Vision loss and 12-year risk of dementia in older adults: the 3C cohort study

To analyze the longitudinal relationships between vision loss and the risk of dementia in the first 2years, from 2 to 4years and beyond 4years 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 65years and over with 12years 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 2years, 149 from 2 to 4years and 593 beyond 4years after inclusion. In Cox multivariate analysis, moderate to severe near VI was associated with an increased risk of dementia in the first 2years (HR2.0, 95% CI 1.2-3.3) and from 2 to 4years (HR1.8, 95% CI 1.1-3.1) but the association was not significant beyond 4years after inclusion even if pointing in similar direction (HR1.3, 95% CI 0.95-1.9). Mild near VI was associated with an increased risk of dementia only in the first 2years (HR1.6, 95% CI 1.1-2.5). Moreover, self-reported distance VF loss was associated with an increased risk beyond 4years after inclusion (HR1.5, 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.