Isolated systolic hypertension (ISH) is defined as a systolic blood pressure over 160 mm/Hg and a diastolic less than 90 mm/Hg. ISH is increasingly prevalent in those 60 years and above. The Systolic Hypertension in the Elderly Program (SHEP) was undertaken to determine "whether antihypertensive drug treatment reduces risk of stroke in a multi-ethnic cohort of men and women 60 years and older with ISH" (SHEP Cooperative Research Group Prevention of Stroke by antihypertensive drug treatment in order persons with isolated systolic hypertension. JAMA 1991;265:3264).
The SHEP design specified a sample size of 4800 to test the primary hypothesis. This sample size was used to detect a difference of at least 32% in stroke incidence with 90% power and alpha of 0.05.
A total of 447,921 individuals were screened to identify 4,736 eligible participants. Of these, 3,161 were not on drugs; the remaining 1,575 met entry criteria after being withdrawn from drugs. Of those ineligible, 90% were excluded because of failure to meet blood pressure criteria
Stratified randomization by antihypertensive drug treatment status at initial contact and by center produced two SHEP groups - assigned to active treatment and placebo (Table 1).