ObjectivesThis study aimed to investigate decision-making competence of midlife and older adults, and its relationship with cognitive reserve and cognitive functions.MethodsA total of 120 healthy adults (aged 50 to 90 years) completed a decision-making task and various neurocognitive tests. In the decision-making task, participants encountered everyday scenarios with two options, including relevant and irrelevant numerical information, formatted as frequencies or percentages. In congruent trials, the relevant and irrelevant information pointed to the same decision, while in incongruent trials they pointed to opposing decisions. Cognitive reserve (CR) was measured using a composite index reflecting lifetime education, professional experiences, and engagement in cognitively demanding leisure activities.ResultsParticipants demonstrated higher accuracy in congruent trials than in incongruent ones, with this difference being more pronounced among individuals with lower CR. Additionally, decision-making performance decreased with increasing age for both number formats, with a steeper decline observed in trials involving frequencies. CR, along with measures of judgement, mental calculation, and health numeracy, accounted for 41% of the variance in decision-making performance. CR also moderated the relationship between decision-making performance and health numeracy: participants with poorer numeracy skills performed accurately if their CR level was high.DiscussionThis study confirms the positive relationship between CR and decision-making ability in advanced age. Higher levels of CR are linked to reduced decline in health numeracy with age and lower susceptibility to conflicting information during decision-making.