An Overview of the Cardiorespiratory Hypothesis and Its Potential Contribution to the Care of Neurodegenerative Disease in Africa

Cardiorespiratory fitness mediates the relationship between depressive symptomatology and cognition in older but not younger adults

Aging is commonly associated with emotional, physical, and cognitive changes, with the latter, particularly affecting executive functioning. Further, such changes may interact. For instance, depressive symptomatology is a known risk factor for developing cognitive deficits, especially at older ages. In contrast, an active lifestyle, reflected in high cardiorespiratory fitness (CRF) levels, has proven to protect against adverse effects on cognition across the adult lifespan. Hence, this study aimed to investigate the relationships between depressive symptomatology, CRF, and cognition during critical developmental stages, namely in young adults (YA), when cognitive abilities are at their peak, and in older adults (OA), when they may start to decline. Eighty-one OA with ages between 60 and 89 years (M = 70.46; SD = 7.18) and 77 YA with ages between 18 and 34 years (M = 22.54; SD = 3.72) went through (i) a sociodemographic interview, (ii) an emotional assessment, (iii) a battery of cognitive tests, and (iv) a physical evaluation assessing CRF levels, visceral fat and body-mass index. Results showed that OA exhibited lower general cognitive performance, inhibitory control, cognitive flexibility, memory, and CRF. Depressive symptoms and anxiety were not different among groups, with CRF mediating the relationship between depressive symptoms and cognition in the OA group. The present study provides valuable insights into the interplay between emotional, physical, and cognitive well-being. Additionally, it calls attention to how lifestyle factors can play a protective role against the adverse effects that depressive symptoms have on cognition, particularly at older ages.

Effects of Cardiorespiratory Fitness on Cerebral Oxygenation in Healthy Adults: A Systematic Review

Introduction

Exercise is known to improve cognitive functioning and the cardiorespiratory hypothesis suggests that this is due to the relationship between cardiorespiratory fitness (CRF) level and cerebral oxygenation. The purpose of this systematic review is to consolidate findings from functional near-infrared spectroscopy (fNIRS) studies that examined the effect of CRF level on cerebral oxygenation during exercise and cognitive tasks.

Methods

Medline, Embase, SPORTDiscus, and Web of Science were systematically searched. Studies categorizing CRF level using direct or estimated measures of V̇O_2max and studies measuring cerebral oxygenation using oxyhemoglobin ([HbO₂]) and deoxyhemoglobin ([HHb]) were included. Healthy young, middle-aged, and older adults were included whereas patient populations and people with neurological disorders were excluded.

Results

Following PRISMA guidelines, 14 studies were retained following abstract and full-text screening. Cycle ergometer or treadmill tests were used as direct measures of CRF, and one study provided an estimated value using a questionnaire. Seven studies examined the effects of CRF on cerebral oxygenation during exercise and the remaining seven evaluated it during cognitive tasks. Increased [HbO₂] in the prefrontal cortex (PFC) was observed during cognitive tasks in higher compared to lower fit individuals. Only one study demonstrated increased [HHb] in the higher fit group. Exercise at submaximal intensities revealed increased [HbO₂] in the PFC in higher compared to lower fit groups. Greater PFC [HHb] was also observed in long- vs. short-term trained males but not in females. Primary motor cortex (M1) activation did not differ between groups during a static handgrip test but [HHb] increased beyond maximal intensity in a lower compared to higher fit group.

Conclusion

Consistent with the cardiorespiratory hypothesis, higher fit young, middle-aged, and older adults demonstrated increased cerebral oxygenation compared to lower fit groups. Future research should implement randomized controlled trials to evaluate the effectiveness of interventions that improve CRF and cerebral oxygenation longitudinally.

Mini-Review of Studies Testing the Cardiorespiratory Hypothesis With Near-Infrared Spectroscopy (NIRS): Overview and Perspectives

The cardiorespiratory hypothesis (CH) is one of the hypotheses used by researchers to explain the relationship between cardiorespiratory fitness and cognitive performance during executive functions. Despite the indubitable beneficial effect of training on brain blood flow and function that may explain the link between physical fitness and cognition and the recognition of the near-infrared spectroscopy (NIRS) as a reliable tool for measuring brain oxygenation, few studies investigated the CH with NIRS. It is still not well understood whether an increase in brain flow by training is translated into an increase in cerebral oxygenation. Thus, the objective of this mini-review was to summarize main results of studies that investigated the CH using the NIRS and to propose future research directions.

Brain Structure, Cardiorespiratory Fitness, and Executive Control Changes after a 9-Week Exercise Intervention in Young Adults: A Randomized Controlled Trial

Cardiorespiratory fitness (CRF) is assumed to exert beneficial effects on brain structure and executive control (EC) performance. However, empirical evidence of exercise-induced cognitive enhancement is not conclusive, and the role of CRF in younger adults is not fully understood. Here, we conducted a study in which healthy young adults took part in a moderate aerobic exercise intervention program for 9 weeks (exercise group; n = 48), or control condition of non-aerobic exercise intervention (waitlist control group; n = 72). Before and after the intervention period maximal oxygen uptake (VO_2max) as an indicator of CRF, the Flanker task as a measure of EC performance and grey matter volume (GMV), as well as cortical thickness via structural magnetic resonance imaging (MRI), were assessed. Compared to the control group, the CRF (heart rate, p < 0.001; VO_2max, p < 0.001) and EC performance (congruent and incongruent reaction time, p = 0.011, p < 0.001) of the exercise group were significantly improved after the 9-week aerobic exercise intervention. Furthermore, GMV changes in the left medial frontal gyrus increased in the exercise group, whereas they were significantly reduced in the control group. Likewise, analysis of cortical morphology revealed that the left lateral occipital cortex (LOC.L) and the left precuneus (PCUN.L) thickness were considerably increased in the exercise group, which was not observed in the control group. The exploration analysis confirmed that CRF improvements are linked to EC improvement and frontal grey matter changes. In summary, our results support the idea that regular endurance exercises are an important determinant for brain health and cognitive performance even in a cohort of younger adults.