Marital status and risk of dementia over 18 years: Surprising findings from the National Alzheimer's Coordinating Center

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Marital status and risk of dementia over 18 years: Surprising findings from the National Alzheimer's Coordinating Center

Selin Karakose, Martina Luchetti, Yannick Stephan, Angelina R. Sutin, Antonio Terracciano

First published: 20 March 2025

https://doi.org/10.1002/alz.70072

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Abstract

INTRODUCTION

Marital status is a potential risk/protective factor for adverse health outcomes. This study tested whether marital status was associated with dementia risk in older adults.

METHODS

Participants (N = 24,107; Mean_age = 71.79) were from the National Alzheimer's Coordinating Center. Cox regressions tested the association between baseline marital status and clinically ascertained dementia over up to 18 years of follow-up.

RESULTS

Compared to married participants, widowed (hazard ratio [HR] = 0.73, 95% confidence interval [95% CI] = 0.67–0.79), divorced (HR = 0.66, 95% CI = 0.59–0.73), and never-married participants (HR = 0.60, 95% CI = 0.52–0.71) were at lower dementia risk, including for Alzheimer's disease and Lewy body dementia. The associations for divorced and never married remained significant accounting for demographic, behavioral, clinical, genetic, referral source, participation, and diagnostic factors. The associations were slightly stronger among professional referrals, males, and relatively younger participants.

DISCUSSION

Unmarried individuals may have a lower risk of dementia compared to married adults. The findings could indicate delayed diagnoses among unmarried individuals or challenge the assumption that marriage protects against dementia.

Highlights

• Widowed, divorced, and never-married older adults had a lower dementia risk, compared to their married counterparts.
• Unmarried older adults were also at a lower risk of Alzheimer's disease and Lewy body dementia, with a pattern of mixed findings for frontotemporal lobar degeneration, and no associations with risk of vascular dementia or mild cognitive impairment.
• All unmarried groups were at a lower risk of progression from mild cognitive impairment to dementia.
• There was some evidence of moderation by age, sex, and referral source. However, stratified analyses showed small differences between groups, and most interactions were not significant, suggesting that the role of marital status in dementia tends to be similar across individuals at different levels of dementia risk due to education, depression, and genetic vulnerability.

1 BACKGROUND

Being married has been related to better health and longevity.^{1, 2} These associations are often explained through the marital resource model, which suggests that marriage provides social, psychological, and economic benefits unavailable through other relationships that, in turn, support healthier and longer lives.^{3, 4} This association may extend to risk for cognitive impairment and dementia, yet there is significant heterogeneity in cognitive health across marital status.^5-10

There is some evidence of a higher risk of Alzheimer's disease (AD) and related dementias among never-married individuals, compared to married ones.^{5, 11} Null results have also been reported.¹⁰ The evidence is also mixed for divorce and widowhood: While two studies reported that both divorced and widowed individuals have a higher dementia risk compared to their married counterparts,^{5, 6} a meta-analysis found that widowed individuals, not divorced ones, had a significantly higher risk of dementia compared to married individuals.⁸ Divorce, in some cases, can lead to increased happiness¹² and life satisfaction,¹³ which may potentially protect against dementia risk.^{14, 15} Indeed, a recent study reported that divorce was associated with a slower rate of cognitive decline.¹⁶ Mixed results have also occurred for specific causes of dementia: One study found that divorced and widowed categories were associated with a greater risk of AD,¹⁷ but other studies have found no associations with AD or vascular dementia (VD).^{8, 11} The association between marital status and Lewy body dementia (LBD) and frontotemporal lobar degeneration (FTLD) is untested. The evolving role of marriage in society and the rising number of unmarried (divorced, widowed, or never-married) individuals,¹⁸ make it critical to examine whether unmarried older adults are vulnerable to developing dementia. Such research may help identify subgroups of individuals at higher risk who may need closer monitoring and support.

Unmarried males are at a higher risk for poor health outcomes than unmarried females.^{19, 20} However, sex differences in the association between marital status and incident dementia is contradictory: One study has reported that both divorce and widowhood increased the risk of dementia more among males compared to females,⁵ and others have reported an association with either widowhood²¹ or divorce,^{6, 22} or found no such effect.²³ Compared to sex, less is known about whether depression and genetic vulnerability moderate the association between marital status and dementia. The risk of dementia among unmarried adults could be pronounced in individuals with higher depressive symptoms or a genetic predisposition to dementia.

Married individuals are more likely to engage in preventive medical care than unmarried individuals,²⁴ potentially due to partners who notice early symptoms. Individuals in the early stages of dementia may not be aware of their symptoms and may miss/delay the diagnosis,²⁵ especially among unmarried individuals who may lack feedback from a close partner. Indeed, a meta-analysis suggests that registry-based studies (e.g., hospital and death records) underestimate dementia risk among widowed and never-married individuals.⁸ Based on the importance of referral source and seeking medical help (i.e., referred by a professional and clinical evaluation) on cognitive outcomes,^{26, 27} it is critical to evaluate whether the association between marital status and risk of dementia differs depending on the referral sources (i.e., self/relative/friend vs. referred by professionals) and the reason for visiting the center (i.e., clinical evaluation vs. research participation).

This study extended prior work in fundamental ways: First, the study used data from the National Alzheimer's Coordinating Center (NACC), one of the largest cohorts with annual clinical evaluation of dementia over one of the longest follow-ups (up to 18 years). The comprehensive clinical assessment and long follow-up increase power and reduce the risk of reverse causality (e.g., individuals in the preclinical or prodromal stage of dementia are more likely to get divorced).²³ Second, the study investigates whether the association differs across cause-specific dementia (AD, LBD, VD, FTLD), and whether it extends to mild cognitive impairment (MCI). Third, the study investigates whether the associations were moderated by sex, age, race, education, depression, diagnostic form, participant's referral source, primary reason for visiting the Alzheimer's Disease Research Centers (ADRCs), and genetic vulnerability to identify contexts or subgroups with higher vulnerability.

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