A recent Nurses’ Health Study paper published in the Annals of Internal Medicine set out to answer if individuals who preferred to stay up late were more likely to develop type 2 diabetes. And if so, how much of the association between sleep timing preference and diabetes risk could be explained by modifiable unhealthy lifestyle behaviors. 

In order to determine a person’s sleep and wake preferences, NHS questionnaires ask participants if they are a “morning or evening type” person. In the sleep medicine community, this categorization is called “chronotype.”

Researchers found that 11% of NHSII participants reported having a “definite evening” chronotype and about 35% reported a “definite morning” chronotype. After adjusting for lifestyle and sociodemographic factors, such as diet, alcohol use, BMI, physical activity, smoking status, shift work, and sleep duration, individuals with a “definite evening” chronotype still had a 19% higher risk of developing type 2 diabetes than individuals with a “definite morning” chronotype.

The same study suggests that nurses may be opting for shifts that align with their chronotype. NHS participants with a “definite evening” chronotype were more likely to have worked night shifts than their “definitely morning” counterparts. And although shift work can be associated with an increased risk of type 2 diabetes, individuals with an evening chronotype who worked night shifts did not see an increased risk of diabetes compared to those who did not work at night. 

What’s next? 

This research adds to the broader effort by the Nurses’ Health Studies to better understand the role of sleep and circadian disruption in chronic disease risk. However, “additional studies are needed to elucidate the…mechanisms through which chronotype interacts with work schedules to influence diabetes risk and the benefits of personalized shift scheduling tailored to the worker’s chronotype,” say sleep researchers Dr. Sina Kianersi and Dr. Tianyi Huang.

Next, Drs. Kianersi and Huang will investigate the joint impact of chronotype and sleep on metabolic health in the NHS3 Sleep Sub-study. Building upon prior research, the NHS3 Sleep Sub-study uses Fitbits to measure sleep disturbances (e.g., short duration, low quality and high variability) that may affect people’s health. By combining sleep data with biomarkers and other lifestyle factors, researchers will be better able to investigate the role of sleep in cardiometabolic disease risk.

Learn More!

Curious about sleep research in the NHS cohorts? Read the full article discussed above or another NHS publication on sleep health and the effects of rotating shift work:

  1. Kianersi S, Liu Y, Guasch-Ferré M, et al. Chronotype, Unhealthy Lifestyle, and Diabetes Risk in Middle-Aged U.S. Women. Ann Intern Med. 2023;176(10):1330-1339. doi:10.7326/M23-0728
  1. Pan A, Schernhammer ES, Sun Q, Hu FB. Rotating night shift work and risk of type 2 diabetes: two prospective cohort studies in women. PLoS Med. 2011;8(12):e1001141. doi:10.1371/journal.pmed.1001141