Effectiveness of the Combined Approach for Assessing Social Gradients in Stroke Risk Among Married Women in Japan

Kaori Honjo,Norie Sawada,Manami Inoue,Noriko Cable,Hiroyasu Iso,Masahiko Iwata,Shoichiro Tsugane

doi:10.2188/jea.je20110147

Abstract

BackgroundAnalysis of the effects of social gradients on women’s health requires a suitable means of assessing social standing.MethodsWe compared social gradients in stroke risk among 9317 married Japanese women from the Japan Public Health Center-based Prospective Study over a 16-year period. Social gradient was estimated by 3 methods of indicating social position: education level derived by using the individual approach (woman’s own educational level), the conventional approach (using her partner’s educational level), and the combined approach (combining the woman’s and her partner’s educational levels).ResultsAs compared with the lowest educational group, stroke risk was similar among women in the highest educational group using the individual approach and lower, but not significantly so, with the conventional approach. With the combined approach, however, the age- and area-adjusted hazard ratio (HR) was significantly lower among the highest education group as compared with the lowest group (HR = 0.52, 95% CI: 0.36, 0.76), and the relative index of inequality was significant (RII = 0.48, 95% CI: 0.32, 0.72). Using the combined approach, the results were similar irrespective of employment status. In the combined highest educational group, stroke risk among unemployed women was significantly reduced by 54%, while stroke risk for employed women was significantly reduced by 46%, as compared with the lowest educational group, with RIIs of 0.42 (95% CI: 0.21, 0.85) and 0.49 (0.30, 0.80), respectively.ConclusionsThe results suggest that a combined approach better reflects social standing among married women in Japan.

Highlights

IntroductionSocial gradients in health have been well documented by using various socioeconomic indicators such as educational level, income, occupational position, and area deprivation.[1,2] assessment of social gradients in health among women, especially partnered women, has been a considerable challenge.[3,4,5,6,7,8,9,10,11,12,13]The validity of using the social position of spouses or partners as a measure of a woman’s social standing (the conventional approach) has been criticized in light of the increasing number of women entering the labor force.[4,8,10,14] use of a woman’s own social position appears to underestimate social inequalities in health.[15,16] Other research has assessed the usefulness of the dominant, or gender-neutral, approach (assessing the most dominant social position in the household) and the combined approach (combining the social positions of all working age adults in the household)[8] for measuring social gradients in women’s health.[4,8,9,17]Krieger et al[8] compared the individual, dominant, and combined approaches and found that social gradients in various health outcomes were greatest using the dominant approach and smallest using the individual approach
The age- and areaadjusted hazard ratio (HR) for stroke risk among women in the high school education group was significantly reduced by 46%, relative to those in the lowest educational group (HR = 0.54; 95% CI: 0.39, 0.77), and remained significantly lower even after controlling for hypothesized mediating factors
As ascertained by using the women’s own educational levels or their partner’s educational levels, was nonlinearly associated with stroke risk in married women, while educational level derived by combining the educational levels of women and their partners identified a significantly lower stroke risk among women in all educational groups as compared with the lowest educational group

Summary

Introduction

Social gradients in health have been well documented by using various socioeconomic indicators such as educational level, income, occupational position, and area deprivation.[1,2] assessment of social gradients in health among women, especially partnered women, has been a considerable challenge.[3,4,5,6,7,8,9,10,11,12,13]The validity of using the social position of spouses or partners as a measure of a woman’s social standing (the conventional approach) has been criticized in light of the increasing number of women entering the labor force.[4,8,10,14] use of a woman’s own social position appears to underestimate social inequalities in health.[15,16] Other research has assessed the usefulness of the dominant, or gender-neutral, approach (assessing the most dominant social position in the household) and the combined approach (combining the social positions of all working age adults in the household)[8] for measuring social gradients in women’s health.[4,8,9,17]Krieger et al[8] compared the individual, dominant, and combined approaches and found that social gradients in various health outcomes were greatest using the dominant approach and smallest using the individual approach. Methods: We compared social gradients in stroke risk among 9317 married Japanese women from the Japan Public Health Center-based Prospective Study over a 16-year period. Results: As compared with the lowest educational group, stroke risk was similar among women in the highest educational group using the individual approach and lower, but not significantly so, with the conventional approach. The age- and area-adjusted hazard ratio (HR) was significantly lower among the highest education group as compared with the lowest group (HR = 0.52, 95% CI: 0.36, 0.76), and the relative index of inequality was significant (RII = 0.48, 95% CI: 0.32, 0.72).

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Results

Conclusion