Staying Up Late Tied to Increased Diabetes Risk
By BRIGHAM AND WOMEN'S HOSPITAL
A new study has an important message for
people who consider themselves night owls. Investigators 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 and were at greater risk of developing diabetes than those with
early-bird sleep habits. Their results were published on September 12 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.
“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 Study’s Findings
The researchers previously found that people
with more irregular sleep schedules are at higher risk of developing diabetes
and cardiovascular disease and that people with evening
chronotypes are more likely to have irregular sleep patterns. For this study,
they wanted to understand the relationship between chronotype and diabetes risk
and looked at the role of lifestyle factors as well.
The team analyzed 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 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, a joint effort
between the Brigham’s Channing Division of Network Medicine and Harvard T.H.
Chan School of Public Health, is among the largest 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.
Approximately 11 percent of participants
reported having a ‘definite evening’ chronotype and about 35 percent reported
having ‘definite morning’ chronotype. The remaining population, around 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 percent increased risk for diabetes before accounting for lifestyle factors. After accounting for lifestyle factors, evening chronotype was associated with a 19 percent increased risk of diabetes.
Among those in the study with the
healthiest lifestyles, only 6 percent had evening chronotypes. Among those with
the unhealthiest lifestyles 25 percent 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.
Implications and Further Research
“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.
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 personalized work
scheduling could be beneficial.”
The Nurses’ Health Study is comprised mainly
of 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,” says Kianersi.
Reference: “Chronotype, Unhealthy Lifestyle,
and Diabetes Risk in Middle-Aged U.S. Women: A Prospective Cohort Study” by
Sina Kianersi, DVM, PhD; Yue Liu, MD; Marta Guasch-Ferré, PhD; Susan Redline,
MD, MPH; Eva Schernhammer, MD, DrPH; Qi Sun, MD, ScD and Tianyi Huang, ScD,
MSc, 12 september 2023, Annals of Internal Medicine.
DOI:
10.7326/M23-0728
Funding: This study was funded by the National
Institutes of Health (U01CA176726 and R01HL155395).
