Effects of physical activity and cognitive stimulation on cognitive functioning, Alzheimer's disease related blood biomarkers and brain glucose metabolism in older adults

[Truncated abstract] Alzheimer's disease (AD) is a progressive and neurodegenerative condition caused by nerve cell death resulting in atrophy of the brain. It is the commonest cause of dementia. The more prevalent type of AD is late onset AD (LOAD) and is believed to commence many years prior to the clinical diagnosis of AD. With no effective pharmacological interventions at present, non-pharmacological interventions such as lifestyle modifications are currently being investigated to prevent and/or delay the onset of AD. Evidence from observational and interventional studies show benefits of physical activity (PA) or staying mentally active at enhancing cognition and reducing the risk of cognitive decline. Very few studies have investigated whether a combination of these activities can further improve cognitive functioning and none has assessed the effects of physical activity together with computerised brain training software in cognition togather with AD related blood biomarkers and neuroimaging markers. In this pilot study (referred to as the physical exercise and cognitive stimulation study-PEACS), 223 cognitively healthy community dwelling older adults were allocated into one of the following four groups of physical activity (PA), cognitive stimulation (CS), a combination of both and a no contact control group. The PA protocol included 3 days of walking and 2 days of resistance training exercises for 16 weeks. Participants undergoing the CS protocol, were either administered the insight program (visual stimulation) or the brain fitness program (BFP-auditory stimulation) (Posit Science, USA) (5 days/week, for 1 hour) for the first 8 weeks, and then the software programs were swapped for the last 8 weeks. Assessments included a neuropsychological battery and blood biomarkers at baseline, 8 weeks and at 16 weeks post intervention. A subset of participants underwent DXA scans to assess body fat content and FDG-PET to assess brain glucose metabolism were performed at week 16 of the study. A follow-up analysis on cognitive performance post-intervention was undertaken at week 52 of the study. The findings presented in this thesis showed that compared to the control (non-training group), the combination of physical activity and computerised brain training only, increased Long-term delayed recall (LTDR) scores, indicating improvements in verbal memory. No significant improvements were observed for other cognitive domains. The improvement in verbal memory was maintained on follow up after completion of the training, suggesting long lasting effects on this particular cognitive domain. Further analysis revealed that auditory followed by visual stimulation had a greater impact on verbal memory than visual followed by auditory stimulation...