The Impact of Weight Loss on the Physiological Endotypes Associated With OSA

Weight loss improves upper airway collapsibility in people with OSA. However, it is unclear how weight loss affects the other physiological traits (ie, endotypes) associated with OSA (loop gain, arousal threshold, and muscle compensation).

What is the effect of metabolic bariatric surgery on the OSA endotypes, and are the baseline endotypes associated with improvements in OSA severity?

Using noninvasive methods, the OSA endotypes were measured during overnight clinical polysomnography in 43 patients before and after (approximately 6-18 months) metabolic bariatric surgery. OSA endotypes were also measured, using reference standard physiological techniques (ie, CPAP dial-down method) in a subset of patients (n = 10). Generalized linear mixed-effects models were used to evaluate the effect on outcome variables.

Metabolic bariatric surgery was associated with improvements in apnea-hypopnea index (AHI; 50.7 ± 26.8 vs 24.6 ± 19.2 events/h; P < .001), BMI (42.1 ± 5.5 vs 32.8 ± 4.5 kg/m²; P < .001), upper airway collapsibility (67.0% ± 21.4% vs 72.8% ± 16.2% V_eupnea; P = .011) and loop gain (0.65 ± 0.19 vs 0.58 ± 0.19; P = .011). Weight loss also reduced arousal threshold (149.7% ± 28.6% vs 142.6% ± 30.1% V_eupnea; P = .011). Reference standard measures showed changes consistent with noninvasively derived endotypes. A greater improvement in airway collapsibility was associated with a greater reduction in AHI (B = -0.62; 95% CI, -0.97 to -0.27; P = .002; R² = 0.23), and greater decreases in arousal threshold were associated with greater improvements in AHI (B = 0.63; 95% CI, 0.33-0.92; P < .001; R² = 0.29). Multivariable models controlling for baseline AHI found that those with less-collapsible upper airways and low loop gain at baseline may be more likely to see improvements in their OSA severity after surgery.

Our results show that metabolic bariatric surgery is associated with improvements in weight, AHI, upper airway collapsibility, and loop gain and may be particularly effective for those with mild upper airway collapsibility and low loop gain.