Middle-aged ‘night owls’ more likely to develop type-2 diabetes

Science and Health

Being overweight, eating too many sweets and other simple carbohydrates, and not exercising are not the only triggers of type-2 diabetes. Researchers at Brigham and Women’s Hospital, which belongs to the Massachusetts General healthcare system, have found that if you’re a “night owl,” you are at higher risk than an “early bird.” 

Postdoctoral research fellows Dr. Sina Kianersi, Dr. Tianyi Huang, and colleagues have just published this in the journal Annals of Internal Medicine under the title “Chronotype, Unhealthy Lifestyle, and diabetes risk in Middle-aged US women: A Prospective Cohort Study in the Nurses’ Health Study II.” 

“Evening chronotype” refers to those who go to bed late and wake up late; it was associated with a 19% higher risk of diabetes after accounting for lifestyle factors compared to those with early-bird sleep habits. People who think they are “night owls” need to pay more attention to their lifestyle because their evening chronotype may add an increased risk for type 2 diabetes, they wrote. 

Diabetes (illustrative) (credit: INGIMAGE)

Previous research

The researchers previously found that people with irregular sleep schedules are at higher risk of developing diabetes and cardiovascular disease. People with evening chronotypes are more likely to have erratic sleep patterns. For this study, they wanted to understand the relationship between chronotype and diabetes risk and looked at the role of lifestyle factors.

The team analyzed data from 63,676 middle-aged female nurses from the Nurses’ Health Study II collected from 2009 to 2017 and included self-reported chronotype (the extent to which participants perceived themselves to be an evening person or a morning person), diet quality, weight and body mass index, sleep timing, smoking behaviors, alcohol use, physical activity, and family history of diabetes. The team determined diabetes status from the participants’ self-reports and medical records.

The Nurses’ Health Study II is among the most extensive investigations into risk factors for major chronic diseases in women. One of the study’s strengths is its regular follow-up of study participants and repeated assessment of health and lifestyle factors.

About 11% of participants reported having a “definite evening” chronotype, and 35 % as having a “definite morning” chronotype. The remaining population – about half – were labeled as “intermediate,” meaning they either identified as being neither a morning nor evening type or as being only slightly more one than the other.

The evening chronotype was associated with a 72% increased risk for diabetes before accounting for lifestyle factors. After accounting for lifestyle factors, evening chronotype was associated with a 19% increased risk of diabetes. Only six percent of those in the study with the most healthful lifestyles were evening chronotypes. Among those with the least healthy lifestyles, a quarter were evening chronotypes.

Evening chronotypes were also more likely to drink alcohol

Those with evening chronotypes were more likely to drink alcohol in higher quantities, have a low-quality food diet, get fewer hours of sleep per night, currently smoke, be overweight and do little or no physical activity.“When we controlled for unhealthful lifestyle behaviors, the strong association between chronotype and diabetes risk was reduced but remained, which means that lifestyle factors explain a notable proportion of this association,” said Kianersi. 

“When chronotype was not matched with work hours, we saw an increase in type-2 diabetes risk,” Huang added. “That was another interesting finding suggesting that more personalized work scheduling could be beneficial.”