Adults 65 and older who report depressive symptoms are 50 to 60 percent more likely to develop diabetes than are their peers, according to a new study.
The study is the first to show that depression alone, apart from lifestyle factors such as poor diet and lack of exercise, can trigger type 2 diabetes in older adults, reports Mercedes Carnethon of the Northwestern University School of Medicine in Chicago.
“This means doctors need to take depressive symptoms in older adults very seriously,” she says. Earlier research had shown the connection in younger adults.
Among all age groups, adults 65 and older suffer the second-highest rate of depression and the highest rate of type 2 diabetes, which appears after tissues develop resistance to the body’s natural insulin.
A link between depression and diabetes emerged in a number of previous studies, leading researchers to wonder which condition came first. “It’s been this whole chicken-and-egg sort of debate,” says Carnethon. “People think that diabetes would come first because the difficulty of dealing with a chronic condition [might lead] to depression.”
But the new research shows that, at least in older adults, depression often precedes diabetes. The four-state study monitored 4,681 men and women for a decade. Each year, participants filled out surveys on mood, lifestyle, and other health-related factors.
Participants who scored poorly on a standard depressive-symptom questionnaire, or whose depressive symptoms increased year by year, faced a 50 to 60 percent increased risk for developing diabetes later, Carnethon and her colleagues report in the April 23 Archives of Internal Medicine.
After the researchers accounted for known diabetes risks such as a high body mass index, smoking, and excessive alcohol consumption, the association between depression and diabetes persisted.
Excess weight is the primary risk factor for diabetes. Carnethon says that overweight adults are two to three times as likely to develop diabetes as their normal-weight peers are. Depression is a “smaller but still very important risk factor, especially given the high prevalence of depressive symptoms in older adults,” she says.
Carnethon suspects that stress hormones—which tend to be elevated in depression—link the two conditions. Too much cortisol, in particular, can build abdominal fat and an apple-shaped body, which are strong risk factors for diabetes. The Northwestern team plans follow-up research investigating cortisol as the depression-diabetes link.
Carnethon urges doctors to be on the lookout for depression in older adults because treating the condition may prevent some diabetes.
Treatment of depression is even helpful for adults who already have diabetes, according to a report in the April Diabetes Care. In that study, Patrick Lustman and his colleagues at Washington University in St. Louis found that treatment with the antidepressant sertraline (Zoloft) was useful in diabetes management. Says Lustman: “We know that controlling depression by whatever method—whether with exercise, activity, cognitive therapy, or medication—improves the likelihood that blood glucose will be better controlled. That’s the key to preventing the complications of diabetes.”