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This JNNP meta-analysis, which included 15 studies with 812 047 participants, showed an elevated dementia risk in lifelong single (42%) and widowed (20%) but not divorced persons compared with those who were married.1 Although one study from Sweden contributed the vast majority (92%) of participants, the other studies were also broadly in agreement and, importantly, came from a wide range of countries across the world: Europe (France, Germany, Italy, Sweden), North and South America (Brazil, USA) and Asia (China, Japan, South Korea, Taiwan). Furthermore, the robustness of the association was shown by sensitivity analyses for demographic factors (sex, whether study subjects were born before or after 1927) and study methodology (type, quality). However, the association with dementia subtypes was not significant likely due to the much smaller number of participants in the studies that reported these outcomes. Moreover, there was evidence for an effect of education, worse physical health and case ascertainment method.
A recent report from the Lancet Commission on Dementia Prevention, Intervention and Care2 listed nine potentially modifiable risk factors for dementia, which had a relative risk of dementia ranging from 1.4 (physical inactivity) to 1.9 (hearing loss). Factors that may be relevant to being single or widowed, such as social isolation with a relative risk of 1.6 and depression with a relative risk of 1.9, were calculated to have a weighted population attributable fraction, an estimate of the proportion of cases of dementia that could be avoided if exposure to specific risk factors were eliminated, of 2.3% and 4%, respectively. Would being single or widowed remain important risk factors after interlinkages with these nine major risk factors are accounted for remains to be determined.
Should being single or widowed enter into the list of risk factors for dementia that are worth acting on, the challenge remains on how these observations can be translated into effective means of preventing dementia. This would require a better understanding of the possible mechanisms. If married people have a healthier lifestyle and more social engagement than lifelong single or widowed persons, then measure to improve such factors may be beneficial. If the stress of widowhood increases the risk of dementia, then means of reducing these effects may be effective. Perhaps future trials on multi-domain lifestyle interventions such as the recent Finnish Geriatric Intervention Study to Prevent Cognitive Impairment and Disability (FINGER) study3 might include single or widowed persons as high-risk subjects? Furthermore, as sexual activity has been found to associate with better cognitive function,4 the frequency of which may be reduced in single or widowed individuals, this could be another plausible mechanism.
This work on marriage and dementia also reminds us of how both are culturally and socially determined as well as intertwined. The institution of marriage is undergoing rapid changes with the acceptance of same-sex marriages and alternatives to marriage such as cohabitation. Moreover, the known effect of race and ethnicity5 as well as education and income6 on marriage rates is changing the proportion of the population getting married. It is also important to acknowledge that dementia and its prodrome has a huge impact on marriage, leading to transition and loss.7 Hence, although potentially modifiable risk factors for dementia exist, this does not mean that dementia is easily preventable. Therefore, ways of destigmatising dementia and producing dementia-friendly communities more accepting and embracing of the kinds of disruptions that dementia can produce should progress alongside biomedical and public health programmes.
Contributors Both authors contributed to and approved the final draft.
Competing interests None declared.
Provenance and peer review Commissioned; internally peer reviewed.
Correction notice Since this editorial commentary was first published online a subtitle has been removed for clarity.
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