A Bayesian shared components modeling approach to develop small area indicators of social determinants of health with measures of uncertainty.

OBJECTIVES: Existing Canadian social determinants of health (SDOH) indicators do not quantify uncertainty to identify priority areas. The objectives of this methodologic study were: (1) to estimate and map small area (dissemination area) shared and variable-specific SDOH indicators with measures of uncertainty using a Bayesian model that accounts for spatial dependence; (2) to quantify geographic variation in the SDOH indicators and their contribution to a shared indicator; and (3) to assess the SDOH indicators' associations with behavioural risk factors and their consistency with the Ontario Marginalization Index (ON-Marg). METHODS: Lower education-, income-, unemployment-, living alone- and visible minority-related variables used in existing Canadian SDOH indices were fit as dependent variables to a Bayesian model to produce area-based SDOH indicators that were mapped with measures of uncertainty in two study areas. The fractions of spatial variation explained by the model components were computed. Bayesian analysis of variance was used to examine the SDOH indicator associations with behavioural risk factors and their consistency with ON-Marg examined using Pearson's correlation coefficient. RESULTS: The shared component was strongly associated with material deprivation (i.e., income) in each study area; however, variable-specific SDOH indicators were important too. The SDOH indicators were associated with behavioural risk factors for chronic disease, particularly alcohol consumption and smoking, and the shared component estimates were consistent with the ON-Marg material deprivation. CONCLUSIONS: The Bayesian approach to produce SDOH indicators met the three study objectives and as such provides a new approach to prioritize areas that may experience health inequalities.

The number and type of food retailers surrounding schools and their association with lunchtime eating behaviours in students.

BACKGROUND: The primary study objective was to examine whether the presence of food retailers surrounding schools was associated with students' lunchtime eating behaviours. The secondary objective was to determine whether measures of the food retail environment around schools captured using road network or circular buffers were more strongly related to eating behaviours while at school. METHODS: Grade 9 and 10 students (N=6,971) who participated in the 2009/10 Canadian Health Behaviour in School Aged Children Survey were included in this study. The outcome was determined by students' self-reports of where they typically ate their lunch during school days. Circular and road network-based buffers were created for a 1 km distance surrounding 158 schools participating in the HBSC. The addresses of fast food restaurants, convenience stores and coffee/donut shops were mapped within the buffers. Multilevel logistic regression was used to determine whether there was a relationship between the presence of food retailers near schools and students regularly eating their lunch at a fast food restaurant, snack-bar or café. The Akaike Information Criteria (AIC) value, a measure of goodness-of-fit, was used to determine the optimal buffer type. RESULTS: For the 1 km circular buffers, students with 1-2 (OR= 1.10, 95% CI: 0.57-2.11), 3-4 (OR=1.45, 95% CI: 0.75-2.82) and ≥5 nearby food retailers (OR=2.94, 95% CI: 1.71-5.09) were more likely to eat lunch at a food retailer compared to students with no nearby food retailers. The relationships were slightly stronger when assessed via 1 km road network buffers, with a greater likelihood of eating at a food retailer for 1-2 (OR=1.20, 95% CI:0.74-1.95), 3-4 (OR=3.19, 95% CI: 1.66-6.13) and ≥5 nearby food retailers (OR=3.54, 95% CI: 2.08-6.02). Road network buffers appeared to provide a better measure of the food retail environment, as indicated by a lower AIC value (3332 vs. 3346). CONCLUSIONS: There was a strong relationship between the presence of food retailers near schools and students' lunchtime eating behaviours. Results from the goodness of fit analysis suggests that road network buffers provide a more optimal measure of school neighbourhood food environments relative to circular buffers.

Field validation of food service listings: a comparison of commercial and online geographic information system databases.

Many studies examining the food retail environment rely on geographic information system (GIS) databases for location information. The purpose of this study was to validate information provided by two GIS databases, comparing the positional accuracy of food service places within a 1 km circular buffer surrounding 34 schools in Ontario, Canada. A commercial database (InfoCanada) and an online database (Yellow Pages) provided the addresses of food service places. Actual locations were measured using a global positioning system (GPS) device. The InfoCanada and Yellow Pages GIS databases provided the locations for 973 and 675 food service places, respectively. Overall, 749 (77.1%) and 595 (88.2%) of these were located in the field. The online database had a higher proportion of food service places found in the field. The GIS locations of 25% of the food service places were located within approximately 15 m of their actual location, 50% were within 25 m, and 75% were within 50 m. This validation study provided a detailed assessment of errors in the measurement of the location of food service places in the two databases. The location information was more accurate for the online database, however, when matching criteria were more conservative, there were no observed differences in error between the databases.

Identification of the appropriate boundary size to use when measuring the food retail environment surrounding schools.

This study included 6,971 students in grades 9 and 10 (ages 13 to 16 years) from 158 schools who participated in the 2009/2010 Health Behaviour in School-aged Children Study. Students provided information on where they typically ate lunch. The number of food retailers was obtained for six road network buffer sizes (500, 750, 1,000, 1,500, 2,000, and 5,000 meters) surrounding schools. Associations between the presence of food retailers near schools and students' lunchtime eating behaviours were examined using multilevel logistic regression. Comparisons of model fit statistics indicated that the 1,000 m buffer provided the best fit. At this distance, students with ≥3 food retailers near their schools had a 3.42 times greater relative odds (95% CI: 2.12-5.52) of eating their lunchtime meal at a food retailer compared to students with no nearby food retailers. Students who had ≥2 food retailers within 750 m of their schools had a 2.74 times greater relative odds (95% CI: 1.75-4.29), while those who had ≥1 food retailer within 500 m of their schools had 2.27 times greater relative odds of eating at food retailer (95% CI: 1.46-3.52) compared to those with no nearby food retailers. For distances greater than 1,000 m, no consistent relationships were found.

Urban sprawl and its relationship with active transportation, physical activity and obesity in Canadian youth.

BACKGROUND: Urban sprawl is a potential environmental influence on youth overweight/obesity. However, little is known about the association between urban sprawl and behaviours that influence obesity such as active transportation and physical activity. METHODS: The study population consisted of 7,017 respondents aged 12 to 19 to the 2007/2008 Canadian Community Health Survey, living in Canada's 33 census metropolitan areas (CMAs). Factor analysis was used to obtain an urban sprawl score for each CMA, incorporating dwelling density, percentage of single or detached dwelling units, and percentage of the population living in the urban core. Multi-level logistic regression examined whether urban sprawl was associated with frequent active transportation (30 or more minutes a day), moderate-to-vigorous physical activity (MVPA) (60 or more minutes a day), and overweight/obesity. RESULTS: Urban sprawl was associated with active transportation among 12- to 15-year-olds, with the relative odds of engaging in at least 30 minutes of active transportation per day increasing by 24% (95% CI: 10-39%) for each standard deviation (SD) increase in the urban sprawl score. For the entire sample aged 12 to 19, higher urban sprawl was associated with MVPA (odds ratio per SD increase = 1.10, 95% CI: 1.01-1.20), but not with overweight/obesity (odds ratio per SD increase = 1.06, 95% CI: 0.94-1.18). INTERPRETATION: Urban sprawl was associated with active transportation and MVPA in Canadian youth, although in the opposite direction to what has been reported in the literature for adults.

Density and type of food retailers surrounding Canadian schools: variations across socioeconomic status.

Lower socioeconomic status (SES) neighbourhoods may have differential access to food retailers, potentially explaining the varying area-level obesity rates. The food retail environment around 188 schools across Canada was examined, including full-service restaurants, fast food restaurants, sub/sandwich retailers, donut/coffee shops, convenience stores, and grocery stores. School addresses were linked to census data to obtain area-level SES measures. Access to food retailers was generally not associated with the neighbourhood SES in the immediate proximity. Within the broader neighbourhood, lower SES neighbourhoods had access to fewer food retailers of all types. This effect was diminished after taking population density into account.

Association between the food retail environment surrounding schools and overweight in Canadian youth.

INTRODUCTION: There is growing interest in how the physical environment influences obesity. Few studies have considered how the food retail environment surrounding schools influences overweight in students. OBJECTIVE: To determine whether there is a relationship between food retailers surrounding schools and overweight among Canadian youth. DESIGN: Cross-sectional study. SETTING/METHODS/SUBJECTS: The number of food retailers was obtained within a 1 km and 5 km radius around 178 schools in Canada. Retailers included full-service restaurants, fast-food restaurants, sub/sandwich retailers, doughnut/coffee shops, convenience stores and grocery stores. An index of total food retailer exposure was also created. Multilevel analyses were used to control for individual- and area-level covariates. RESULTS: None of the individual food retailers was associated with an increased likelihood of overweight. The total food retailer index was most strongly related to overweight, but in the opposite direction to that hypothesized. At 1 km, students attending schools with at least one food retailer had a lower relative odds of overweight (OR = 0.70, 95% CI 0.61, 0.81). At 5 km, students attending schools with the highest exposure to the total food retailer index had a lower relative odds of overweight (OR = 0.56, 95% CI 0.47, 0.68) compared with students attending schools with no exposure. CONCLUSIONS: Exposure to various types of food retailers in school neighbourhoods was not associated with an increased likelihood of overweight in Canadian school-aged youth. The opportunity to make healthy choices from a variety of options and the unique Canadian context may explain the findings.