The ACTIVE study, a five-year follow-up of a randomized controlled trial, investigated the long-term effects of cognitive training on everyday functional outcomes in older adults. The study involved 2,832 participants aged 73.6 on average, living independently in six U.S. cities. Participants were randomly assigned to one of four groups: three cognitive training groups (memory, reasoning, speed of processing) and a control group. Cognitive training interventions included 10 sessions targeting specific cognitive abilities, with booster sessions at 11 and 35 months for a subset of participants. The study found that reasoning training significantly reduced difficulty in instrumental activities of daily living (IADL) compared to the control group, with an effect size of 0.29. Booster training for the speed of processing group showed a significant effect on performance-based functional measures, with an effect size of 0.30. Cognitive training effects on specific abilities were maintained over five years, with effect sizes ranging from 0.23 to 0.76. Booster training further improved outcomes for reasoning and speed of processing, with effect sizes of 0.28 and 0.85, respectively. The study concluded that cognitive training, particularly reasoning training, led to less functional decline in self-reported IADL. Cognitive training improved specific cognitive abilities that continued for five years. The results suggest that cognitive interventions can reduce age-related decline in self-reported IADL, which are precursors to dependence in basic ADLs. However, the effects on functional outcomes were modest and not observed until the five-year follow-up, possibly due to a delayed relationship between cognitive decline and functional deficits. The study highlights the importance of both self-report and performance-based measures in assessing the impact of cognitive training on daily function. It also underscores the need for future research to explore the mechanisms of training-related improvements, such as self-efficacy, in more detail. The ACTIVE study is the first large-scale, randomized trial to show that cognitive training improves cognitive function in well-functioning older adults and that these improvements last up to five years. The results support the clinical meaningfulness of cognitive training interventions in preventing or delaying functional disability in an aging population.The ACTIVE study, a five-year follow-up of a randomized controlled trial, investigated the long-term effects of cognitive training on everyday functional outcomes in older adults. The study involved 2,832 participants aged 73.6 on average, living independently in six U.S. cities. Participants were randomly assigned to one of four groups: three cognitive training groups (memory, reasoning, speed of processing) and a control group. Cognitive training interventions included 10 sessions targeting specific cognitive abilities, with booster sessions at 11 and 35 months for a subset of participants. The study found that reasoning training significantly reduced difficulty in instrumental activities of daily living (IADL) compared to the control group, with an effect size of 0.29. Booster training for the speed of processing group showed a significant effect on performance-based functional measures, with an effect size of 0.30. Cognitive training effects on specific abilities were maintained over five years, with effect sizes ranging from 0.23 to 0.76. Booster training further improved outcomes for reasoning and speed of processing, with effect sizes of 0.28 and 0.85, respectively. The study concluded that cognitive training, particularly reasoning training, led to less functional decline in self-reported IADL. Cognitive training improved specific cognitive abilities that continued for five years. The results suggest that cognitive interventions can reduce age-related decline in self-reported IADL, which are precursors to dependence in basic ADLs. However, the effects on functional outcomes were modest and not observed until the five-year follow-up, possibly due to a delayed relationship between cognitive decline and functional deficits. The study highlights the importance of both self-report and performance-based measures in assessing the impact of cognitive training on daily function. It also underscores the need for future research to explore the mechanisms of training-related improvements, such as self-efficacy, in more detail. The ACTIVE study is the first large-scale, randomized trial to show that cognitive training improves cognitive function in well-functioning older adults and that these improvements last up to five years. The results support the clinical meaningfulness of cognitive training interventions in preventing or delaying functional disability in an aging population.