Socioeconomic differences in the benefits of structured physical activity compared with health education on the prevention of major mobility disability in older adults: the LIFE study

Background Evidence is lacking on whether health-benefiting community-based interventions differ in their effectiveness according to socioeconomic characteristics. We evaluated whether the benefit of a structured physical activity intervention on reducing mobility disability in older adults differs by education or income. Methods The Lifestyle Interventions and Independence for Elders (LIFE) study was a multicentre, randomised trial that compared a structured physical activity programme with a health education programme on the incidence of mobility disability among at-risk community-living older adults (aged 70-89years; average follow-up of 2.6years). Education ( high school (0-12years), college (13-17years) or postgraduate) and annual household income were self-reported (<$24999, $25000 to $49999 and $50000). The risk of disability (objectively defined as loss of ability to walk 400m) was compared between the 2 treatment groups using Cox regression, separately by socioeconomic group. Socioeconomic groupxintervention interaction terms were tested. Results The effect of reducing the incidence of mobility disability was larger for those with postgraduate education (0.72, 0.51 to 1.03; N=411) compared with lower education (high school or less (0.93, 0.70 to 1.24; N=536). However, the education groupxintervention interaction term was not statistically significant (p=0.54). Findings were in the same direction yet less pronounced when household income was used as the socioeconomic indicator. Conclusions In the largest and longest running trial of physical activity amongst at-risk older adults, intervention effect sizes were largest among those with higher education or income, yet tests of statistical interactions were non-significant, likely due to inadequate power. Trial registration number NCT01072500.