Abstract
BackgroundA previous meta-analysis (Kuiper et al., 2016) has shown that multiple aspects of social relationships are associated with cognitive decline in older adults. Yet, results indicated possible bias in estimations of statistical effects due to the heterogeneity of study design and measurements. We have updated this meta-analysis adding all relevant publications from 2012 to 2020 and performed a cumulative meta-analysis to map the evolution of this growing field of research (+80% of studies from 2012-2020 compared to the period considered in the previous meta-analysis).MethodsScopus and Web of Science were searched for longitudinal cohort studies examining structural, functional and combined effects of social relationships. We combined Odds Ratios (OR) with 95% confidence intervals (CI) using random effects meta-analysis and assessed sources of heterogeneity and the likelihood of publication bias. The risk of bias was evaluated with the Quality of Prognosis Studies in Systematic Reviews (QUIPS) tool.ResultsThe review was prospectively registered on PROSPERO (ID: CRD42019130667). We identified 34 new articles published in 2012-2020. Poor social relationships were associated with cognitive decline with increasing precision of estimates compared to previously reviewed studies [(for structural, 17 articles, OR: 1.11; 95% CI: 1.08; 1.14) (for functional, 16 articles, OR: 1.12; 95% CI: 1.05; 1.20) (for combined, 5 articles, OR: 1.15; 95% CI: 1.06; 1.24)]. Meta-regression, risk and subgroup analyses showed that the precision of estimations improved in recent studies mostly due to increased sample sizes.ConclusionsOur cumulative meta-analysis would confirm that multiple aspects of social relationships are associated with cognitive decline. Yet, there is still evidence of publication bias and relevant information on study design is often missing, which could lead to an over-estimation of their statistical effects.
Highlights
A previous meta-analysis (Kuiper et al, 2016) has shown that multiple aspects of social relationships are associated with cognitive decline in older adults
Following criteria used in the previous systematic review [32], articles were included if they: (i) were peer reviewed; (ii) reported an association between social relationships measured at baseline and the follow-up in a quantitative way; (iii) included a longitudinal prospective cohort study design conducted on the general population
By means of a cumulative meta-analysis, we found that the precision and accuracy of estimations increased with a progressive reduction of 95% confidence intervals for all aspects of social relationships
Summary
A previous meta-analysis (Kuiper et al, 2016) has shown that multiple aspects of social relationships are associated with cognitive decline in older adults. Results indicated possible bias in estimations of statistical effects due to the heterogeneity of study design and measurements We have updated this meta-analysis adding all relevant publications from 2012 to 2020 and performed a cumulative meta-analysis to map the evolution of this growing field of research (+80% of studies from 2012-2020 compared to the period considered in the previous meta-analysis). The total number of people with dementia and severe cognitive impairment is projected to reach 78 million in 2030 and 139 million in 2050 (see: https://www.who.int/ news-room/fact-sheets/detail/dementia). The WHO estimates that the total global societal cost of dementia was US $ 1.3 trillion in 2019 but these costs are expected to surpass US$ 2.8 trillion by 2030, with half of them attributed to informal care (see: https://www.who.int/news-room/factsheets/detail/dementia). Understanding prevention and protection mechanisms that can minimise the risk of dementia and postpone its onset in an ageing population is key to reduce pressure on health care systems and welfare institutions, as well as to improve the quality of life of both families and caregivers
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