Background Cognitive capacity and function affect daily activities, independence, and overall well-being across the life course. Objective To map and synthesise evidence on interventions that measured cognitive capacity at any life stage across the life course from Cochrane and Campbell systematic reviews. Design Mapping review. Methods The Cochrane and Campbell libraries were searched up to 1 May 2024 for systematic reviews of interventions that measured cognitive capacity across all ages. Data on interventions and outcomes were coded using the International Classification of Function and the International Classification of Health Interventions. We coded for equity characteristics using PROGRESS-Plus. Methodological quality was assessed with AMSTAR2. Results We included 34 Campbell and 31 Cochrane reviews, with over half (55%) rated as high quality. Most reviews (80%) included studies from high-income countries, with only 12% including studies from low-income countries. Of the 30 reviews that planned a subgroup analysis across equity characteristics, only eight did so. Most reviews included multiple age groups (63%), but none evaluated differences in cognitive outcomes across more than two age categories. Practical support interventions (60%) and intellectual function outcomes (51%) were most common; however, the interventions and outcomes varied at different life stages, reflecting a focus on development in younger ages and on maintaining cognitive function or prevention of decline in older ages. Conclusion This work highlights the need for a comprehensive life course approach to cognitive interventions, incorporating equity considerations and age-appropriate outcome measures.