Does choice of spatial unit matter for estimating small-area disparities in health and place effects in the Vancouver Census Metropolitan Area?

Bigger isn't better: Why small area geographies are best for actionable index development

Area-level measures of the social exposome provide powerful tools to understand how context contributes to health disparities. Due to the geographic phenomenon of the modifiable aerial unit problem, the geographic level at which the index is constructed can threaten it utility. Previous work indicates that using smaller geographic levels lead to increased measurement precision which may result in closer alignment to policies that directly address health disparities. To provide an illustrative example of this phenomenon, we use Medicare 100% Fee-for Service hospitalization claims data to evaluate the association between area-level disadvantage and 30-day readmissions when the Area Deprivation Index (ADI) is constructed at different geographic levels. When area-level disadvantage is summarized at the "neighborhood" census block group-the study's smallest geographic level-there was a 20% higher odds of readmissions for those living in the top 20% most disadvantaged neighborhoods compared to those living in the lowest 80% neighborhoods nationwide. Yet, evidence for an association with readmissions was not found when neighborhood disadvantaged was summarized at larger geographic levels. Smaller geographic levels appear most optimal to capture these effects. In order to provide publicly available data that is truly publicly useable, greater attention in providing small area health data is needed.

Scale effects in food environment research: Implications from assessing socioeconomic dimensions of supermarket accessibility in an eight-county region of South Carolina

Choice of neighborhood scale affects associations between environmental attributes and health-related outcomes. This phenomenon, a part of the modifiable areal unit problem, has been described fully in geography but not as it relates to food environment research. Using two administrative-based geographic boundaries (census tracts and block groups), supermarket geographic measures (density, cumulative opportunity and distance to nearest) were created to examine differences by scale and associations between three common U.S. Census-based socioeconomic status (SES) characteristics (median household income, percentage of population living below poverty and percentage of population with at least a high school education) and a summary neighborhood SES z-score in an eight-county region of South Carolina. General linear mixed-models were used. Overall, both supermarket density and cumulative opportunity were higher when using census tract boundaries compared to block groups. In analytic models, higher median household income was significantly associated with lower neighborhood supermarket density and lower cumulative opportunity using either the census tract or block group boundaries, and neighborhood poverty was positively associated with supermarket density and cumulative opportunity. Both median household income and percent high school education were positively associated with distance to nearest supermarket using either boundary definition, whereas neighborhood poverty had an inverse association. Findings from this study support the premise that supermarket measures can differ by choice of geographic scale and can influence associations between measures. Researchers should consider the most appropriate geographic scale carefully when conducting food environment studies.

Smoking in context: a multilevel analysis of 49,088 communities in Canada

BACKGROUND

The extent to which the prevalence of smoking in Canada varies across geographic areas independently of individual characteristics has not been quantified.

PURPOSE

To estimate the extent and potential sources of geographic variation in smoking among communities, health regions, and provinces/territories in Canada.

METHODS

Data are from the Canadian Community Health Surveys conducted between 2001 and 2008 (n=461,709). Current cigarette smoking among adults (aged ≥18 years) was the primary outcome. Individual-level markers of SES were education, household income, and occupation. Contextual variables potentially related to smoking considered were provincial cigarette taxes, workplace smoking bans, and collective family norms discouraging smoking in communities. A multilevel logistic regression analysis was conducted to model variation in smoking at the geographic scale of communities, health regions, and provinces.

RESULTS

Overall, the contribution of geography as a percentage of the total variation in smoking was 8.4%, with 2.4% attributable to provinces, 1.2% attributable to health regions, and 4.8% attributable to communities after adjusting for age, gender and survey period. In models that accounted for socioeconomic and demographic characteristics in addition to age and gender, the contribution of geography to the total variation in smoking was attenuated to 4.1%; with 2.0% at the province level, 0.4% at the health region level, and 1.7% at the community level. Within provinces/territories, the community variation in smoking ranged from 2.4% in Prince Edward Island to 9.1% in British Columbia. Nationally, 71% of community and 21% of provincial differences in smoking were explained by individual, socioeconomic, and demographic factors alone; the inclusion of contextual covariates explained an additional 27% of the variation among communities. Collective family norms discouraging smoking in a community was the strongest contextual predictor of individual smoking; provincial cigarette taxes and workplace bans were only modestly related to individual smoking behavior.

CONCLUSIONS

Geographic variation in smoking remained after accounting for individual, socioeconomic, and demographic characteristics, suggesting the importance of place, at the level of provinces and communities in Canada. Remaining community variation in smoking was largely attenuated after accounting for collective family norms discouraging smoking. Area-level influences such as the social and/or environmental conditions of provinces and communities may be important sources of variation in smoking and therefore need to be considered if rates of smoking are to be modified.

The socio-spatial neighborhood estimation method: an approach to operationalizing the neighborhood concept

The literature on neighborhoods and health highlights the difficulty of operationalizing "neighborhood" in a conceptually and empirically valid manner. Most studies, however, continue to define neighborhoods using less theoretically relevant boundaries, risking erroneous inferences from poor measurement. We review an innovative methodology to address this problem, called the socio-spatial neighborhood estimation method (SNEM). To estimate neighborhood boundaries, researchers used a theoretically informed combination of qualitative GIS and on-the-ground observations in Texas City, Texas. Using data from a large sample, we assessed the SNEM-generated neighborhood units by comparing intra-class correlation coefficients (ICCs) and multi-level model parameter estimates of SNEM-based measures against those for census block groups and regular grid cells. ICCs and criterion-related validity evidence using SF-36 outcome measures indicate that the SNEM approach to operationalization could improve inferences based on neighborhoods and health research.

Neighbourhood characteristics, individual attributes and self-rated health among older Canadians

This study drew on three cycles of the Canadian Community Health Survey and the 2001 Census to examine between-neighbourhood variation in positive and negative self-rated health and the relative effect of individual and neighbourhood characteristics on self-rated health among Canadian adults aged > or = 65. Multilevel logistic regression results showed that there was modest, but significant between-neighbourhood variation in self-rated health. Neighbourhood factors including income, education, and percentage of people aged > or = 65, and visible minority accounted for about 50% and 30% of the neighbourhood variation in negative and positive self-rated health, respectively. Relative to neighbourhood-level characteristics, individual characteristics had a stronger effect on self-rated health with involvement in physical activity, alcohol consumption, sense of community belonging, income, and education being the most important. Although the findings suggest that neighbourhood effects on self-rated health are modest and that individual-level factors are relatively more important determinants of health, research concern for contextual influences on health should continue.

Disentangling the relative influence of built and socioeconomic environments on walking: the contribution of areas homogenous along exposures of interest

The geography of small areas has important implications for studying the contextual determinants of health because of potential errors when measuring ecologic exposures and estimating their effects on health. In this paper, we present an approach for designing homogeneous zones optimising the spatial distribution of an area-level exposure, active living potential (ALP), based on data collected in Montreal, Canada. The objectives are to (1) assess and compare variation in walking behaviours between these purposefully designed zones and between standard administrative units, census tracts; and (2) disentangle the relative influence of ALP and area-level socioeconomic conditions on walking using the alternative geographies. Zones were designed by statistically classifying smallest census areas (disseminations areas) into seven categories of exposure similar along three indicators of ALP: population density, land use mix, and geographic accessibility to services. Mapping of categories resulted in the delineation of zones characterised by one of seven levels of ALP. A sample of 2716 adults aged >/=45 years was geocoded and cross-classified in 270 zones and 112 census tracts. Individuals reported on minutes and motives of walking and provided socioeconomic information. Data were analysed using cross-classified multilevel models. Variation in utilitarian walking was larger across the purposefully defined zones than across census tracts. Total walking varied significantly between census tracts only. Greater ALP was associated with more utilitarian walking but with less recreational walking. Higher socioeconomic position in census tracts was positively associated with total, utilitarian, and recreational walking. The soundness of standard administrative units for measuring ecologic exposure and their associations with health should be considered prior to conducting analyses. The added value of different approaches for understanding how place relates to health remains to be established and should be the focus of further investigations.

The joint influence of area income, income inequality, and immigrant density on adverse birth outcomes: a population-based study

BACKGROUND

The association between area characteristics and birth outcomes is modified by race. Whether such associations vary according to social class indicators beyond race has not been assessed.

METHODS

This study evaluated effect modification by maternal birthplace and education of the relationship between neighbourhood characteristics and birth outcomes of newborns from 1999-2003 in the province of Québec, Canada (N = 353,120 births). Areas (N = 143) were defined as administrative local health service delivery districts. Multi-level logistic regression was used to model the association between three area characteristics (median household income, immigrant density and income inequality) and the two outcomes preterm birth (PTB) and small-for-gestational age (SGA) birth. Effect modification by social class indicators was evaluated in analyses stratified according to maternal birthplace and education.

RESULTS

Relative to the lowest tertile, high median household income was associated with SGA birth among Canadian-born mothers (odds ratio (OR) 1.13, 95% confidence interval (CI) 1.06, 1.20) and mothers with high school education or less (OR 1.13, 95% CI 1.02, 1.24). Associations between median household income and PTB were weaker. Relative to the highest tertile, low immigrant density was associated with a lower odds of PTB among foreign-born mothers (OR 0.79, 95% CI 0.63, 1.00) but a higher odds of PTB among Canadian-born mothers (OR 1.14, 95% CI 1.07, 1.21). Associations with income inequality were weak or absent.

CONCLUSION

The association between area factors and birth outcomes is modified by maternal birthplace and education. Studies have found that race interacts in a similar manner. Public health policies focussed on perinatal health must consider the interaction between individual and area characteristics.