Do leisures activities and rest-activity rythm explain executive performance in aging?

There exists a large inter-individual variability regarding the effects of aging on cognition. Sleep-wake rhythms and cognitive reserve may contribute to explain why some people appear to be more resistant to the effects of aging than others. Particularly, individuals who have developed a high level of reserve resist better to the effects of aging than individuals with lower cognitive reserve. Conversely, a decrease of day-to-day stability of sleep-wake rhythms and an increase of sleep fragmentation may contribute to potentiate the effects of aging. In this study, we describe the impact of cognitive reserve and rest-activity rhythm on executive functions in normal aging. One hundred and sixty five healthy participants aged from 59 to 81 years were recruited. We assessed the three major executive functions: Inhibition (Stroop test, Hayling test, TAP Incompatibility subtest), Shifting (TAP Flexibility subtest, Plus-Minus task), and Updating (Letter-Number Sequencing subtest from MEM III, Letter memory task, 2-back task). Cognitive reserve was measured by questionnaires assessing leisure activities across the lifespan. Actigraphy was used to measure parameters of sleep-wake cycle (24-h fragmentation and 24-h stability) over a minimal period of 12 days. In a first model, multiple linear regressions (p<0.05) adjusted for age, Mattis score and processing speed showed that education did not explained executive performance. Conversely, current practice of at least one social leisure activity has a positive impact on flexibility and a minimum of 3 intellectual activities or a minimum of two social activities regularly performed are necessary to have a positive impact on updating. In a second model adjusted for age, Mattis score and processing speed and formal education, we did not observed a significant effect of day-to-day stability and sleep fragmentation on executive functioning. These results suggest that the cognitive reserve is related to abilities in some executive tests while rest-activity rhythm does not seem to explain the inter-individual variability of executive performance.