title: Does walking speed mediate the association between visual impairment and self-report of mobility disability? The Salisbury Eye Evaluation Study.
abstract: OBJECTIVE
  To determine whether performance speeds mediate the association between visual impairment and self-reported mobility disability over an 8-year period.
  
  
  METHODS
  Longitudinal analysis.
  
  
  METHODS
  Salisbury, Maryland.
  
  
  METHODS
  Salisbury Eye Evaluation Study participants aged 65 and older (N=2,520).
  
  
  METHODS
  Visual impairment was defined as best-corrected visual acuity worse than 20/40 in the better-seeing eye or visual field less than 20°. Self-reported mobility disability on three tasks was assessed: walking up stairs, walking down stairs, and walking 150 feet. Performance speed on three similar tasks was measured: walking up steps (steps/s), walking down steps (steps/s), and walking 4 m (m/s).
  
  
  RESULTS
  For each year of observation, the odds of reporting mobility disability was significantly greater for participants who were visually impaired (VI) than for those who were not (NVI) (odds ratio (OR) difficulty walking up steps=1.58, 95% confidence interval (CI)=1.32-1.89; OR difficulty walking down steps=1.90, 95% CI=1.59-2.28; OR difficulty walking 150 feet=2.11, 95% CI=1.77-2.51). Once performance speed on a similar mobility task was included in the models, VI participants were no longer more likely to report mobility disability than those who were NVI (OR difficulty walking up steps=0.84, 95% CI=0.65-1.11; OR difficulty walking down steps=0.96, 95% CI=0.74-1.24; OR difficulty walking 150 feet=1.22, 95% CI=0.98-1.50).
  
  
  CONCLUSIONS
  Slower performance speed in VI individuals largely accounted for the difference in the odds of reporting mobility disability, suggesting that VI older adults walk slower and are therefore more likely to report mobility disability than those who are NVI. Improving mobility performance in older adults with visual impairment may minimize the perception of mobility disability.
authors.affiliation: Department of Epidemiology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland; Dana Center for Preventive Ophthalmology, Wilmer Eye Institute, School of Medicine, Johns Hopkins University, Baltimore, Maryland.
authors.forename: Bonnielin K
authors.initials: BK
authors.lastname: Swenor
authors.forename: Karen
authors.initials: K
authors.lastname: Bandeen-Roche
authors.forename: Beatriz
authors.initials: B
authors.lastname: Muñoz
authors.forename: Sheila K
authors.initials: SK
authors.lastname: West
mesh_terms: D000054:Acceleration; D000368:Aged; D000369:Aged, 80 and over; D004185:Disability Evaluation; D005260:Female; D015577:Geriatric Assessment; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008396:Maryland; D051346:Mobility Limitation; D012307:Risk Factors; D014792:Visual Acuity; D019987:Persons with Visual Disabilities
keywords: aging; disability; mobility; visual impairment