Socioeconomic inequality in small area use of elective total hip replacement in the English National Health Service in 1991 and 2001

Abstract

Objectives To compare socioeconomic inequality in small area use of elective total hip replacement in the English National Health Service (NHS) in 1991 and 2001. Methods Hospital Episode Statistics and Census data were aggregated to a common geography of ‘frozen’ 1991 English electoral wards. The Townsend deprivation score was used as the primary indicator of socioeconomic status for each ward, and the sensitivity analysis used other Census indicators. Two main measures of inequality were examined: the indirectly age-sex standardized utilization rate ratio between most and least deprived quintile groups, and the concentration index of deprivation-related inequality in age-sex standardized utilization ratios between small areas. Each standardized utilization ratio is the observed use divided by the expected use, if each age and sex group in the study population had the same use rate as the national population. Results In both years, observed use was below expected use for the bottom third of areas by socioeconomic status. The standardized utilization rate ratio between top and bottom Townsend quintiles fell from 1.41 (95% confidence interval [CI] 1.36-1.47) in 1991 to 1.27 (95% CI 1.23-1.32) in 2001. The proportionate increase in use required to bring the bottom quintile to the level of top thus fell significantly from 41% to 27%. The Town-send-based concentration index also fell from 0.069 (95% CI 0.059-0.079) in 1991 to 0.060 (95% CI 0.050-0.071) in 2001, although this fall was not statistically significant (P=0.085). Other socioeconomic indicators yielded a similar pattern. Conclusions Socioeconomic small area inequality in use of total hip replacement appears to have fallen between 1991 and 2001. One possible explanation is that increased hip replacement rates in the 1990s may have lowered barriers to access, thus allowing this health technology to diffuse further among lower socio-economic groups.