Self-reported “Night Owls” More Likely to Have Unhealthy Lifestyle Behaviors, Significantly Increased Diabetes Risk

A recent large-scale study conducted by researchers from Brigham and Women’s Hospital and Harvard Medical School has shed light on the health risks associated with one’s chronotype, or circadian preference.

The study, published in the Annals of Internal Medicine, focused on middle-aged nurses and revealed a concerning link between being a “night owl” and engaging in unhealthy lifestyle behaviors, including smoking, poor sleep, and physical inactivity. Most notably, the research uncovered a staggering 72 percent higher risk of developing diabetes among individuals with an evening chronotype.

Understanding Chronotype

Chronotype, or circadian preference, is a trait influenced by genetics that determines an individual’s inclination towards early or late sleeping and waking times. Approximately 8% of the population falls into the “evening chronotype” category, meaning they feel most energetic later in the day. Previous studies have associated the evening chronotype with poor metabolic regulation, disrupted glycemic control, metabolic disorders, and an elevated incidence of type 2 diabetes. However, the underlying reasons for this connection have remained unclear.

The Study

The study involved a comprehensive analysis of 63,676 nurses aged 45 to 62 years, all of whom had no history of cancer, cardiovascular disease, or diabetes. The research took place over an eight-year period from 2009 to 2017. The findings revealed that individuals with a “definite evening” chronotype were 54 percent more likely to engage in an unhealthy lifestyle compared to those with a “definite morning” chronotype.

Furthermore, those with an evening chronotype faced a remarkable 72 percent higher risk of developing diabetes during the follow-up period. Even after adjusting for various lifestyle and sociodemographic factors, the association between evening chronotype and diabetes risk remained statistically significant. Importantly, these results primarily pertained to individuals who had not recently worked night shifts.

Implications and Future Research

While the study’s findings provide crucial insights into the link between chronotype, lifestyle choices, and diabetes risk, the authors caution that several factors may influence these results. Psychological factors, the type of work an individual engages in, and potential changes in chronotype over one’s lifetime are among the factors that could confound the outcomes. However, the study suggests that circadian misalignment—caused by a mismatch between an individual’s chronotype and work schedule—may play a pivotal role in these results.

The authors of an accompanying editorial, hailing from the Harvard T.H. Chan School of Public Health and Harvard Medical School, highlight the potential benefits of reassigning evening chronotype workers to night shifts to improve their sleep and metabolic health. They also stress the importance of developing standardized tools to regularly assess an individual’s chronotype throughout their life.

Conclusion

In summary, this groundbreaking study emphasizes the substantial impact of chronotype on lifestyle choices and health outcomes. Individuals with an evening chronotype are at a significantly higher risk of developing diabetes, which is exacerbated by unhealthy behaviors such as smoking, poor sleep, and physical inactivity.

While further research is needed to explore the nuances of these findings in different populations and settings, this study underscores the importance of considering circadian preferences in healthcare and workplace design. Understanding and addressing chronotype-related health risks can lead to more tailored interventions and better overall health outcomes.