into the design and development of the study and interview questions to ensure they were applicable and relevant, as well as interviewers with lived experience of SCI, are further important strengths of this study.
This research may be prone to recall bias due to the pre-SCI characteristics being collected in an interview 6 months post-SCI. This could have caused participants to over-or under-estimate pre-SCI characteristics depending on their post-SCI status. However, the SCI is likely to have provided a clear 'anchor point' from which to recall prior characteristics, reducing recall bias, and previous research with injured New Zealanders suggests recall bias is likely to be minimal [56].
While this study was the largest undertaken in NZ and included 118 participants at baseline, the sample size was small, particularly at 10 years post-SCI. The number of participants at the 10-year timepoint was reduced due to participants changing contact details and being uncontactable, as opposed to declining participation (only one person declined). This made 10-year analyses difficult as only a limited number of variables could be included in the multivariable analyses. However, this analysis was adapted to suit the small sample size and the available resources. Future research including a larger sample size would be valuable to investigate these findings further. Further research is also needed on older adults and young people with SCIs.
Of the 118 participants recruited to the study, 15 (13%) were lost to follow-up at 18 months, and 63 participants (53%) were followed up 10 years post-SCI. A greater proportion of Māori were lost to follow-up at 18 months (p = 0.004) and 10 years (p = 0.014). Also at 10 years, a higher proportion of participants who always used a wheelchair were lost to follow-up (p = 0.042). Further research should be conducted to assess the relationships between life satisfaction and SCI for Māori, and life satisfaction and wheelchair usage.
Disability at 6 months post-SCI was associated with life satisfaction at both 18 months and 10 years post-SCI. Efforts from healthcare providers and rehabilitation centres should focus on work with individuals to minimise the experiences or impacts of disability. This could be done by organising appropriate mobility aids, home help, or vocational rehabilitation. Additionally, policy makers should implement regulations around accessible environments, improved public transport, and community participation, while further work should be done on reducing disability stigma and stereotypes to create a more accessible and supportive environment.

Conclusion
This research has found that most people were satisfied with their lives after a SCI, with a higher proportion of participants being satisfied 10 years on compared to 18 months post-SCI. However, more work is needed to ensure that those who were not satisfied with life are able to receive the support they need to improve their level of satisfaction.
This study has identified experiences of disability and SHCs 6 months post-SCI as key areas to improve to increase the proportion of people experiencing satisfaction with life, in both the short and longer terms.
Author contributions RD led the preparation of the manuscript and analyses supported by SD, AS, HH, and EW. SD, AS, HH, EW, CB, and MS all contributed to interpreting the results and to revisions of the manuscript and approved the final version. MS and SD designed the study that collected the data analysed in this paper, and CB was the interviewer leading the data collection.
Funding Open Access funding enabled and organized by CAUL and its Member Institutions. The New Zealand Longitudinal Study of the Life Histories of People with SCI was funded by the Health Research Council of New Zealand (HRC07/302). Funding from the Rob Porter Educational Fund in Spinal Research supported longer-term data collection. The views and conclusions expressed herein are the authors' and may not reflect those of the funders.
Data availability Data use is restricted due to the Study Participant Information Sheet and Consent Form, which explicitly state collected data will not be shared publicly. Qualified researchers, and postgraduate students, may request to collaborate with the research team by contacting the corresponding author.

Conflicts of interest
The authors declare that they have no conflict of interest. Sarah Derrett is a member of the EuroQol Group which developed the EQ-5D-3L measure used in this study.
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