A longitudinal study of the association between visual impairment and mobility performance in older adults: The salisbury eye evaluation study

Few longitudinal studies have examined how visual impairment affects mobility as people age. Data from the Salisbury Eye Evaluation Study, a population-based sample of 2,520 adults aged 65 years and older, were used to investigate the longitudinal association between visual impairment and mobility. Baseline, 2-year, 6-year, and 8-year visits occurred between 1993 and 2001. Mobility was assessed by measuring speeds on the following 3 tasks: walking up 7 steps, walking down 7 steps, and walking 4 m. Random-effects linear regression was used to model factors affecting speed. For each year of observation, speeds declined, and the visually impaired had significantly slower speeds than the non-visually impaired on all 3 tests after accounting for other covariates (β_{walking up steps} =-0.08 steps/second, 95% confidence interval (CI):-0.10,-0.06; β_{walking down steps} =-0.11 steps/second, 95% CI:-0.14,-0.08; and β_{walking 4 m} =-0.08 m/second, 95% CI:-0.10,-0.06). However, the interaction between years since baseline and visual impairment status was not significant, indicating that mobility speeds declined at a similar rate in the visually impaired and the non-visually impaired. These results suggest that the impact of visual impairment on speed is significant but does not change as people age.