Education modifies the association of wealth with obesity in women in middle-income but not low-income countries: an interaction study using seven national datasets, 2005-2010
METHODS: The seven largest national surveys were selected from a list of Demographic and Health Surveys (DHS) ordered by decreasing sample size which resulted in a range of country income levels. These were nationally representative data of women aged 15-49 years collected in the period 2005-2010. Wealth was derived from an asset-based index; education was based on the self-reported highest level of attainment. The separate and joint effects, unadjusted and adjusted for age group, parity, and urban/rural residence using a multivariate logistic regression model are presented.
RESULTS: In the four middle-income countries (Colombia, Peru, Jordan, and Egypt), an interaction was found between education and wealth on obesity (P-value for interaction <0.001). Among women with no/primary education the wealth effect was positive whereas in the group with higher education it was either smaller in magnitude or inverted (negative). In the poorer countries (India, Nigeria, Benin), there was no evidence of an interaction. Instead, the associations between each of education and wealth with obesity were independent and positive. There was a statistically significant difference between the average interaction estimates for the low-income and middle-income countries (P<0.001).
CONCLUSIONS: These results suggest that, as countries undergo economic development, education may protect women against the obesogenic effects of increased household wealth. Further research could examine this protective pathway including the role of cognitive factors and the food environment.