Visual impairment and cognitive dysfunction in Alzheimer's disease.

OBJECTIVE: To determine whether impaired visual acuity is associated with dementia and cognitive dysfunction in older adults.
DESIGN: Paired case-control comparisons of the relative frequencies of visual impairment in demented cases and nondemented controls. Cohort analyses of correlation between visual acuity and cognitive functioning in demented cases.
SETTING: Internal medicine clinics at two academically affiliated medical centers. PARTICIPANTS: Eighty-seven consecutively selected patients greater than or equal to 65 years of age with mild-to-moderate, clinically diagnosed Alzheimer's disease (cases) and 87 nondemented controls matched to the cases by age, sex, and education.
MEASUREMENTS AND MAIN RESULTS: The prevalence of visual impairment was higher in cases than in controls [unadjusted odds ratio for near-vision impairment = 2.7 (95% CI = 1.4, 5.2); unadjusted odds ratio for far-vision impairment = 2.1 (95% CI = 1.02, 4.3); odds ratios adjusted for family history of dementia, depression, number of medications, and hearing loss were 2.5 (95% CI = 1.1, 10.5) for near-vision impairment and 1.9 (95% CI = 0.8, 4.6) for far-vision impairment]. When further stratified by quartiles of visual acuity, no statistically significant "dose-response" relationship between vision impairment and dementia risk was observed. Among cases, the degree of visual impairment was significantly correlated with the severity of cognitive dysfunction for both near and far vision (adjusted ps less than 0.001).
CONCLUSIONS: Visual impairment is associated with both an increased risk and an increased clinical severity of Alzheimer's disease, but the increased risk may not be consistent with a progressive dose-response relationship. Further studies are needed to determine whether visual impairment unmasks and exacerbates the symptoms of dementia or is a marker of disease severity.