More effective agents are needed

EDITOR—O'Brien and Ballard in their editorial outlined the approval by the National Institute for Clinical Excellence of cholinesterase inhibitors for the treatment of mild to moderate Alzheimer's disease.1 We believe, however, there are limitations in the evidence of the efficacy of cholinesterase inhibitors that should be considered.

Pharmaceutical companies have sponsored most of the studies so far, which may lead to overestimation of the effect size.2 Many studies have been conducted in selected samples in secondary care, and the drugs may be less effective in the wider population. Most studies used “intention to treat” analyses (all randomised cases are included in the results, whether they completed the study or not) with “last observation carried forward” (including the last observation as the final result). Since people …