The relationship between interhemispheric transfer time and physical activity as well as cardiorespiratory fitness in healthy older adults.

The structural and functional degradation of the corpus callosum (CC) has been shown to play an important role in the context of cognitive aging (Reuter-Lorenz and Stanczak, 2000). This is also reflected by findings of elongated interhemispheric transfer time (IHTT) in older adults (Riedel et al., 2022). At the same time, a protective effect of physical activity (PA) and cardiorespiratory fitness (CRF) on brain health including the CC is widely accepted (Hillman et al., 2008; Loprinzi et al., 2020). Based on this idea, the present study investigated the relationship between IHTT and PA/CRF in 107 healthy older adults (m: 64, f: 43) aged 67.69 ± 5.18. IHTT was calculated detecting event-related potentials (ERPs) using an established Dimond-Task. PA was evaluated using accelerometry resulting in estimates of overall bodily motion and time spent at higher intensity PA. CRF was estimated using graded exercise testing, approximating running speed at 4 mmol/l blood lactate concentration. The results showed a negative correlation between IHTT and PA overall as well as in the male subgroup and between IHTT and CRF in women. This indicates a potential relationship between IHTT and PA/CRF. While the present investigation is only the first to hint at such a relationship taking into account the differential effects with regards to sex, mode of PA/CRF and IHTT direction, it is in line with previous findings and theoretical suggestions linking brain health to PA/CRF in the context of aging. Further research is needed in order to increase our understanding of the underlying mechanisms and of the influence of sex, PA intensity, degree of CRF and significance of IHTT direction.