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Cognitive function in adults with obesity
thesisposted on 21.02.2017, 05:00 by Prickett, Christina Louise
The prevalence of obesity and its associated negative health consequences are a significant public health concern. Recent research has demonstrated an association between mid life obesity and increased risk of later life dementia. This worrying relationship has prompted investigation and identification of an association between obesity and cognitive impairment in mid life. However, many questions remain regarding the domains of cognition affected; the independent contribution of obesity to cognitive function above and beyond obesity related comorbidities; and the subjective experience of such impairment in individuals with obesity. A series of three studies addressed these identified limitations of the literature. A systematic review assessed evidence of domain specific cognitive impairment, and the independent contribution of obesity to cognitive function in mid life adults (Aim 1). Seventeen articles were reviewed, with evidence of obesity related cognitive impairment in the domains of intellectual functioning, psychomotor performance and speed, visual construction, concept formation and set shifting, and decision making. However, as few studies considered comorbidities relevant to investigating an independent link, evidence regarding an independent relationship between obesity and cognitive function was limited. The remaining two empirical studies of this thesis examined a sample of 69 treatment seeking individuals with obesity and 65 healthy weight individuals (matched for age and gender). Individuals with obesity were recruited consecutively from a private surgical weight loss clinic in Melbourne, Australia. The healthy weight control group were volunteers recruited from the general community. Participants completed a range of clinical health, psychological, and neuropsychological measures. The first empirical paper assessed domain specific cognitive functioning in adults with obesity (Aim 2) and the independent contribution of obesity to this performance (Aim 3). Individuals with obesity demonstrated poorer cognitive performance (independent of education) compared to healthy weight control participants in psychomotor performance and speed, verbal learning and memory, complex attention, semantic verbal fluency, working memory, and concept formation and set shifting. Obesity related impairments remained significant in each of these domains (except verbal memory) following control for obesity related comorbidities (e.g., mood, sleep, and cardiovascular disease risk factors). The second empirical paper employed a self report questionnaire to investigate the subjective experience of cognitive impairment in adults of obese and healthy weight, and the variables associated with these reports (Aim 4). The majority of both obese and healthy weight participants reported low levels of self-reported cognitive dysfunction, with no differences demonstrated between groups. Self reported cognitive dysfunction was not associated with objective cognitive performance, but with depression and anxiety symptoms in both groups and fatigue and sleepiness in the healthy weight group. In multivariate analyses, anxiety was the only significant independent predictor of self reported cognitive dysfunction in both obese and healthy weight individuals. Overall, this thesis adds to the growing evidence of cognitive impairment in adults with obesity, along with providing initial evidence that obesity independently contributes to this performance. Findings that individuals with obesity report similar levels of cognitive dysfunction compared to healthy weight individuals indicate that these early cognitive deficits may not be subjectively experienced during mid life. Further research however, is required to clarify the brain regions and mechanisms underlying obesity related cognitive impairment, and confirm the clinical significance of this impairment. Ultimately, the long term aim of this research should be to examine whether mid life weight loss can improve mid life obesity related cognitive impairment and attenuate late life dementia risk. This will be particularly important in the context of the growing levels of obesity and an ageing population.