Visual acuity and the risk of cycling injuries: register-based cohort study from adolescence to middle-age.

BACKGROUND Cycling is increasingly encouraged in many countries as an inexpensive and healthy choice of transportation. Operating any vehicle on the road requires high visual acuity, but few studies to our knowledge have examined the association between vision and cycling injuries. METHODS We examined whether poorer visual acuity is associated with increased risk of fatal and non-fatal cycling injuries. We used prospectively recorded register data for 691,402 men born between 1970 and 1992 in Sweden. We followed these men from an average age of 18 years, when visual acuity was assessed during the conscription assessment, to age 45 at the latest. We identified fatal and non-fatal cycling and car injuries using Patient and Cause of Death registers. Cox regression models were used to estimate hazard ratios (HR) and 95% confidence intervals (95%CI). RESULTS Based on visual acuity for the eye with the best vision, moderately impaired acuity 0.9 to 0.6 when wearing refractive correction was associated with increased risk for cycling injuries (HR=1.44, 95%CI 1.16-1.79) compared with unimpaired vision (uncorrected visual acuity 1.0) and after adjustment for a wide range of potential confounders. This association remained consistent across various sensitivity analyses. Visual acuity was not associated with car injury risk. CONCLUSIONS In this cohort study, poorer vision was specifically associated with a higher rate of cycling injuries.