Association of poor sleep and HbA1c in metformin-treated patients with type 2 diabetes: Findings from the UK Biobank cohort study

The American Diabetes Association recommends a glycated haemoglobin target of less than 7% for treating type 2 diabetes mellitus. However, it is still being determined if poor sleep affects this therapeutic goal, despite being treated with the blood-glucose-lowering medication metformin. Thus, we used data from 5703 patients on metformin monotherapy participating in the UK Biobank baseline investigation between 2006 and 2010. We combined self-reported chronotype, daily sleep duration, insomnia, daytime sleepiness and snoring into a multidimensional poor sleep score ranging from 0 to 5, with higher scores indicating a less healthy sleep pattern. With each point increase on the poor sleep score scale, the odds of patients having an glycated haemoglobin of >= 7% increased by 6% (odds ratio [95% confidence interval], 1.06 [1.01, 1.11], p = 0.021). When examining the components of the poor sleep score separately, snoring was specifically associated with a glycated haemoglobin of >= 7% (1.12 [1.01, 1.25] versus no snoring, p = 0.038). However, adjusting for health and lifestyle conditions, such as body mass index, weekly physical activity level and hypertension status, eliminated the significant associations between the poor sleep score and snoring with glycated haemoglobin of >= 7%. Our findings suggest that poor sleep, specifically snoring, a symptom of obstructive sleep apnea, may interfere with the therapeutic goal of achieving a glycated haemoglobin below 7%. However, other factors known to be promoted by poor sleep, such as high body mass index, low physical activity and hypertension, may also contribute to the link between poor sleep and higher glycated haemoglobin levels.