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Thesis (M. S.)--Texas A&M University, 2005. / "Major Subject: Epidemiology" Title from author supplied metadata (automated record created on Feb. 23, 2007.) Vita. Abstract. Includes bibliographical references.

Heat-related illness (HRI) is of growing public health importance, particularly with climate change and an anticipated increased frequency of heat waves. A syndromic surveillance system for HRI could provide new information on the population impact of excessive heat and thus be of value for public health planning. This study describes the association between 911 medical dispatch calls for HRI and temperature in Toronto, Ontario during the summers of 2002-2005. A combination of methodological approaches was used to understand both the temporal trend and spatial pattern in the relationship between 911 medical dispatch data and temperature. A case definition for HRI was developed using clinical and empirical assessments. Generalized Additive Models (GAM) and Zero inflated Poisson regression (ZIP) were used to determine the association between 911 calls and mean and maximum temperature. The validity of the HRI case definition was investigated by making comparisons with emergency department visits for HRI. Descriptive, aberration detection, and cross-correlation methods were applied to explore the timing and volume of HRI calls in relation to these visits, and the declaration of heat alerts. Finally, the existence of neighbourhood level spatial variation in 911 calls for HRI was analyzed using geospatial methods. This is the first study to demonstrate an association between daily 911 medical dispatch calls specifically for HRI and temperature. On average, 911 calls for HRI increased up to a maximum of 36% (p<.0001) (median 29%) for each 1°C increase in temperature. The temporal trend of 911 calls for HRI was similar to emergency department visits for HRI and heat alerts, improving confidence in the validity of this data source. Heterogeneity in the spatial pattern of calls across neighbourhoods was also apparent, with recreational areas near the waterfront demonstrating the highest percentage increase in calls. Monitoring 911 medical dispatch data for HRI could assist public health units carrying out both temporal and geospatial surveillance, particularly in areas where synoptic based mortality prediction algorithms are not being utilized. This previously untapped data source should be further explored for its applications in understanding the relationship between heat and human health and more appropriately targeting public health interventions.

The objectives of the thesis were to examine the associations between vascular and metabolic risk factors, carotid atherosclerosis and cognitive function in a Canadian First Nations population. Eligible individuals were ≥18 years and with First Nations status who had undergone cognitive function assessment by the Clock Drawing Test (CDT) and the Trail Making Test Parts A and B. Parts A and B were combined into an executive function score (TMT-exec). Anthropometric, vascular and metabolic risk factors were assessed by interview, clinical examinations and blood tests. Doppler ultrasonography assessed carotid atherosclerosis (carotid stenosis, plaque volume). For the 190 individuals with TMT-exec scores, obese individuals were at a 4-fold increased risk for lowered cognitive performance compared to those who were not obese (odds ratio [OR]: 3.77, 95% confidence interval [CI]: 1.46-9.72). Those having an increased waist circumference also had 5 times the risk compared to those without an increased waist circumference (OR: 5.41, 95% CI: 1.83-15.99). Individuals having the metabolic syndrome were at a 4-fold increased risk compared to those without the metabolic syndrome (OR: 3.67, 95% CI: 1.34-10.07). No other cardiovascular risk factors were associated and no associations were shown for the CDT. For TMT-exec only, individuals with elevated levels of left (LCS) and total carotid stenosis (TCS) were less likely to demonstrate lowered cognitive performance (LCS, OR: 0.47, 95% CI: 0.24-0.96; TCS, OR: 0.40, 95% CI: 0.20-0.80). In structural equation modeling, for every 1-unit change in the anthropometric factor in kg/m2, there was a 0.86-fold decrease in the percent of TCS (p<0.05). The etiology of VCI is vascular and is affected by non-traditional risk factors such as obesity. The health effects of obesity beyond traditional disease endpoints warrants further study. Mild-moderate levels of carotid stenosis are not detrimental to cognitive functioning and may additionally include acting as a mediator.

Heat-related illness (HRI) is of growing public health importance, particularly with climate change and an anticipated increased frequency of heat waves. A syndromic surveillance system for HRI could provide new information on the population impact of excessive heat and thus be of value for public health planning. This study describes the association between 911 medical dispatch calls for HRI and temperature in Toronto, Ontario during the summers of 2002-2005. A combination of methodological approaches was used to understand both the temporal trend and spatial pattern in the relationship between 911 medical dispatch data and temperature. A case definition for HRI was developed using clinical and empirical assessments. Generalized Additive Models (GAM) and Zero inflated Poisson regression (ZIP) were used to determine the association between 911 calls and mean and maximum temperature. The validity of the HRI case definition was investigated by making comparisons with emergency department visits for HRI. Descriptive, aberration detection, and cross-correlation methods were applied to explore the timing and volume of HRI calls in relation to these visits, and the declaration of heat alerts. Finally, the existence of neighbourhood level spatial variation in 911 calls for HRI was analyzed using geospatial methods. This is the first study to demonstrate an association between daily 911 medical dispatch calls specifically for HRI and temperature. On average, 911 calls for HRI increased up to a maximum of 36% (p<.0001) (median 29%) for each 1°C increase in temperature. The temporal trend of 911 calls for HRI was similar to emergency department visits for HRI and heat alerts, improving confidence in the validity of this data source. Heterogeneity in the spatial pattern of calls across neighbourhoods was also apparent, with recreational areas near the waterfront demonstrating the highest percentage increase in calls. Monitoring 911 medical dispatch data for HRI could assist public health units carrying out both temporal and geospatial surveillance, particularly in areas where synoptic based mortality prediction algorithms are not being utilized. This previously untapped data source should be further explored for its applications in understanding the relationship between heat and human health and more appropriately targeting public health interventions.

The objectives of the thesis were to examine the associations between vascular and metabolic risk factors, carotid atherosclerosis and cognitive function in a Canadian First Nations population. Eligible individuals were ≥18 years and with First Nations status who had undergone cognitive function assessment by the Clock Drawing Test (CDT) and the Trail Making Test Parts A and B. Parts A and B were combined into an executive function score (TMT-exec). Anthropometric, vascular and metabolic risk factors were assessed by interview, clinical examinations and blood tests. Doppler ultrasonography assessed carotid atherosclerosis (carotid stenosis, plaque volume). For the 190 individuals with TMT-exec scores, obese individuals were at a 4-fold increased risk for lowered cognitive performance compared to those who were not obese (odds ratio [OR]: 3.77, 95% confidence interval [CI]: 1.46-9.72). Those having an increased waist circumference also had 5 times the risk compared to those without an increased waist circumference (OR: 5.41, 95% CI: 1.83-15.99). Individuals having the metabolic syndrome were at a 4-fold increased risk compared to those without the metabolic syndrome (OR: 3.67, 95% CI: 1.34-10.07). No other cardiovascular risk factors were associated and no associations were shown for the CDT. For TMT-exec only, individuals with elevated levels of left (LCS) and total carotid stenosis (TCS) were less likely to demonstrate lowered cognitive performance (LCS, OR: 0.47, 95% CI: 0.24-0.96; TCS, OR: 0.40, 95% CI: 0.20-0.80). In structural equation modeling, for every 1-unit change in the anthropometric factor in kg/m2, there was a 0.86-fold decrease in the percent of TCS (p<0.05). The etiology of VCI is vascular and is affected by non-traditional risk factors such as obesity. The health effects of obesity beyond traditional disease endpoints warrants further study. Mild-moderate levels of carotid stenosis are not detrimental to cognitive functioning and may additionally include acting as a mediator.

The impact of the 2009 influenza pandemic and other recent epidemics are still being assessed. Appropriate allocation of protection and control strategies depend on accurate estimation of disease burden, with high risk groups generally being a key focus especially for distribution of influenza vaccine to maximize the disease burden prevented per vaccine when resource is limited. Therefore, better understanding the impact of influenza and control of influenza among the high risks groups with greater burden is particularly important. In this thesis, I estimated the years of life lost (YLL) associated with influenza correcting for underlying risk factors in addition to age and provided a new methodology for disease burden estimation of influenza. I focused on three vaccine target groups - healthcare workers (HCWs), cancer patients and obese people - to estimate the influenza impact and control among them using multiple approaches. I applied a new comprehensive method to take into account the shorten life expectancy for influenza deaths with underlying risk factors compared to general population by adding excess hazards of these risk factors in the baseline life tables, finally correcting for 25% overestimation of YLL associated with 2009 pandemic. For vaccine target groups, I analyzed the serum data from a cross-sectional study and found there was no occupation-related excess infection risk for unvaccinated HCWs following the first wave of the 2009 pandemic, supporting the effectiveness of the intensive protection and control strategies in Hong Kong. However, the reasons for the unexpectedly poor immune response observed in this study for HCWs with receipt of the 2009 pandemic influenza vaccine requires further exploration. In a large elderly cohort study with follow-up period of 1998-2012, I identified substantial impact of influenza on cancer mortality and several risk factors particularly aggravating effect of influenza on cancer mortality. With the data from this elderly cohort study, I also found that obesity was an independent risk factor for increased respiratory mortality associated with seasonal influenza. The findings from this research have provided new evidence on high risk groups who were more vulnerable to severe outcomes after influenza infection. The insights gained suggest that effective protection policy, including an influenza vaccine program, should be prudently applied for HCWs, cancer patients (especially those with certain risk factors), and obese people during epidemics and pandemics. / published_or_final_version / Public Health / Doctoral / Doctor of Philosophy

<p> <b><u>Background:</u></b> Weight gained during childbearing has significant implications for maternal and child health. Both too much and too little weight gained during pregnancy can result in adverse outcomes. Recommendations for ideal gestational weight gain (GWG) have been developed by the Institute of Medicine, but achieving these standards remains a challenge. Better understanding of the wider context in which women experience pregnancy may aid in the development of novel interventions to improve trends in healthy GWG. Neighborhoods define one such dimension of women&rsquo;s wider context that is emerging as a promising factor in this area of research. However, limited work has considered long-term exposure to neighborhood environments or the role of women&rsquo;s perceptions of their neighborhood environments in relation to either inadequate or excessive GWG. </p><p> <b><u>Methods:</u></b> This dissertation explores the associations between long- and short-term exposure to neighborhood social and socioeconomic context and GWG using data from the 1979 National Longitudinal Survey of Youth. It additionally investigates associations between objective and perceived measures of neighborhood social context in relation to GWG. The first paper investigates associations between long-term, cumulative neighborhood socioeconomic deprivation and GWG. The second paper investigates associations between objectively measured and perceptions of point-in-time neighborhood social environment and GWG. Objective neighborhood social environment is measured using neighborhood socioeconomic deprivation. Perceived neighborhood social environment is assessed from women&rsquo;s self-report of problems within their neighborhood environment. The final paper in this dissertation conducts a systematic review of the literature to characterize the reporting error associated with use of self-reported, pregnancy-related weight in efforts to move the field toward developing bias correction techniques to address methodological limitations of this measure. While not directly related to understanding neighborhoods and GWG, this issue is relevant to future studies in this area that rely on self-reported weight. </p><p> <b><u>Conclusion:</u></b> The papers included in this dissertation illustrate the importance of considering both long-term and short-term measures of neighborhood social context in order to fully understand how neighborhood environments impact inadequate and excessive GWG. In particular, long-term measures of exposure to neighborhood environments should be more fully considered in order to better understand how neighborhoods can support healthy GWG. Interventions based on this improved knowledge of the environment in which women experience weight gain during pregnancy may improve GWG outcomes and health trajectories of both mother and child. Future studies in this area may also benefit from more rigorous study of variation of reporting error in self-reported pregnancy-related weight by maternal characteristics, which will aid in the development of bias correction techniques for these widely used measures.</p>