We've seen a great deal of research that indicates a strong link between sleep disorders and Type 2 diabetes. Now there's evidence that this link may be genetic. A new study reveals scientists have found a relationship between a gene associated with the "sleep hormone" melatonin, and the risk of developing Type 2 diabetes.
A group of researchers from France, Canada and the UK have discovered a link between the risk of Type 2 diabetes and several mutations in the body's melatonin receptor gene, a gene known as MTNR1B. Working with a group of 7,632 European women—3,186 of whom already had Type 2 diabetes—researchers found:
• 40 different—and rare—mutations to the melatonin receptor gene associated with varying degrees of increased risk of Type 2 diabetes.
• 4 of these rare mutations actually caused a total loss of function in the melatonin receptor gene
• Analyzing these 4 mutations in an additional 11,854 people, researchers found that the presence of any single one was associated with a significantly increased risk of Type 2 diabetes-a risk as much as six times higher than average.
Previous research had already established a link between diabetes risk and other, more common mutations to the melatonin receptor gene MTNR1B. This new study has revealed both a wider range of mutations to the gene that can affect diabetes risk, as well as the elevated risk among the 4 rare mutations that disable the receptor gene altogether.
Melatonin plays a critical role in synchronizing the body's biological clock, and regulating its sleep-wake cycle. The rise-and-fall cycle of melatonin release is critical to our ability to sleep at night. A disruption in the body's ability to produce melatonin will lead to disordered sleep.
There's also evidence that disturbances to melatonin production may affect the body's insulin levels. Insulin resistance—the body's inability to use insulin effectively—is a fundamental characteristic of Type 2 diabetes. When functioning normally, the body produces just the amount of insulin it needs to help cells absorb glucose from the blood stream. Disturbances to insulin levels can lead this finely-tuned process to go awry.
This is complicated stuff. These latest results also raise questions, and remind us just how much we still have to learn about the body's biological sleep functions and the relationship to diabetes, as well as other chronic diseases.
What we do know is that there is a compelling and growing body of evidence that sleep—and it's biological and genetic underpinnings—plays a significant role in determining risk for diabetes. Recent studies have shown:
• Poor sleep is linked to both weight gain and insulin resistance in healthy adults
• Sleeping fewer than 6 hours increases the risk of developing Type 2 diabetes. And the less sleep you get, the greater the risk-this same study found sleeping fewer than 5 hours elevates diabetes risk even further
• Just one night of sleeping only 4 hours—rather than the recommended 7 to 8—can trigger insulin resistance.
Type 2 diabetes is most often thought of as a disease related to diet and exercise. There's no question that poor diet and a sedentary lifestyle increase risk for diabetes. But often sleep is overlooked as a risk factor. When assessing risk for developing diabetes, disordered sleep should be considered as seriously as a diet full of fatty, starchy and processed foods, or a lack of physical activity. Too often, I'm afraid, this is not the case. In the meantime, all of us—doctors and patients both—need to give more attention to sleep as a risk factor for diabetes, and an overall indicator of general health.
Michael J. Breus, PhD
The Sleep DoctorTM