The epidemic of diabetes in the United States is being fueled by multiple medical, social, and demographic forces. Among those forces is sleep apnea, which is now recognized as a major contributor to the development of diabetes. In sleep apnea, people stop breathing for periods of 10 seconds or more while they’re asleep, sometimes hundreds of times a night. These periods without breathing, known as apneas, both disrupt sleep and lower the level of oxygen in the blood. When breathing restarts after an apnea, it is generally with a loud gasp or snort.
People with sleep apnea are more than twice as likely to have diabetes as those who don’t. In addition, 50% of men with Type 2 diabetes have sleep apnea, compared to an estimated 4% of middle-aged men overall. Several recent studies have suggested that insulin sensitivity—the body’s ability to respond to insulin—decreases as sleep apnea severity increases.
A high body-mass index (BMI, a measure of body mass that takes both height and weight into consideration) is a risk factor for both sleep apnea and diabetes.
Link to diabetes
A number of mechanisms are thought to be involved in the interaction between sleep apnea and diabetes, including the following:
Stress response. Repeated arousals from sleep and interruptions in the delivery of oxygen to the body’s tissues caused by sleep apnea lead to the stress, or “fight or flight,” response. In the short term, the stress response causes increased heart rate and increased blood pressure. When it occurs repeatedly over time, it is a risk factor in the development of chronic high blood pressure, insulin resistance (one of the hallmarks of Type 2 diabetes), and cardiovascular disease.
Increased cortisol levels. Sleep deprivation or fragmentation may increase blood levels of cortisol (a stress hormone), which in turn raises both blood glucose levels and insulin secretion.
Inflammatory response. Sleep apnea is associated with both local inflammation of the upper airways and systemic inflammation, or inflammation of the endothelium (the lining of the blood vessels) and other organ systems. Similarly, obesity is associated with systemic inflammation, as well as dyslipidemia (unhealthy levels of cholesterol and triglycerides in the blood). Both systemic inflammation and dyslipidemia are associated with atherosclerosis and cardiovascular disease.
Lack of oxygen. Repeated episodes of oxygen deprivation may also cause the release of proinflammatory cytokines—proteins involved in the body’s immune response—that are associated with glucose intolerance (higher-than-normal blood glucose levels) and insulin resistance.
Link to metabolic syndrome
Both Type 2 diabetes and sleep apnea have also been linked to the metabolic syndrome, which is also sometimes called syndrome X. The metabolic syndrome is defined by a set of five medical conditions that together double the risk of atherosclerosis and confer a fivefold increase in the risk of diabetes. The five conditions are elevated fasting glucose levels, abdominal fat, high blood pressure, high triglycerides, and low high-density lipoprotein (HDL, or “good”) cholesterol. There is broad overlap between the suspected mechanisms of interaction between sleep apnea and diabetes and the features of the metabolic syndrome.
