How does sleep impact type 2 diabetes mellitus (T2DM) risk? A prospective cohort study following nearly 248,000 people over an average of 12.5 years found that those who habitually slept 5 hours or 4 hours per night were more likely to develop T2DM (hazard ratios 1.16 and 1.41, respectively) than those who habitually slept 7-8 hours per night. Potentially confounding variables were controlled, but when quality of diet was incorporated, there were two key findings: 1) those with the healthiest diets were not protected from T2DM risk if they had habitually short sleep; and 2) those with the healthiest diets and 7-8 hours of sleep had no additive protection against T2DM. However, when participants were categorized by quality of diet (in this case less red meat, more fruits and vegetables, and 2 or more servings of fish per week), those in the top 40% of diet quality had a reduced risk of developing T2DM compared to those in the bottom 20% of diet quality (HR 0.75). Would T2DM risk decrease further with even more fruits and vegetables, more legumes, less lean meat, or less fish? We do see such trends in the Adventist Health Study-2 and many others. Could more exclusively plant-based diets confer protection against T2DM even in those with habitually short sleep? They might, but don’t get any ideas. Habitually short sleep is thought to increase T2DM risk via a combination of increased sympathetic tone, insulin resistance, and gut dysbiosis. Short sleep is implicated in dementia risk for many of the same reasons, hence Alzheimer disease lately being referred to as type 3 diabetes. Limitations of the original cohort study include self-reporting of sleep and dietary habits, and generalizability since participants were 93% white. The study was partially funded by a Novo Nordisk Foundation grant, thought the conflict of interest here is less apparent than in the egregiously biased drug trials. Alas, sweet dreams.
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