Because diabetes and hypertension often go together, Dixon said he was not surprised that high systolic blood pressure accounted for one-third to one-half of significantly worse scores on four tests. That finding, said the authors, suggests that diabetes and cognition may be connected via diabetics' vascular problems. For example, diabetes and hypertension may both play a role in a larger metabolic syndrome that includes high blood sugar and insulin resistance.

However, the other two factors raised new questions. Combined gait and balance had the greatest influence, accounting for between 32 percent and 62 percent of performance on seven cognitive tests. Diabetes might affect the specific nerves that control gait and balance, the authors wrote, or more broadly affect the overlapping brain areas that support both gait-balance and cognition.

Like blood pressure, what people said about their health accounted for about one-third to one-half of performance on five different cognitive tests. Negativity about one's health could reflect related factors such as stress or depression, which did not, in this study, directly mediate between diabetes and cognition. Self-reported health is "an important indicator of ways in which a cluster of health-related beliefs and behaviors can modulate the effect of this disease on cognitive adaptation," Dixon said.

"It's important to pay attention to the health beliefs of older adults, not because they are necessarily accurate or valid indicators of specific health status, but because they might track overall health," Dixon said.

Type 2 diabetes in adults accounts for 90 percent to 95 percent of all diagnosed cases of diabetes, according to the National Institute of Diabetes and Digestive & Kidney Diseases.

Source: American Psychological Association