0586 The Mathematical Relationship Between Body Mass Index and Apnea-Hypopnea Index in Women and Men

Abstract Introduction High body mass index (BMI) is a risk factor for obstructive sleep apnea (OSA). The apnea-hypopnea index (AHI) approximates OSA severity. Since BMI and AHI are positively correlated, a mathematical formula may estimate the impact of BMI on AHI. Multiple studies have proposed a positive correlation between BMI and AHI. One study evaluated 690 patients (56% male, 44% female) with OSA, and found that, in all, a 10% BMI increase correlated with a 32% AHI increase. In our prior study of 434 Veterans, we found that for every 1-unit drop in BMI (5-7 lb.), one could expect a 6.2% decrease in AHI. In another 598 of our Veterans, a 1-unit drop in BMI was associated with a 6.6% decrease in AHI. But our Veteran samples consisted of >90% men. A female sample would be important, due to the different obesity patterns between women and men. For a given BMI, women have less fat-free mass than men, and fat distribution is peripheral in women and centralized in men. This may affect the relationship between BMI and AHI in women and men. Therefore, we obtained a new sample with females. Methods We reviewed 1000 random charts of female and male patients (aged 18-89 years) who had polysomnograms at the University of Iowa between 2019-2024. Log-transformed linear regression models and Spearman’s correlation evaluated the relationship between BMI and AHI. Results Of the 1000 charts, 193 were excluded due to incomplete data. The final sample was 807 patients: 473 (58.6%) females and 334 (41.4%) males. Linear regression models estimated that a 1-unit BMI decrease corresponded with a 6.3% decrease in AHI in females, and 6.5% decrease in males. Spearman’s correlation found that BMI and AHI were positively associated in both sexes (rho = 0.37, p < 0.001). Conclusion The formulas were not significantly different between sexes. We conclude the relationship between BMI and AHI is the same in females and males. A 1-unit drop in BMI results in a 6-7% decrease in AHI in both sexes. Healthcare workers could encourage female and male patients to lose 6-7 lbs. to improve AHI by 6-7%. Support (if any)