Abstract Rationale The apnea time/disordered breathing time ratio (AT/DBT) quantifies the fraction of total respiratory-disturbance time spent in complete airflow cessation (apnea) rather than partial limitation (hypopnea). Higher AT/DBT may reflect greater upper-airway collapsibility or less effective dilator muscle recruitment. Estrogen has neuromodulatory and anti-inflammatory effects on upper-airway and ventilatory control pathways and could plausibly reduce the propensity for complete collapse, lowering AT/DBT in women with sleep apnea. Methods We analyzed women from the Sleep Heart Health Study baseline exam, excluding participants with heart failure, type 2 diabetes, or stroke. Sleep apnea was defined using AHI based on ≥ 3% desaturation (AHI3%) ; analyses were restricted to AHI3% ≥5 events/h and categorized as 5–14. 9, 15–29. 9, and ≥30. The exposure was current estrogen use (EST). Outcome was AT/DBT (proportion). We fit a generalized linear model with binomial family and logit link: glm atdbt est#ahi3pcat c. ageₛ1 c. bmiₛ1 i. race1, vce (robust). Adjusted predictive margins estimated mean AT/DBT within AHI–EST strata; pairwise contrasts compared groups. Results Among 1, 487 women, increasing AHI severity was associated with higher AT/DBT (non-EST: 0. 154 at 5–14. 9; 0. 246 at 15–29. 9; 0. 364 at ≥ 30; all within-group increases p 0. 001 from low to higher AHI). Estrogen users showed a similar pattern (0. 160; 0. 241; 0. 335), with increases from 5–14. 9 to 15–29. 9 (Δ = 0. 081, p = 0. 002) and to ≥ 30 (Δ = 0. 174, p 0. 001). Between-group differences (EST vs non-EST) within AHI categories were small and not statistically significant: +0. 006 at AHI 5–14. 9 (p = 0. 657), −0. 005 at 15–29. 9 (p = 0. 844), and −0. 029 at ≥ 30 (p = 0. 567). Pairwise patterns suggested a modestly smaller rise in AT/DBT across severity among estrogen users, but formal contrasts did not demonstrate significant between-group differences. Conclusions In community-dwelling women with sleep apnea, AT/DBT increases with AHI severity, indicating a greater share of apnea time as disease worsens. Current estrogen use was not associated with a statistically significant reduction in AT/DBT within AHI strata. Any attenuation of the AT/DBT rise among estrogen users was modest and not statistically supported. These findings suggest that, after excluding major cardiometabolic comorbidities, estrogen use does not materially alter the event-morphology profile (apnea vs hypopnea time) in cross-sectional analyses. Longitudinal studies incorporating hormone formulation, dose, and duration, as well as mechanistic measures of upper-airway collapsibility and ventilatory control, are warranted to clarify hormonal influences on event phenotype. This abstract is funded by: NIH
Hurst et al. (Fri,) studied this question.