To compare and rank the relative and additive effects of lifestyle components including exercise, diet, cognitive training, vascular management, and digital delivery on cognitive outcomes and dementia prevention in older adults without dementia.

Multidomain lifestyle interventions have shown promise in preserving cognition, but the specific contribution of individual components remains uncertain. Most prior meta analyses compare interventions as whole programs rather than modeling overlapping elements shared across trials.

Randomized controlled trials enrolling cognitively unimpaired or at-risk adults with global or domain-specific cognitive outcomes were systematically identified. Ten trials (~8,000 participants; follow-up 20 weeks–6.7 years) were included, spanning multidomain (FINGER, MAPT, preDIVA, US POINTER, HATICE, GOIZ ZAINDU), exercise (EXERT), factorial (SYNERGIC), cognitive training (ACTIVE), and diet-based (PREDIMED) interventions. Arm-level data were coded for lifestyle components, and a random-effects component network meta-analysis estimated standardized mean differences (Hedges g) for individual and combined components.

Exercise (g = 0.15; 95% CI 0.05 to 0.25) and diet (g = 0.10; 95% CI 0.01 to 0.18) produced the largest independent improvements in global cognition. Cognitive training (g = 0.08; 95% CI −0.02 to 0.19) and vascular management (g = 0.07; 95% CI −0.03 to 0.17) provided modest additive benefits, while digital delivery (g = 0.05; 95% CI −0.04 to 0.14) contributed small incremental gains. Predicted combined effects increased cumulatively with exercise and diet (g ≈ 0.23), exercise diet and cognitive training (g ≈ 0.31), and full multidomain programs (g ≈ 0.40). Between study heterogeneity was moderate (tau squared ≈ 0.03).

Exercise and diet showed the greatest individual benefits, with added gains from cognitive training and vascular management. Modeling combined components revealed synergistic cognitive protection, supporting precision-targeted dementia prevention. Using a component network meta-analysis, this study disentangled and ranked the relative and additive effects of key lifestyle factors, offering insights beyond conventional analyses.