posted on 2015-06-25, 10:37authored byJennifer Stock
Dementia incidence is rising as our population is ageing. There is growing evidence for the protective effect of physical activity against cognitive decline. However, there are inconsistent results across studies despite the large number of high quality trials. The role of psychosocial factors on cognitive outcomes was investigated in the present thesis due to the evidence of their relationship with physical activity and for their effect on cognitive ability in other contexts. The psychosocial factors investigated were attitudes towards ageing, perceived control, mental health, and self-efficacy using cross-sectional studies and pilot randomised controlled exercise trials to test proof of concept. Study 1a found that more positive attitudes towards ageing were associated with better self-reported subjective and functional health. Perceived control mediated the effect of attitudes related to psychosocial loss with ageing and physical activity level mediated the effect of attitudes related to psychological growth with ageing on subjective health. Attitudes towards ageing mediated the effect of perceived control on functional health. Study 1b and 1c explored attitudes towards ageing in more detail and found that older adults attitudes towards ageing were similarly negative to those held by young adults in the UK. A substantial proportion of attitudes reported by older adults related to physical functioning and cognitive ability. Attitudes towards ageing in China were more positive than those in the UK which suggested a potential relationship with socio-cultural and environmental factors and possible scope for attitude change from an intervention. A higher proportion of attitudes towards ageing reported in the UK were related to physical functioning and cognitive ability compared to China. These findings highlighted the potential for attitudes towards ageing and perceived control to play a role in the context of physical activity, cognitive ability and subjective health. Study 2a found that physical, social, and mental activities were independently associated with cognitive ability which informed the study design of exercises to include a pseudo control group that controlled for social interaction and mental stimulation. Study 2b found that mental health partially mediated the association between walking and cognitive ability. In older adults with better mental health, walking was not associated with cognitive ability. In older adults with poorer mental health walking was associated with better cognitive ability. Study 3 utilised available data from a pilot resistance training randomised controlled trial with middle-aged adults to test proof of concept for the role of psychosocial factors in this context. Preliminary evidence was provided for a potential association between improvements on some psychosocial factors and cognitive performance improvements. The associations of cognitive gains with psychosocial factors were independent to those of physical fitness improvements, which may indicate a potentially additive effect. Study 4 assessed the feasibility of the pilot randomised controlled trial of resistance training with older adults. Recruitment was successful but high drop-out rates lead to between group differences in age and baseline cognitive ability. Adaption of exercise to suit individual capabilities increased participation and adherence of those who completed the programmes was high. The limited usefulness of analysis by group was highlighted due to the large variation in response to exercise within groups on psychosocial and cognitive measures. Older participants were more likely to report a negative effect of resistance training on psychosocial measures, which indicated a potential confound on outcomes of exercise interventions with older adult populations. Preliminary analysis indicated that improvements on some psychosocial factors were associated with domain specific cognitive gains. This association could be due to a variety of mechanisms, such as meta-cognitive motivational processes, for example sustained effort and attention and the use of memory strategies. However, these findings need to be interpreted with caution due to the parallel change of variables, small sample size and feasibility and pilot nature of the interventions. There is a potential implication for the design of exercise programmes if they facilitate improvements in psychosocial factors as well as physical fitness, then this could enhance the effect of exercise on cognitive outcomes. Future research should replicate these studies with larger sample sizes to further understand the role of psychosocial factors in cognitive gains during exercise interventions in older adults.
The work in this thesis was funded by the Research School of Health and Life Sciences through nomination for a Development Fund PhD Studentship, Loughborough University.
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A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University. Appendix J has been removed for copyright reasons.