# Redefining cognitive testing: the impact of cognitive reserve and sex from early to late adulthood

## TL;DR

This study shows that cognitive reserve and sex influence cognitive performance across adulthood, with cognitive reserve reducing age-related decline and diminishing sex differences.

## Contribution

The study introduces a refined cognitive testing approach that accounts for cognitive reserve and sex, revealing their combined impact on cognitive performance.

## Key findings

- A single global cognition factor was identified after removing redundant tests.
- Cognitive performance declined significantly after age 60, but high cognitive reserve slowed this decline.
- Sex differences in cognitive performance were largely explained by differences in cognitive reserve, especially from work-related activities.

## Abstract

Cognition involves interconnected functions which may overlap across tasks. Thus, neuropsychological assessment should be optimized in tests, while integrating socio-demographic and socio-cultural factors like Sex and Cognitive Reserve (CR). This study aims to (1) determine whether a global cognitive factor can be identified from a comprehensive battery and whether it remains detectable after removing redundant tests; and (2) examine the combined effects of Age and Cognitive Reserve (CR) on performance across sexes.

One thousand and one healthy individuals (599 females) aged 18–99 underwent a battery of tests and the Cognitive Reserve Index questionnaire (CRIq) was administered to estimate CR.

Reducing the number of overlapping tests revealed a single Cognition factor representing overall performance. Performance remained relatively stable up to the age of 60, then a marked decline was observed. Overall, test scores tended to be higher in males, and in most tasks, the higher CR the better the performance. However, when CR was considered, sex differences were no longer evident in most tasks. Notably, CR had a strong impact on female performance -especially CR gained through workrelated activities.

Reducing the number of redundant tests enhances the efficiency of the assessment. High CR reduces decline and slows its progression. Differences in sex-related performance seem to depend on CR, mainly in relation to occupation, which may differentially benefit males in terms of cognitive performance. This underscores the importance of promoting cognitively enriching life experiences for both sexes and equal career opportunities across the lifespan to support cognitive health in ageing.