I have been treating snoring and sleep apnea patients for more than three decades. As a surgeon I try to do operate on these patients, but those who are unable to undergo surgery or unwilling for surgery I prescribe CPAP machine (Continuous Positive Airway Pressure).I must say CPAP is a wonderful machine having its advantages and disadvantages.
If you think that starting CPAP for obstructive sleep apnea would help you to lose weight, then read the recent study published in the Journal of Clinical Sleep Medicine find that this is not the case. In fact, using CPAP is found to cause statistically significant mild weight gain compared to sham CPAP users in this prospective randomized study.
After treating OSA patients over these years by CPAP therapy, I have heard many patients complaining of gaining weight and some say losing weight. Initially I thought patient who gets good sleep should lose weight and poor sleep should promote weight gain.
I read conflicting results on CPAP use and weight status. There are a number of possible reasons why this can happen, but no one is absolutely sure. Of course, I’ve also had many patients who did lose significant weight after CPAP, which only adds to my confusion.
So I thought write this article based on my experience, but I stress that more studies need to be done in this subject. Physicians should stress an active weight loss plan and not assume CPAP alone will lead to weight loss. A larger, prospective study may help clarify these findings.
Obesity and Sleep Apnea
Obesity is causally linked to OSA. Why weight change after treatment with CPAP is not yet clear. Although hormonal changes would predict weight gain or loss, decreasing energy expenditure by reducing work of breathing would predict weight gain.
Metabolic Response in OSA
Sleep Apnea and Insulin Resistance
Obstructive sleep apnea (OSA) is characterized by sleep-related airway obstructions that produce apnea. These events provoke arousals and cause oxygen desaturations and heightened sympathetic activity during sleep and waking hours that may play a role in the development of insulin resistance. Obesity is a strong risk factor for OSA and both obesity and OSA are associated with increased insulin resistance and diabetes.
Obstructive sleep apnea (OSA) is associated with obesity, insulin resistance (IR) and diabetes. Continuous positive airway pressure (CPAP) rapidly mitigates OSA in obese subjects but its metabolic effects are not well recognized.
CPAP effectively improved hypoxia. However, subjects had increased insulin and IR. Fasting ghrelin decreased significantly while leptin, adiponectin and resistin remained unchanged. Changes in body weight directly correlated with changes in insulin and IR. Ghrelin changes inversely correlated with changes in IR but did not change as a function of weight.
Hormonal Changes
Hormones involved in the regulation of body weight and glucose metabolism include ghrelin, leptin, adiponectin and resistin. Ghrelin is an orexigenic hormone and it has been proposed as a cause of increased appetite and obesity .
Ghrelin is an appetite-increasing hormone postulated as a contributor to OSA-associated obesity as ghrelin levels were elevated .Leptin is secreted by adipocytes in proportion to body fat, being elevated in obese individuals and decreasing with weight loss. Adiponectin is decreased in obese individuals and in those with type 2 diabetes. It is thought to play a role in many of the metabolic complications suffered by these patients including metabolic syndrome and cardiovascular disease. However, its role in patients with OSA remains controversial.
CPAP treatment induced a decrease in fasting ghrelin levels, although body weight increased in most subjects. Adipokines such as leptin, adiponectin and resistin also appear to be influenced much more by adiposity rather than hypoxia. The fact that these adipokines remain unchanged after 6 months of CPAP treatment suggests that they are unlikely to play an important role in the development of the metabolic complications seen in the setting of OSA.
CPAP and Body Weight
CPAP alone may not reduce body weight and that in the face of weight gain CPAP treatment may not reduce insulin resistance and leptin or increase adiponectin in obese subjects. It is possible that CPAP use has only a transient effect on insulin sensitivity and that changes in body weight are a much more important factor in the long-term regulation of insulin sensitivity.
Hypothyroidism and Sleep Apnea
Hypothyroidism is a condition where the body produces insufficient amounts of thyroid hormones, the most important of which is Thyroxine. Hypothyroidism produces many complications in the body including fatigue, loss of muscle tone, weight gain and sleep apnea, among others. It is thought that the symptoms of Hypothyroidism (swollen tongue and soft tissue in the mouth and throat) are responsible for the Sleep Apnea. As stated earlier, another frequent symptom of hypothyroidism is obesity, which can also cause sleep apnea.
This similarity in presenting symptoms raises a question on how patients with suspected OSA should be evaluated.
 Fluid retention may lead to pulmonary edema and cardiac failure
Complications of sleep apnea may lead to cardiac failure in some patients. Patients with hypertension are already at risk of developing cardiac failure and it is thought sleep apnea may increase the likelihood of this occurring. This in turn may result in gain in weight in some CPAP users.
Conclusion
It’s all may be confusing to patients. I would recommend CPAP users must monitor their weight regularly and if there is substantial gain, then they should consult the physician. They also should start workout programmes to burn excess calories they saved overnight by decreased energy expenditure during work of breathing which is taken over by CPAP machine.
