A growing body of research links divorce to a wide range of poor health outcomes, including greater risk for early death. However, the reason for the connection is not well understood.

A new study by the University of Arizona points to two possible culprits: a greater likelihood of smoking after divorce and lower levels of physical activity.

"We were trying to fill in the gap of evidence linking marital status and early mortality," said UA psychology doctoral student Kyle Bourassa, lead author of the study, which is published in Annals of Behavioral Medicine. "We know marital status is associated with both psychological and physical health, and one route from divorce to health risk is through health behaviors, like smoking and exercise. We also know that health behaviors are often linked to psychological variables, like life satisfaction."

Bourassa and his UA colleagues David Sbarra and John Ruiz based their findings on data from the English Longitudinal Study of Aging, a long-term health study of adults over age 50 living in Great Britain. The study includes seven waves of data, collected from participants every two years beginning in 2002.

The researchers analyzed data from 5,786 study participants, 926 of whom were divorced or separated and had not remarried, and the rest of whom were married. They looked at participants' self-reported life satisfaction, exercise frequency and smoking status, as well as measurements of participants' lung function and levels of inflammation.

They also kept track of who passed away during the study period, finding that participants who were divorced or separated had a 46 percent greater risk of dying during the study than their still-married counterparts.

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As to why that might be, Bourassa and his co-authors found that divorced or separated participants, especially women, reported lower life satisfaction than married participants. Lower life satisfaction, in turn, predicted lower levels of physical activity, which is linked to greater risk for early death.

Divorced participants also were more likely than married participants to smoke and, as a result, had poorer lung function, which predicted early mortality.

The researchers controlled for variables like gender, self-reported health, age and socioeconomic status.

While the study didn't explicitly examine why divorce seems to be associated with greater likelihood of smoking and lower levels of exercise, one possible explanation, supported by existing research, is that divorced individuals no longer have spouses holding them accountable for their health behaviors, Bourassa said.

"Partner control of health might play a role," he said. "If you imagine a husband or wife who doesn't smoke and their partner does, one might try to influence the other's behavior. In many ways, when relationships end, we lose that important social control of our health behaviors."

Future research should consider the roles of other health behaviors, like diet and alcohol consumption, as well as other marital statuses, such as widowed or remarried adults, Bourassa said. In addition, studies might look at the effects of changes in behavior -- for example, quitting smoking or starting smoking for the first time -- which is something the current study did not consider, he said. More work also is needed to know if the findings regarding smoking and exercise for aging adults after divorce are generalizable to younger divorced populations, too.

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It's important to note that divorce doesn't always lead to negative health outcomes. Quality of life, for example, can significantly improve for individuals who have ended unhealthy relationships.

Still, since divorce overall continues to be linked to poorer health, knowing that smoking and exercise may be part of the explanation could help inform interventions for those who've gone through a separation, Bourassa said.

"This is a subgroup of people that are at greater risk for these poorer health behaviors, so the goal might be to target them for interventions to hopefully improve their long-term health," he said.

"We have interventions for people who smoke, and we have interventions for people who don't get enough exercise, so if we know someone who is divorced, maybe we should ask, 'Are you smoking? Are you getting enough physical activity?'" he said. "Finding that life satisfaction seems to link divorce to physical activity levels also suggests that interventions to improve people's life satisfaction and psychological wellbeing could translate downstream to physical health improvements."