Combining data from 15 studies — which looked at more than 812,000 people from around the world — researchers in the U.K. compared people who were divorced, widowed or never married with people who were married.
Their results showed that, compared with married people, widowed people had a 20 percent higher risk of developing dementia, and those who never married had a 42 percent increased risk, after adjusting for age- and sex-related risk factors.
Being married likely reduces the risk of developing dementia in a number of ways, researchers said. Marriage may lead to a different level of social engagement and interpersonal interaction on a day-to-day basis, which may improve an individual’s “cognitive reserve.”
“Cognitive reserve is a person's resilience against the damage that is caused to their brain by dementia,” said lead study author Andrew Sommerlad, a geriatric psychiatrist and Wellcome Trust Research fellow. “This means that their brain has strategies that allow them to withstand the damage without showing symptoms of dementia.”
Past research has also demonstrated that being married tends to result in healthier decision-making — things like increasing exercise and healthier eating, while smoking less and drinking less alcohol — all of which are believed to reduce the risk of dementia.
As for the increased risk of dementia in widowed people compared with divorced people, the researchers hypothesize that this may be due to the fact that bereavement brings greater stress than divorce and that stress may take a harder toll on memory-forming and cognitive areas of the brain.
However, the authors said, preventing dementia is more complicated than simply walking down the aisle. This study shows a correlation between marriage and dementia risk, but understanding how specific factors related to marital status affect dementia risk remains largely unknown.
Further complicating the question, developing dementia could be associated with cognitive or personality traits that make a person less likely to get married. “It may be that their dementia risk plays a part in whether they find a partner many years earlier,” said Sommerlad.
More research is also needed to understand what the unwed and widowed can do to reduce their risk of dementia.
“In a society where isolation of older people is becoming more common, steps might need to be taken to connect older people back together — to reduce social isolation,” said Sommerlad.