The Incidence of Visual Impairment, its Risk Factors, and its Mobility Consequences: The Canadian Longitudinal Study on Aging

Abstract

INTRODUCTION: Canada has yet to conduct high quality, prospective, population-based surveys that measure incident visual impairment, its risk factors, and adverse consequences, creating an unmet need to obtain more rigorous analysis in this regard QUESTIONS: What is the 3-year incidence of visual impairment in each province? What are the risk factors for the 3-year incidence of visual impairment? Do they include geographic, sociodemographic, lifestyle, social, health and healthcare factors? Does vision loss increase the odds of balance problems after three years? METHODS: Baseline and 3-year follow-up data were used from the Canadian Longitudinal Study on Aging. The Comprehensive Cohort included 30,097 adults ages 45-85 years old recruited from 11 sites across 7 provinces. Presenting binocular visual acuity was measured using the Early Treatment of Diabetic Retinopathy Study chart. Incidence of VI was defined as the development at follow-up of visual acuity worse than 20/40 in those with acuity better than or equal to 20/40 at baseline. Balance was measured using the one-leg balance test. Those who could not stand on one leg for at least 60 seconds were classified as having failed the test. Participants were asked about the self-report of a diagnosis of cataract, macular degeneration, or glaucoma. RESULTS: 3.88% (95% Confidence Interval (CI) 3.61, 4.17) of Canadian adults developed VI over a 3-year period. There was a high degree of variability in the incidence between Canadian provinces with a low of 1.42% in Manitoba and a high of 7.33% in Nova Scotia. Uncorrected refractive error was the leading cause of incident VI. Risk factors for incident VI included older age (odds ratio (OR)=1.07, 95% CI 1.06, 1.07), Black race (OR=2.64, 95% CI 1.36, 5.14), lower household income (OR=1.73 for those making less than $20,000 per year, 95% CI 1.24, 2.40), current smoking (OR=1.78, 95% CI 1.37, 2.32), and province. Of the 12,158 people who could stand for 60 seconds on one leg at baseline, 18% were unable to do the same at follow-up 3 years later. After adjustment for demographic and health variables, those with worse visual acuity (per 1 line) were more likely to fail the balance test at follow-up (OR=1.15, 95% CI 1.10, 1.20). Those with a report of a former (OR=1.59, 95% CI 1.17, 2.16) or current cataract (OR=1.31, 95% CI 1.01, 1.68) were more likely to fail the test at follow-up. CONCLUSION: The incidence of visual impairment is common in older Canadian adults, varies markedly between provinces, and is largely due to treatable causes. Risk factors for VI suggest sub-groups that may benefit from interventions to improve access to eye care. These data provide longitudinal evidence that vision loss increases the odds of balance problems over a 3-year period. Efforts to prevent avoidable vision loss are needed as are efforts to improve the balance of visually impaired people.