To determine if NIDDM and blood pressure are risk factors for poor cognitive performance and if history and duration of NIDDM and blood pressure interact such that the risk of poor performance is greater for subjects with both NIDDM and hypertension.
We used a large prospective cohort sample with 187 NIDDM subjects and 1,624 nondiabetic subjects who were followed for 28–30 years. Cognitive function was assessed using eight tests of learning, memory, visual organization, verbal fluency attention, concept formation, and abstract reasoning. A composite score was also calculated. Odds ratios were used to estimate the relative risk of performing below the lower 25th percentile of z scores on these tests.
NIDDM and blood pressure interacted such that diagnosis and duration of NIDDM were associated with greater risk of poor performance on tests of visual memory and on the composite score for hypertensive subjects. Duration of NIDDM was associated with increased risk for poor performance on tests of verbal memory and concept formation. Insulin-treated NIDDM subjects were at higher risk for poor cognitive performance than those NIDDM subjects treated with oral agents or diet. Blood pressure level was associated independently with a measure of verbal fluency.
History and duration of NIDDM and high blood pressure are significant risk factors for poor cognitive performance. Hypertensive people with NIDDM are at greatest risk for poor performance on tests measuring visual organization and memory.