Background: The cause of the "treatment-risk paradox" reported for patients with coronary disease is unknown; however, determining the factors that contribute to this paradox is essential to properly design quality improvement interventions.
Methods: Prospective cohort study enrolling consecutive patients with angiographically proved coronary disease between February 1, 2004, and November 30, 2005, in Alberta.
Results: One month after an angiogram, statins were being taken by 2436 (62.9%) of 3871 patients (mean age, 64 years). High-risk patients were less likely to be taking statins than lower-risk patients (55.8% vs 63.5%; crude odds ratio [OR], 0.72 [95% confidence interval {CI}, 0.57-0.92]; risk ratio [RR], 0.88 [95% CI, 0.79-0.97]), but this treatment-risk paradox was completely attenuated by adjusting for exertional capacity and depressive symptoms (OR, 0.98 [95% CI, 0.75-1.28]; RR, 0.99 [95% CI, 0.89-1.09]). These results were robust across drug classes: while high-risk patients were less likely to be taking angiotensin-converting enzyme inhibitors, aspirin, and statins (25.8% vs 32.3%; crude OR, 0.73 [95% CI, 0.56-0.95]; RR, 0.80 [95% CI, 0.65-0.97]), this association did not persist in the adjusted model (OR, 0.98 [95% CI, 0.72-1.33] [P = .87]; RR, 0.99 [95% CI, 0.79-1.20]).
Conclusions: The treatment-risk paradox reported in administrative database analyses is attributable to clinical factors not typically captured in these databases (such as functional capacity and depressive symptoms). Interventions to address the treatment-risk paradox should recognize that patients with reduced functional capacity, depression, or both are at higher risk for underuse of these beneficial therapies and should target physicians and patients.