Exercise and cerebral haemodynamics for brain health in older adults

Feron, Jack ORCID: 0009-0001-3928-2135 (2024). Exercise and cerebral haemodynamics for brain health in older adults. University of Birmingham. Ph.D.

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Abstract

The global population is ageing. With age, inevitably, comes declines in all aspects of health, including to brain health. Brain health is particularly important in later life, as this dictates cognitive function and thus our ability to live independently and maintain a good quality of life. Age-related changes in cerebral haemodynamics are hypothesised to contribute to age-related cognitive declines. Identifying strategies or individual characteristics that delay age-related changes to cerebral haemodynamics could help to enable a healthy ageing process. Cardiorespiratory fitness and exercise training are commonly assumed to increase cerebral blood flow; however, there are large disparities within the available literature. Therefore, the purpose of this thesis was to investigate the impact of cardiorespiratory fitness and exercise training on resting cerebral blood flow (CBF) and arterial transit time (ATT) in healthy older adults. Furthermore, the importance of these cerebral haemodynamic markers for cognitive function was assessed.

Chapter 1 describes some key concepts and theories in this field and provides an overview of the existing literature. Chapter 2 includes cross-sectional analyses which revealed that older adults with a higher BMI had lower global CBF and a longer global ATT. Cardiorespiratory fitness was not associated with CBF, but fitter older adults unexpectedly had longer ATT in parietal and occipital regions. Regarding cognitive function, neither CBF or ATT were associated with processing speed, working memory, or attention performance. Chapter 3 investigates the impact of exercise training on CBF and ATT. Older adults were randomised into a control or exercise group (lifestyle maintenance vs. six-month home-based high-intensity exercise programme). Following the intervention, there were no group-level differences in CBF or ATT, despite increased cardiorespiratory fitness in the exercise group. However, sub-group analysis of exercise participants revealed that those with the greatest cardiorespiratory fitness gains (>2 mL/kg/min) experienced significant global CBF reductions. Moreover, across the whole exercise group, changes in cardiorespiratory fitness and global CBF were negatively associated. Regarding cognitive function, there were also no group-level differences, nor were changes in CBF or ATT associated with cognitive function changes. Chapter 4 focusses on associations between accelerometer-derived physical activity behaviours and CBF or ATT, including both cross-sectional and longitudinal analyses. Neither set of analyses identified associations between cerebral haemodynamics and sedentary behaviour, light physical activity, or moderate-to-vigorous physical activity. Chapter 5 explored whether adherence to the exercise intervention predicted subsequent changes to cardiorespiratory fitness. Exploratory analyses indicated that superior general adherence and adherence specifically to exercise volume or intensity were associated with greater fitness gains, but these associations were strongest for exercise volume. Finally, Chapter 6 summarises conclusions relating to the preceding experimental chapters and discusses future work required to assess the impact of longer-term exercise training on cerebral haemodynamics in older adults, and whether cerebral haemodynamics predict cognitive function over the longer-term.

Overall, the findings from this thesis show that exercise training appears to reduce resting CBF in older adults, but only when cardiorespiratory fitness gains were evident. Further, changes in physical activity behaviours had no clear effect on cerebral haemodynamics within this population, and cerebral haemodynamics were not associated with cognitive function.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):