Since lifestyle factors are critical for diabetes prevention, improving these behaviors could mitigate the increased risk linked with evening chronotype.
Chronotype, a personal trait determined by both genetics and environment, is relevant to everyone, explains Tianyi Huang, MSc, ScD. Therefore, he says, understanding the health impact of different chronotypes has broad implications.
“Our prior research 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,” Huang says.
For a study published in the Annals of Internal Medicine, Huang and colleagues assessed the role of modifiable lifestyle behaviors in their correlation between chronotype and risk for diabetes. “We investigated whether evening chronotype is associated with other unhealthy behaviors in addition to poor sleep and whether it is linked with increased risk for diabetes compared with people with morning chronotype,” he says. “We studied more than 60,000 female nurses who did not have diabetes when they provided information on their different lifestyles and chronotype. We then compared how women who reported as evening chronotype versus morning chronotype were adhering to recommendations for a healthy lifestyle. We also followed these women for 8 years to examine if the incidence of diabetes differed by chronotype.”
Evening Chronotypes 54% More Likely to Have Unhealthy Lifestyle
Compared with participants reporting a “definite morning” chronotype, those reporting a “definite evening” chronotype were 54% more likely to have an unhealthy lifestyle, according to Huang and colleagues. Over 469,120 person-years of follow-up, 1,925 diabetes cases were documented.
The study team observed that the adjusted HR for diabetes was 1.21 (95% CI, 1.09-1.35) for the “intermediate” chronotype and 1.72 (95% CI, 1.50-1.98) for the “definite evening” chronotype after adjustment for sociodemographic factors, shift work, and family history of diabetes versus the “definite morning” chronotype.
Additional adjustment for BMI, physical activity, and diet quality lessened the correlation comparing the “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. Taking into consideration all lifestyle and sociodemographic factors resulted in an attenuated but still positive correlation (HR comparing “definite evening” vs “definite morning” chronotype, 1.19; 95% CI, 1.03-1.37).
Lifestyle Factors Are Key in Chronotype Link With Diabetes
Evening compared with morning chronotype was found to increase the risk for diabetes by 72% after the researchers controlled for sociodemographic factors, shift work, and family history of diabetes (Table). “When we further took into account lifestyle factors, this increased risk was reduced to 19%,” Huang notes. “This supports a positive link between evening chronotype and risk for diabetes and highlights the important role that lifestyles factors play in this association.”
He adds that the findings have implications for the post-pandemic period when many people work from home and do not need to sleep and wake up as early to commute to work. “This could push their daily chronotype toward the evening, which may have a negative influence on their lifestyles and risk for diabetes,” he says.
Improving Lifestyle Behaviors Could Mitigate Increased Risk
People with evening chronotype should pay more attention to their lifestyle behaviors, not only sleep behaviors but also other lifestyles factors throughout the day, according to Huang and colleagues. “Because lifestyle factors are critical for diabetes prevention, improving lifestyle behaviors could mitigate the increased risk associated with evening chronotype,” Huang says.
Since chronotype is influenced by both environment and genetics, the study team seeks to conduct future research to evaluate whether genetic predisposition to evening chronotype is associated with diabetes risk. “This will provide additional supporting evidence for the link between chronotype and risk for diabetes,” Huang says. “We also aim to explore the associations between chronotype with other chronic diseases such as cardiovascular disease. Finally, future research should also focus on evaluating whether targeted promotion of healthy lifestyles/lifestyle interventions for evening chronotype may be beneficial for diabetes prevention.”
