Résumé
Activity limitations, which induce loss of autonomy in the elderly, are a major public health problem. We investigated the associations between objectively determined visual impairments and activity limitations and assessed the visual acuity thresholds associated with these restrictions.
The study sample consisted of 1887 people aged 63 years and over from a population-based cohort. Moderate to severe visual impairment was defined as presenting visual acuity lower than 20/70, according to the World Health Organization (WHO) definition. In addition, we studied mild visual impairment, defined as visual acuity [20/70-20/40]. Multivariate logistic regressions were used to estimate the associations between vision and instrumental activities of daily living (IADL) limitations. Using receiver-operating characteristic (ROC) curves, we identified visual acuity thresholds that maximized the Youden index ([sensitivity + specificity]-1) for predicting IADL limitations.
After adjustment for potential confounders, moderate to severe visual impairment and mild visual impairment were strongly associated with IADL limitations (odds ratio [OR] = 3.49; 95% confidence interval [CI] = 1.93, 6.32 and OR = 1.77; 95% CI = 1.07, 2.91, respectively). Visual acuity was a strong predictor of IADL limitations, with an area under the ROC curve of 0.72 (95% CI = 0.68, 0.76). The best discrimination between subjects with or without IADL limitations (global, physical and cognitive) was obtained for visual acuities around 20/40-20/50.
This study confirms major increased risk for IADL limitations in subjects with moderate to severe visual impairment. In addition, it suggests that milder visual impairments (in particular below 20/40) may also be related to an increased risk for IADL limitations and should be considered for early medical intervention, before the decline of the subject autonomy.