10 studies were included in the review (n=447 patients); five placebo controlled RCTs (all double blind and one crossover trial, n=356 patients), one placebo controlled trial (double blind, n=36 patients), one crossover randomised study (n=22 patients). two open label studies (n=27 patients) and one case series (n=5 patients). Sample sizes ranged from five to 251.
Long-term memory: There was a statistically significant increase in long-term memory (eight studies) at the end of acetylcholinesterase inhibitor treatment compared with before treatment (effect size 0.362, 95% confidence interval (CI): 0.0617 to 0.663, p=0.019). When individual acetylcholinesterase inhibitors were analysed this remained significant for donepezil (five studies) but not rivastigmine (two studies) or galantamine (one study).
Short-term memory: There was no significant difference in short-term memory (nine studies). Similar results were seen with the random-effect and fixed-effects models. However, when individual acetylcholinesterase inhibitors were analysed there was a significant increase in short-term memory with donepezil (effect size 0.246, 95% CI: 0.182 to 0.780; p=0.034, four studies) but not rivastigmine (four studies) or galantamine (one study).
There was no evidence of a significant difference in either short-term memory or long-term memory when control and intervention groups were compared at the end point, this remained non-significant when results of the double blinded, placebo controlled studies only were pooled.
There was no evidence of statistically significant heterogeneity.
Further analyses were reported in the paper.