Type 2 diabetes affects a large number of patients and can lead to serious adverse health outcomes including cardiovascular disease, retinopathy, nephropathy and neuropathy.
Patients with type 2 diabetes have also been shown to have an increased the risk of cognitive impairment and dementia. Achievement of good glycaemic control is associated with a reduction in the risk of many of adverse health outcomes and this can be attained through weight loss, but the evidence for an improvement in cognitive impairment is currently mixed. In this study, researchers from several centres in the US have reported on the results from the Action for Health in Diabetes (look AHEAD) study which suggests that it is glycaemic control, rather than weight reduction, which has the greatest impact on cognitive functioning. The look AHEAD study is a single blind, randomised trial that recruited 5145 individuals during 2001 to 2004 with a BMI >25kg/m2, a HbA1c < 11%, triglycerides < 600mg/dl and a systolic/diastolic blood pressure < 160/100 mmHg. Participants were randomised to either an intensive lifestyle intervention (ILI) or a diabetes support and education (DSE) control group and the interventions continued until 2012, which was an average of 9.9 years. For the cognitive assessment arm, 1089 participants from the original study were recruited at year 8 or 9 of follow-up and undertook 2 or 3 cognitive assessments, that evaluated verbal learning, memory, speed of processing, executive function and global cognitive functioning.
There was an equal number of participants from the ILI and DSE groups; the mean age of both samples was 58 years, and 42% of both groups was male and roughly 10% had pre-existing cardiovascular disease. Improvements in blood sugar control was associated with greater improvements in cognitive scores for most measures. In contrast, the association between improvements in weight loss and cognitive scores was less clear and depended to some extent, on the cognitive measure.
The authors were unable to account for these findings and concluded that any improvements in cognitive function were largely dependent on baseline levels of adiposity and cardiovascular disease history.
Carmichael OT et al. Long-term change in physiological markers and cognitive performance in type 2 diabetes: the look AHEAD trial. J Clin Endrocrinol Metab 2020; doi:10.1210/clinem/dgaa591