STATISTICAL CONSIDERATIONS IN MONITORING THE SYSTOLIC HYPERTENSION INTHE ELDERLY PROGRAM (SHEP)

The Systolic Hypertension in the Elderly Program (SHEP), a randomized, double-masked, placebo-controlled trial of 4736 persons, was designed to assess the efficacy of antihypertensive drug treatment to reduce t he risk of fatal and nonfatal strokes among people age 60 and over wit h isolated systolic hypertension. The statistical method used in inter im monitoring of results was conditional power (or stochastic curtailm ent). The findings did not become conclusive until near the completion of the trial, and therefore SHEP was continued to its scheduled closi ng date. The trial demonstrated a 36% reduction in the incidence of st roke in the active treatment group (P = .0003). In addition to evaluat ing overall efficacy of treatment, the monitoring process considered s uch other issues as nonstroke outcomes, lag time between first report of stroke and final confirmation of stroke diagnosis, consistency of r esults across subgroups, and completeness of follow-up. The purpose of this article is to review these factors with primary emphasis on the statistical aspects.