Dementia and disability outcomes in large hypertension trials: Lessons learned from the Systolic Hypertension in the Elderly Program (SHEP) trial

In the Systolic Hypertension in the Elderly Program (SHEP) trial (1985-1990 ), active treatment reduced the incidence of cardiovascular events, but not that of dementia and disability, as compared with placebo. This study aims to evaluate it assessment of cognitive and functional outcomes was biased by differential dropout. Characteristics of subjects who did or did not par ticipate in follow-up cognitive and functional evaluations were compared. T he relative risks of incident cognitive impairment and disability were asse ssed in the two treatment groups, with the use of the reported findings and under the assumption that the proportions of cognitive and functional impa irment among dropouts increased. Assignment to the placebo group and the oc currence of cardiovascular events independently predicted missed assessment s. From the reported findings, the risk of cognitive and functional impairm ent was similar between the two treatment groups. However, when 20-30% and 40-80% of the subjects who missed the assessment were assumed to be cogniti vely and, respectively, functionally impaired, assignment to active treatme nt reduced the risk of these outcomes. In the SHEP, the cognitive and funct ional evaluations were biased toward the null effect by differential dropou t. This might have obscured the appraisal of a protective effect of treatme nt on the cognitive and functional decline of older hypertensive adults.