Evening Chronotypes Linked to Unhealthy Lifestyle, Increased Diabetes Risk in Women


An analysis of data from more than 60,000 women details associations between specific chronotypes and risk of unhealthy lifestyle behaviors as well as risk of developing type 2 diabetes.

Tianyi Huang, MSc, ScD | Credit: LinkedIn

Tianyi Huang, MSc, ScD
Credit: LinkedIn

An analysis of data from the Nurses’ Health Study II indicates could be promoting an unhealthy lifestyle and increasing a person’s risk of developing type 2 diabetes.

Led by investigators from Brigham and Women’s Hospital and Harvard Medical School, results of the analysis, which included data from more than 63,000 nurses surveyed from 2009-2017, suggest participants with a “definite evening” chronotype were 54% more likely to have an unhealthy lifestyle and had a 72% greater risk for developing type 2 diabetes than their counterparts with a “definite morning” chronotype.1

“People who think they are ‘night owls’ may need to pay more attention to their lifestyle because their evening chronotype may add increased risk for type 2 diabetes,” said study investigator Tianyi Huang, MSc, ScD, an associate epidemiologist in the Brigham’s Channing Division of Network Medicine.2

With statistics from the US Centers for Disease Control and Prevention indicating more than 37 million in the US have type 2 diabetes and recent research indicating this number could continue to balloon in the coming decades, a greater understanding of drivers or factors associated with increased likelihood of develop type 2 diabetes could stand to have a significant impact on population-level health.3,4 With this in mind, Huang and a team of colleagues launched the current study with the intent of assessing whether different chronotypes might be associated with varying degrees of risk for development of type 2 diabetes.1

To do so, investigators designed their study as an analysis of data from the Nurses’ Health Study II. A prospective cohort study initiated in 1989 among 116,429 female and predominantly White registered nurses aged 25-42 years, study participants were required to complete comprehensive questionnaires about lifestyle and health-related information at baseline and every 2 years. Excluding those with a history of cardiovascular disease, cancer, or diabetes, investigators identified 63,676 nurses aged 45-62 years with follow-up between 2009-2017 for inclusion in their analyses.1

The overall study cohort had a mean age of 54 (Standard deviation [SD], 4.6) years, 97% were White, and 67% were postmenopausal. Among the 63,676 included in the overall sample, 22,380 had a definite morning chronotype, 34,167 had an intermediate chronotype, and 7129 had a definite evening chronotype. Baseline analysis indicated different chronotypes had similar distributions in age and race, but those with a definite evening chronotype were less likely to live in the Northeast or to work in an outpatient setting but more likely to have ever worked night shifts, to have worked any rotating night shift work in the previous 2 years, and to have depression than those with a definite morning chronotype. Additionally, investigators highlighted unhealthy lifestyle behaviors were more common among participants with a definite evening chronotype.1

Investigators pointed out chronotype and incident diabetes cases were both self-reported. For the purpose of analysis, self-reported chronotype for participants was derived using data from a validated question within the Morningness-Eveningness Questionnaire and incident diabetes was confirmed using a supplementary questionnaire. Investigators also pointed out plans to adjust analyses for lifestyle behaviors of interest, including diet quality, physical activity, alcohol intake, BMI, smoking, and sleep duration.1

Upon analysis, results suggested those reporting a “definite evening” chronotype had a 54% greater risk of having an unhealthy lifestyle relative to their counterparts reporting a “definite morning” chronotype (adjusted Prevalence Ratio, 1.54; 95% Confidence Interval [CI], 1.49-1.59). Further analysis revealed 1925 cases of incident diabetes were recorded during 469,120 person-years of follow-up. An increased risk for diabetes was observed among those with either an “intermediate” (adjusted Hazard Ratio [aHR], 1.21; 95% CI, 1.09-1.35) or a “definite evening” (aHR, 1.72; 95% CI, 1.50-1.98) chronotype relative to those with a “definite morning” chronotype.1

Upon adjustment for BMI, physical activity, and diet quality, results indicated the association comparing “definite evening” and “definite morning” chronotypes to 1.31 (95% CI, 1.13-1.50), 1.54 (95% CI, 1.34-1.77), and 1.59 (95% CI, 1.38-1.83), respectively. When adjusting for all measured lifestyle and sociodemographic factors, the increase in risk for those with “definite evening” chronotypes relative to the “definite morning” chronotype was reduced but remained positive (aHR, 1.19; 95% CI, 1.03-1.37).1

“If we are able to determine a causal link between chronotype and diabetes or other diseases, physicians could better tailor prevention strategies for their patients,” added lead investigator Sina Kianersi, DVM, PhD, a postdoctoral research fellow in the Brigham’s Channing Division of Network Medicine.2


  1. Kianersi S, Liu Y, Guasch-Ferré M, et al. Chronotype, Unhealthy Lifestyle, and Diabetes Risk in Middle-Aged U.S. Women : A Prospective Cohort Study [published online ahead of print, 2023 Sep 12]. Ann Intern Med. 2023;10.7326/M23-0728. doi:10.7326/M23-0728
  2. Brigham and Women’s Hospital. “night owls” more likely than “early birds” to develop diabetes. EurekAlert! September 11, 2023. Accessed September 12, 2023. https://www.eurekalert.org/news-releases/1000853.
  3. Diabetes quick facts. Centers for Disease Control and Prevention. April 4, 2023. Accessed September 12, 2023. https://www.cdc.gov/diabetes/basics/quick-facts.html.
  4. Campbell P. Study warns of significant increases in diabetes and cardiovascular disease by 2060. HCP Live. August 1, 2022. Accessed September 12, 2023. https://www.hcplive.com/view/study-warns-increases-in-diabetes-and-cardiovascular-disease-by-2060.
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