Abstract
Recent studies suggest that cardiorespiratory fitness (CRF) mitigates the brain’s atrophy typically associated with aging, via a variety of beneficial mechanisms. One could argue that if CRF is generally counteracting the negative effects of aging, the same regions that display the greatest age-related volumetric loss should also show the largest beneficial effects of fitness. To test this hypothesis we examined structural MRI data from 54 healthy older adults (ages 55–87), to determine the overlap, across brain regions, of the profiles of age and fitness effects. Results showed that lower fitness and older age are associated with atrophy in several brain regions, replicating past studies. However, when the profiles of age and fitness effects were compared using a number of statistical approaches, the effects were not entirely overlapping. Interestingly, some of the regions that were most influenced by age were among those not influenced by fitness. Presumably, the age-related atrophy occurring in these regions is due to factors that are more impervious to the beneficial effects of fitness. Possible mechanisms supporting regional heterogeneity may include differential involvement in motor function, the presence of adult neurogenesis, and differential sensitivity to cerebrovascular, neurotrophic and metabolic factors.
Highlights
The brains of seemingly healthy individuals undergo various degrees of cortical and subcortical atrophy with aging (Raz et al, 2005, 2010; Gordon et al, 2008)
In other words, are the profiles of the effects of cardiorespiratory fitness (CRF) and of aging similar throughout the brain or does CRF preferentially influence only some of the brain regions that are affected by aging and not others? To address these questions we report a direct comparison of the profiles of the effects of aging and fitness on volumetric measures obtained throughout the brain in older adults between the ages of 55 and 87
To determine that the lack of correlation or consistency between the effect of age and fitness on brain volume is not merely due to lack of power, it is important to show that regional volumetric measures are sensitive to each of these two independent variables
Summary
The brains of seemingly healthy individuals undergo various degrees of cortical and subcortical atrophy with aging (Raz et al, 2005, 2010; Gordon et al, 2008). The exact mechanisms underlying these changes are not completely known, vascular (Brown and Thore, 2011; Davenport et al, 2012; Lähteenvuo and Rosenzweig, 2012; Fabiani et al, 2014), genetic (McGue and Johnson, 2008; Papenberg et al, 2015), oxidative stress (Muller et al, 2007; Dai et al, 2014; Thorin and Thorin-Trescases, 2014) and hormonal (Morrison and Baxter, 2012) factors may all contribute significantly These anatomical changes are considered to have important functional consequences, and to influence some of the cognitive decline that accompanies aging (e.g., Salthouse, 2011; Fabiani, 2012; Nyberg et al, 2012).
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