Posted Apr 6 , 2018 04:05 AM

HbA1c, diabetes and cognitive decline: the English Longitudinal Study of Ageing

Zheng F, et al. Diabetologia 2018: Online January 17th

What were the findings (excerpted from the Abstract)?

The aim of the study was to evaluate longitudinal associations between HbA1c levels, diabetes status and subsequent cognitive decline over a 10-year follow-up period. Data from wave 2 (2004–2005) to wave 7 (2014–2015) of the English Longitudinal Study of Ageing (ELSA) were analyzed. Cognitive function was assessed at baseline (wave 2) and reassessed every 2 years at waves 3–7. Linear mixed models were used to evaluate longitudinal associations. The study comprised 5189 participants (55.1% women, mean age 65.6 years) with baseline HbA1c levels ranging from (3.6–13.7%). The mean follow-up duration was 8.1 years and the mean number of cognitive assessments was 4.9. A 0.1% increment in HbA1c was significantly associated with an increased rate of decline in global cognitive z scores, memory z scores, and executive function z scores after adjustment for baseline age, sex, total cholesterol, HDL-cholesterol, triacylglycerol, high-sensitivity C-reactive protein, BMI, education, marital status, depressive symptoms, current smoking, alcohol consumption, hypertension, CHD, stroke, chronic lung disease and cancer. Compared with participants with normoglycemia, the multivariable adjusted rate of global cognitive decline associated with prediabetes and diabetes was increased by −0.012 SD/year and −0.031 SD/year respectively (p for trend <0.001). Similarly, memory, executive function and orientation z scores showed an increased rate of cognitive decline with diabetes.

Why is this important?

Cognitive change in individuals with diabetes has been known since 1922, and changes in cognition and brain structure were well documented in 2007 using cognitive testing and MRI scans (Brands MA, et al, Dement. Geriatr. Cogn. Disord. 2007;23:343-350). While the changes have been associated with low grade inflammation and oxidative stress, more recently some have suggested a role for the gut microbiome in the ‘microbiota-gut-brain axis’ (Xu Y, et al. Front. Ageing Neurosci. 2017;9:Article 106). Whatever the cause(s), the relationship between diabetes and cognitive decline is well established. Significant longitudinal associations between HbA1c levels, diabetes status and long-term cognitive decline were observed in this study. Future studies are required to determine the effects of maintaining optimal glucose control on the rate of cognitive decline in people with diabetes. This is yet another complication that healthcare professionals should be aware of. Were you aware of this? Do you do any screening for cognitive function in your patients?

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