Obstructive sleep apnea (OSA) is a common sleep disorder characterized by repeated episodes of complete or partial blockage of the upper airway during sleep. This results in oxygen desaturations, loud snoring, and frequent arousals from sleep. OSA has been linked to serious health consequences including daytime sleepiness, cognitive dysfunction, cardiovascular disease, and metabolic disorders.
Being overweight or obese is a major risk factor for OSA. Many people believe that being overweight directly causes OSA, and that losing weight is the key to curing it. However, the relationship between excess weight and OSA is complex, as weight gain can also be a consequence of OSA. This article examines the evidence on the link between obesity and OSA, and whether weight loss alone can reliably cure this troublesome condition.
You Have Sleep Apnea Because You Are Overweight?
A common assumption is that excess weight causes the airway to collapse during sleep, leading to apneas and hypopneas. Obese individuals are indeed at a much higher risk of OSA, but correlation does not prove causation.
To examine the strength of the relationship between weight and OSA severity, data was analyzed from 2,117 patients at a sleep center. Their body mass index (BMI) was plotted against their apnea-hypopnea index (AHI), which measures OSA severity. The results showed people across the whole BMI spectrum with varying degrees of OSA. Several overweight and obese patients had only mild OSA, while some underweight patients had severe OSA.
Statistical analysis found only a weak correlation between BMI and AHI. BMI was a poor predictor of OSA, with a diagnostic accuracy of around 50%. So while obesity is a risk factor, there are clearly other factors at play. Crucially, the arrow of causation may go the other way, with OSA promoting weight gain.
How OSA Can Lead to Weight Gain
Growing evidence suggests that OSA may come first and directly cause weight gain through multiple mechanisms:
Metabolic Effects
- Leptin – This hormone regulates appetite and metabolism. OSA suppresses leptin, increasing appetite.
- Ghrelin – This hormone stimulates hunger. OSA elevates ghrelin, promoting overeating.
- Insulin – OSA causes insulin resistance and impairs glucose metabolism, predisposing to diabetes.
Fat Storage Effects
- Cortisol – This stress hormone increases visceral fat storage around the abdomen. OSA elevates cortisol.
- Growth hormone – Deficiency in this hormone promotes increased body fat. OSA reduces growth hormone secretion.
Lifestyle Effects
- Fatigue – OSA leaves people too tired to exercise and burn calories.
- Cravings – OSA amplifies cravings for fat, salt, and carbohydrates.
OSA essentially tricks the body into thinking it is starving or under severe stress, even as excess calories are consumed. This drives relentless weight gain, which further worsens OSA in a vicious cycle.
Losing Weight Will Cure Your Sleep Apnea?
If obesity causes OSA, then losing weight should cure OSA. But this overly simplistic view is contradicted by research.
In one study, obese OSA patients who lost an average of 20 kg (48 lbs) saw their AHI drop from 52.5 to 28.3. While a major improvement, most still had moderate to severe OSA. Total cures were rare.
In another study, only 24 out of 216 patients (11%) achieved a full OSA cure through weight loss alone. Of those 24, 6 regained OSA despite keeping the weight off. Meanwhile, 3 of the 11 who regained weight were still cured of OSA.
Overall, studies show that losing weight yields a 30% average improvement in OSA severity, with only 10-20% of patients experiencing a full cure. Benefits are often temporary, with OSA recurring even if lost weight is maintained.
A More Nuanced Approach
The relationship between obesity and OSA is bidirectional and complex. While major weight loss can help, it is unrealistic for many patients and unlikely to be curative. A more thoughtful, patient-centered approach is needed.
Step 1 – Treat OSA First
Since OSA drives weight gain, immediately treating it with CPAP, oral devices, or surgery helps halt this cycle. Even modest improvements may aid weight loss efforts.
Step 2 – Lifestyle Changes
With OSA treated, increased energy and regulated metabolism facilitate healthier eating and activity habits. Gradual, sustainable weight loss can then occur.
Step 3 – Adjust OSA Treatment
As weight decreases, retitrate CPAP, get a new oral device, or consider additional procedures. The goal is optimal control of remaining OSA.
Step 4 – Continued Follow Up
Monitor progress and provide ongoing support. Weight maintenance is challenging. Relapse of OSA is possible and requires prompt action.
OSA and Obesity Have A Bidirectional Relationship
OSA and obesity have a bidirectional relationship, where each can influence the other. While substantial weight loss may not cure OSA, it remains beneficial. Conversely, effective OSA treatment helps enable weight loss in the first place. This necessitates an integrated approach tackling both conditions simultaneously.
Rather than scolding patients to simply lose weight, physicians must appreciate the complex physiology involved. Offering compassion, practical assistance, and a variety of therapy options provides the greatest chance of breaking free from the vicious cycle of obesity and OSA.
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