Here's another reason to keep your body fit as you enter middle age: two conditions often associated with physical inactivityhigh blood pressure and diabetesare now linked to more rapid cognitive decline. David Knopman of the Mayo Clinic and his colleagues tested 10,963 people between age 47 and age 70 from four sites across the country, measuring each subject's mental abilities at the start of the study and six years later. Their results appear in the January 9 issue of Neurology, the scientific journal of the American Academy of Neurology.

Overall, the researchers found that the average scores for all of the subjects fell, but those for people with high blood pressure and diabetes dropped most dramatically. Not that it was a lot. "It probably wasn't even enough for the participants to notice any change in their mental abilities," Knopman says. "But it shows that diabetes and high blood pressure start affecting cognitive abilities as early as late middle age. If these diseases can be treated earlybefore age 60it might lessen the burden of cognitive problems later in life."

Looking at the results by age, the scientists discovered that the two diseases followed slightly different patterns: whereas diabetes was associated with greater cognitive decline in people both under and over age 58, high blood pressure was a risk factor only for the older group. In addition, they found no association between smoking, high cholesterol or the use of nonsteroidal anti-inflammatory drugs (NSAIDs) and cognitive decline. It is still unclear how the two conditions might cloud mental acuity, but Knopman says, "it could be due to microinfarctions, or tiny areas of brain damage, in the brain's white matter."