Table 1Number needed to treat with statins to prevent one cardiovascular event in 5 years

TrialsNumber of SubjectsBaseline Risk of CHD Mortality per 100 Person-YearsRate RatiosNumber Needed To Treat (5 years)
Total MortalityCHD MortalityAll CV EventsTotal MortalityCHD MortalityAll CV Events
Primary Prevention
AFCAPS/TexCAPS6,6050.11.041.360.69167*1,000*28
WOSCOPS6,5950.40.780.670.711818228
Secondary Prevention
Scandinavian simvastatin survival study trial4,4441.60.710.590.6433318
CARE4,1591.20.920.810.751339511
Long-term intervention with pravastatin in ischemic disease9,0141.40.780.770.8416417
Combined Effects (95% CI)0.80 (0.74 to 0.87)0.73 (0.66 to 0.81)0.74 (0.71 to 0.77)113 (77 to 285)500 (222 to -)**20 (17 to 25)

Adapted by permission from BMJ Publishing Group Limited. BMJ. Smeeth L, Haines A, Ebrahim S, vol. 318, pp. 1548–51, 1999.

CHD = coronary heart disease; CV = cardiovascular

*

AFCAPS/TexCAPS study reported a nonsignificant increased total and CHD mortality in the intervention group. Numbers needed to treat are derived from the lower limit of the 95% CIs of the risk differences in event rates to illustrate the lower limit within which the numbers might lie.

**

No upper number needed to treat can be calculated as the upper 95% CI of pooled absolute risk difference is greater than zero. In these circumstances, the number needed to treat is a number needed to harm.

From: Expanded Guidance on Selected Quantitative Synthesis Topics

Cover of Methods Guide for Effectiveness and Comparative Effectiveness Reviews
Methods Guide for Effectiveness and Comparative Effectiveness Reviews [Internet].

NCBI Bookshelf. A service of the National Library of Medicine, National Institutes of Health.