Study sees major depression connection to diabetes

[Al-khiyal]

WASHINGTON, April 23 (Reuters) - Elderly people who are depressed are more likely to become diabetic than those who are not, according to a study that suggests depression may play a role in causing the most common form of diabetes.

Writing on Monday in the Archives of Internal Medicine, the researchers said people with a high number of symptoms of depression were about 60 percent more likely to develop type 2 diabetes, formerly called adult-onset diabetes, than people not considered depressed.

Unlike some other studies examining a link between depression and diabetes, this one looked at the effects not only of single bouts of depression but also of chronic depression and depression that worsened over time. It found an increased risk for diabetes in each of those scenarios.

Researchers tracked 4,681 men and women in North Carolina, California, Maryland and Pennsylvania ages 65 and older, with an average age of 73, who did not have diabetes when the study began in 1989.

For 10 years, they were screened annually for 10 symptoms of depression, including those related to mood, irritability, calorie intake, concentration and sleep.

"People who report higher depressive symptoms may not take as good a care of themselves as they should," lead researcher Mercedes Carnethon of the Northwestern University's Feinberg School of Medicine said in an interview.

"For example, they may be less physically active, and thus more likely to gain weight, which is the primary risk factor for diabetes," Carnethon said.

But the study statistically accounted for known lifestyle risk factors for diabetes like being overweight and sedentary, and still found that depression increased the risk of diabetes.

Carnethon said the findings suggest depression may play a role in causing diabetes. While the study did not explore possible biological mechanisms, Carnethon said a high level of the stress hormone cortisol in depressed people may be the reason.

Diabetes is marked by high levels of blood glucose resulting from defects in the production or action of insulin, which allows glucose to enter the body's cells for use as fuel. High cortisol levels, the researchers said, may cut insulin sensitivity and raise fat deposits around the waist.

"Diabetes not only causes heart disease, but is strongly related to strokes, blindness, kidney failure, amputations. Diabetes is a very serious condition that's highly prevalent in older adults," Carnethon said.

Diabetes is a growing worldwide problem, closely tied to obesity. Type 2 diabetes accounts for about 95 percent of all cases.

The findings point to the importance of doctors screening older adults for depression and, if it's present, for diabetes risk, Carnethon said.

Study sees major depression connection to diabetes

[Al-khiyal]

Depression is associated with an increased risk for diabetes in older adults, even in people who have no other risk factors for the disease, a new study reports.

Researchers studied 4,681 men and women over 65, following them over a 10-year period, after excluding anyone who already had diabetes at the start of the project. They used a well-validated questionnaire to measure symptoms of depression each year, and tested all participants at two- to four-year intervals for blood sugar. They also calculated body mass index and noted alcohol intake, smoking status and antidepressant use.

After controlling for these factors, they found that even a single report of high depressive symptoms was associated with an increase in the incidence of diabetes. Increases in symptoms over time and persistently high symptoms of depression were also associated with the disease. Overall, people with the highest scores on the depression questionnaire were roughly 50 percent more likely to develop diabetes than those with the lowest scores. Adjusting for race, sex, smoking status, alcohol intake and body mass index made no difference in the result.

Mercedes R. Carnethon, the lead author and an assistant professor of preventive medicine at Northwestern University, said there was no evidence one way or the other on whether treating depression could reduce the risk for diabetes. "People in our study who were on antidepressants didn't have an elevated risk for diabetes," she said.

"But we don't know if that's because of the antidepressants" or for some other reason. The study appeared April 23 in The Archives of Internal Medicine.

Jonathan W. Stewart, a research psychiatrist at the New York State Psychiatric Institute who was not involved in the work, said that the conclusions "fit with what else we think we know," but he was troubled by one aspect of the work.

"I worry that some of the items on the questionnaire could be attributed to diabetes rather than to depression," suggesting that there is some overlap between the symptoms of the two disorders, he said. "This doesn't make the study wrong or inaccurate, but it's a serious limitation which they didn't mention."

Inflammation has been proposed as an explanation for the connection because it is associated with both diabetes and depression. But this study found that having higher or lower levels of C-reactive protein, a marker of inflammation, did not alter the association between the two disorders.

Instead, the authors suggest, other biological mechanisms may be at work in the autonomic nervous system, which controls heart, digestive, respiratory, glandular and other involuntary processes. Previous studies have shown that depression is associated with dysfunction in that system, which has also been detected before the development of diabetes. The stress response associated with depression may increase the risk for diabetes by decreasing insulin secretion from the pancreas, which then causes increasing glucose levels in the blood.

This can result in a blood sugar level above normal, the defining characteristic of diabetes.

The authors acknowledge some weaknesses in their study. Measures of physical activity were not consistently available during followup, and assumptions about this may have introduced error. Also, some of their data were gathered with self-reports, which are not always reliable.

In addition, while their questionnaire detected depressive symptoms, the researchers were not able to make definitive diagnoses of clinical depression.

Still, Carnethon said, depression "is a novel risk factor for diabetes, so we need to look at factors beyond physical inactivity and diet for an explanation." Depression is common in older people, she added, and 15 percent of those over 65 have diabetes.

"The most important thing to keep in mind," Carnethon said, "is that depression has a lot of effects on the body, one of which may be the development of diabetes, which can lead to a number of other diseases. So addressing depression is important not only for improving mood, but for protecting overall health."

Depression raises risk of diabetes, study finds