“Night Owls” at greater risk of diabetes

Persons with an evening ‘chronotype”’ (going to bed late and waking up late), have a 19 percent increased risk of diabetes compared to those with a morning chronotype, and after accounting for lifestyle factors. These findings were published on Sept. 11, 2023 in the Annals of Internal Medicine.

“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 and Women’s Hospital’s Channing Division of Network Medicine in Boston, USA.

The investigators analyzed data from 63,676 female nurses from the Nurses’ Health Study II collected from 2009-2017. The data included self-reported chronotype (self-perception as 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 researchers determined diabetes status from the self-reports and medical records.

Approximately 11 percent of the subjects reported having a ‘definite evening’ chronotype, and about 35 percent reported having ‘definite morning’ chronotype. The remaining population, around half, were labeled as ‘intermediate,’ with no clear chronotype.

The researchers reported that, before accounting for lifestyle factors, an evening chronotype was associated with a 72 percent increased risk for developing diabetes compared to a morning chronotype.

After accounting for lifestyle factors, an evening chronotype was still associated with a 19 percent increased risk of diabetes.

Corresponding author Tianyi Huang, MSc, ScD, an associate epidemiologist in the Brigham’s Channing Division of Network Medicine said, ““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. 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.”

The authors concluded, “Middle-aged nurses with an evening chronotype were more likely to report unhealthy lifestyle behaviors and had increased diabetes risk compared with those with a morning chronotype. Accounting for BMI, physical activity, diet, and other modifiable lifestyle factors attenuated much but not all of the increased diabetes risk.”