Abstract
IntroductionWe investigated the association between glucose tolerance status and trajectories of change in blood glucose, and cognitive function in adults aged 25 to 85.MethodsThe sample (n = 4547) was drawn from a national, population-based cohort study in Australia (AusDiab). Fasting plasma glucose (FPG), glycated haemoglobin (HbA1c) and general health were assessed at 0, 5 and 12 years. Covariates included age, education, body mass index, blood pressure and physical activity. At 12 years, participants completed assessments of memory, processing speed and verbal ability.ResultsKnown diabetes at baseline was associated with slower processing speed at 12 years in both younger (25–59 years) and older (>60 years) age-groups. After 12 years of follow-up, adults aged < 60 with diabetes at baseline had a mean speed score of 49.17 (SE = 1.09) compared with 52.39 (SE = 0.20) in normals. Among younger males without diagnosed diabetes, reduced memory at 12 years was associated with higher HbA1c at 5 years (β = −0.91, SE = 0.26, p < 0.001). No effects were apparent for females or older males. Adjusting for insulin sensitivity (HOMA-%S) and hs-C reactive protein attenuated these associations, but depression and CVD risk did not. Latent class analysis was used to analyse the associations between trajectories of HbA1C and glucose over 12 years, and cognition. Identified classes were described as 1) normal and stable blood glucose over time (reference), 2) high intercept but stable blood glucose over time, and 3) increasing blood glucose over time. In both young males and females, high stable glucose measures were associated with poorer cognitive function after 12 years.ConclusionThose with type 2 diabetes, younger males with high non-diabetic HbA1c, and adults with high stable blood glucose are at increased risk of poorer cognition. The findings reinforce the need for management of diabetes risk factors in midlife.Electronic supplementary materialThe online version of this article (doi:10.1186/s13195-015-0131-4) contains supplementary material, which is available to authorized users.
Highlights
We investigated the association between glucose tolerance status and trajectories of change in blood glucose, and cognitive function in adults aged 25 to 85
Compared with the AusDiab sample at recruitment (N = 11,247), the study sample did not differ in gender distribution but was younger, had lower body mass index (BMI) (26.6 vs. 27.3, p
Analysis of glucose tolerance status as a function of death status at 12 years indicated that those who had died prior to the third wave of data collection were more likely to be classified as Known diabetes (KDM) and impaired glucose tolerance (IGT), and less likely to be classified as normal glucose tolerance (NGT) at baseline (χ2 (4) = 510.94, p
Summary
We investigated the association between glucose tolerance status and trajectories of change in blood glucose, and cognitive function in adults aged 25 to 85. Recent research on both middle-aged adults [1] and older adults [2] has shown that type 2 diabetes increases the risk of late-life cognitive decline, Alzheimer’s disease (AD) and all-cause dementia [3,4,5]. Show associations between type 2 diabetes and mild cognitive impairment (MCI) in middle age (50–65 years old) [7], and between type 2 diabetes and cognitive decline in mid-life [8]. Analysis of the Whitehall II mid-life cohort found that cognitive change in prediabetes and new diabetes was not different from that in NGT [15]
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