Daniel J. Dutton

Explained and unexplained regional variation in Canadian obesity prevalence.

The objective of our study was to examine sociodemographic and behavioral variables underlying the geographic variation of obesity in Canada. We aimed to quantify the share of regional variation in average BMI attributable to commonly cited determinants of obesity and the remaining share, which is attributable to the idiosyncrasies of the regional environment (“regional effects”). Using data from the Canadian Community Health Survey (CCHS) (2004), ordinary least squares (OLS) regression, and Blinder–Oaxaca decomposition to decompose the difference in mean BMI between regions, we quantify two parts of the difference: a share explained by different levels of the covariates and a share explained by those covariates having different effects on BMI in the different regions, using the Atlantic provinces as the reference group. We observed that some differences (e.g., average BMI for males in Quebec compared to the Atlantic provinces) are mostly explained by the different levels of socio‐demographic and behavioral covariates, while others (e.g., average BMI for females in Quebec compared to the Atlantic provinces) are mostly explained by the different effects of the covariates on BMI. In the latter scenario, even if covariates were made to be identical in the different regions, the difference in average BMI would persist. Thus, targeting covariates in different regions through plans like physical activity or nutrition policy, income equalization, or education subsidies will have ambiguous effects for addressing disparate obesity levels, being plausible policy options in some regions but less so in others. Future research and policy would benefit from identifying these region‐specific attributes that have local implications for BMI.

Longitudinal analysis of the association between removal of dental amalgam, urine mercury and 14 self-reported health symptoms

BackgroundMercury vapor poses a known health risk with no clearly established safe level of exposure. Consequently there is debate over whether the level of prolonged exposure to mercury vapor from dental amalgam fillings, combining approximately 50% mercury with other metals, is sufficiently high to represent a risk to health. The objective of our study is to determine if mercury exposure from amalgam fillings is associated with risk of adverse health effects.MethodsIn a large longitudinal non-blind sample of participants from a preventative health program in Calgary, Canada we compared number of amalgam fillings, urine mercury measures and changes in 14 self-reported health symptoms, proposed to be mercury dependent sub-clinical measures of mental and physical health. The likelihood of change over one year in a sample of persons who had their fillings removed was compared to a sample of persons who had not had their fillings removed. We use non-parametric statistical tests to determine if differences in urine mercury were statistically significant between sample groups. Logistic regression models were used to estimate the likelihood of observing symptom improvement or worsening in the sample groups.ResultsAt baseline, individuals with dental amalgam fillings have double the measured urine mercury compared to a control group of persons who have never had amalgam fillings. Removal of amalgam fillings decreases measured urine mercury to levels in persons without amalgam fillings. Although urine mercury levels in our sample are considered by Health Canada to be too low to pose health risks, removal of amalgam fillings reduced the likelihood of self-reported symptom deterioration and increased the likelihood of symptom improvement in comparison to people who retained their amalgam fillings.ConclusionsOur findings suggest that mercury exposure from amalgam fillings adversely impact health and therefore are a health risk. The use of safer alternative materials for dental fillings should be encouraged to avoid the increased risk of health deterioration associated with unnecessary exposure to mercury.

A repeated cross-sectional study of socio-economic inequities in dietary sodium consumption among Canadian adults: implications for national sodium reduction strategies

IntroductionIn many countries including Canada, excess consumption of dietary sodium is common, and this has adverse implications for population health. Socio-economic inequities in sodium consumption seem likely, but research is limited. Knowledge of socio-economic inequities in sodium consumption is important for informing population-level sodium reduction strategies, to ensure that they are both impactful and equitable.MethodsWe examined the association between socio-economic indicators (income and education) and sodium, using two outcome variables: 1) sodium consumption in mg/day, and 2) reported use of table salt, in two national surveys: the 1970/72 Nutrition Canada Survey and the 2004 Canadian Community Health Survey, Cycle 2.2. This permitted us to explore whether there were any changes in socio-economic patterning in dietary sodium during a time period characterized by modest, information-based national sodium reduction efforts, as well as to provide baseline information against which to examine the impact (equitable or not) of future sodium reduction strategies in Canada.ResultsThere was no evidence of a socio-economic inequity in sodium consumption (mg/day) in 2004. In fact findings pointed to a positive association in women, whereby women of higher education consumed more sodium than women of lower education in 2004. For men, income was positively associated with reported use of table salt in 1970/72, but negatively associated in 2004.ConclusionsAn emerging inequity in reported use of table salt among men could reflect the modest, information-based sodium reduction efforts that were implemented during the time frame considered. However, for sodium consumption in mg/day, we found no evidence of a contemporary inequity, and in fact observed the opposite effect among women. Our findings could reflect data limitations, or they could signal that sodium differs from some other nutrients in terms of its socio-economic patterning, perhaps reflecting very high prevalence of excess consumption. It is possible that socio-economic inequities in sodium consumption will emerge as excess consumption declines, consistent with fundamental cause theory. It is important that national sodium reduction strategies are both impactful and equitable.

The association between amalgam dental surfaces and urinary mercury levels in a sample of Albertans, a prevalence study

ObjectiveThe objective of this study was to quantify the relationship between number of dental amalgam surfaces and urinary mercury levels.MethodsThis study uses participant data from a large philanthropic chronic disease prevention program in Calgary, Alberta, Canada. Urine samples were analysed for mercury levels (measured in μg/g-creatinine). T-tests were used to determine if differences in urine mercury were statistically significant between persons with no dental amalgam surfaces and one or more dental amalgam surfaces. Linear regression was used to estimate the change in urinary mercury per amalgam surface.ResultsUrinary mercury levels were statistically significantly higher in participants with amalgam surfaces, with an average difference of 0.55 μg/g-creatinine. Per amalgam surface, we estimated an expected increase of 0.04 μg/g-creatinine. Measured urinary mercury levels were also statistically significantly higher in participants with dental amalgam surfaces following the oral administration of 2,3-dimercaptopropane-l-sulfonate (DMPS) and meso-2,3-dimercaptosuccinic acid (DMSA) which are used to mobilize mercury from the blood and tissues.DiscussionOur estimates indicate that an individual with seven or more dental amalgam surfaces has 30% to 50% higher urinary mercury levels than an individual without amalgams. This is consistent with past literature that has identified seven amalgam surfaces as an unsafe level of exposure to mercury vapor. Our analysis suggests that continued use of silver amalgam dental fillings for restorative dentistry is a non-negligible, unnecessary source of mercury exposure considering the availability of composite resin alternatives.

Effect of provincial spending on social services and health care on health outcomes in Canada: an observational longitudinal study

BACKGROUND: Escalating health care spending is a concern in Western countries, given the lack of evidence of a direct connection between spending and improvements in health. We aimed to determine the association between spending on health care and social programs and health outcomes in Canada. METHODS: We used retrospective data from Canadian provincial expenditure reports, for the period 1981 to 2011, to model the effects of social and health spending (as a ratio, social/health) on potentially avoidable mortality, infant mortality and life expectancy. We used linear regressions, accounting for provincial fixed effects and time, and controlling for confounding variables at the provincial level. RESULTS: A 1-cent increase in social spending per dollar spent on health was associated with a 0.1% (95% confidence interval [CI] 0.04% to 0.16%) decrease in potentially avoidable mortality and a 0.01% (95% CI 0.01% to 0.02%) increase in life expectancy. The ratio had a statistically nonsignificant relationship with infant mortality (p = 0.2). INTERPRETATION: Population-level health outcomes could benefit from a reallocation of government dollars from health to social spending, even if total government spending were left unchanged. This result is consistent with other findings from Canada and the United States.

An overview of the statistical methods reported by studies using the Canadian community health survey

BackgroundThe Canadian Community Health Survey (CCHS) is a cross-sectional survey that has collected information on health determinants, health status and the utilization of the health system in Canada since 2001. Several hundred articles have been written utilizing the CCHS dataset. Previous analyses of statistical methods utilized in the literature have focused on a particular journal or set of journals to understand the statistical literacy required for understanding the published research. In this study, we describe the statistical methods referenced in the published literature utilizing the CCHS dataset(s).MethodsA descriptive study was undertaken of references published in Medline, Embase, Web of Knowledge and Scopus associated with the CCHS. These references were imported into a Java application utilizing the searchable Apache Lucene text database and screened based upon pre-defined inclusion and exclusion criteria. Full-text PDF articles that met the inclusion criteria were then used for the identification of descriptive, elementary and regression statistical methods referenced in these articles. The identification of statistical methods occurred through an automated search of key words on the full-text articles utilizing the Java application.ResultsWe identified 4811 references from the 4 bibliographical databases for possible inclusion. After exclusions, 663 references were used for the analysis. Descriptive statistics such as means or proportions were presented in a majority of the articles (97.7%). Elementary-level statistics such as t-tests were less frequently referenced (29.7%) than descriptive statistics. Regression methods were frequently referenced in the articles: 79.8% of articles contained reference to regression in general with logistic regression appearing most frequently in 67.1% of the articles.ConclusionsOur study shows a diverse set of analysis methods being referenced in the CCHS literature, however, the literature heavily relies on only a subset of all possible statistical tools. This information can be used in identifying gaps in statistical methods that could be applied to future analysis of public health surveys, insight into training and educational programs, and also identifies the level of statistical literacy needed to understand the published literature.

Child care: Implications for overweight/obesity in Canadian children?

INTRODUCTION Over recent decades, two prominent trends have been observed in Canada and elsewhere: increasing prevalence of childhood overweight and obesity, and increasing participation of women (including mothers) in the paid labour force and resulting demand for child care options. While an association between child care and childrens body mass index (BMI) is plausible and would have policy relevance, its existence and nature in Canada is not known. METHODS Using data from the National Longitudinal Survey of Children and Youth, we examined exposure to three types of care at age 2/3 years (care by non-relative, care by relative, care in a daycare centre) in relation to change in BMI percentile (continuous and categorical) between age 2/3 years and age 6/7 years, adjusting for health and sociodemographic correlates. RESULTS Care by a non-relative was associated with an increase in BMI percentile between age 2/3 years and age 6/7 years for boys, and for girls from households of low income adequacy. CONCLUSION Considering the potential benefits of high-quality formal child care for an array of health and social outcomes and the potentially adverse effects of certain informal care options demonstrated in this study and others, our findings support calls for ongoing research on the implications of diverse child care experiences for an array of outcomes including those related to weight.

How important are determinants of obesity measured at the individual level for explaining geographic variation in body mass index distributions? Observational evidence from Canada using Quantile Regression and Blinder-Oaxaca Decomposition

Background Obesity prevalence varies between geographic regions in Canada. The reasons for this variation are unclear but most likely implicate both individual-level and population-level factors. The objective of this study was to examine whether equalising correlates of body mass index (BMI) across these geographic regions could be reasonably expected to reduce differences in BMI distributions between regions. Methods Using data from three cycles of the Canadian Community Health Survey (CCHS) 2001, 2003 and 2007 for males and females, we modelled between-region BMI cross-sectionally using quantile regression and Blinder-Oaxaca decomposition of the quantile regression results. Results We show that while individual-level variables (ie, age, income, education, physical activity level, fruit and vegetable consumption, smoking status, drinking status, family doctor status, rural status, employment in the past 12 months and marital status) may be Caucasian important correlates of BMI within geographic regions, those variables are not capable of explaining variation in BMI between regions. Discussion Equalisation of common correlates of BMI between regions cannot be reasonably expected to reduce differences in the BMI distributions between regions.

The authors respond to “Fueling the culture of distrust in doctors”

The authors respond to a letter from Dr. Nadia Alam.[1][1] In discussing the findings of our study on the effect of provincial spending on social services and health care on outcomes in Canada, we chose the physician remuneration example because it is a classic funding issue in Canadian health care