HealthDay News — Among middle-aged female nurses, those reporting an evening chronotype are more likely to have an unhealthy lifestyle, with an increased risk for type 2 diabetes, even after accounting for lifestyle variables, according to a study published online Sept. 12 in the Annals of Internal Medicine.
Sina Kianersi, D.V.M., Ph.D., from Brigham and Women’s Hospital and Harvard Medical School in Boston, and colleagues examined the role of modifiable lifestyle behaviors in the association between chronotype and diabetes risk in a prospective cohort study involving 63,676 nurses aged 45 to 62 years.
The researchers found that compared with those reporting a definite morning chronotype, participants reporting a definite evening chronotype were 54 percent more likely to have an unhealthy lifestyle. During 469,120 person-years of follow-up, 1,925 diabetes cases were documented. The adjusted hazard ratio for diabetes was 1.21 and 1.72 for intermediate and definite evening, respectively, versus definite morning chronotype after adjustment for sociodemographic factors, shift work, and family history of diabetes. The association comparing definite evening and definite morning chronotypes was attenuated to 1.31, 1.54, and 1.59 after further adjustment for body mass index, physical activity, and diet quality, respectively. A reduced, but still positive, association was seen after accounting for all measured lifestyle and sociodemographic factors (hazard ratio, 1.19).
“Accounting for all measured sociodemographic and lifestyle factors resulted in a reduced but still positive association between evening chronotype and diabetes risk, which was primarily observed among day workers,” the authors write. “Future studies are needed to assess whether lifestyle interventions and personalized shift scheduling could reduce the adverse effect of evening chronotype on diabetes risk.”