Purpose: The present study aimed to evaluate the efficiency of traditional anthropometric and body composition parameters in predicting apnea hypopnea index (AHI) change after weight loss.
Patients and Methods: Chinese adults with overweight and obesity were included into this study containing two parts. A cross-sectional study was conducted in 137 individuals using the baseline data from two weight loss intervention trials. The second part was the weight-loss intervention study conducted in 60 overweight and obese patients with obstructive sleep apnea (OSA). All participants underwent physical examination, bioelectrical impedance analysis and overnight polysomnography. Multivariate linear regression models were used to identify the most accurate parameters to predict AHI and the mediation analysis to evaluate the mediators between weight loss and AHI reduction.
Results: Waist circumference (WC), body mass index and fat mass were positively associated with AHI after adjusting multiple collinearities in the cross-sectional study. After weight-loss intervention, body weight decreased from 94.6 ± 15.3 to 88.0 ± 13.9 kg, and AHI decreased from 41.9 (13.0,66.9) to 20.7 (8.7,51.2) events/h. Among these parameters, only percentage changes in WC and AHI across the intervention were positively intercorrelated after controlling for covariates (adjusted r = 0.271, P = 0.041). The mediation analysis supported WC as a mediator between weight loss and AHI reduction (standardized indirect effect [95% CI] = 4.272[0.936,7.999]).
Conclusion: Both general and abdominal obesity are of high prognostic value for OSA. WC as an easily accessible parameter mediates the effects of weight loss in decreasing OSA severity.

Plain Language Summary: Current Knowledge: Obesity is a well-recognized risk factor for the development of obstructive sleep apnea (OSA), whereas weight loss has been written into the treatment guidelines for overweight and obese patients with OSA. However, the anthropometric parameters more related to OSA have not been fully clarified, and an easily acquired index is needed to predict the effect of weight loss on apnea hypopnea index (AHI) improvement.
Study Impact: This study found that both general obesity and abdominal obesity were positively associated with AHI, and waist circumference mediated the effect of weight loss in improving AHI. These results provide an easily acquired index to monitor the effect of weight loss on OSA.

Keywords: obesity, obstructive sleep apnea, weight loss, waist circumference, body composition