Symptoms of depression increase older people’s likelihood of becoming cognitively impaired, and this risk is especially high for men, a new study in the Journal of the American Geriatrics Society shows.

The findings support the theory that depression might result from the effects of blood vessel disease on the brain, and represent the early stages of declining mental function, Dr. Tze Pin Ng of the National University of Singapore and colleagues point out.

There has been some research suggesting a link between depression and worse cognitive function in older people, and a couple of studies have found the link in men, but not women, the researchers say. The gender difference could be due to men’s greater likelihood of having disease of their blood vessels (vascular disease), they add.

To investigate, the researchers followed 1,497 Chinese men and women who were 55 years of age or older, all of whom had strong mental functioning. At the study’s outset, 10.6 percent were depressed. Within 2 years, 44 people, or 3 percent, had developed cognitive impairment. All of these individuals had high blood pressure or risk factors for vascular disease such as diabetes or stroke.

While 2.6 percent of people who weren’t depressed developed cognitive impairment, 5.7 percent of those who were depressed did. After the researchers accounted for factors that could influence both depression and cognitive function, including gender, education, baseline mental function, and blood vessel disease risk factors, they found that depressed people were 2.29 times more likely to have lost cognitive function than people who weren’t depressed.

The increased risk was only statistically significant among men, who were 4.74 times more likely to become cognitively impaired if they were depressed.

The findings suggest that underlying blood vessel disease may account for some of the increased cognitive impairment risk seen in depressed men, the researchers say. “Depressive symptomology in women may reflect a greater diversity of underlying psychosocial pathology or other physical illness,” they add, “which might mask the cognitive effect of vascular depression even if it were present.”

SOURCE: Journal of the American Geriatrics Society, June 2009.