To analyze the longitudinal relationships between vision loss and the risk of dementia in the first 2 years, from 2 to 4 years and beyond 4 years after inclusion and to determine the roles of depressive symptomatology and engagement in cognitively stimulating activities in these associations. This study is based on the Three-City (3C) study, a population-based cohort of 7736 initially dementia-free participants aged 65 years and over with 12 years of follow-up. Near visual impairment (VI) was measured and distance visual function (VF) loss was self-reported. Dementia was diagnosed and screened over the 12-year period. At baseline, 8.7% had mild near VI, 4.2% had moderate to severe near VI, and 5.3% had distance VF loss. Among the 882 dementia cases diagnosed over the 12-year follow-up period, 140 cases occurred in the first 2 years, 149 from 2 to 4 years and 593 beyond 4 years after inclusion. In Cox multivariate analysis, moderate to severe near VI was associated with an increased risk of dementia in the first 2 years (HR 2.0, 95% CI 1.2-3.3) and from 2 to 4 years (HR 1.8, 95% CI 1.1-3.1) but the association was not significant beyond 4 years after inclusion even if pointing in similar direction (HR 1.3, 95% CI 0.95-1.9). Mild near VI was associated with an increased risk of dementia only in the first 2 years (HR 1.6, 95% CI 1.1-2.5). Moreover, self-reported distance VF loss was associated with an increased risk beyond 4 years after inclusion (HR 1.5, 95% CI 1.1-2.0) but the association was no longer significant after taking into account baseline cognitive performances. Further adjustment for engagement in cognitively stimulating activities only slightly decreased these associations. However, there was an interaction between vision loss and depressive symptomatology, with vision loss associated with dementia only among participants with depressive symptomatology. These results suggest that poor vision, in particular near vision loss, may represent an indicator of dementia risk at short and middle-term, mostly in depressed elderly people.
Keywords: Cohort study; Dementia; Epidemiology; Vision loss.