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Bonnielin Swenor, Beatriz Munoz, Sheila West; Is visual impairment just another comorbid condition?. Invest. Ophthalmol. Vis. Sci. 2013;54(15):5334.
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Determine if the association between visual impairment status and mobility disability is due to visual impairment or is a result of the total number of comorbid conditions
We used baseline data from the Salisbury Eye Evaluation study, a population-based sample of 2,520 adults 65 years or older. Visual impairment (yes/no) was defined by visual and visual fields. Walking speed on three mobility tasks was measured: walking up 7 steps (steps/second), walking down 7 steps (steps/second), and walking 4 meters (meters/second). Mobility disability was classified as 1 standard deviation below the population mean for each task. Data on 16 conditions thought to impact mobility, including visual impairment, was categorized (1, 2, 3, or 4+ comorbid conditions). Non-visually impaired individuals without any other comorbid conditions were excluded. Logistic regression models using mobility disability as the outcome and visual impairment status as a predictor were built for each strata. We then compared, for example, individuals with visual impairment and 1 other comorbid condition (a total of 2 comorbid conditions), to individuals without visual impairment and 2 other comorbid conditions. Odds ratios (OR) and 95% confidence intervals (CI) were determined after adjusting for age, sex, and race.
Visually impaired who did not have any other comorbid conditions were significantly more likely to be disabled on all three mobility tasks than the non-visually impaired who had 1 other comorbid condition (OR disability walking up 7 steps = 4.2; 95% CI: 1.3-16.1; OR disability walking down 7 steps = 6.4, 95% CI: 1.8-23.2; OR disability walking 4 meters =6.7, 95% CI: 1.8-24.8). For strata indicating 2, 3 or 4+ comorbid conditions, the associations between visual impairment status and mobility disability declined and were not statistically significant for any of the mobility tasks.
Among older adults with 1 comorbid condition, mobility disability is more likely if that condition is visual impairment than if that condition is any of the other 15 conditions examined. However, as the number of comorbid conditions increases, the unique association between visual impairment and mobility disability was attenuated. This may indicate that while visual impairment is an important factor contributing to mobility disability, as comorbid conditions accumulate this association is diluted by the combined impact on mobility of all conditions.
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