‘Night owls’ are more likely than ‘early birds’ to develop diabetes, according to a new study.
American researchers found people who stay up all hours and wake up late are at a 19 per cent greater risk.
Corresponding author Dr Tianyi Huang, an associate epidemiologist at Brigham and Women’s Hospital, 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 research team previously found that people with more irregular sleep schedules are at higher risk of developing diabetes and heart disease - and that people with evening chronotypes are more likely to have irregular sleep patterns.
For the new study, they wanted to understand the relationship between chronotype and diabetes risk and looked at the role of lifestyle factors as well.
The team analysed data from more than 63,000 female nurses and included self-reported chronotype - the extent to which the participants perceived themselves to be an evening person or a morning person, as well as diet quality, weight and body mass index (BMI), sleep timing plus drinking and smoking habits.
Around one in nine of the participants reported having a “definite evening” chronotype while just over a third (35 per cent) reported having ‘definite morning’ chronotype.
The rest were labelled 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 per cent increased risk for diabetes before accounting for lifestyle factors.
After accounting for lifestyle, evening chronotype was associated with a 19 per cent increased risk of diabetes.
Among those in the study considered to have the healthiest lifestyles, only six per cent had evening chronotypes.
But among those with the unhealthiest lifestyles, 25 per cent were evening chronotypes, according to the findings published in the Annals of Internal Medicine.
Those with evening chronotypes were found to be more likely to drink alcohol in higher quantities, have a low-quality food diet, get fewer hours of sleep per night, smoke, and have weight, BMI, and physical activity rates in the “unhealthy” range.
First author Dr Sina Kianersi said: “When we controlled for unhealthy lifestyle behaviours, 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.”
The research team also found the association between evening chronotype and diabetes risk only in those nurses who worked day shifts and not those who worked overnight shifts.
Dr Huang said: “When chronotype was not matched with work hours we saw an increase in type 2 diabetes risk.
“That was another very interesting finding suggesting that more personalised work scheduling could be beneficial.”
The team now plan to investigate genetic determinants of chronotype and its association with heart disease as well as diabetes.
Dr Kianersi added: “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.”
