In the last decade, several large multi-institutional neuroimaging studies have emerged, the chief amongst them being the Alzheimer's Disease Neuroimaging Initiative (ADNI). The data obtained from these studies are free to access for researchers, and are an invaluable resource in areas where getting a large enough cohort takes too long or becomes too expensive to fund. However, one should proceed with caution as the sample consists mostly of highly educated American Caucasians, reducing its generalisability to other countries. For those who have an interest in cross-ethnicity differences however, the ADNI dataset is ideal for this purpose. This thesis begins with a cross-sectional look at cognitively normal, elderly Hong Kong Chinese subjects and matched ADNI Caucasian ones. When comparing total cortical grey matter volumes and the summed volumes of cortex that are often associated with Alzheimer's disease, it was found that Chinese subjects had significantly smaller cortical volumes than American Caucasians, even after adjusting for brain volume, despite having similar cognitive test scores. Unable to control for extrinsic factors such as environment and culture, however, no strong conclusions could be made. The second study of this thesis consists of a replication of the first, this time using American Chinese and American Caucasian subjects, all long-time residents of San Francisco. The same results were found regarding total cortical grey matter volume, leading to the implication that the Chinese population have inherently smaller cortices than Caucasians, but with no obvious cognitive detriment. Having found that ethnicity can have an effect on brain structure, the focus then shifts to how the brain changes during healthy ageing. The concept of healthy ageing has been gaining in popularity in recent years, especially as more and more age-related diseases are being thought of as "pathological ageing". In order to help diagnose and monitor diseases related to ageing, it is therefore important to understand the trajectory and effects of normal ageing. As such, a pilot fMRI study was conducted to try and see how attention and increased vulnerability to interference from presented stimuli changed with age. The results from the pilot study matched generally well with the literature and opens up the door towards using cognitive paradigms in neuroimaging to act as baseline markers of cognitive function, which can then be correlated with other measures to paint a more detailed portrait of the healthy ageing brain. / published_or_final_version / Diagnostic Radiology / Doctoral / Doctor of Philosophy

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This dissertation contributes to the existing literature on aging and health in human geography by exploring the relationships among homelessness, stable housing, and opportunities for healthy aging. Over the last 30 years, various social, economic, spatial, and political trends have reshaped Canadian society. These trends have resulted in a more complex, individualized life course in the 21st century, characterized by a greater number of delays and divergences as people adapt to the societal changes that have unfolded. Outcomes of such trends have been increasing rates of household financial problems, a greater incidence of absolute poverty, and growth in the homeless population. At the same time, Canada is undergoing demographic changes as the population ages and by 2030, it is estimated that approximately 25 percent of Canada’s population will be 65 years of age or older (Moore and Rosenberg, 2001). In this context, it is likely a greater proportion of the older population will have experienced homelessness in their life compared to previous generations (McDonald et al., 2006). Presently, academic research and public policy have failed to consider how people with histories of homelessness will fare in older age. This dissertation addresses this unexplored area of research through the achievement of three broad objectives. First, the research contributes an original conceptualization of the long-term effects of homelessness on health and aging. Second, it explores how stable housing can improve homeless people’s opportunities for healthy aging. Third, the research provides a better understanding of how being homeless in earlier life can affect experiences of health and aging in later stages of the life course. The fieldwork to achieve these goals involved a structured survey (N=50) and interviews (n=29) with a sample of formerly homeless older people in Toronto, Canada. The findings reveal that older people with histories of homelessness are aging in a more disadvantaged context than the general older population. Various aspects of stable housing can improve health and offer a better opportunity for positive experiences of aging. However, formerly homeless people continue to face barriers to affordable, quality housing and other determinants of a healthy lifestyle in older age. / Thesis (Ph.D, Geography) -- Queen's University, 2013-09-05 16:08:50.051

We continually encounter different ground terrain such as slippery, compliant, uneven, rocky, and irregular terrain when walking, yet we know very little about how individuals safely negotiate this type of complex environment. Furthermore, we know little about how aging affects stability in these situations despite the increased risk of falls and fall-related injuries among older adults. Paramount to our comprehension of how individuals safely traverse challenging ground terrain is to understand how visual information is utilized as vision is the first line of defense for preparing for and/or avoiding potentially hazardous terrain or obstacles. Thus, the objective of this thesis was to provide a better understanding towards how individuals negotiate different ground terrain in the environment to maintain dynamic stability and prevent the occurrence of a fall. In particular, the role of vision and the effects of aging were investigated. Three studies focused on the role of vision while negotiating varying ground terrain while two studies examined stability across these surfaces. Two main conclusions can be drawn from the results of the three studies on the role of vision. First, regardless of age individuals fixate on highly task-relevant areas (i.e. surfaces eventually stepped on) in an on-line manner and by fixating approximately two steps ahead. Second, visual information from the lower visual field is important for negotiating varying ground terrain. This latter finding has implications for older adults who wear multi-focal glasses and suggests that these individuals should be cautious when wearing these glasses in complex environments. In terms of stability, the results suggest that young and older adults demonstrate greater instability when walking across varying unstable ground terrain compared to solid level ground. Older adults are particularly more unstable in the medial-lateral direction when negotiating the challenging terrain, which may explain the frequency of laterally directed falls and increased hip-fracture risk with advancing age. Interestingly, older adults appear more stable in the anterior-posterior direction; although, this can largely be explained by the cautious gait strategy (i.e. slower walking speed and shorter steps) adopted by these individuals. The results of the studies of my thesis provide valuable insight into how individuals safely negotiate different types of challenging ground terrain when walking. Importantly, this knowledge can serve as an initial step in attempting to reduce falling among those at risk.

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Elderly subjects are known to perform less well than young subjects on laboratory tests of recall from episodic memory. Although the elderly report increased difficulty in recalling information from semantic memory, experimental attempts to demonstrate this deficit are equivocal. It is suggested that studies which use multiple choice tests to measure recall from semantic memory fail to find age-related deficits because the tests provide cues to aid in recall, a procedure known to reduce age-related differences in recall from episodic memory. When time to retrieve a single item of information from semantic memory is measured, some studies show an age-related deficit while others do not. When episodic recall is tested using categorized lists, the elderly show recall deficits largely because they access fewer categories than do young subjects. Semantic cues increase the number of categories recalled by the elderly subjects more than for young subjects in such tasks, Since studies with young subjects show that recall both from categorized lists and from a taxonomic category (a semantic recall task) proceeds via temporal clusters of related items, it was hypothesized that elderly subjects would show increased difficulty in accessing clusters of related items in a semantic recall task, just as they do in recall of categorized lists. Further, it was hypothesized that semantic cues would reduce the time taken by the elderly to access sequential clusters of information from semantic memory. In one experiment, healthy, well-educated young (ages 19-21) and old (ages 67-72) subjects were required to perform a Bousfield task: to generate examples from two taxonomic categories, foods and animals, for 15 minutes. The slope-difference algorithm, a procedure developed by Gruenewald and Lockhead, was used to categorize each subject's inter- item times (IIT's) into times between temporal clusters (BIIT's) and times between items within temporal clusters (WIIT). In a second experiment, a group of old subjects were given semantic differential labels as cues for recall on one of their two experimental trials. Results for the first experiment showed no age effect on mean BUT, number of clusters, or average cluster size for recall of food items. There were also no age effects during the first 5 minutes of recall of animals. Later in the task old subjects had longer mean BIIT's for animals than did young subjects. The differences appeared to result because old subjects tended to report primarily mammals, while young subjects reported birds, fish, reptiles/amphibians, and insects as well, A trend toward slower mean WIIT's for old subjects was attributed to slower vocalization rates. Thus, Experiment 1 failed to demonstrate age- related differences in time to access successive clusters of related items in semantic memory or in the rate at which items in a cluster are emitted. Higher repetition rates observed for the old subjects do support an age-related deficit in recognition. In the second experiment, only half the subjects reported that the semantic -differential cues were helpful in finding new items. No effect of cuing was observed for the food category. Cuing did significantly reduce mean BIIT for animals during the last 5 minutes of recall. However, the actual effect of cuing on number of clusters produced was minimal. It was suggested that more practice with the cues might have led to higher cue usage and a greater impact on BIIT. / This thesis was digitized as part of a project begun in 2014 to increase the number of Duke psychology theses available online. The digitization project was spearheaded by Ciara Healy.

<p> Treating aging as a disease has led to what Carrol Estes termed &ldquo;the aging enterprise:&rdquo; the development of services to house and care for elders. Much is known about the power structures in such facilities, but the issue of socio-economic decline and its relation to elder health has not received a great deal of attention. This thesis analyzes interview and participant-observation data from a sample of residents in an assisted living facility (ALF) to ethnographically explore the way physical and socio-economic experiences of decline emerge in participant narratives. Findings indicate elders construct identities of illness that draw from institutional discourses that diminish their personhood. The narrative structure of declining health is also found to be compatible with other socio-economic descriptions of decline. The multiple discursive patterns of decline culminate in a model of ALF resident dependency. Based on this model, recommendations are made to affirm elder personhood and enact agency in ALF.</p>

The purpose of this thesis is to explore the writings of early American sociologists for attitudes and theoretical ideas concerning aging which individually and collectively have formed the basis for current social theory in gerontology.

Oxygen availability is critical for survival for most organisms. The nematode, C. elegans, has been useful for studying genetic regulation of anoxia tolerance due to the oxygen deprivation response mechanisms shared with other metazoans. Studies examining long-term anoxia (72h, LTA) tolerance have only been conducted at adult day 1. To investigate the effect of aging on anoxia tolerance wild-type and mutant strains were exposed to LTA between adult day 1 and day 9. Wild-type isolates and daf-16(mu86) (FOXO transcription factor regulated by insulin-signaling) and aak-2(gt33) (catalytic subunit of AMP-activated protein kinase) strains were anoxia sensitive at day 1 and displayed increased LTA tolerance with aging correlated with reproductive senescence followed by a decline in survivorhsip through day 9. The daf-2(e1370) (insulin receptor homologue of C. elegans), glp-1(e2141) (a lin-12/Notch receptor) and fog-2(q71) (required for spermatogenesis) strains were LTA-tolerant through day 5. I conclude that aging influences LTA-tolerance in a strain- and age-dependent manner. In addition to being LTA-tolerant the daf-2(e1370) and glp-1(e2141) strains have a longevity phenotype that is suppressed by loss of kri-1 or daf-12. While loss of kri-1 did not suppress the LTA-tolerant phenotype of glp-1(e2141) at day 1 the portion of impaired survivors increased at day 3 and by day 5 tolerance was suppressed. Similarly, when exposed to 4 days of anoxia the glp-1(e2141);daf-12(rh41rh611) double mutant had a reduced survivor rate at all ages analyzed compared to glp-1(e2141) controls. To better understand formation of an anoxia-tolerant physiology I exposed adults to one or more 24h bouts. Recurrent bouts increased LTA tolerance in wild-type hermaphrodites in a dose-dependent manner. Bout-treated daf-16(mu86) animals had increased survival rate compared to controls yet maximum survival remained below age-matched wild-type. Anoxia bouts decreased LTA-tolerance in aak-2(gt33) mutants, indicating the requirement for ATP regulation in establishing an LTA-tolerant phenotype. These data support the idea that anoxia tolerance is multi-factorial and influenced by environment, metabolism, food, reproduction, sex phenotype and likely additional factors.