Is taking part in clinical trials good for your health? A cohort study

The prognosis of patients included in clinical trials is often better than might be anticipated from epidemiological data. Patients volunteering to take part in a study might be unrepresentative of the potential treatment population or the trial itself may confer benefit by offering closer supervision. A total of 2332 consecutive patients (average +/- SD age 70.1 +/- 10.8; 26% female) who presented to a community heart failure clinic were diagnosed as having heart failure due to left ventricular systolic dysfunction. All patients were asked whether they would be prepared to take part in clinical research projects at their initial visit. During a median follow-up in survivors of 55.7 months (interquartile range 30.4-74.3), 792 (34%) patients died. Agreeing to take part in clinical trials strongly predicted a good outcome (approximately halving the risk of death). In multivariate modelling, willingness to take part [hazard ratio (95% confidence intervals) 0.33 (0.26-0.40)] was a predictor of good outcome independent of age, severity of left ventricular dysfunction, renal function, sodium levels, drug use, and comorbidities. In a subset in whom N-terminal pro-B type natriuretic peptide (NT-proBNP) was available (n = 1256), agreeing to take part in trials remained an independent predictor of survival with log [NT-proBNP]. Those patients with chronic heart failure who express a willingness to take part in a clinical trial, appear to have a better prognosis than those who do not.