A new study from Brigham and Women’s Hospital in Massachusetts has revealed that people who prefer to stay up late and wake up late may have a higher risk of developing type 2 diabetes than those who are early birds. The study, published in the Annals of Internal Medicine, analyzed data from more than 63,000 female nurses over eight years and found that evening chronotype, or going to bed late and waking up late, was associated with a 19 percent increased risk of diabetes after accounting for lifestyle factors.
What is chronotype and how does it affect health?
Chronotype, or circadian preference, refers to a person’s preferred timing of sleep and waking and is partly genetically determined. It can be influenced by environmental factors such as light exposure, social cues, and work schedules. Chronotype can affect various aspects of health, such as metabolism, hormone levels, immune function, and mood.
Previous studies have shown that people with irregular sleep patterns or evening chronotypes are more likely to have metabolic disorders, cardiovascular diseases, obesity, depression, and cognitive impairment. However, the mechanisms behind these associations are not fully understood.
How did the researchers measure chronotype and diabetes risk?
The researchers used data from the Nurses’ Health Study II, a large-scale prospective cohort study that has been following female nurses since 1989. The participants completed questionnaires every two years about their health and lifestyle factors, such as diet, physical activity, smoking, alcohol use, family history of diabetes, and sleep habits. They also reported their chronotype by answering whether they considered themselves a morning person or an evening person.
The researchers identified 3,104 cases of type 2 diabetes among the participants during the follow-up period. They then compared the diabetes risk among different chronotypes after adjusting for various confounding factors. They found that compared with definite morning types, definite evening types had a 72 percent increased risk of diabetes before accounting for lifestyle factors. After adjusting for lifestyle factors, the risk was reduced to 19 percent but still remained significant.
What are the possible explanations for the link between chronotype and diabetes?
The researchers suggested several possible explanations for the link between chronotype and diabetes. One is that evening types may have a misalignment between their internal biological clock and their external social clock, resulting in a condition called social jet lag. This can disrupt the normal rhythms of hormones such as insulin and cortisol, which regulate blood sugar levels and stress responses.
Another explanation is that evening types may have less healthy lifestyles than morning types. The study found that evening types were more likely to have poor diet quality, low physical activity, high alcohol consumption, smoking, obesity, and short or long sleep duration. These factors can increase the risk of insulin resistance, inflammation, oxidative stress, and impaired glucose tolerance, which are all precursors of type 2 diabetes.
What are the implications and limitations of the study?
The study has several implications for public health and clinical practice. It suggests that chronotype may be an important factor to consider when assessing and preventing type 2 diabetes. It also highlights the need for more awareness and education about the potential health consequences of being a night owl. Moreover, it indicates that modifying lifestyle factors may help reduce the risk of diabetes among evening types.
However, the study also has some limitations that should be noted. First, it relied on self-reported data from the participants, which may be subject to recall bias or measurement error. Second, it only included female nurses who were mostly white and well-educated, which may limit the generalizability of the findings to other populations. Third, it did not measure the actual sleep timing or quality of the participants using objective methods such as actigraphy or polysomnography. Fourth, it did not examine the causal relationship between chronotype and diabetes or the underlying biological mechanisms.