Psychosocial determinants of functional independence among older adults: A systematic review and meta-analysis

Background: In current years, the increase in older population has led to creating one of the main public health challenges, worldwide. Because of the special characteristics of older adults, this age group is exposed to possible problems, such as mental and physical disorders, that usually affect their functional independence. The study aimed to determine the psychosocial determinants (e.g., depression, social support, and self-efficacy) affecting functional independence among older population. Methods: Our search was conducted on three international databases (Web of Sciences, PubMed/Medline, and Scopus) for all the observational studies (cross-sectional, cohort or longitudinal designs) on the social and psychological determinants of functional independence among older adults. Papers published in English without limitation of time were reviewed from inception to 26 August 2023. The quality assessment tool was the Newcastle-Ottawa Scale (NOS). The I2 index was used to quantify the degree of heterogeneity among the studies. In the case of heterogeneity higher than 50%, the random effects model has been used for overall estimation of the effects; otherwise, the fixed effects model was used. The pooled associations were expressed as odds ratio (OR) and 95% confidence intervals (CIs). Stata version 14 software (StataCorp LP) was used for data analysis. The significance level was considered at 0.05. Results: In the initial search, 6978 articles were retrieved, and finally, considering the inclusion criteria, 46 articles were examined. Finally, 18 articles were eligible for meta-analysis. The findings indicated that among all the determinants affecting functional independence among older adults, depression could lead to a 76% increase in functional dependence. Conclusion: The findings provide a statistically significant relationship between psychosocial factors and functional independence. Depression was the strongest determinant of functional dependence among older adults.


Introduction
The maintenance of the older adult's independence in physical and mental activities is an important determinant that improves their quality of life.Therefore, a useful way of assessing health in older people is through functional assessment. 1 Functional independence, on the other hand, is a crucial factor in determining an older person's quality of life. 2 Functional independence has become an important public health issue because of its impact on the quality of life of individuals, families, and health services. 3unctional independence has been used to characterize a person's capacity to carry out activities of daily living (ADLs). 4ADLs and instrumental activities of daily living (IADLs) are used to assess functional independence. 5he ADLs include eating, dressing, undressing, bathing, toileting, going to bed, waking up, and grooming.More reliable indicators of functional independence include IADLs, such as preparing food, shopping, using a telephone, housekeeping, and doing laundry, signifying functional ability among older adults, and dependence on performing each of the mentioned activities indicates a functional impairment. 6,7he evidence demonstrates that the loss of independence is an important concern to older adults.Incapacitated older adults have a lower quality of life and are more prone to depression and death. 8,9The ability to perform daily activities is known to maintain independence and is an effective determinant in the success and older adults' health. 1,102][13] In addition, the prevalence of dependence in IADLs among older adults in Taiwan 14 and Spain 13 was 26.2% and 53.5%, respectively.Psychosocial determinants of ageing can have an impact on a person's well-being, quality of life and health.The quality of life of older adults goes beyond physical health that focuses on capacity or active social participation, it can affect the performance of independent ADLs among older adults. 15In addition, loss of functional independence and increased incidence of chronic disease are associated with psychosocial factors such as depression, social isolation, anxiety, stress, and weak relationships. 16According to the results of the previous studies, depression leads to a decline in performance [17][18][19] ; nonetheless, some other studies suggest that decreased performance leads to depression.On the other side, independence among older adults is related to their mental state. 1,2,20s ageing results in dramatic changes in all dimensions of the lives of older adults, a thorough understanding of these changes and their associated determinants not only improves their physical, mental and social conditions, but also plays an important role in healthy and active ageing. 21,22Considering that the studies on functional independence among older adults have been carried out in a specific geographical area and on a limited population in Iran and other countries, it seems necessary to conduct a systematic search and prepare a more accurate report using systematic data.This systematic review would yield more accurate results, which can significantly help experts improve functional independence and, consequently, the quality of life among older adults.Therefore, the study aimed to determine the social and psychological determinants (e.g., social support, self-efficacy, depression) affecting the functional independence (e.g., ADL, IADL) of older adults through a systematic review and meta-analysis based on observational studies.

Materials and Methods
This systematic review and meta-analysis adhered to PRISMA standards. 23

Data sources and search strategy
The study was conducted on three international databases (Web of Sciences, PubMed/Medline, and Scopus) for all the observational articles on the social and psychological determinants of functional independence among older people in English without limitation of time that were reviewed from inception to 26 August 2023.The search strategy was developed using Medical Subject Headings (MeSH) with the related keywords.For example, the search method used in the PubMed/Medline database was shown in Supplementary file 1.

Inclusion and exclusion criteria
The Inclusion and exclusion criteria were set based on PEO framework (Population, Exposure, and Outcome).All observational studies (cross-sectional, cohort or longitudinal designs) assessed the psychosocial determinants of functional independence among older adults.The study subjects were healthy older adults ( ≥ 60 years) without functional limitations.The exclusion criteria included the studies conducted on unhealthy people to assess the psychosocial determinants affecting functional independence, the studies that regarded functional independence as an independent variable, review articles, clinical trial studies (RCT), systematic studies, letters, interventional qualitative, and interpretive studies, case reports, meta-analyses, and studies with a final outcome other than functional independence.

Data extraction
The articles (titles, abstracts, and full texts) were independently searched and retrieved by two researchers.EndNote X7 (Thomson Reuters) software was used to enter the articles identified in the initial search.After eliminating duplicates, two researchers independently assessed the titles and abstracts of the obtained studies.Studies were identified based on the inclusion criteria.In case of disagreement between the researchers about the inclusion of the study, a final consensus was reached through discussion and a third person's opinion.Then, the full text of all the studies that met the inclusion criteria was retrieved (Figure 1).The following information was extracted from the included studies: author names, year of publication, age, sex, study type and design, sample size, country of study, functional independence assessment tool, psychosocial determinants, study results, descriptive statistics (ratio/ratio, number/ratio, mean/standard deviation) and analytical statistics (a 95% confidence interval [CI], risk ratio [RR], odds ratio [OR], standard error [SE]).Then, the data of the selected articles were independently entered into the table by two researchers.

Quality assessment tools
The quality evaluation tool was the Newcastle-Ottawa Scale (NOS). 24Two authors used this tool independently.In case of disagreement between the researchers, a final consensus was reached through discussion and a third person's opinion.The NOS assesses the potential of bias in observational studies using three criteria: 1) study group selection (four questions), 2) group comparability (two items), and 3) exposure/outcome assessment (three items).The NOS assigns a star rating to each study, with a maximum of nine stars.An article is considered to be of high quality if it receives seven stars or more, while six stars or less indicates that the article is of low quality.

Statistical analysis
The effect size indicators, such as the odds ratio, a 95% CI, and estimate standard error, were extracted from the studies that reported the adjusted effect size in terms of confounders.The I 2 index was used to quantify the degree of heterogeneity between articles.In case of heterogeneity was greater than 50%, the random effects model was used for the overall effect estimate, otherwise the fixed effects model was used.
A forest plot diagram was used to report the results.
The funnel plot, Egger's test, and Begg's test were applied to determine publication bias.Subgroup analyses (study design, sample size, continent, and NOS-rating scale) of the included studies in meta-analysis were conducted.Stata version 14 software (StataCorp LP) was used for data analysis.The significance level was considered at 0.05.

Search results
In total, 6975 articles were retrieved from three databases (Web of Sciences (n = 2075), PubMed (n = 568) and Scopus (4332)).Three articles were identified by the manual check by controlling references list of the included studies.A number of 991 articles were removed due to duplication.Then, the titles of the remaining 6017 articles were checked, out of which 744 articles remained for abstract review, and 627 irrelevant articles were removed.The full text of the remaining 126 studies was reviewed.After removing 80 articles, 46 articles were finally reviewed in this study.Finally, 18 studies were eligible for inclusion in the meta-analysis (Figure 1).
A significant relationship between these social determinants and functional independence was found in the studies.Social determinants were more frequently investigated in America and China than in other countries. 2,3,25,26,29,35,37,38,51,53,54,57,60,65,66upplementary file 2 provides details of the studies included in this systematic review.

Meta-analysis results
][60][61][62][63][64]67 The results pointed out that depression can increase the risk  of functional dependence by 76% (I 2 index: 93% with a significance level of less than 0.001).There was no publication bias in cohort studies; however, some degrees of publication bias were observed in cross-sectional studies (Figure 3).The results of subgroup analyses of are shown in Table 1.Subgroup analyses based on study design, sample size, continent, and NOS-rating scale are presented in Figures 4, 5, 6 and 7 respectively.

Discussion
This study aimed to determine the psychosocial predictors (e.g., social support, self-efficacy, and, depression) affecting the functional independence (e.g., ADL, IADL) of older adults.In this review, 46 studies were reviewed.
Totally, the results were categorized in two sections of psychological and social determinants.Psychological determinants were depression, emotional status, mental health, affect, self-efficacy, cognitive status, anxiety, and psychological distress.Social determinants included social support, social participation, self-care, social isolation, and social capital.Among psychological determinants, depression was the most frequently investigated determinant.Evidence indicates that depression is one of the psychological conditions related to functional independence among older adult.As the psychological status of older adults is closely related to functional independence. 74Therefore, Figure 3. Funnel plot for assessing the risk of publication bias of studies included in the meta-analyses: Relationship between depression and functional independence among older adults depression is one of the most important predictors of functional independence in older adult population. 56ccording to the previous study, the most important feature of depression is mood swings, which can lead to disability in performing ADLs among older adults. 20Furthermore, Boga and Saltan reported that the levels of dependence on activities in daily living were related to mental status and depression among older adults.In addition to the financial cost, depression in older adults has negative consequences. 17,40Also, depression reduces the quality of life in older adults, and lower quality of life is associated with more severe ADL and IADL problems. 75Therefore, depression, as one of the psychological determinants affecting functional independence, should be prioritized in preventive activities. 1 This is because depression in older people can be reduced by performing ADLs. 20According to Storeng et al, the most significant risk variables for needing assistance with one or more basic/instrumental daily living activities were life satisfaction, depression, and health perception.These elements can be among the potential targets for preventative measures. 61The fact that America places more emphasis on the issue of depression than other countries may be because it recognizes the problem of depression in older adults as a serious public health issue due to the rapidly growing older population in the country and the resulting increase in demand for mental health services. 76According to studies, older adults' ability to perform daily living activities is a good indicator of their likelihood of experiencing depression.As a result, by carefully assessing their health and functional ability, older adults' depression and physical inability to perform daily living activities can be avoided. 1,56On the other hand, it seems that there is a major difference between countries, both developed and developing in the readiness of their government and people to face the challenge caused by the increasing number of older adults and developed countries are more prepared in this regard.Nonetheless, most developing countries lack the sufficient and necessary knowledge about this issue, additionally, its consequent health, economic and societal issues. 77,78he findings of our research showed that other effective psychological determinants of functional independence were emotional status, mental health, affect, self-efficacy, and psychological distress, which play an effective role in functional independence.These determinants are strong predictors for functional independence.Intervention strategies based on these determinants have been shown to successfully improve functional independence among older adults.It's crucial to consider certain elements in older people at risk for declining functional independence.Therefore, it is proposed to include them in programs aimed at preventing the decreased of functional independence among older adults.Another effective determinant in this regard was self-efficacy, which alludes to a person's belief in his/ her capacity to perform desired activities. 79In general, the studies indicated that self-efficacy is significantly correlated with -
The goal of the current meta-analysis study was to examine the connection between older persons' functional independence and depression.The outcomes showed that depression can lead to a 76% increase in functional dependence.The most prevalent and significant factor detrimentally affecting psychosocial functioning in older persons might be considered to be depression, a condition characterized by feelings of sadness and hopelessness.Depression in older persons is linked to lower functional levels, a worsening of health, and a lower quality of life. 88,89he relationship between daily activity and psychological determinants, including depression, has been highlighted in multiple studies.1][92] Therefore, decision-makers in the field of health can benefit from having a complete grasp of older persons' psychosocial state and how it affects their functional independence in order to plan and implement effective interventions to maintain and raise the level of daily activities in older individuals.

Strengths and weaknesses
This study is the first systematic review to particularly look at the psychosocial determinants of functional independence among older persons is the current study's most significant strength.Most of the reviewed studies had assessed the impact of a limited how many psychological or social determinants on functional independence; nonetheless, the present research provided strong evidence of the most important psychosocial determinants of functional independence among older people in a relatively comprehensive systematic evaluation.Therefore, the results of this study can be useful for researchers in implementing intervention programs to promote independence in older people.Among the notable limitations of this study, we can refer to the mere inclusion of articles published in the English language.Second, our study is not exempt from risk of bias.One of the reasons may be non-English studies being excluded from our studies.Also, most of the included studies had cross-sectional design.This can have an effect on the study results.The third limitation was the lack of access to the full text of some articles.Forth, there could be some selection bias in the results that overlooks unpublished studies, gray texts, studies found in other databases, and perhaps even non-English papers.

Conclusion
The results of this study found a statistically significant relationship between psychosocial determinants and functional independence among older adults.Since functional independence among older adults is a multi-dimensional concept that is affected by various determinants, the identification of these determinants can help design and implement interventions related to the prevention, control, and management of determinants that lead to dependence in older adults.Additionally, depression has a considerable effect and is a reliable indicator of the decline in functional independence in older persons when compared to other psychosocial variables.Consequently, depression and physical disability to perform ADLs in older adults can be prevented by a careful examination of their health and functional capacity for medical teams and their household members.So, depression and functional independence to perform daily living activities among older adults can be prevented by a careful examination of their functional capability by health providers and their family.

Figure 1 .
Figure 1.PRISMA flow diagram of the selection process for systematic reviews and meta-analysis

Figure 2 .
Figure 2. Forest plot for meta-analysis of association between depression and Functional independence

Figure 4 .Figure 5 . 37 Ocs
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Table 1 .
Subgroup analyses of included studies in meta analyses * I I--s sq qu ua ar re ed d: : t th he e v va ar ri ia at ti io on n i in n E ES S a at tt tr ri ib bu ut ta ab bl le e t to o h he et te er ro og ge en ne ei it ty y) ) H He et te er ro og ge en ne ei it ty y d de eg gr re ee es s o of f T Te es st t( (s s) ) o of f h he et te er ro og ge en ne ei it ty y: :