Respiratory disturbance index - An independent predictor of mortality in coronary artery disease

Cardiovascular mortality was prospectively investigated in consecutive coro nary artery disease (CAD) patients with versus without obstructive sleep ap nea (OSA) during a follow-up period of 5 yr. An overnight sleep/ventilatory study was performed in patients requiring intensive care (n = 62, mean age 67.6 +/- 10.4 yr, range 44 to 86) during a stable condition (New York Hear t Association [NYHA] functional class 1-11) 4 to 21 mo after discharge from the hospital. OSA, defined as a respiratory disturbance index (RDI) of 10/ h or more was found in 19 patients (mean RDI 17.5 +/- 8.3). Three OSA subje cts who were successfully treated with continuous positive airway pressure (CPAP) during the observation period were excluded from the final analysis. There was no statistically significant difference (Fisher two-tailed exact test) between the OSA and non-OSA patient groups in terms of number of eld erly subjects (age greater than or equal to 65 yr), gender, obesity (body m ass index [BMI] greater than or equal to 30 kg/m(2)), smoking history, pres ence of hypertension, diabetes mellitus, hypercholesterolemia, or history o f myocardial infarction at the study start. During the follow-up period, ca rdiovascular death occurred in six of 16 OSA patients (37.5%) compared with 4 (9.3%) in the non-OSA group (p = 0.018). The univariate predictors of ca rdiovascular mortality were RDI (p = 0.007), OSA (p = 0.014), age at baseli ne (p = 0.028), hypertension at baseline (p = 0.036), history of never-smok ing (p = 0.031), and digoxin treatment during the follow-up period (p = 0.0 13). In a Cox multiple conditional regression model, RDI remained as an ind ependent predictor of cardiovascular mortality (erp beta = 1.13, 95% confid ence interval [CI] 1.05 to 1.21, two-sided p < 0.001). We conclude that unt reated OSA is associated with an increased risk of cardiovascular mortality in patients with CAD. Furthermore, it appears appropriate that RDI is take n into consideration when evaluating secondary prevention models in CAD.