Abstract: Fifteen RCTs were included in the review. Six of these had been included in the previous review of RO. The studies included participants from a variety of settings, interventions that were of varying duration and intensity, and were from several different countries. The quality of the studies was generally low by current standards but most had taken steps to ensure assessors were blind to treatment allocation. Data were entered in the meta-analyses for 718 participants (407 receiving cognitive stimulation, 311 in control groups). The primary analysis was on changes that were evident immediately at the end of the treatment period. A few studies provided data allowing evaluation of whether any effects were subsequently maintained. A clear, consistent benefit on cognitive function was associated with cognitive stimulation (standardised mean difference (SMD) 0.41, 95% CI 0.25 to 0.57). This remained evident at follow-up one to three months after the end of treatment. In secondary analyses with smaller total sample sizes, benefits were also noted on self-reported quality of life and well-being (standardised mean difference: 0.38 [95% CI: 0.11, 0.65]); and on staff ratings of communication and social interaction (SMD 0.44, 95% CI 0.17 to 0.71). No differences in relation to mood (self-report or staff-rated), activities of daily living, general behavioural function or problem behaviour were noted. In the few studies reporting family caregiver outcomes, no differences were noted. Importantly, there was no indication of increased strain on family caregivers in the one study where they were trained to deliver the intervention. There was consistent evidence from multiple trials that cognitive stimulation programmes benefit cognition in people with mild to moderate dementia over and above any medication effects. However, the trials were of variable quality with small sample sizes and only limited details of the randomisation method were apparent in a number of the trials. Other outcomes need more exploration but improvements in self-reported quality of life and well-being were promising. Further research should look into the potential benefits of longer term cognitive stimulation programmes and their clinical significance.

Plain-language summary: This review included 15 trials with a total of 718 participants. The findings suggested that cognitive stimulation has a beneficial effect on the memory and thinking test scores of people with dementia. Although based on a smaller number of studies, there was evidence that the people with dementia who took part reported improved quality of life. They were reported to communicate and interact better than previously. No evidence was found of improvements in the mood of participants or their ability to care for themselves or function independently, and there was no reduction in behaviour found difficult by staff or caregivers. Family caregivers, including those who were trained to deliver the intervention, did not report increased levels of strain or burden. The trials included people in the mild to moderate stages of dementia and the intervention does not appear to be appropriate for people with severe dementia. More research is needed to find out how long the effects of cognitive stimulation last and for how long it is beneficial to continue the stimulation. Involving family caregivers in the delivery of cognitive stimulation is an interesting development and merits further evaluation.