Objective measure of smoking status highlights disparities by sex.

Current smoking is the strongest predictor of future morbidity and mortality in those with cardiovascular disease, yet clinically, smoking status is usually ascertained through self-report. We objectively measured smoking status, using exhaled carbon monoxide (CO), for 1122 consecutive patients entering cardiac rehabilitation. Within those with elevated CO levels (≥4 ppm), females had CO levels almost twice that of males (20.4 vs. 11.6), suggesting higher amounts of smoking.