Cross-national comparison of socioeconomic inequalities in obesity in the United States and Canada.

Arjumand Siddiqi,Rachel Loopstra,Rashida Brown,Ichiro Kawachi,Quynh C Nguyen

doi:10.1186/s12939-015-0251-2

Abstract

IntroductionPrior cross-national studies of socioeconomic inequalities in obesity have only compared summary indices of inequality but not specific, policy-relevant dimensions of inequality: (a) shape of the socioeconomic gradient in obesity, (b) magnitude of differentials in obesity across socioeconomic levels and, (c) level of obesity at any given socioeconomic level. We use unique data on two highly comparable societies – U.S. and Canada - to contrast each of these inequality dimensions.MethodsData came from the 2002/2003 Joint Canada/U.S. Survey of Health. We calculated adjusted prevalence ratios (APRs) for obesity (compared to normal weight) by income quintile and education group separately for both nations and, between Canadians and Americans in the same income or education group.ResultsIn the U.S., every socioeconomic group except the college educated had significant excess prevalence of obesity. By contrast in Canada, only those with less than high school were worse off, suggesting that the shape of the socioeconomic gradient differs in the two countries. U.S. differentials between socioeconomic levels were also larger than in Canada (e.g., PR quintile 1 compared to quintile 5 was 1.82 in the U.S. [95 % CI: 1.52-2.19] but 1.45 in Canada [95 % CI: 1.10-1.91]). At the lower end of the socioeconomic gradient, obesity was more prevalent in the U.S. than in Canada.ConclusionsOur results suggest there is variation between U.S. and Canada in different dimensions of socioeconomic inequalities in obesity. Future research should examine a broader set of nations and test whether specific policies or environmental exposures can explain these differences.

Highlights

Prior cross-national studies of socioeconomic inequalities in obesity have only compared summary indices of inequality but not specific, policy-relevant dimensions of inequality: (a) shape of the socioeconomic gradient in obesity, (b) magnitude of differentials in obesity across socioeconomic levels and, (c) level of obesity at any given socioeconomic level
While in the United States, all but the university/college educated group had prevalences above twenty percent, in Canada, no education stratum had a prevalence of obesity that exceeded twenty percent
Sex-specific strata US women demonstrated a higher prevalence of obesity compared to women in Canada (22.1 % vs. 13.3 %)

Summary

Introduction

Prior cross-national studies of socioeconomic inequalities in obesity have only compared summary indices of inequality but not specific, policy-relevant dimensions of inequality: (a) shape of the socioeconomic gradient in obesity, (b) magnitude of differentials in obesity across socioeconomic levels and, (c) level of obesity at any given socioeconomic level. A growing body of work has documented that socioeconomic inequalities in obesity are present in a range of other countries but the magnitude of inequalities varies considerably between them [1, 2, 14,15,16]. On their face, these societal-level findings lend credence to the hypothesis that societal-level exposures –e.g. policies and other environmental exposures– may be a ‘cause. These indices provide a global sense of the difference between socioeconomic groups, but, in the process, these indices tend to obscure specific dimensions of inequalities between particular socioeconomic groups that can help to shed light on the processes that generate the inequalities

Methods

Results

Conclusion