Socioeconomic inequalities in physical function decline: multilevel longitudinal results from the HABITAT study

Background Australia’s population is ageing, with a projected continued increase in the proportion of individuals aged 65 years and older. Good physical function is important to ensure independence and mobility among older adults. This study examined changes in physical function by socioeconomic indicators including education, occupation, household income and neighbourhood socioeconomic disadvantage. Methods Data were from waves four (2013) and five (2016) (1,186 men and 1,673 women) of the HABITAT study, a multilevel longitudinal study of adults aged 40–65 at baseline (2007) living in 200 neighbourhoods in Brisbane, Australia. Individual-level socioeconomic indicators were self-reported and physical function was self-reported using the 10-item subscale of the Short-Form 36 survey, with scores ranging from 0 to 100. Neighbourhood socioeconomic disadvantage was obtained from a census-based Index of Relative Socioeconomic Disadvantage score. Data were analysed using multilevel linear regression. Results Pooled analysis showed graded inequalities in physical function across all socioeconomic groups: those with lower levels of education, occupation and household income all had lower function, while residents of the most disadvantaged neighbourhoods had 8.16 lower function (95%CI: 10.21, 6.12) than those in the most advantaged neighbourhoods. Over the three-year period, there was a mean reduction in physical function scores of 1.97 (95%CI: -2.58, -1.36), though physical function inequalities did not widen over time between socioeconomic groups. Conclusion There was little evidence of inequalities in the magnitude of decline in physical function across socioeconomic groups between the two time points. Future research should consider more objective performance-based measures to better understand the complexity of physical function among the ageing population.