Many studies have looked into the correlation between mean (average) sleep duration and mortality risk among the general population.
The inability to sleep a normal 7-8 hours per night may be an indicator of underlying health or a cause of deteriorating health.
Studies have consistently shown an increased risk of death.
- From restricted sleep duration, defined as 5 or fewer hours of sleep per night
- From excess sleep duration, defined as 10 or more hours of sleep per night
Until now, it was not known if these findings held true for those living with type 2 diabetes.
A new study of the relationship between sleep duration and mortality in those living with type 2 provides some answers.
Effects of Sleep Duration on All-Cause Mortality
As part of the survey, participants self-reported their average daily sleep duration.
The researchers then compared these answers with mortality causes among the more than 17,000 participants that died within the nearly 7 year follow-up period. Mortality rates were age-standardised using the age groups of 18–44 years, 45–64 years and 65 years or older.
In respect to all-cause mortality, data collected on non-diabetic participants found a similar pattern as previous studies: both restricted and excess sleep duration was associated with an increased risk of mortality.
A similar but exaggerated pattern was found in participants with diabetes.
People with diabetes who had restricted sleep duration were found to have a 63% increase in all-cause mortality compared to those who got 7 hours of sleep. By comparison, the mortality rate increase for the same sleep duration in people without diabetes was just under 30%.
Those living with diabetes for more than 20 years saw the greatest detrimental effects of restricted sleep.
Excess sleep appeared to have the greatest impact on all-cause mortality in people with diabetes.
People who slept more than 10 hours per day saw a substantial increase in all-cause mortality
- People with diabetes had a 117% increase
- People without diabetes had an 80% increase
Interestingly, type 2’s on oral diabetes medications and/or insulin had a higher overall mortality rate for both excess and restricted sleep durations compared to non-medicated type 2s.
Sleep Duration and CVD Mortality Risk
Those type 2s who died of cardiovascular disease (CVD) were much more likely to sleep over 10 hours per night. However, the CVD mortality type most prominently associated with sleep durations was stroke, with an increased risk of 195% for those who needed excess sleep.
Once again, those being treated with oral diabetes medications or insulin showed the highest increase in CVD mortality risk for both restricted and excess sleep durations.
Duration of diabetes also played a role in CVD risk:
- Those living with T2D for more than 20 years who slept 5 or fewer hours had a 41% increased CVD mortality rate.
- Those living with T2D between 11 and 20 years who slept for 10 or more hours had a 118% increase.
- And those living with T2D for over 20 years who slept for 10 or more hours had a 88% increase.
Sleep Duration and Other-Cause Mortality Risk
In addition to CVD, many other mortality causes were found to be associated with sleep duration in people with diabetes, including kidney disease, Alzheimer’s, cancer, and CLRD.
The association between Alzheimer’s and sleep duration was most pronounced for sleep durations of greater than 10 hours per day. Type 2s diagnosed at a younger age, who had been living with the disease for a longer period of time, and used both oral meds and insulin had the highest increased risk of Alzheimer’s mortality.
Cancer mortality risk was found to be elevated in all type 2s compared to the general population who slept 7 hours per day:
- Those who slept 5 or fewer hours had a 41% increased risk.
- Those who slept 8 hours had a 26% increased risk.
- And those who slept 10 or more hours had a 59% increased risk.
How Excess and Restricted Sleep Duration Increases Mortality Risk
Why sleep duration affects a person’s overall health and mortality risk, specifically for people with diabetes, is still a matter of speculation.
When considering the deleterious effects restricted sleep appears to have on people living with type 2, the researchers were quick to point out the connection between glucose metabolism and insufficient sleep.
- Restricted sleep schedules are associated with a 40% slower glucose clearance rate and higher sympathetic nervous system activity in people without diabetes.
- These factors can aggravate insulin resistance, obesity, and hypertension–all of which are independently associated with a higher mortality rate.
- On the flip side, those with excess sleep duration may be suffering from reduced functioning due to diabetes complications and poor health status, which would already make them more likely to suffer an early death than people who are healthier, and therefore, sleep less.
- Additionally, longer sleep duration is associated with chronic inflammatory responses within the body. Chronic inflammation is known to accelerate the appearance of diabetes complications and make the disease itself harder to control.
While this study may not give us an absolute explanation for how sleep duration contributes to mortality, it certainly does highlight the importance of a normalized sleep pattern with a mean sleep duration of 7 hours per night.
It also, hopefully, will provide incentives for physicians and patients to consider the role sleep plays in our overall health and make discussions concerning sleep and sleep problems much more common.