Irregular sleep has been linked to type 2 diabetes risk, though this effect was reduced when data was adjusted for obesity, comorbidities, and lifestyle factors.
Researchers from Boston, M.A., and Manchester, the U.K, found that individuals with the most variability in how much they slept each night, were 59% more likely to develop diabetes over a 7.5-year follow-up than those whose sleep pattern was the most consistent.
The results were published in Diabetes Care.
Risk increases as sleep becomes more inconsistent
To investigate the link between irregular sleep and diabetes risk, researchers used UK Biobank data, gaining permission to use the data of 84,421 participants for this study. Sleep data was available as participants had been invited to wear an accelerometer, a device that captures activity levels, much like a fitness watch, for seven days, at some point between 2013–2015.
The participants had a mean age of 62 and researchers also used genetic data held on individuals by the Biobank to calculate polygenic risk scores for diabetes, using known genetic risk variants for the condition.
The researchers discovered that participants with a sleep duration deviation of between 31 and 45 minutes from their average, had a 15% increased risk of diabetes compared with those whose sleep duration deviated by 30 minutes or less. Those with the most variability, with a sleep duration deviation of 91 minutes or more had a 59% increased risk, after adjusting for age, sex, and race.
The researchers also analyzed differences in sleep duration of over and under 60 minutes and found a 34% increased risk for those who had a difference of over 60 minutes, but this decreased to 11% when data was adjusted for lifestyle, comorbidities, environmental factors, and adiposity.
The cohort was 97% white, and over 45% had a college degree, both of which are unrepresentative of the U.K. population as a whole.
How sleep affects hormones
The authors did not look at the mechanisms underpinning the link they discovered in this prospective cohort study but explained it may be due to irregular sleep patterns disrupting circadian rhythms. They suggested this unstable circadian cycle could interfere with glucose metabolism and lead to reduced insulin sensitivity.
They looked at the effect of sleep variation on diabetes risk as there is increasing evidence sleep variation can have an impact on metabolic health. Sleep duration, sleep quality, and other sleep disturbances have been linked to diabetes risk in previous studies.
Sudha Tallavajhula, MD, neurologist, and sleep medicine physician at UTHealth Houston who was not involved in the research, told Medical News Today:
“In both clinical and research goals, we see that sleep disorders change hormonal pathways. During sleep, the whole endocrine axis, that is the pathway that encompasses all hormonal function, undergoes a cyclical change. Hormones that are not required during sleep, because of low activity, for example, insulin and steroids are usually reduced. Their levels rise in the mornings, to meet demand for activity. Impaired sleep contributes to poor utilization of glucose and fat.”
It wasn’t clear if one caused the other and the issue could be bidirectional, she explained.
Circadian rhythm and type 2 diabetes risk
Previously the researchers looked at the role of circadian rhythm on type 2 diabetes risk. For this study published in the Annals of Internal Medicine, they looked at the Nurses’ Health Study II, and discovered that ‘night owls’ were more likely to develop type 2 diabetes than ‘early birds’.
Chronotype, or whether people find they need to go to bed and wake up earlier or later, is linked to an individual’s circadian rhythm, which describes a person’s body clock. It is thought to be affected by light levels, among other things.
The researchers also found that ‘night owls’ were more likely to report unhealthy lifestyle behaviors. When data were adjusted for these factors, the effect of chronotype was still there but attenuated.
Although the study did not elucidate underlying mechanisms, it affirmed the importance of healthy routines for the prevention of type 2 diabetes, Becca Anne Krukowski P.h.D, professor of public health sciences at the University of Virginia School of Medicine, who was not involved in the research, told MNT.
“Maintaining healthy routines– including consistent sleep but also regular physical activity and healthy, balanced meals–contribute to overall health and likely prevention of type 2 diabetes,” she said.