Abstract
Abstract: :
Purpose: To examine whether older adults with losses in visual acuity, contrast sensitivity, or visual fields over a 2–year period were more likely to stop driving and to consider potential effect modifiers. Methods: Prospective data were used from the Salisbury Eye Evaluation project, a population–based cohort study of 2,520 older adults followed for four rounds of data collection. Driving information was obtained via self–report at all 4 rounds and date of driving cessation was determined retrospectively by telephone to living participants or proxies. Cognitive status was assessed by mini–mental state exam. Of those who were driving at baseline and returned to round 2 (n=1824), the proportions of those who stopped driving were compared by each type of visual function loss. Cox proportional hazards regression was used to assess whether each type of visual function loss influenced the adjusted hazard of cessation, and interactions with level of visual function at round (RD) 2, other drivers in household, and mini–mental score were examined. The proportionality assumption was checked. Results: Of those driving at baseline and returning to RD 2, 386 (21%) stopped driving during the 8– year follow–up. Losses in acuity, central fields, lower peripheral fields, and total fields were associated with driving cessation in univariate analyses. After age, sex, and race adjustment, losses in acuity, contrast sensitivity, and central visual fields were associated with driving cessation (linear trend p–values <0.05). After further adjustment for co–morbid conditions and cognitive score, only acuity loss was associated with driving cessation (linear trend p=0.027). However, an interaction was found in which those with central visual field loss were more likely to stop driving only if they scored >=24 on the mini–mental exam (interaction p–value p=0.05). Conclusions: Greater levels of acuity loss increased the probability of driving cessation. A similar, but not statistically significant, trend was present for contrast sensitivity. However, greater levels of central visual field loss only resulted in a higher probability of cessation in those with good cognitive scores. Those who lost central visual field and had worse cognition were less likely to stop driving. This highlights the complex interplay of factors that influence whether older persons decide to stop driving or not.
Keywords: visual acuity • visual fields • contrast sensitivity