Evening chronotype tied to unhealthy behaviors, diabetes risk

Key takeaways:

• So-called “night owls” were more likely to report unhealthy behaviors and faced an increased risk for developing diabetes.
• The findings align with previous research.

Middle-aged women with an evening chronotype were more likely to report unhealthy lifestyle behaviors and faced an increased risk for diabetes, a study in the Annals of Internal Medicine found.

“Our prior work has shown that short/long sleep duration and irregular sleep schedules are associated with increased risk for diabetes, and we know that people with evening chronotype (night owls) are more likely to have these unhealthy sleep habits,” Tianyi Huang, ScD, MSc, an assistant professor of medicine at Harvard Medical School, told Healio. “So, this work is to investigate whether evening chronotype is associated with other unhealthy behaviors in addition to poor sleep and whether they have increased risk of diabetes compared with morning chronotype.”

Huang and colleagues analyzed data from 63,676 women aged 45 to 62 years who participated in the Nurses’ Health Study II. They had no prior history of cancer, diabetes or cardiovascular disease in 2009.

Chronotypes were self-reported by participants through a questionnaire.

Patients were followed until 2017, with 1,925 diabetes cases identified over 469,120 person-years of follow-up.

Participants who reported having an evening chronotype were 54% (95% CI, 49%-59%) more likely to have an unhealthy lifestyle compared with those who reported having a morning chronotype.

The researchers accounted for sociodemographic factors, shift work and a family history of diabetes. The adjusted HR for diabetes was 1.21 (95% CI, 1.09-1.35) for an intermediate chronotype and 1.72 (95% CI, 1.5-1.98) for an evening chronotype vs. a morning chronotype.

The researchers found that the adjusted HR for diabetes in evening vs. morning chronotypes decreased to:

• 1.59 (95% CI, 1.38-1.83) after adjusting for diet quality;
• 1.54 (95% CI, 1.34-1.77) after adjusting for physical activity; and
• 1.31 (95% CI, 1.13-1.5) after adjusting for BMI.

Adjusting for all lifestyle and sociodemographic factors resulted in a reduced but still positive association evening chronotypes and diabetes risk (aHR = 1.19; 95% CI, 1.03-1.37), the researchers said.

Huang and colleagues noted the positive association was seen only in those who had not worked the night shift and urged caution for generalizing the results due to the study population’s demographics.

According to Huang, people with an evening chronotype “should pay more attention to their lifestyle behaviors, not only sleep behaviors during the night but also other healthy lifestyles during the day.”

“Because these lifestyle factors are critical for diabetes prevention, improving these lifestyle behaviors could mitigate the increased risk associated with evening chronotype,” he said. “This also has implications for the post-COVID period, when a lot of people work from home and don't have the pressure to get up early and commute to work. This could make their daily schedules/chronotype toward more evening that may have a negative influence on their lifestyles and diabetes risk.”

In a related editorial, Kehuan Lin, MS, a clinical research coordinator at Massachusetts General Hospital, and colleagues noted that potential cofounders, such as psychological factors, were not considered in the study.

However, they said the research builds upon the idea that circadian misalignment is due to a mismatch between work timing and chronotype rather than from the chronotype itself, and that fixing circadian misalignment “may be an approach to improving metabolic health.”

“Indeed, removing people with late chronotypes from morning shifts and those with early chronotypes from night shifts has been shown to improve sleep among shift workers,” they wrote. “Further study is needed to determine the long-term benefit of such interventions.”

References:

• Kianersi S, et al. Ann Intern Med. 2023;doi:10.7326/M23-0728.
• Lin K, et al. Ann Intern Med. 2023;doi:10.7326/M23-2257.