Background Sarcopenia and age-related cognitive decline (ARCD) are important age-related conditions which significantly impact upon the quality of life of older adults. ARCD is a well-established research area, whereas sarcopenia is a relatively new field. Research into the inter-relationships between them and possible common underlying mechanistic processes is lacking. Methods Several research techniques were used: a large systematic review; the development of an image analysis technique to measure neck muscle size on volumetric MR brain scans; the subsequent use of the technique in elderly cohort studies; statistical modelling to investigate the role of glucocorticoids in sarcopenia; and an invasive clinical study to develop a novel technique to measure the activity of 11beta-hydroxysteroid dehydrogenase (11βHSD1) in the human brain in vivo. Results I consistently found a relationship between: some measures of brain structure and muscle size; markers of brain structure and muscle function, mostly grip strength and gait speed; and cognition and muscle function. However, I found no relationship between current cognition and muscle size in any of the above studies. Cortisol was identified as a possible explanatory factor in the relationship between both cognition and brain volume with gait speed. I found an association between markers of immunosenescence and sarcopenia (neck muscle CSA and grip strength) and an association between expression of the cortisol amplifying enzyme 11βHSD1 and quadriceps strength. I developed a technique to measure 11βHSD1 activity across the human brain, which found that the amount of cortisol produced within the brain was not detectable and highlighted the asymmetries within the cerebrovascular venous system. Conclusions Further longitudinal studies looking at the association between sarcopenia and ARCD are now required to investigate these important relationships further and hopefully this will lead to improved therapeutic options.

This dissertation proposes that while traditional cognitive psychology literature suggests that cognitive function decreases with age, these decreases are dependent on the types of testing being performed. While traditional cognitive tests of memory and processing speed show declines associated with age, this research suggests these declines are not robust across all types of learning. The coming pages present four studies aimed at furthering our understanding of how different age cohorts of consumers learn about products in active and complex marketplaces. Study one reveals an age advantage associated with learning experientially; an interesting and somewhat surprising result that warrants further investigation given the rapid rate at which populations are aging. The additional studies presented here begin that investigation through the application of several psychological theories. This research explores increased vigilance associated with the security motivation system (based on the principles of evolutionary psychology), the possible impact of mortality salience through the application of Terror Management Theory and a positive correlation between age and cognitive control, as possible explanations. / Business Administration/Marketing

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