Scanning through my daily schedule of patients, I noticed Mr. Johnson was on the schedule. I have been following him for over 10 years since diagnosing and prescribing CPAP for his severe obstructive sleep apnea. I last saw him 3 years ago. He was faithful in using his CPAP 100% of the time, and his adherence numbers were perfect, with an average AHI of 1, minimal leaks, and being used 8-9 hours every night. As I entered the exam room and greeted him, I was shocked to see how much weight he had gained (30 pounds) over the past few years.
One of the basic tenets of sleep medicine is that poor sleep leads to weight gain. It naturally follows that sleeping better with CPAP will lead to weight loss. It’s not uncommon to see patients losing weight after sleeping better with CPAP, dental appliances or even after surgery. However, I had seen a few studies over the years showing that a small proportion of people using CPAP may gain some weight, but what I discovered over the past few weeks studying basal metabolic rates and weight loss in relation to CPAP was surprising.
It turns out that overall, CPAP use has been found to increase weight significantly, in proportion to how long you use CPAP. The more hours you use CPAP every night and the more number of years, the higher the amount of cumulative weight gain.
- Researchers from Harvard and Stanford Universities found that patients randomized to receive CPAP for 6 months gained 0.77 pounds, whereas people on sham CPAP lost 1.5 pounds. Of note, people who more highly compliant (using more than 4 hours/night, at least 4/7 days/week) had higher degrees of weight gain.
- In another study, overall BMI did not increase in CPAP compliant patients after one year, but women and non-obese subjects did gain significant weight.
- A Finnish study in 2016 found that CPAP compliant, more obese patients had higher levels of weight gain after 5 years.
- However, this one retrospective study did not find and significant weight gain in complaint CPAP users.
- Lastly, a meta-analysis of randomized only studies analyzed over 3181 patients from 25 studies, finding significant weight increase in compliant CPAP users.
A number of explanations are given as to why CPAP can promote weight gain. The one most reasonable proposal that I saw is that when you have obstructive sleep apnea, your basal metabolic rate (BMR) in higher. Due to the extra energy demands of having sleep apnea, you burn up more calories. It’s been shown that using CPAP reduces your BMR. Since dietary intake and your body’s baseline weight thermostat does not change, you’ll end up with positive energy balance, leading to slow weight gain. This concept may also explain weight gain in some children who undergo tonsillectomy for sleep apnea.
Based on this finding, should people with sleep apnea stop using CPAP? Absolutely not. The overall risks of not treating sleep apnea (especially severe cases) far outweigh the potential risk of getting heavier. However, I do think that this potential side effect should to mentioned to all new CPAP users, just like any potential side effects for drugs or surgical procedures.
It’s also important to emphasize the importance of radically changing your dietary habits once you’re able to sleep better with CPAP.
For those of you currently on CPAP, did you gain any weight? If so, about how many pounds?