Effects of Type 2 Diabetes on 12-Year Cognitive Change

Results from the Maastricht Aging Study

Diabetes Care Published online before print December 28, 2012, doi:10.2337/dc12-0746

Corresponding author: Peggy J. J. Spauwen, peggy.spauwen@maastrichtuniversity.nl.

OBJECTIVE To examine the effects of baseline and incident diabetes on change in cognitive function over 12 years.

RESEARCH DESIGN AND METHODS A sample of 1,290 individuals aged ≥40 years at baseline, participating in the Maastricht Aging Study, were cognitively tested at baseline, after 6 years, and after 12 years. Of these, 68 participants had type 2 diabetes at baseline, and 54 and 57 had incident diabetes at the 6- and 12-year follow-up, respectively. Changes in performance on tests of information-processing speed, executive function, and verbal memory from baseline to 6- and 12-year follow-up were compared between groups using linear mixed models. Effects of diabetes on cognitive decline were adjusted for demographic variables, history of smoking, alcohol intake, and comorbid conditions, including hypertension, cardiovascular disease, BMI, and depression.

RESULTS Participants with baseline diabetes showed larger decline in information-processing speed (estimate −7.64; P < 0.01), executive function (21.82; P < 0.01), and delayed word recall (−1.35; P < 0.05) over the 12-year follow-up compared with control subjects. No significant difference in decline was observed for immediate word recall. Compared with control subjects, participants with incident diabetes showed subtle early decline in information-processing speed only. Interestingly, they did not show larger decline in any other cognitive domain.

CONCLUSIONS Individuals with baseline type 2 diabetes show accelerated cognitive decline, particularly in information-processing speed and executive function, compared with individuals without diabetes. In incident diabetes, decline in speed becomes detectable first, and cognitive decline seems to increase with increasing exposure time.

 COMMENT: Investigators have increasingly been concerned with the cognitive effects of hyperglycemia and have demonstrated that hyperglycemia has acute negative effects on cognition.  In a prior longitudinal study on the effects of diabetes on the development of Alzheimer’s disease and non-stroke-related cognitive impairment, Jose A. Luchsinger and colleagues (Am. J. Epidemiol. (2001) 154 (7):635-641.) demonstrated that: “The adjusted relative risk of Alzheimer's disease among persons with diabetes as compared with those without diabetes was 1.3 (95% confidence interval (CI): 0.8, 1.9). The adjusted relative risk for the composite outcome of Alzheimer's disease and cognitive impairment without dementia (without stroke) in subjects with diabetes was 1.6 (95% CI: 1.2, 2.1). The adjusted relative risk of stroke-associated dementia in persons with diabetes was 3.4 (95% CI: 1.7, 6.9). Among Blacks and Hispanics, approximately one third of the risk of stroke-associated dementia was attributable to diabetes (33% (95% CI: 31, 36) and 36% (95% CI: 33, 37), respectively), as compared with 17% (95% CI: 13, 22) among Whites.”  They concluded that “The finding of an association between diabetes and the composite outcome of Alzheimer's disease and cognitive impairment without dementia (without stroke) is consistent with prior reports of a modest relation between diabetes and Alzheimer's disease.” http://aje.oxfordjournals.org/content/154/7/635.short The Maastricht paper adds significantly to the body of literature that at least for type 2 diabetes there is an increased risk of cognitive impairment and the decline in cognition is related to the duration of diabetes.  This decline was independent of generally accepted risk factors in this population.  With the increasing ageing of the population, this will become another personal and economic burden of diabetes.

TITLE: History of Medically Treated Diabetes and Risk of Alzheimer Disease in a Nationwide Case-Control Study

CITATION: Diabetes Care Published online before print January 22, 2013, doi:

URL: http://care.diabetesjournals.org/content/early/2013/01/15/dc12-1287.abstract.html?papetoc

CORRESPONDING AUTHOR: Anna-Maija Tolppanen, anna-maija.tolppanen@uef.fi

SUMMARY: In this retrospective study the authors started with people with Alzheimer’s disease and looked for their history of diabetes.  The study conducted in Finland examined administrative records for 28,093 persons reimbursed for Alzheimer’s disease medications and diabetes medications and compared them to those free of Alzheimer’s disease from 1972-2005. They found that the overall prevalence of diabetes was 11.4%, 10.7% (n = 3,012) among control subjects, and 12.0% (n = 3,372) among Alzheimer’s disease subjects. They concluded that people with Alzheimer’s disease were more likely to have diabetes than matched control subjects (unadjusted OR 1.14 [95% CI 1.08–1.20]), even after adjusting for cardiovascular diseases (OR 1.31 [1.22–1.41]). The associations were stronger with diabetes diagnosed at midlife (adjusted OR 1.60 [1.34–1.84] and 1.25 [1.16–1.36] for midlife and late-life diabetes, respectively).

COMMENT: This nice population-based study confirms the others that we have been discussing in that the association between Alzheimer’s disease and diabetes is small, but significant and is related to the duration of diabetes.  It does not, however, address the issue of cognitive impairment.