It is sometimes difficult to tease apart the consequences of obesity and consequences from sleep apnea. Because being overweight is the biggest risk factor for developing sleep apnea (at least in the young to middle-aged population), more often than not, the apnea sufferer is over what is considered a healthy weight. This makes it complicated when trying to decide whether body weight or sleep apnea worsen problems such as hypertension, depression, or diabetes. In particular, insulin resistance and insulin sensitivity, two of the issues associated with diabetes, are associated with both excess weight and also sleep apnea. So how can we get to the bottom of whether apnea affects these things independently of weight?
A research team cleverly devised a method of testing out this question. By examining a group of subjects with sleep apnea but without obesity, a direct relationship could be examined without that messy weight factor getting in the way. In this study, 38 men who were considered non-obese underwent an overnight sleep study in order to assess the presence and severity of sleep apnea. Physiological samples were taken as well to measure insulin resistance and insulin sensitivity.
Results showed that these subjects did show a relationship between waist size and insulin resistance/sensitivity and also the average amount of oxygen in their blood during the night. Oxygen levels in the blood are decreased by apneas and hypopneas throughout the night, basically because we lose oxygen in our entire body when we stop breathing. Interestingly, when taking into account other factors that could affect insulin resistance and sensitivity, the strongest predictor of dysfunction was the amount of oxygen in the blood (caused by sleep apnea) and not body weight1.
In this unique population of non-obese sleep apnea sufferers (who do not represent a typical population, by the way), insulin resistance and sensitivity was related more to sleep apnea consequences than to body weight. This study sheds light on the consequences of untreated sleep apnea, which are harmful to the body even in absence of obesity. To sum up, sleep apnea can still be present without excess weight, and consequences are seen across the board of apneics. Luckily, treatment works across the board as well.
References:1. Borel AL, Monneret D, Tamisier R, Baguet JP, Faure P, Levy P, Halimi S, Pépin JL. The severity of nocturnal hypoxia but not abdominal adiposity is associated with insulin resistance in non-obese men with sleep apnea. PLoS One. 2013;8(8):e71000. doi: 10.1371/journal.pone.0071000.