World Diabetes Day: The little-known link between sleep apnea and diabetes

This is what a 2016 article published in the medical journal Diabetes Spectrum, studying research on the link between Obstructive Sleep Apnea (OSA) and Type 2 Diabetes, observed: “Obstructive sleep apnea (OSA) alters glucose metabolism, promotes insulin resistance, and is associated with development of type 2 diabetes...However, chronic exposure to intermittent hypoxia and other pathophysiological effects of OSA affect glucose metabolism directly, and treatment of OSA can improve glucose homeostasis.”

Simply put, it indicts sleep apnea as a potential cause of Type 2 diabetes mellitus. Sleep apnea is a condition when the muscles in the back of the throat relax too much during sleep, causing the upper airways to collapse and the sleeper to periodically stop breathing for a few seconds at a time, till the brain senses the impaired breathing and causes the sleeper to wake up briefly--often the period of awakening is so short that the sleeper doesn’t have any memory of it. Many snorers, though not all, suffer from sleep apnea -- if you’ve noticed someone whose snoring is punctuated by brief periods of silence and they seem to snore more when they are sleeping on their back, it might be a good idea to get them tested for sleep apnea.

While OSA has long been understood to cause daytime sleepiness and drowsiness, leading to impaired cognitive function and even, possibly, cardiovascular issues like high blood pressure, the link between the condition and type 2 diabetes has been studied only in the past few years. “There have been several clinical research studies to prove that there is an association between sleep apnea and diabetes. One of the studies showed that as many as 48% people diagnosed with type 2 diabetes have also been diagnosed with sleep apnea. It may be presumed that OSA and Type 2 DM has an association but enough data is not available to implicate OSA as causative of Type 2 DM,” says Dr Sibasish Dey, Head, Medical Affairs, Asia, and Latin America, ResMed.

In order to understand the relationship between sleep apnea and diabetes, there are two terms that we need to be familiar with: glucose intolerance and insulin resistance, says Dr Dey. Since OSA causes sleep fragmentation and intermittent hypoxia (lower than optimal levels of oxygen in the blood), it can result in oxidative stress, higher circulation of inflammatory cells, and an increase in the levels of a hormone called leptin. All these factors, in turn, cause insulin resistance, which is the primary cause of Type 2 diabetes mellitus, he explains. “Under such circumstances, our body cells are unable to absorb blood glucose efficiently, resulting in higher sugar levels in our blood stream. This is glucose intolerance,” he adds.

There is not enough evidence to show that all patients who suffer from sleep apnea will eventually develop diabetes or vice-versa. However, there is evidence that the treatment of OSA in a diabetic individual does have some benefits, such as improving insulin efficiency and thereby taking blood glucose levels closer to optimal levels. The International Diabetes Federation (IDF) has recognized that all individuals with type 2 DM should consider being screened for sleep apnea. “We should be aware of signals and triggers that our body is giving us. If you are experiencing morning headaches, tiredness even after 8 hours of sleep, and snoring, you must conduct a home sleep test or consult a sleep specialist and find out if you have sleep apnea and get it treated,” says Dr Dey.

Given the prevalence of diabetes in India, why is its link with sleep apnea not so well-known or treated more aggressively? After all, as a study on respiratory medicine published in The Lancet in 2019 found, an estimated 5.4% of all Indians between the age group of 30-69 (28.8 million) have moderate to severe sleep apnea. “Sleep disorders by themself are not given much importance in India, given that we have only 300 sleep labs in a country with 1.3 billion people. Currently, insomnia is one of the most prominent sleep disorders and yet people do not pay attention and consider going to a sleep specialist and getting appropriate treatment. Similarly, snoring is one of the most important symptoms of sleep apnea, but in India, it is considered normal to snore. People do not look at it as a medical condition that needs treatment,” says Dr Dey.

The National Health Policy of India, revised in 2017, fails to address the critical issue of the requirement of adequate sleep for the population as a whole, which may influence the public health statistics related to sleep disorders in India. “A comprehensive national sleep policy is the need of the day,” says the doctor.