'Smoker's paradox' in heart failure not fully explained

18 August 2008

MedWire News: Smokers hospitalized with heart failure (HF) have a lower risk for in-hospital mortality than non-smokers, while the risk for re-hospitalization or post-discharge mortality is similar between the two groups, study findings suggest.

Although cigarette smoking is a well-established risk factor for cardiovascular disease, several studies have demonstrated a lower mortality rate after acute coronary syndromes in smokers than in non-smokers - the so called "smoker's paradox" - explain Gregg Fonarow (University of California at Los Angeles Medical Center, USA) and colleagues.

Fonarow and team investigated this paradox in a cohort of hospitalized heart failure patients included in the OPTIMIZE-HF (Organized Program to Initiate Lifesaving Treatment in Hospitalized Patients with Heart Failure) registry. They determined the impact of current or recent smoking exposure on outcomes during hospitalization and in the first 60-90 days following discharge.

Data were collected on 48,612 patients from 259 hospitals; there were 7743 (15.9%) smokers, 39,126 (80.5%) non-smokers, and the remaining 1743 (3.6%) patients had missing data.

Smokers were more likely than non-smokers to have left ventricular systolic dysfunction (59% vs 51%), were more likely to be male (61% vs 46%), and had higher levels of B-type natriuretic peptide (895 vs 789 pg/ml). However, smokers were much younger (63 vs 75 years of age), were less likely to have a previous history of hospital admission for heart failure (84% vs 89%), and were less likely to have a diagnosis of diabetes requiring insulin therapy (14% vs 17%) than non-smokers.

The risk for in-hospital mortality was lower in smokers than in non-smokers, with a mortality rate of 2.34% versus 3.90%, respectively (p<0.0001). After adjusting for potential confounders, the risk for in-hospital mortality was still approximately 30% lower in smokers than in non-smokers, with an adjusted odds ratio of 0.69 (p=0.001).

The risk for re-hospitalization or post-discharge mortality was similar between the smoking and non-smoking groups (27.5% vs 30.3% of patients and 6.71% vs 8.42% of patients, respectively).

"The residual association of smoking and better prognosis, the 'smoker's paradox,' was not fully explained by measured covariates," comment Fonarow and team in the European Heart Journal.

"However, residual confounding cannot be excluded and this study may illustrate limitations of observational analyses."

Commenting on the study, Neville Suskin (University of Western Ontario, London, Canada) and colleagues write in an accompanying editorial that "the main 'take home' message from this study is that while smoking is associated with earlier onset and more severe symptoms of heart failure, smoking cessation at the time of hospitalization for heart failure probably has a powerful beneficial effect on heart failure outcomes while in hospital."

They add that systematic efforts should therefore be made while patients are in hospital to identify smokers and begin cessation counseling immediately.

Eur Heart J 2008; 29:1983-1991