Haemoglobin A1c and cognitive function in very old, cognitively intact men

Abstract

SIR—Type 2 diabetes has long been associated with cognitive decline [1–6] and both Alzheimer's and vascular dementia [7–14]. Diagnosis and glycaemic control can be assessed by measuring glycosylated haemoglobin—or haemoglobin A1c (HbA1c)—level, which is a reflection of average blood glucose levels in the past 3 months. Previous studies have found high levels of HbA1c associated with worse memory, although most of these considered samples of young elderly (with mean age under 75 years) or included only diabetics [15, 16]. To date, very few studies have investigated the relationship between HbA1c level and cognition in populations of the very old (75+ years of age). One recent study found the interesting result that higher HbA1c level is associated with a decelerated decline in memory in patients over 85 years of age [17], suggesting that the harmful effect of elevated HbA1c levels on cognitive function may be less severe with increasing age. In this study, we studied the association between HbA1c and cognitive function in a sample of cognitively normal men greater than 75 years of age to examine whether this association varies by age.