Age-dependent association of body mass index and obstructive sleep apnea severity in women

Purpose Obstructive sleep apnea (OSA) is influenced by body mass index (BMI), age, and sex. Although obesity is a major risk factor for OSA, the strength of the association between BMI and OSA severity may vary across demographic groups. We investigated whether age modifies the relationship between BMI and OSA severity in men and women. Methods We performed a cross-sectional analysis of adults who underwent polysomnography at a university-based sleep laboratory. The relationship between BMI and apnea-hypopnea index (AHI), including supine AHI, was evaluated. Participants were categorized into younger and older age groups (< 55 vs. ≥55 years). Linear regression models with interaction terms were used to assess whether age modified the association between BMI and OSA severity. Results A total of 752 participants were included. The associations of BMI categories with normalized AHI and normalized supine AHI were weaker in older women than in younger women ( P for interaction = 0.03 and 0.02, respectively), whereas no significant interaction by age group was observed in men. Results were similar for log-transformed BMI ( P for interaction = 0.03 for both in women). However, the three-way interaction among BMI, age group, and sex was not significant. Conclusions The association between BMI and OSA severity was attenuated in women aged 55 years or older compared with younger women. Because a sex difference in this age-related attenuation was not statistically confirmed, these findings should be interpreted with caution. They suggest that BMI alone may be a less informative indicator of OSA severity in older women.