Background: Little is known regarding the dose-response function in multidomain interventions for dementia prevention.

Method: The Multidomain Alzheimer Preventive Trial is a 3-year randomized controlled trial comprising cognitive training, physical activity, nutrition, and omega-3 polyunsaturated fatty acids for at-risk older adults. The dose delivered (number of sessions attended) was modeled against global cognition, memory, and fluency in 749 participants. Interaction effects were assessed for age, sex, education, dementia score (CAIDE), frailty score, and apolipoprotein E (APOE) ε4 status.

Results: The dose-response models were non-linear functions indicating benefits up to about 12 to 14 training hours or 15 to 20 multidomain sessions followed by a plateau. Participants who benefited from a higher dose included women, younger participants, frail individuals, and those with lower education or lower risk of dementia.

Discussion: The non-linear function indicates that a higher dose is not necessarily better in multidomain interventions. The optimal dose was about half of the potentially available sessions.