A cross-sectional study led by researchers from Nantong University in China and published in BMJ Open Diabetes Research & Care found that just under 7.32 hours of sleep was ideal for the estimated glucose disposal rate.
The team said this was associated with improved estimated rates, but increasing these hours to or above this amount was associated with worse estimated glucose disposal rates.
Medical News Today reports that further analysis suggested that moderate weekend catch-up sleep may be helpful for insulin resistance, but possibly harmful for people already getting enough sleep.
Experts have always been interested in finding the optimal amount of sleep for different aspects of health, with one particular area of interest being how sleep relates to metabolic syndrome, a cluster of conditions that increase risk for serious diseases like coronary heart disease.
One recent study explored how sleep duration relates to insulin sensitivity, which can be a driving factor for type 2 diabetes.
The authors said that in metabolic syndrome, the body is less responsive to insulin, and that a little less than seven and a half hours of sleep was linked to the best level of insulin sensitivity, but for people having less sleep than this, catching one to two hours’ more sleep on the weekend appeared to help insulin sensitivity the most.
What’s the ideal amount of sleep?
For this cross-sectional study, researchers gathered their data from the National Health and Nutrition Examination Survey.
They looked at how sleep was related to estimated glucose disposal rate. This measurement takes into account haemoglobin A1C, high blood pressure, and waist circumference, which also reflects insulin resistance. An increased estimated glucose disposal rate (eGDR) would indicate less insulin resistance.
They also examined how catching up on sleep over the weekend played into things.
Researchers excluded certain individuals, such as pregnant women and people under 20, ultimately including 23 475 participants in their analysis. They had access to participants’ answers to how much they typically slept on weekdays. For about 11 000 participants, they also had data on about how many hours they slept on weekends.
They then broke down the amounts of weekend catch-up sleep into four categories, ranging from no weekend catch-up sleep to more than two hours of weekend catch-up sleep.
Seven and a half hours of sleep was the median for sleep during the week, while eight hours was the median over the weekend.
Researchers identified a non-linear relationship between weekday sleep and eGDR, specifically an inverted U-shape. They estimated the turning point to be about 7 hours and 19 minutes of sleep, or 7.32 hours. Up to this amount, getting more sleep was linked to higher eGDR. But once people slept 7 hours and 19 minutes or more, getting even more sleep was linked to lower eGDR.
When they looked at different groups separately, the results were mostly the same. The connection between sleeping 7 hours and 19 minutes or more and having lower eGDR was especially strong for women, aged 40 to 59, and people with a body mass index (BMI) of 30 or higher.
How does weekend catch-up sleep change things?
Next, researchers looked at how weekend catch-up sleep came into play. They found that for people with sleep duration of less than 7.32 hours, getting up to two hours of extra sleep on the weekend was linked to increased eGDR levels.
The greatest benefit was seen in those who were in the more than one hour and up to two hours of extra sleep group. For participants who were getting at least 7.32 hours or more, weekend catch-up sleep didn’t have a significant link to eGDR.
Further analysis revealed that getting more than two hours of weekend catch-up sleep moderated the negative link between the amount of sleep during the week and eGDR, compared with no weekend catch-up sleep. This suggests that getting higher amounts of weekend catch-up sleep could ultimately worsen blood sugar control.
With additional analysis, the authors suggest that getting excessive amounts of weekend catch-up may not be “recommended for optimal health outcomes”. They did find that for people getting less than 7.32 hours of sleep, the ideal amount of weekend catch-up sleep was 1.16 hours, and for people getting at least 7.32 hours, the amount was 1.12 hours.
David Cutler, MD, board certified family medicine physician at Providence Saint John’s Health Centre in California, who was not involved in the study, noted that the study showed that getting enough sleep during the week was important for health.
“An interesting aspect of this study’s findings was that while 7.32 hours was found to be the ideal sleep duration, getting weekend catch-up sleep when a sleep debt occurred was only beneficial in moderation, not when it exceeded two hours. The take-home message seems to be to get seven to eight hours’ sleep per night and only use the weekends to make up for two hours of lost sleep during the week.”
Does this mean a lack of sleep causes insulin resistance?
This data has some limitations. First, it cannot establish a causal relationship, so the sleep durations don’t necessarily cause insulin resistance, and researchers note that reverse causality is possible. More long-term data will be helpful.
Second, it relies on participant reporting about things like sleep duration, which might not be accurate. Researchers note that reports of sleep on the weekend may have a decrease in accuracy.
They also note that “the proportion of the extreme population in this study is approximately 3.0%”, which could impact the effect size.
It’s also possible that researchers didn’t adjust for important confounders, like sleep quality, and this could have led to residual confounding and ultimately bias. There may also be problems with generalisability, and more work in other countries and populations may be helpful.
Researchers also only had data about weekend sleep for less than half of the participants they analysed. Another challenge was that researchers couldn’t distinguish between sleep that occurred at night and sleep that occurred during the day.
Kaushik Govindaraju, DO, board certified internist with Medical Offices of Manhattan, who was also not involved in the study, noted the following about the limits and possibilities of this research:
“This has major implications for potentially predicting incidence of metabolic syndrome and cardiovascular disease in adults. The limitation is that it excludes pregnant women and those under 20, which limits the findings’ potential utility as a longitudinal predictive measure for young adults and pregnant adults.
“It is interesting to be able to better put into objective scientific parameters why seven to eight hours of sleep serves a true benefit. Furthermore, it gives clinicians objective clinical evidence guidance as to the risks and benefits of napping and ‘catching up’ on sleep during weekends and vacations.”
Consistency most important for healthy sleep
A major emphasis from the study authors is the need for personalised sleep recommendations. They also note that guidelines should encourage consistent sleep rather than trying to catch up on sleep over weekends.
Cutler also noted how addressing sleep could ultimately help address diabetes.“Diet and exercise are major determinants in controlling the development of diabetes. But since poor sleep will often trigger a worse diet and a diminished capacity for exercise, focusing on sleep can target many birds with one stone,” he said.
“While this connection between sleep and diabetes may seem remote, the increasing prevalence of obesity and diabetes in our society should make everyone take notice of any factors which may prevent this major contributor to cardiovascular morbidity and mortality. This is especially true when it is something as cheap, easy, and safe to get as more sleep.”
See more from MedicalBrief archives:
Artificial ‘light at night’ exposure raises diabetes risk – Chinese study
Exposure to light during sleep linked to health risks – Chicago study
Sleep catch-up does not reverse metabolic disruption from sleep loss
Hospitals no place for sleep or rest