Identifying global patterns of income inequality in smoking & obesity: comparing six emerging economies with a high-income country

INTRODUCTION: The prevalence rates of obesity and smoking are increasing globally and behave like epidemics. Their social distribution appears to change as countries develop but it is not clear how or why this occurs. This study examines income inequalities in these two key non-communicable disease risk factors comparing England with six middle-income countries to identify common and differing patterns.

METHODS: Nationally representative data from the Health Survey for England 2009 (N=3740), and the World Health Organisation Study on Global Ageing and Adult Health 2010 (SAGE) are used. SAGE is unique in providing standardised data for six middle-income countries (LMICs) including China (N=14,888), Ghana (N=5565), India (N=12,198), Mexico (N=2737), Russia (N=4670) and South Africa (N=4225). Relative and absolute inequalities in total household income for smoking (current/non-smoker) and obesity (BMI ≥30) are calculated, respectively, as the age-adjusted relative index of inequality and the slope index of inequality (RII and SII) by sex and country for adults ≥18years.

RESULTS: In terms of obesity, England was the only country where poor women were at a disadvantage with a large magnitude of relative inequality in obesity (RII = 1.90; 95%CI: 1.41, 2.59; P-value <0.001) and there was no gradient of inequality in obesity for men. In contrast, in the lower-income countries, both poor men and women were at lower risk of obesity reflecting a higher level of food insecurity. In terms of smoking, poor men and women were at a disadvantage in all countries with England displaying the highest magnitude of relative inequality (RII = 3.4; 95%CI: 2.7, 4.1, P-value <0.001).

CONCLUSIONS: The findings suggest that the smoking gradient may reverse before the obesity gradient indicating that low income groups may forego essential needs (food) before non-essential needs (cigarettes). This raises questions as to the potentially harmful nature of the global consumer environment.