Aims/hypothesis: This study aimed to examine the association between diabetes and hyperglycaemia-assessed by HbA1c-and change in cognitive function in persons with and without diabetes. Methods: This was a prospective cohort study of 8,442 non-diabetic and 516 diabetic participants in the Atherosclerosis Risk in Communities (ARIC) study. We examined the association of baseline categories of HbA1c with 6 year change in three measures of cognition: the digit symbol substitution test (DSST); the delayed word recall test (DWRT); and the word fluency test (WFT). Our primary outcomes were the quintiles with the greatest annual cognitive decline for each test. Logistic regression models were adjusted for demographic (age, sex, race, field centre, education, income), lifestyle (smoking, drinking) and metabolic (adiposity, blood pressure, cholesterol) factors. Results: The mean age was 56 years. Women accounted for 56% of the study population and 21% of the study population were black. The mean HbA1c was 5.7% overall: 8.5% in persons with and 5.5% in persons without diabetes. In adjusted logistic regression models, diagnosed diabetes was associated with cognitive decline on the DSST (OR 1.42, 95% CI 1.14-1.75, p = 0.002), but HbA1c was not a significant independent predictor of cognitive decline when stratifying by diabetes diagnosis (diabetes, p trend = 0.320; no diabetes, p trend = 0.566). Trends were not significant for the DWRT or WFT in either the presence or the absence of diabetes. Conclusions/interpretation: Hyperglycaemia, as measured by HbA1c, did not add predictive power beyond diabetes status for 6 year cognitive decline in this middle-aged population. Additional work is needed to identify the non-glycaemic factors by which diabetes may contribute to cognitive decline.
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Acknowledgements This research was supported by NIH/NIDDK grant R21 DK080294. E. Selvin was also supported by NIH/NIDDK grant K01 DK076595. A. L. Christman was also supported by NIH/NIDDK training grant T32 DK062707. F. Hill-Briggs was supported by NIH/NIDDK Diabetes Research and Training Center grant P60 DK079637. The Atherosclerosis Risk in Communities Study is carried out as a collaborative study supported by National Heart, Lung, and Blood Institute contracts N01-HC-55015, N01-HC-55016, N01-HC-55018, N01-HC-55019, N01-HC-55020, N01-HC-55021, and N01-HC-55022.
- Haemoglobin A