The most incisive guide to issues facing the American family today . . . An invaluable resource for anyone wishing to stay on the cutting edge of research on family trends.

-W. Bradford Wilcox
Associate Professor of Sociology, University of Virginia 

Divorce and Dementia

Bryce J. Christensen and Nicole M. King

As the American population ages, physicians find themselves treating more and more patients suffering from the cruel mental disease of dementia, a disease often requiring the institutionalization of its victims. In a study recently completed at Umeå University in Sweden, researchers identify marital status as a statistical predictor of this dreaded mental condition. It thus appears that the American retreat from wedlock of recent decades will translate into an epidemic of dementia in the years ahead.

In initiating their inquiry into dementia, the Umeå researchers are aware that “owing to the global increase in life expectancy, the number of people suffering from age-related diseases such as dementia will rise substantially . . . [so] represent[ing] one of the most serious challenges of the 21st century.” The researchers note that some earlier research has linked “aspects of social relationships . . . with the incidence of dementia,” with a few studies suggesting that “marriage/cohabitation . . . [has] a beneficial effect on dementia risk.”

To assess the relationship between marital status and dementia, the Umeå scholars pore over data for 2,288,489 Swedes ages 50 to 74, none of whom had been diagnosed with dementia at the beginning of the period under analysis. Because aging itself increases vulnerability to dementia, the researchers separate the data into two sets, one for the “young-old” individuals (50–64 years), and a second for “middle-old” individuals (65–74 years). As expected, the incidence of dementia ran much higher among the older group than among the younger group. However, the relationship between marital status and dementia was largely the same in both sets of data: individuals in intact marriages face a significantly lower risk of dementia than do unmarried peers.   

In their simplest statistical model (which adjusts only for age and gender), the researchers discern a clear pattern in the data for young-old individuals: “each non-married subcategory was significantly associated with a higher risk of dementia relative to the married sample.” In the young-old data set, the researchers find the highest comparative risk of dementia among divorced individuals (Hazard Ratio of 2.05). But the comparative risk runs almost as high among singles (Hazard Ratio of 1.91). Compared to young-old married individuals, widowed men and women face an elevated risk of dementia, but the comparative risk appears notably lower than among the divorced and single (Hazard Ratio of 1.38).

The numbers come in a bit different when the researchers apply this same statistical model to the middle-old individuals in this study, but the overall pattern is the same: “each non-married subcategory showed a significantly higher risk of dementia compared with the married group.” As with the young-old group, in the middle-old group the comparative risk of dementia ran highest among the divorced (Hazard Ratio of 1.42) and slightly lower among singles (Hazard Ratio of 1.26). Though still significantly elevated above the risk of dementia faced by peers in intact marriages, the risk of dementia for widowed men and women again came in noticeably lower than that for divorced and single individuals (Hazard Ratio of 1.12). The data indicate that marital status affects the risk of dementia similarly for both men and women, though the results gleaned from the simplest statistical model did reveal that, compared to married peers, divorced men face a higher relative risk of the disease than do divorced women (Hazard Ratios of 2.1 vs. 1.7).    

The findings returned from using the simplest statistical model are little changed when researchers re-analyze their data in a more sophisticated model that accounts not only for age and gender but also for education, taxable income, parenthood status, and history of cardiovascular disease. To be sure, the Hazard Ratios calculated for the unmarried subgroups do drop a bit in this more sophisticated model. But all of these ratios remain statistically unfavorable for all of the unmarried groups, in both the young-old and middle-old data sets. The only truly notable difference between the results produced by the simper statistical model and those returned by the more sophisticated model is that the disparity between the Hazard Ratio for divorced men and divorced women in the young-old group falls to statistical insignificance.  

With good reason the researchers remark, “Our results suggest that those living alone as non-marrieds may be at risk for early-onset and late-onset dementia.” The Umeå scholars thus interpret their findings as a confirmation of  “previous study results showing a beneficial effect of marriage on dementia,” a confirmation suggesting that  the relationship between marital status and risk of dementia is “highly robust.”

The researchers admit that “the specific mechanisms by which marital status influences the risk of dementia remain to be understood,” and they call for additional research to illuminate those mechanisms. But they do offer a few plausible conjectures. “A close relationship may be one of the best sources of cognitive stimulation,” they suggest, reasoning that such stimulation may give married individuals more “cognitive reserve” than their unmarried peers. “A higher cognitive reserve,” they explain, “[may] provide the individual with resilience against neuropathological damage to the brain, such as occurs in dementia.” 

The authors of the study further speculate that the married enjoy some protection from dementia because “marriage may serve as a buffer against the negative consequences of adverse life events,” while those who lose a spouse through divorce or death lose that buffer  as the consequence of “a severely stressful event.” 

Reflecting on the policy implications of their findings, the researchers see a need for “social-based interventions [that] may provide an opportunity to reduce the overall dementia risk.” Readers may puzzle over just what “social-based interventions” might look like. Indeed, unless it means that policymakers need to do more to promote marriage and prevent divorce, the phrase may indicate very little and protect very few.

(Anna Sundström, Olle Westerlund, and Elena Kotyrlo, “Marital Status and Risk of Dementia: A Nationwide Population-Based Prospective Study from Sweden,” BMJ Open 6.1 [2016]: e008565. Web.)