Cognitive decline and type 2 diabetes - Diabetes

Nutrition Research Newsletter, March, 2004

Multiple population-based studies have suggested that type 2 diabetes increases the risk of dementia. Cognitive decline is an intermediate stage between normal ageing and dementia. Although many investigations have examined diabetes in relation to early cognitive decline, not many have focused on women. Type 2 diabetes disproportionately affects older women and is a stronger risk factor for cardiovascular disease in women than in men. Furthermore, few studies have evaluated the influence of different treatments for diabetes on the association between type 2 diabetes and cognition.

Researchers assessed the associations between type 2 diabetes, different treatments for diabetes, and cognitive function in more than 16,000 women, utilizing data from the Nurses Health Study. This study is a prospective cohort of 121,700 US female registered nurses, who were aged 30 yrs to 55 yrs in 1976, when the study began. Participants' health information has been updated with biennial mailed questionnaires. From 1995-2001, participants aged 70 yrs and older were given baseline cognitive assessments via telephone. A follow-up cognitive assessment began about two years following the baseline interview. Cognitive assessments included immediate and delayed recalls of the East Boston memory test, test of verbal fluency, delayed recall of a 10 word list, and digit span backwards.

Following multivariate adjustment, women with type 2 diabetes performed worse on all cognitive tests than women without diabetes, at baseline. For example, women with diabetes were at 25% to 35% increased odds of poor baseline score (defined as bottom 10% of the distribution) compared with women without diabetes--on the telephone interview of cognitive status and the global composite score (odds ratios 1.34, 95% CI 1.14 to 1.57, and 1.26, 1.06 to 1.51, respectively). The odds of poor cognition were particularly high for women who had had diabetes for a long time (1.52, 1.15 to 1.99, and 1.49, 1.11 to 2.00, respectively, for greater than or equal to 15 years duration). In contrast, women with diabetes who were on oral hypoglycemic agents performed similarly to women without diabetes (1.06 and 0.99), while women not using any medication had the greatest odds of poor performance (1.71, 1.28, to 2.281, and 1.45, 1.04 to 2.02) compared with women without diabetes. There was also a modest increase in the odds of poor cognition among women using insulin treatment. All findings were similar when cognitive decline was examined over time.

Women with diabetes had an increased risk of cognitive decline when compared to women without diabetes. It appears that the use of oral hypoglycemic therapy can reduce the risk of cognitive decline in diabetic women.

G. Logroscino, J. Kang. F. Grodstein. Prospective study of type 2 diabetes and cognitive decline in women aged 70-81 years. BMJ 10:1136-1142 (February 23, 2004) [Correspondence: G. Logroscino, Department of Epidemiology, Harvard School of Public Health, Boston, MA 02115, USA. E-mail: glogrosc@hsph.harvard.edu]