Differential Associations of Visceral Adiposity with Pulmonary Function Impairment by Sex: Identification of a...

Visceral adiposity, a core aspect of nutritional status, is increasingly recognized as a modifiable risk factor for extra-metabolic diseases. However, evidence regarding its sex-specific impact on pulmonary function, a key determinant of healthy aging, remains scarce. This study aimed to investigate the differential associations between the Visceral Adiposity Index (VAI) and impaired pulmonary function in middle-aged and older males and females.

This study included 6,749 participants (3,374 males, 3,375 females) from the 2015 China Health and Retirement Longitudinal Study (CHARLS). Pulmonary function was assessed by peak expiratory flow (PEF), with impairment defined as PEF <80 % of the predicted value. The nonlinear association between visceral adiposity index (VAI) and pulmonary function impairment was examined using restricted cubic splines within multivariate logistic regression models, with knots placed at the 5th, 25th, 75th, and 95th centiles. To assess the robustness of the identified VAI threshold, we performed knot placement sensitivity analyses and generated bootstrap 95 % confidence intervals (500 replicates). A formal VAI × sex interaction term was included in a combined model to test for sex differences.

The association between visceral adiposity index (VAI) and pulmonary function impairment was explored. A potential threshold effect at VAI ≈ 103 was observed in males, beyond which the risk of impairment appeared to increase. In females, a more linear association was suggested. However, in the primary formal test within a combined model, the VAI × sex interaction term was not statistically significant (P = 0.095). Therefore, while a threshold pattern was noted in males, the evidence for a differential association by sex was inconclusive.

The observed VAI threshold in males (≈103) could provide a useful reference for identifying individuals who might benefit most from targeted lifestyle or nutritional interventions. In contrast, the more linear pattern observed in females suggests that early and sustained management of visceral adiposity may be important across a wider range of values. These preliminary findings highlight the potential value of considering sex in strategies aimed at reducing visceral adiposity to promote respiratory health, though they require prospective validation before clinical application.