November 2023
Night owls or early birds: who gets diabetes?

Women with ‘evening chronotype’ had greater risk for developing diabetes than those with ‘morning chronotype,’ even after adjustment for other relevant risk factors. 

Evening chronotype – or circadian preference to go to sleep late at night – has been associated with unhealthy lifestyle behaviours, obesity and disrupted glycaemic control. Although cross-sectional studies have linked evening chronotype to diabetes risk, prospective investigations are lacking. Researchers used data from the prospective Nurses’ Health Study II to determine diabetes incidence among about 64,000 middle-aged women – mostly white and middle-class – with no history of diabetes who reported a definite evening or morning chronotype (about half of participants said neither category clearly fitted their circadian pattern).

Participants with evening chronotype were 1.5 times more likely to have unhealthy lifestyle behaviours than were those with morning chronotype. During a mean 7.4 years of follow up, those with evening chronotype were significantly more likely to develop diabetes (hazard ratio 1.2), even after adjustment for life-style behaviours (e.g. diet, physical activity, alcohol intake, smoking, sleep duration), body mass index, sociodemographic factors, family history of diabetes and type of shift work.

Comment: Even after adjustment for unhealthy lifestyle behaviours and other factors, evening chronotype was still linked to higher risk for developing diabetes, compared with daytime chronotype. These data might help clinicians counsel or screen patients with clear circadian preferences regarding their behavioural and diabetes risks.

Daniel D. Dressler, MD, MSc, MHM, FACP, Professor of Medicine, Emory University School of Medicine, Atlanta, USA.

Kianersi S, et al. Chronotype, unhealthy lifestyle, and diabetes risk in middle-aged US women: a prospective cohort study. Ann Intern Med 2023 Sep 12; e-pub (

This summary is taken from the following Journal Watch titles: General Medicine, Ambulatory Medicine.

Ann Intern Med