Multilevel analysis of explanatory mechanisms in the relationship between income inequality and use of dental services

Objectives: To determine the role of disinvestment in public services, social capital and psychosocial stress in explaining the association between income inequality and use of dental services.
Methods: This study pooled individual-level data from 42 of the 70 countries participating in the World Health Organization’s World Health Survey (WHO/WHS, 2002-2004) and country-level data from World Bank and WHO statistics. Individual-level data included participants’ socio-demographic characteristics (age, sex, education and household wealth index), edentulous status, and use of dental services. Use of dental services was defined as having had dental problems in the last 12 months for which treatment was received. Country-level data included income inequality (Gini coefficient for years 1994-2005) and average national income (Gross Domestic Product in US$ for year 2000) respectively. Potential intermediate variables were disinvestment in public services (total health expenditure and government share as a proportion of GDP, dental health systems and responsiveness of health systems), social capital (trust, safety, participation) and psychosocial stress (control and coping). A two-level binomial logit model with individuals nested within countries was used to test the association between Gini coefficient and use of dental services.
Results: Data from 137121 adults aged 18 years and older in 42 countries, covering the 6 WHO regions (16 from Africa, 5 from the Americas, 3 from South-East Asia, 12 from Europe, 2 from the Eastern Mediterranean and 4 from the Western Pacific) were analysed. Gini coefficient was negatively associated with use of dental services. This association was attenuated but remained significant after adjustments for indicators of social capital (OR: 0.82; 95% CI: 0.69-0.87) and psychosocial stress (OR: 0.83; 95% CI: 0.70-0.98), but not for disinvestment in public services (OR: 0.94; 95% CI: 0.79- 1.10).
Conclusions: Disinvestment in public services provided the strongest explanation in the association between income inequality and utilisation of dental services.