Background: Obesity and physical inactivity rates have reached epidemic levels in Canada, but differ based on whether they are self-reported or directly measured. Canadian research examining the combined and independent effects of social and built environments on adult physical activity (PA) and body mass index (BMI) is limited. Furthermore there is a lack of Canadian studies to assess these relationships using directly measured PA and BMI. Objectives: The objectives of this thesis were to systematically compare self-reported and directly measured PA and to examine associations between neighbourhood built and social environmental factors with both self-reported and directly measured PA and overweight/obesity in adults living in Ottawa, Canada. Methods: A systematic review was conducted to identify observational and experimental studies of adult populations that used both self-report and direct measures of PA and to assess the agreement between the measures. Associations between objectively measured neighbourhood-level built recreation and social environmental factors and self-reported individual-level data including total and leisure-time PA (LTPA) and overweight/obesity were examined in the adult population of Ottawa, Canada using multilevel models. Neighbourhood differences in directly measured BMI and PA (using accelerometry) were evaluated in a convenience sample of adults from four City of Ottawa neighbourhoods with contrasting socioeconomic (SES) and built recreation (REC) environments. Results: Results from the review generally indicate a poor level of agreement between self-report and direct measures of PA, with trends differing based on the measures of PA, the level of PA examined and the sex of the participants. Results of the multilevel analyses identified that very few of the built and social environmental variables were ii significantly associated with PA or overweight/obesity. Greater park area was significantly associated with total PA in females. Greater green space was shown to be associated with lower odds of male LTPA. Factors from the social environment were generally more strongly related to male outcomes. Further to the recreation and social environment, factors in the food landscape were significantly associated with male and female PA and overweight/obesity. Results of the directly measured PA and BMI investigation showed significant neighbourhood-group effects for light intensity PA and sedentary time. Post-hoc tests identified that the low REC/high SES neighbourhood had significantly more minutes of light PA than the low REC/low SES. BMI differed between the four neighbourhoods, but the differences were not significant after controlling for age, sex and household income. Conclusions: Results of this dissertation show that the quantity of PA can differ based on its method of measurement (i.e. between self-report and direct methods) with implications for the interpretation of study findings. It also identifies that PA and BMI can differ by neighbourhood and recognizes that the relationships between neighbourhood environments and PA and body composition are complex, may be differ between males and females, and may not always follow intuitive relationships. Furthermore it suggests that other factors in the environment not examined in this dissertation may influence adult PA and BMI and that longitudinal and intervention studies are needed.

The relationship between body mass index (BMI) and physical activity level of daughters and their mothers’ body type/size and attitude towards physical activity in African Americans was investigated. 51 subjects were recruited. Subjects completed the Short International Physical Activity Questionnaire (IPAQ) and an attitudinal questionnaire. Subjects’ height and weight were measured. Mother’s body type/size was found to be weakly associated with daughter’s BMI (r=0.28, p=0.051). Mother’s overall attitude towards physical activity was not associated with daughter’s IPAQ score. The results suggest mother’s body type/size and select components of the mother’s attitude are related daughter’s BMI and physical activity level.

Over the past 30 years, obesity has been primarily identified by the body mass index (BMI). Due to its ease of calculation, the BMI has become the most widely used diagnostic tool to identify weight problems. This study examined the association between hypertension and BMI in White, Black, and Hispanics in the United States. The study’s hypothesis was that this relationship was weaker in Blacks than in the other groups. Data for the study came from the 2007-2008 and 2009-2010 National Health and Nutrition Examination Surveys. The association was weaker in Black men than in Whites or Hispanics on a univariate basis, and at most BMI levels on a multivariate basis. For females, it was also weaker in Blacks at most BMI levels on a univariate basis. However, multivariate logistic regression analysis did not indicate that the hypothesis held for Black women when adding covariates to the models.

Syfte Syftet med denna studie var att undersöka sensitiviteten och specificiteten hos BMI vid klassificering av övervikt, samt att jämföra gränsvärdena för övervikt mätt med BMI med gränsvärdena för övervikt mätt i fettprocent med BodPod. Metod Urvalet i studien bestod av 359 deltagare mellan 30-50 år (medelvärde – 39,7 år). Av dessa 359 var 192 kvinnor och 167 män. Deltagarna var indelade i fyra aktivitetsnivåer – stillasittande, lågaktiva, aktiva och mycket aktiva. Dessa delades in i två grupper där stillasittande och lågaktiva slogs ihop och aktiva och mycket aktiva slogs ihop. Därefter har gränsvärden för övervikt jämförts, mätt med två olika mätinstrument – BMI (body mass index) och ADP (air displacement plethysmography) samt givit nya förslag på gräns för övervikt med BMI som mätinstrument. Sensitiviteten och specificiteten för BMI för män och kvinnor och olika aktivitetsnivåer har uppmäts. Resultat Resultatet visade att gränsvärdena för övervikt hos kvinnor bör fortfarande ligga runt 25, oavsett aktivitetsnivå, men för män bör gränsvärdena ligga mellan 26-27, beroende på aktivitetsgrad. Sensitiviteten för kvinnor ligger mellan 69-76% beroende på aktivitetsgrad och specificiteten är 83-91%. För män ligger sensitiviteten mellan 76-88% beroende på aktivitetsgrad och specificiteten är 56-68%. Med föreslagna nya BMI-gränser minskar sensitiviteten för män, men specificiteten ökar. Ingen större förändring hos kvinnor. Slutsats Då sensitiviteten och specificiteten är relativt låg för BMI kan det vara bra för en lärare i idrott och hälsa att känna till BMI:s begränsningar. Idrottslärare ska utveckla elevens färdigheter och kunskap inom hälsa och bör lyfta BMI:s styrkor och svagheter i undervisningen eftersom det är ett mått de flesta känner till. BMI är inte ett perfekt mått utan bör kompletteras med andra enkla mätmetoder. Om olika BMI gränsvärden för olika aktivitetsnivåer ska användas bör denna mätning vara mer ingående och inkludera träning på fritiden, vilket inte gjorts i denna studie. / Aim The aim of this study was to examine the sensitivity and specificity of BMI for classification of overweight, as well compared the cutoffs for overweight measured with BMI with the cutoffs for overweight measured in %FM with BodPod. Method The selection of the study consisted of 359 participants between 30-50 years of age (mean age – 39,7 years). Of these 359, 192 were women and 167 were men. The participants were divided into four activity levels – sedentary, low active, active, very active. These were divided into two groups – sedentary and low active into one group and active and very active into another. Then cutoffs for overweight were measured, with two different methods – BMI (body mass index) and ADP (air displacement plethysmography), as well given new suggestions for cutoff levels for overweight measured with BMI. The sensitivity and specificity, for BMI, for men and women and different levels of activity were calculated. Result The result showed that the cutoffs for overweight in women still should be around 25, no matter the level of activity, but for men cutoffs should be between 26-27, considering level of activity. Sensitivity for women is between 69-76% depending on level of activity and specificity 83-91%. For men the sensitivity is between 76-88% depending on level of activity and the specificity 56-68%. With suggested new BMI cutoffs the sensitivity for men decreases, but the specificity increases. No larger change for women. Conclusion As the sensitivity and specificity is relatively low for BMI it could be good for teachers in physical education to know of BMI limitations. PE teachers are supposed to develop the pupils’ skills and knowledge in health and should inform about BMI strengths and weaknesses in education since it is a measure known by most. BMI is not a perfect measurement but should be accompanied by other simple measurements. If BMI cutoffs should take activity into account, this measurement should be more detailed and include physical activity in their leisure time, which was not done in this study.

Neural prostheses are being developed to provide motor capabilities to patients who suffer from motor-debilitating diseases and conditions. These brain-computer interfaces (BCI) will be controlled by activity from the brain and bypass damaged parts of the spinal cord or peripheral nervous system to re-establish volitional control of motor output. Spike sorting is a technologically expensive component of the signal processing chain required to interpret population spike activity acquired in a BCI. No systematic analysis of the need for spike sorting has been carried out and little is known about the effects of spike sorting error on the ability of a BCI to decode intended motor commands. We developed a theoretical framework and a modelling environment to examine the effects of spike processing on the information available to a BCI decoder. Shannon information theory was applied to simulated neural data. Results demonstrated that reported amounts of spike sorting error reduce mutual information (MI) significantly in single-unit spike trains. These results prompted investigation into how much information is available in a cluster of pooled signals. Indirect information analysis revealed the conditions under which pooled multi-unit signals can maintain the MI that is available in the corresponding sorted signals and how the information loss grows with dissimilarity of MI among the pooled responses. To reveal the differences in non-sorted spike activity within the context of a BCI, we simulated responses of 4 neurons with the commonly observed and exploited cosine-tuning property and with varying levels of sorting error. Tolerances of angular tuning differences and spike sorting error were given for MI loss due to pooling under various conditions, such as cases of inter- and/or intra-electrode differences and combinations of various mean firing rates and tuning depths. These analyses revealed the degree to which mutual information loss due to pooling spike activity depended upon differences in tuning between pooled neurons and the amount of spike error introduced by sorting. The theoretical framework and computational tools presented in this dissertation will BCI system designers to make decisions with an understanding of the tradeoffs between a system with and without spike sorting. / Dissertation

Obesity is a rapidly growing public health threat as well as an economic problem in the United States. The recent changes in eating habits, especially the relative increase of food away from home (FAFH) consumption over the last three decades raised the possibility of causal linkage between obesity and FAFH. This study confirms the positive, significant association between the body mass index and FAFH consumption in adults, consistent with previous findings in the economic and nutrition literature. This work goes a step further, however. We demonstrate FAFH consumption at quick-service restaurants has a significantly larger effect on body mass index than FAFH consumption at full-service restaurants. Further disaggregation of FAFH by meal occasion reveals that lunch consumed away from home has the largest positive effect on body mass index compared to other meal occasions (breakfast, dinner and snacks). Survey data with missing observations or latent variables are not rare phenomena. The missing value imputation methods are combined into two groups, contingent upon the existence or absence of an underlying explicit statistical model. Explicit modeling methods include unconditional mean value imputation, conditional mean and regression imputation, stochastic regression imputation, and multiple imputation. The methods based on implicit modeling include hot deck and cold deck imputation. In the second essay, we review imputation methods commonly used in the agricultural economics literature. Our analysis revealed strong preference of researchers for the regression imputation method. We consider several alternative (regression, mean and median) single imputation methods to impute and to append prices of foods consumed at home (foods commercially purchased and prepared from ingredients) from the National Health and Nutrition Examination Survey (NHANES) dietary intake data. We also demonstrate the superiority of regression imputation method compared to the mean and median imputation methods for commercially prepared foods. For ingredient foods, the results are ambiguous with no imputation method clearly outperforming the others.

Thesis (M.S.P.H.)--University of South Florida, 2009. / Title from PDF of title page. Document formatted into pages; contains 137 pages. Includes bibliographical references.

The purpose of the current study was to examine putative mediators and moderators in the association between adiposity and anxiety in a sample of overweight and obese youth. In addition, anxiety was examined as a potential moderator between adiposity and health-related quality of life (HRQOL). Participants were youth (N = 137) between 8 and 17 years old (M = 13.09, SD = 2.61) and their legal caregivers recruited from four medical clinics affiliated with the University of South Florida. Youth were primarily overweight (28.5%) or obese (64.2%) and ethnically diverse. Data were analyzed by path analysis. Weight-related teasing significantly mediated the association between adiposity and child reported anxiety, but competency-related teasing and peer victimization were not significant mediators. Internalization of appearance ideals significantly moderated the association between adiposity and anxiety by child report; however, no significant moderations were found for parent report. Additionally, sociocultural pressures to meet appearance ideals were not significant moderators by child or parent report. Notably, anxiety significantly moderated the association between adiposity and social functioning by child report, with those experiencing greater anxiety evidencing poorer social quality of life. However, anxiety did not moderate the association between adiposity and other domains of HRQOL by parent or child report. Given the significant increase in pediatric overweight and obesity in recent decades, it is particularly important to understand the psychosocial implications of excess adiposity in youth. Clinical and research implications are discussed focusing on the mechanisms between adiposity and anxiety and suggested clinical interventions to address said mechanisms.

The present study assessed the relationship between Body Mass Index (BMI) and healthcare cost, utilization and health-related quality of life (HRQoL) of type 2 diabetes patients using the Medical Expenditure Panel Survey (MEPS) database. Study subjects were at least 18 years of age, diagnosed with diabetes and taking ≥1 oral antidiabetic medication. Data were extracted over a 5-year period (01/01/2006-12/31/2010). The main study outcomes were healthcare costs and utilization and HRQoL. The study covariates were age, gender, race, smoking status, census region of residence, marital status, insurance status, Charlson comorbidity index score and additional bed days. Study objectives were addressed using generalized linear model, negative binomial and multivariate regression analyses. A final un-weighted sample size of 7,003 patients was obtained. Mean age (±SE) was 61.2 (±0.24) years, mean BMI (±SE) was 32.2 (±0.12), and 50.4% were males. The majority was white (77.4%), did not smoke (84.5%), and were married (60.4%). Based on BMI categories, 12.6% had normal weight (BMI: 18.0-24.9); 29.2% were overweight (BMI: 25.0-29.9); 45.6% were obese (BMI: 30.0-39.9), and 12.6% were morbidly obese (BMI≥ 40.0). Compared to normal-weight patients; overweight, obese or morbidly obese patients had significantly higher (p<0.05) diabetes-related direct medical costs. However, overweight patients had significantly lower (p=0.021) all-cause direct medical costs. Furthermore, compared to normal weight patients, obese patients had a significantly higher (p=0.009) number of ambulatory care visits, while overweight patients had a significantly lower (p=0.035) number of emergency department visits. In addition, being obese or morbidly obese was associated with a significantly higher (p<0.0001) number of prescribed medicines compared to normal-weight patients. Compared to normal-weight patients; being obese or morbidly obese was also significantly (p<0.0001) associated with lower physical component summary (PCS-12) scores (i.e., worse quality of life) while being overweight was significantly (p=0.038) associated with higher mental component summary (MCS-12) scores (i.e., better quality of life). In conclusion, the present study suggests that among type 2 diabetes patients, being obese may be associated with negative consequences (in terms of healthcare costs, utilization and outcomes). Hence, there is the need to address obesity among type 2 diabetes patients in order to improve their health outcomes and significantly reduce healthcare costs and resource utilization. / text

Estimates indicate that by 2010 RN demand will exceed supply by over 400,000 full-time equivalents and by 2020 the RN shortage will increase to over 1 million. Turnover is a major contributor to the nursing shortage and job dissatisfaction is a well-established cause of nursing turnover. Understanding RN job satisfaction is an objective that is critical to keeping experienced nurses working in nursing and minimizing RN turnover. Many facets of RN job satisfaction have been examined in previous studies; however, much of the variance in job satisfaction remains unexplained. The purpose of this study was to explore job strain, body mass index, and background information variables (age, education, ethnicity, number of years in nursing, and perceived general health) as possible predictors of job satisfaction among hospital staff nurses. Resilience was examined for its mediating and moderating effects on the relationships between job strain and job satisfaction and body mass index and job satisfaction. The research design was cross-sectional and correlational. Surveys were mailed to RNs across the state of Texas. Reliable instruments were used to measure hospital staff RN job satisfaction, job strain, and resilience. Body mass index was calculated based on self-reported height and weight. From a sampling frame of full-time, hospital staff RNs purchased from the Texas Board of Nursing, a random sample of 556 RNs was obtained. The response rate was 27.6% (n = 147). Results showed that 25.2% of the RNs sampled reported high job strain. Job strain was significantly related to body mass index, and high job strain was significantly negatively related to job satisfaction. High job strain explained 24.7% of the variance in job satisfaction. None of the background information variables were significantly related to job satisfaction. Resilience had a moderating effect on the relationship between job strain and job satisfaction. Resilience did not mediate or moderate the relationship between body mass index and job satisfaction. Future research should focus on creating a nurse-specific instrument that measures job strain in hospital staff RNs. Intervention studies that investigate the effects of resilience training on the job satisfaction of hospital staff RNs should also be conducted. / text