Researchers have uncovered a potential association between marital loss and dementia, adding to the well of knowledge about the relationship between stressful life events and mental illness.

The study, published March 2 in Social Science and Medicine, used publicly longitudinal available data from the Health and Retirement Study, which is collected by the University of Michigan and funded by the National Institute on Aging and the Social Security Administration.

Zhenmei Zhang, the lead author of the paper and a professor of sociology at Michigan State University, told The Academic Times that she's always been interested in studying how marital dissolution affects health.

"Divorce and widowhood are two of the most stressful life events one can experience and numerous research has examined how they affect individuals' mental and physical health," she said. "Yet, very few have examined their relationships to dementia, a brain disease that has become a public health priority due to its impact on the quality of life, family caregiving and society."

Zhang added that most of the existing research has also focused on white people, "and we know little about how divorce and widowhood affect the risk of dementia for Blacks."

The Health and Retirement Study surveys a nationally representative sample of 21,384 non-institutionalized adults over 50 years old every two years. The researchers' final sample consisted of 14,788 respondents — 1,953 Black and 12,835 white. They followed these respondents over a 16-year period from 2000 to 2016.

The survey gathers detailed information on cognitive, physical, economic, work and family conditions in addition to health behaviors. Since the survey is robustly detailed, the researchers were able to adjust for, among other things, age, gender, education, household income and health-related factors. 

"Based on the data, we can know with reasonable confidence whether a respondent has dementia or not," Zhang said. "Then we excluded those who already had dementia in 2000 and followed those who were dementia-free for 16 years."

The researchers then used a statistical method to compare the odds of dementia among those who were divorced or widowed with those who were married.

The researchers found that widowhood is associated with a higher risk of dementia for both white and Black people, with the association stronger among Blacks. The odds of dementia were 19% and 58% higher among widowed white and Black people, respectively, when compared to their married counterparts. 

Divorce was also associated with a higher risk of dementia, more so for Black people and white men. The odds of dementia were 48% higher among divorced white men and 58% higher for both Black men and women compared to their married counterparts. 

The researchers were surprised to uncover that "whereas divorce significantly increased the risk of dementia for both Black men and Black women, It increased the risk for dementia for white men only, not for white women," Zhang said. 

The researchers also noted that economic disadvantage was a major factor that accounted for the higher risk of dementia among widowed and divorced people, according to the researchers. 

Among white people, household income accounted for about 52% of the association between widowhood and dementia risk, Zhang said; among white men specifically, household income accounted for about 13% of the association between divorce and dementia risk.

He added that among Black people, household income accounted for about 19% of the association between widowhood and dementia risk, and 25% of the association between divorce and dementia risk. 

Higher rates of smoking among divorced and widowed white people may also have played a role in the higher risk of dementia. Smoking accounted for 13% of the association between widowhood and dementia risk among all white people, while it accounted for 11% of the association between divorce and dementia risk among white men only. 

These findings suggest that "remaining divorced or widowed in midlife and beyond may be a risk factor for the onset of dementia for Blacks as well as whites," according to the researchers. 

They also noted that, based on these results, the effect of marital loss on dementia is saliently stronger for Blacks than they are for whites, and that it is stronger for white men than white women. 

While this research helps to fill the dearth of knowledge about the potential relationship between dementia and marital loss, there are some limitations in the data and design of this study.  

"One limitation is that we do not have a clinical diagnosis of dementia in the data, and so there may be some misclassification of dementia vs. no-dementia in our study," Zhang said. "This is a common limitation in population-based surveys."

The researchers also did not examine whether the duration of divorce and widowhood mattered for the risk of dementia, according to the researchers, and therefore the impact of duration of marital loss is still unknown.

Lastly, Zhang said the researchers could not rule out "the small possibility that the underlying pathological process before the onset of dementia may have contributed to marital stress and marital dissolution," suggesting that the relationship between marital loss and dementia could be a spurious one — a third variable may be impacting both, which would dissolve the relationship observed in this study. 

"Given the high rates of divorce and younger age at widowhood among Blacks, it is important to continue to explore factors that contribute to their relatively higher risk of dementia than their married counterparts, so that effective interventions can be implemented to reduce the risk," Zhang said. "As for policy recommendations, improving economic conditions among the divorced and the widowed may help lower their risk of dementia."

The study "Marital loss and risk of dementia: Do race and gender matter?," published March 2 in Social Science and Medicine, was co-authored by Zhenmei Zhang and Hui Liu, Michigan State University; and Seung-won Emily Choi, Texas Tech University.

Correction: A previous version of this article used the incorrect pronouns when referring to Zhenmei Zhang. The error has been corrected.