Association between relative fat mass and sleep disorder among US adults: Results from NHANES 2007 to 2014

Sleep disorders affect a large share of adults, and excess body fat is a recognized risk factor. Relative fat mass (RFM) is a recently developed anthropometric index intended to estimate body fat percentage more closely than body mass index (BMI). This study examined the association between RFM and physician-diagnosed sleep disorders in a nationally representative sample of U.S. adults.

We analyzed data on 21,115 participants (≥20 years) from the National Health and Nutrition Examination Survey 2007 to 2014. RFM was calculated from measured waist circumference and height with adjustment for gender. Logistic regression assessed associations between RFM (continuous and quartile) and sleep disorder, adjusting sequentially for demographic, socioeconomic, lifestyle, and clinical factors. Restricted cubic splines and segmented models explored nonlinear trends, and stratified analyses evaluated consistency across subgroups.

Participants with sleep disorders had markedly higher mean RFM than those without. After full adjustment, higher RFM remained positively linked to sleep disorder, with risk rising steeply up to an inflection around RFM = 39.3 and then attenuating. The pattern was consistent across age, gender, smoking, alcohol use, and comorbidity strata, indicating a broad, dose-dependent relationship between adiposity and impaired sleep.

This cross-sectional analysis suggests a strong association between elevated RFM and a greater prevalence of sleep disorders among U.S. adults. These findings highlight adiposity as a modifiable contributor to poor sleep health and support integrating body fat reduction into preventive and therapeutic strategies. Prospective and interventional research is needed to clarify causality, mechanisms, and the potential sleep benefits of targeted fat-loss interventions.