Background: A socioeconomic gradient in obesity (all classes), where greater prevalence of obesity is observed in more disadvantaged groups, has been reported in most developed countries. However, no previous study has explored the relative differences in the prevalence of obesity classes I, II and III, across socioeconomic strata.
Objective. To examine socio-economic differences in the prevalence and treatment of severe obesity in Australian adults during 2012.
Methods. Prevalence data were sourced from the National Health Survey 2011-12 for the Australian population aged 18+ years. Obesity classifications were based on measured height and weight (class-I BMI [kg/m2]: 30.0-34.9, class-II: 35.0-39.9and class-III: ≥40.0). Severe obesity was defined as either class-II or III obesity. Socioeconomic position was classified according to an area-level measure; the Index of Relative Socio-economic Disadvantage (IRSD). The Australian Institute of Health and Welfare provided IRSD data for all national bariatric surgery episodes (n=14,056) undertaken in the population aged 18+ years during 2011-12.
Results. The prevalence of class-I obesity generally increased with increasing levels of disadvantage; ranging from 14.1% in quintile 5 (least disadvantaged) to 19.3% in quintile 1 (most disadvantaged). Corresponding figures for class-II obesity were 8.6 and 5.5%; and for class-III obesity 4.8 and 1.7%. The relative risks of class-I, II and III obesity in the most disadvantaged group, relative to the least disadvantaged group were 1.4, 1.9 and 2.8 (all P<0.05). Severe obesity affected 1/16 people in the least disadvantaged and 1/7 people in the most disadvantaged quintile. Bariatric surgery treatment rates decreased with increasing levels of disadvantage.
Conclusion. During 2011-12, obesity prevalence increased with increasing levels of disadvantage in Australian adults, and the gradient was most pronounced in more severely obese classes. Observed socioeconomic inequalities in the use of bariatric surgery may further increase existing inequalities in obesity and related health outcomes.