Association between relative fat mass and obstructive sleep apnea and the potential mediating effect of hypertension:...

Obesity has been identified as one of the contributing factors to obstructive sleep apnea (OSA). The current obesity assessment indicators have poor ability to distinguish between fat and muscle. Relative fat mass (RFM) a new indicator of obesity that takes into account gender differences and can predict body fat conditions has advantage in this respect. This study aimed to investigate the potential association between RFM and OSA, as well as the possible mediating effect of hypertension.

This cross-sectional study used data from the National Health and Nutrition Examination Survey conducted in 2005-2008 and 2015-2018. Multivariate logistic regression, restricted cubic splines (RCS), and subgroup analyses were performed to evaluate the association between RFM and OSA. In addition, the receiver operating characteristic curve (ROC) of different obesity indicators was compared to assess their predictive ability for OSA. Mediation analysis was used to explore the potential mediating role of hypertension in the positive correlation.

The study included 13,532 participants with complete study data, of which 6854 were assessed as having OSA according to the criteria, accounting for 50.65% of the study population. The results of the multivariate logistic regression model with fully adjusted covariates showed that the odds ratio of RFM was 1.096 (95%CI:1.084-1.109, P < 0.001). The results of the RCS show that RFM is nonlinearly correlated with OSA (P for nonlinear < 0.01). Subgroup analysis showed that the association between RFM and OSA was stronger in female and people younger than 60. The ROC also indicates that, compared with the body roundness index and weight-adjusted-waist index, RFM showed potential as a predictor. Mediation analysis and sensitivity analysis showed that hypertension had a statistically significant but poorly robust mediating effect between RFM and OSA.

There is a positive and nonlinear correlation between RFM and OSA. Hypertension plays a potential mediating role in the positive association between RFM and OSA, but its robustness is poor. RFM shows potential as a predictor of OSA, but more prospective studies are needed to confirm these findings and determine the causal relationship between RFM and OSA.