“Chronotype, or circadian preference, refers to a person’s preferred timing of sleep and waking and is partly genetically determined so it may be difficult to change,” said corresponding author Tianyi Huang, MSc, ScD, an associate epidemiologist at Brigham’s Channing Division of Network Medicine. “People who think they are ‘night owls’ may need to pay more attention to their lifestyle because their evening chronotype may add increased risk for type 2 diabetes.”
For this study, data was analyzed from 63,676 female nurses who were enrolled in the Nurses’ Health Study which included self-reported chronotype, diet, weight, BMI, sleep habits, smoking history, alcohol use, exercise levels, and family history of diabetes. 11% of the participants reported having an evening type chronotype and 35% reported having a morning chronotype, the rest of the participants were labeled as intermediate- meaning they didn’t identify as with chronotype.
According to the researchers, the Night Owls were associated with a 72% increased risk for diabetes before accounting for lifestyle factors, this dropped to 19% after they were taken into account. Among those with the healthiest lifestyle, only 6% were evening chronotypes, but among those with the unhealthiest lifestyles, 25% were Night Owls who were found to be more likely to have a bad diet, carry extra weight, get less sleep, smoke, drink more alcohol, and have BMI and physical activity rates in the unhealthy range.
“When we controlled for unhealthy lifestyle behaviors, the strong association between chronotype and diabetes risk was reduced but still remained, which means that lifestyle factors explain a notable proportion of this association,” said first author Sina Kianersi, DVM, PhD, a postdoctoral research fellow in the Brigham’s Channing Division of Network Medicine.
“When chronotype was not matched with work hours we saw an increase in type 2 diabetes risk,” said Huang. “That was another very interesting finding suggesting that more personalized work scheduling could be beneficial.”
“If we are able to determine a causal link between chronotype and diabetes or other diseases, physicians could better tailor prevention strategies for their patients,” says Kianersi.
