Long-term depression may double stroke risk for middle-aged adults

Adults over 50 who have persistent symptoms of depression may have twice the risk of stroke as those who do not, according to a new study led by researchers at Harvard T.H. Chan School of Public Health. Researchers found that stroke risk remains higher even after symptoms of depression go away, particularly for women.

The study will be published online May 13, 2015 in the Journal of the American Heart Association.

"This is the first study evaluating how changes in depressive symptoms predict changes in stroke risk," said lead author Paola Gilsanz, Yerby Postdoctoral Research Fellow at Harvard Chan School. "If replicated, these findings suggest that clinicians should seek to identify and treat depressive symptoms as close to onset as possible, before harmful effects on stroke risk start to accumulate."

The study looked at health information from 16,178 men and women ages 50 and older participating in the Health and Retirement Study between 1998 and 2010. Participants were interviewed every two years about a variety of health measures, including depressive symptoms, history of stroke, and stroke risk factors. There were 1,192 strokes among participants during the study period.

Compared to people with low depressive symptoms at two consecutive interviews, those with high depressive symptoms at two consecutive interviews were more than twice as likely to have a first stroke. Stroke risk remained elevated even among participants whose depressive symptoms went away between interviews, particularly for women. Those with depressive symptoms that began between interviews did not show signs of elevated stroke risk. Participants younger than 65 had greater stroke risk linked to their depressive symptoms than older participants with depressive symptoms.

The researchers suggest that depression may influence stroke risk through physiological changes involving accumulation of vascular damage over the long term. Damage may also be incurred indirectly through depression's effect on health behaviors, including increased risk of smoking and physical inactivity.

"Because this is the first study to take this approach, we need replication of findings in independent samples, with people of different age groups, and exploring different reasons that depressive symptoms get better," said senior author Maria Glymour, associate professor in the Department of Epidemiology and Biostatistics at the University of California, San Francisco, who worked on the research while at Harvard Chan School. "The surprising results make such replications even more urgent."