Annals of Internal MedicineChronotype, Unhealthy Lifestyle, and Diabetes Risk in Middle-Aged US Women

Modifiable Lifestyle Factors Partially Mitigate Increased Diabetes Risk

A recent prospective cohort study from the Nurses’ Health Study II reveals that middle-aged nurses with an evening chronotype are at a heightened risk for developing type 2 diabetes. The study also explores how lifestyle modifications can attenuate this risk.

HCN Medical Memo
This study underscores the importance of considering chronotype when assessing diabetes risk in middle-aged women. Although lifestyle modifications can mitigate some of the increased risk, they do not entirely eliminate it. Tailoring lifestyle interventions according to chronotype may offer a more effective approach to diabetes prevention.

Study Design

• Setting: Nurses’ Health Study II
• Participants: 63,676 nurses aged 45 to 62 years with no history of cancer, cardiovascular disease, or diabetes in 2009
• Duration: Followed prospectively from 2009 until 2017
• Measurements: Self-reported chronotype, diet quality, physical activity, alcohol intake, BMI, smoking, and sleep duration. Diabetes cases were confirmed through supplementary questionnaires.

Fifty-four percent (54%) of nurses with an evening chronotype are more likely to have an unhealthy lifestyle compared to those with a morning chronotype.

Key Findings

• Nurses with a “definite evening” chronotype were 54% more likely to have an unhealthy lifestyle compared to those with a “definite morning” chronotype.
• A total of 1,925 diabetes cases were documented over 469,120 person-years.
• Adjusted hazard ratios for diabetes were 1.21 for “intermediate” and 1.72 for “definite evening” chronotypes, compared to “definite morning” chronotypes.
• After accounting for lifestyle and sociodemographic factors, the hazard ratio was reduced but remained significant at 1.19 for “definite evening” vs. “definite morning” chronotypes.

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