Differential response to cognitive stimulation in moderate versus moderately severe Alzheimer's disease.

Alzheimer's disease (AD) is characterized by impairments across several neurocognitive domains, particularly memory and executive function. The study explored the effectiveness of an individual cognitive stimulation (iCS) program on cognitive outcomes in older adults with moderate to moderately severe AD. A multicentre randomized controlled trial was conducted with 80 Portuguese older adults (Mage: 83.0 ± 7.1 years) with AD. Participants were randomly assigned to either iCS (n = 39; 49%) or treatment as usual (n = 41; 51%). Alzheimer's Disease Severity (ADS) categorized two groups based on Mini-Mental State Examination score: 10-14 in the ADS moderately severe group and 15-20 in the ADS moderate group. In participants with moderate AD, iCS led to significant improvements in memory-related outcomes (particularly Memory Assessment Test) and a trend toward improvement in global cognition. In contrast, no significant effects were observed in participants with moderately severe AD. Meta-analytic comparisons and meta-regression confirmed a significant difference in intervention effectiveness between severity levels. iCS was significantly more effective in individuals with moderate AD than in those with moderately severe AD. This difference in responsiveness between severity levels was statistically confirmed (Q = 11.29, p < .001). iCS was effective in enhancing memory in individuals with moderate AD, with additional indications of global cognitive benefit. However, no meaningful effects were observed in participants with moderately severe impairment, suggesting diminished responsiveness to iCS as disease severity increases. (PsycInfo Database Record (c) 2026 APA, all rights reserved).