People who go to bed late and wake up late have more chance of developing diabetes than those who are “early to bed and early to rise”, say researchers in one of the largest investigations into risk factors for major chronic diseases in women.
Research from Brigham and Women’s Hospital, a founding member of the Mass General Brigham healthcare system, found that people with later sleep and wake times had less healthy lifestyles, with evening “chronotype” – going to bed late and waking up late – being linked to a 19% increased risk of diabetes, after accounting for lifestyle factors
Their results are published in the Annals of Internal Medicine.
“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 in the Brigham’s Channing Division of Network Medicine (CDNM).
“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 researchers had previously found that people with more irregular sleep schedules had a higher risk of diabetes and cardiovascular disease and that people with evening chronotypes were more likely to have irregular sleep patterns, and for this study, wanted to understand the relationship between chronotype and diabetes risk, looking at lifestyle factors as well.
They analysed data from 63 676 female nurses from the Nurses’ Health Study II collected from 2009-2017, 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, 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, a joint effort between the Brigham’s CDNM and Harvard TH Chan School of Public Health, is among the largest investigations into risk factors for major chronic diseases in women. One of its strengths is its regular follow-up of study participants and repeated assessment of health and lifestyle factors.
Of the participants, 11% reported having a “definite evening” chronotype and about 35% reported having “definite morning” chronotype. The remaining population, around half, 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% 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.
Among those in the study with the healthiest lifestyles, only 6% had evening chronotypes. Among those with the unhealthiest lifestyles, 25% were evening chronotypes.
Those with evening chronotypes were found to be more likely to drink alcohol in higher quantities, have a low-quality food diet, get less hours of sleep per night, currently smoke, and have weight, BMI, and physical activity rates in the unhealthy range.
“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,” said first author Sina Kianersi, PhD, a postdoctoral research fellow in the CDNM.
They 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.
“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 personalised work scheduling could be beneficial.”
The Nurses’ Health Study comprises mainly white female nurses. Future investigations will be needed to determine if the patterns detected here are consistent across populations.
The study’s results point to associations but cannot determine causality: it’s possible that other factors may contribute to a person’s chronotype, propensity for unhealthy habits and risk of diabetes.
Next, the researchers plan to investigate genetic determinants of chronotype and its association with cardiovascular disease, in addition to diabetes, in larger, more diverse populations.
“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,” Kianersi said.
Study details
Chronotype, Unhealthy Lifestyle, and Diabetes Risk in Middle-Aged US Women
Sina Kianersi, Yue Liu, Marta Guasch-Ferré, Susan Redline, Eva Schernhammer, Qi Sun, Tianyi Huang.
Published in the Annals of Internal Medicine on 12 September 2023
Abstract
Evening chronotype may promote adherence to an unhealthy lifestyle and increase type 2 diabetes risk.
Objective
To evaluate the role of modifiable lifestyle behaviours in the association between chronotype and diabetes risk.
Design
Prospective cohort study.
Setting
Nurses’ Health Study II.
Participants
A total of 63 676 nurses aged 45 to 62 years with no history of cancer, cardiovascular disease, or diabetes in 2009 were prospectively followed until 2017.
Measurements
Self-reported chronotype using a validated question from the Morningness-Eveningness Questionnaire. The lifestyle behaviours that were measured were diet quality, physical activity, alcohol intake, body mass index (BMI), smoking, and sleep duration. Incident diabetes cases were self-reported and confirmed using a supplementary questionnaire.
Results
Participants reporting a “definite evening” chronotype were 54% (95% CI, 49% to 59%) more likely to have an unhealthy lifestyle than participants reporting a “definite morning” chronotype. A total of 1925 diabetes cases were documented over 469 120 person-years of follow-up. Compared with the “definite morning” chronotype, the adjusted hazard ratio (HR) for diabetes was 1.21 (CI, 1.09 to 1.35) for the “intermediate” chronotype and 1.72 (CI, 1.50 to 1.98) for the “definite evening” chronotype after adjustment for sociodemographic factors, shift work, and family history of diabetes. Further adjustment for BMI, physical activity, and diet quality attenuated the association comparing the “definite evening” and “definite morning” chronotypes to 1.31 (CI, 1.13 to 1.50), 1.54 (CI, 1.34 to 1.77), and 1.59 (CI, 1.38 to 1.83), respectively. Accounting for all measured lifestyle and sociodemographic factors resulted in a reduced but still positive association (HR comparing “definite evening” vs. “definite morning” chronotype, 1.19 [CI, 1.03 to 1.37]).
Limitations
Chronotype assessment using a single question, self-reported data, and homogeneity of the study population.
Conclusion
Middle-aged nurses with an evening chronotype were more likely to report unhealthy lifestyle behaviours 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.
See more from MedicalBrief archives:
Early rising linked to greater well-being — large genomic analysis
Minimum of five hours’ sleep for good health and longevity – UK study
Accelerometer-derived sleep timing and CVD — UK Biobank cohort study
‘Night owls’ risk dying sooner than ‘larks’