Cardiorespiratory fitness and cognitive function in midlife: Neuroprotection or neuroselection?

Abstract

Objective To determine if better cognitive functioning at midlife among more physically fit individuals reflects “neuroprotection,” in which fitness protects against age-related cognitive decline, or “neuroselection,” in which children with higher cognitive functioning select into more active lifestyles. Methods Children in the Dunedin Longitudinal Study (N=1,037) completed the Wechsler Intelligence Scales and the Trail-Making, Rey-Delayed-Recall, and Grooved-Pegboard tasks as children and again at midlife (age-38). Adult cardiorespiratory fitness was assessed using a submaximal exercise test to estimate maximum-oxygen-consumption-adjusted-for-body-weight in milliliters/minute/kilogram (VO2max). We tested if more-fit individuals had better cognitive functioning than their less-fit counterparts (which could be consistent with neuroprotection), and if better childhood cognitive functioning predisposed to better adult cardiorespiratory fitness (neuroselection). Finally, we examined possible mechanisms of neuroselection. Results Participants with better cardiorespiratory fitness had higher cognitive test scores at midlife. However, fitness-associated advantages in cognitive functioning were present already in childhood. After accounting for childhood-baseline performance on the same cognitive tests, there was no association between cardiorespiratory fitness and midlife cognitive functioning. Socioeconomic and health advantages in childhood, and healthier lifestyles during young adulthood explained most of the association between childhood cognitive functioning and adult cardiorespiratory fitness. Interpretation We found no evidence for a neuroprotective effect of cardiorespiratory fitness as of midlife. Instead, children with better cognitive functioning are selecting into healthier lives. Fitness interventions may enhance cognitive functioning. But, observational and experimental studies testing neuroprotective effects of physical fitness should consider confounding by neuroselection.

Cardiorespiratory Fitness Is Associated with Selective Attention in Healthy Male High-School Students

“…Moreover, Belsky et al (2015) found that children with higher IQ scores grew up to be adults who were less sedentary and less obese, and in turn, had better cardiorespiratory fitness. They suggest that socioeconomic status, household and neuroselection must be considered when investigating the fitness-executive function hypothesis.…”

Multi-modal characterization of rapid anterior hippocampal volume increase associated with aerobic exercise

“…However, there is little evidence on the effects of exercise on the brain in early to middle adulthood, despite clear relevance of this question to lifelong cognitive health (Voelcker-Rehage and Niemann, 2013). For example, epidemiological studies have shown that lifestyle during middle age has significant consequences for cognitive performance decades later (Wilson et al, 2002; Karp et al, 2006; Belsky et al, 2015). It is also unknown whether brain plasticity in humans requires exercise interventions measured in months or years, although see Sagi et al (2012) for an example of a more rapid structural change in the hippocampus with a non-exercise intervention and Tavor et al (2013) for an exploration of the time course of this change.…”

Leisure-Time Physical Activity and Academic Performance: Cross-Lagged Associations from Adolescence to Young Adulthood

“…For example in a British longitudinal study, higher mental ability at age of 10 years predicted a significantly higher level of physical activity in adulthood16. A more recent longitudinal New Zealand study showed that children with better cognitive ability achieved a higher level of physical fitness in adulthood17. Thus, the reported associations between physical activity and academic performance may partly reflect the associations between cognitive ability and physical activity.…”

“…When reviewing the findings of the studies that examine the association between physical activity and academic performance, it is important to bear in mind that childhood intelligence and cognitive ability have shown to predict subsequent health15, physical activity16 and physical fitness17. For example in a British longitudinal study, higher mental ability at age of 10 years predicted a significantly higher level of physical activity in adulthood16.…”