Professor’s Study Named AJE Article of the Year.

A School of Public Health study has been named an American Journal of Epidemiology 2019 Article of the Year.

The study, led by Jaimie Gradus, associate professor of epidemiology, found that a stress disorder diagnosis could as much as triple the risk of dementia, particularly among men.

“People are currently experiencing stress and trauma on a scale we have never before seen, and it will be critical to know as much as we can about possible outcomes in the years and decades to come,” Gradus says.

Having the study highlighted by the American Journal of Epidemiology is an honor, she says. “Personally, to have a paper accepted at AJE has always felt like a stamp of approval from the most scientifically rigorous of my peers,” she says. “To get this additional recognition means a lot to me.”

Previous research has shown an association between post-traumatic stress disorder (PTSD) and dementia, but few previous studies have examined associations between dementia and other stress disorders, or looked at these associations by sex.

The study led by Gradus found that people experiencing less severe stress-related mental health symptoms have similarly elevated rates of dementia.

“This suggests that people with some stress-related mental health symptoms should also be the focus of intervention and prevention efforts, even if they do not meet diagnostic criteria for a stress disorder,” she says.

Like much of Gradus’s research, the study draws from Denmark’s extensive, nationwide registries of social and medical information, and is part of her long-running collaboration with researchers at the Department of Clinical Epidemiology at Aarhus University Hospital in Denmark. Henrik T. Sørensen, chair of the Department of Clinical Epidemiology at Aarhus University Hospital in Denmark and adjunct professor of epidemiology at SPH, served as senior author on the study.

The study looks at a cohort of 47,047 Danish residents over 40 years old who received stress disorder diagnoses between 1995 and 2011 and did not have dementia in 1995. They categorized diagnoses as PTSD, acute stress reaction (similar to PTSD but lasting no more than about a month), adjustment disorder (difficulty coping with or adjusting to a source of stress), other stress reactions, and unspecified stress reactions.

The researchers also created a comparison cohort: for each member of the first cohort, this second cohort included five Danish residents of the same age and sex, but without a stress disorder diagnosis for the period and without dementia in 1995. They then compared the two cohorts as members were diagnosed with dementia, emigrated or died, or until the end of 2011.

They found that people with acute stress reaction had 1.6 times the rate of dementia than comparison cohort members, those with PTSD had 2.0 times the rate of dementia, those with adjustment disorder had 2.4 times the rate of dementia, those with other stress reactions had 2.8 times the rate of dementia, and those with unspecified stress disorders had 2.2 times the rate of dementia.

Men with stress disorder diagnoses were more likely to develop dementia than women with the same diagnoses, with the exception of PTSD. Among those diagnosed with PTSD, women were more likely to develop dementia than men.

The researchers also analyzed the data to see if the results could be explained by an event or illness/injury causing both a stress disorder and dementia. However, they found that the amount of time between a stress disorder diagnosis and a dementia diagnosis varied widely among members of the cohort, suggesting that this was not the case.

Although there are many hypotheses about what might tie stress disorders and dementia together, more research is needed to understand the mechanisms of the association, the authors wrote.

—Michelle Samuels