Diabetes in Midlife Raises Dementia Risk

Abstract

Adults with type 2 diabetes or prediabetes in midlife had greater cognitive decline over the next 20 years than did people without diabetes, according to the findings from a large prospective cohort study. The Atherosclerosis Risk in Communities (ARIC) study of 13,351 adults aged 48-67 years found those with diabetes in midlife had a 19% greater cognitive decline over a 20-year period than did people without diabetes (adjusted global z-score difference, −0.15 [95% CI, −0.22 to −0.08]), according to the findings published in Annals of Internal Medicine (Ann Intern Med 2014;161:785-93). The investigators used three neuropsychological tests to assess cognitive function: the delayed word recall test, the digit symbol substitution test of the Wechsler Adult Intelligence Scale-Revised, and the word fluency test. Cognitive decline was significantly greater in people with prediabetes (HbA1C level of 5.7%-6.4%), compared with those with an HbA1C level lower than 5.7%, reported the study authors, led by Andreea M. Rawlings of the Johns Hopkins Bloomberg School of Public Health in Baltimore. People with poorly controlled diabetes (HbA1C ≥ 7%) had greater cognitive decline than did people with better-controlled disease (adjusted global z-score difference, −0.16; P = .071). The association with cognitive decline was stronger for longer-duration diabetes (P < .001), and the findings were similar for black and white adults (P = .44). Maintaining cognitive function is a critical aspect of successful aging and ensuring a high quality of life, the study authors said. “Diabetes and glucose control are potentially modifiable and may offer an important opportunity for the prevention of cognitive decline, thus delaying progression to dementia,” they wrote. At the population level, delaying the onset of dementia by even a couple of years could reduce its prevalence by more than 20% over the next 30 years, according to the investigators. Diabetes was assessed at baseline, and cognitive function was assessed at baseline and periodically during the 20-year follow-up. The study was supported by the National Heart, Lung, and Blood Institute.