Number of patients needed to prescribe statins in primary cardiovascular prevention: mirage and reality.

Background: Number of patients needed to treat (NNT) with a statin in primary prevention of coronary heart disease (CHD) is often misinterpreted because this single statistic averages results from heterogeneous studies.

Objective: To provide estimates of the number of individuals needed to be prescribed a statin to prevent one CHD event accounting for their level of CHD risk and for persistence to treatment.

Methods: A post hoc analysis was conducted based on a Cochrane review on statins for the primary prevention of cardiovascular diseases. Five-year NNTs were calculated separately from randomized clinical trials (RCTs), including 'lower' and 'higher' risk populations (CHD mean event rates of 3.7 and 14.4 per 1000 person-years, respectively). NNTs were adjusted for 5-year persistence to treatment using a value of 65%.

Results: Persistence-adjusted 5-year NNTs to prevent one CHD for the lower and higher CHD risk categories were 146 [95% confidence interval (CI): 117-211] and 53 (95% CI: 39-88) respectively, values 25% and 15% higher than their unadjusted counterpart (117, 95% CI: 94-167 and 46, 95% CI: 34-78).

Conclusions: Five-year NNTs for statins to prevent a first CHD is almost three times higher in those at lower versus higher risk populations. Reporting combined results from RCTs including subjects at different cardiovascular risks should be avoided. Individualizing the risk of CHD should orient family physicians and their patients in their choice of preventive approaches and generate more realistic expectations about compliance and outcomes.