Associations between vision impairment and eye diseases with dementia, dementia subtypes and cognitive impairment: An umbrella review.

Vision impairment (VI) and eye diseases such as age-related macular degeneration (AMD), diabetic retinopathy (DR), glaucoma and cataract have been reported to be associated with cognitive impairment and dementia, however, to date, very little attempt has been made to collate and synthesizes such literature. Therefore, the aim of this umbrella review is to systematically assesses the credibility and certainty of evidence of associations between vision impairment (VI) and eye diseases with cognitive impairment, dementia and dementia subtypes. We conducted an umbrella review of meta-analyses by screening articles in any language in PubMed, MEDLINE (Ovid), EMBASE, Web of Science, Cochrane CENTRAL and CDSR published from database inception up to May 30, 2024. Quality appraisal of each included original meta-analysis was assessed using A Measurement Tool for Assessing Systematic Reviews 2 (AMSTAR2). The certainty of the evidence was based on statistical significance, study size, heterogeneity, small study effects, prediction intervals (PI), and bias. We followed an a-priori protocol registered with PROSPERO (CRD42024564249). We identified 13 meta-analyses (AMSTAR 2; high accuracy of the findings 1, moderate 10, and low 2) that included 232 original articles based on 99,337,354 participants. Overall, no evidence was highly suggestive or convincing. Suggestive evidence was found for associations between cataract and dementia (equivalent odds ratio [eOR] 1.20, 95 %CI, 1.16-1.25), cataract and Alzheimer's disease (eOR 1.21, 95 %CI, 1.15-1.28), and AMD and Alzheimer's disease (eOR 1.27, 95 %CI, 1.27-1.27). Weak evidence was found for associations between VI and dementia (eOR 1.50, 95 %CI, 1.23-1.84), DR and dementia (eOR 1.33, 95 %CI, 1.17-1.50), cataract and vascular dementia (eOR 1.26, 95 %CI, 1.09-1.45), VI identified by cross-sectional studies and cognitive impairment (eOR 2.37, 95 %CI, 2.31-2.44), and VI identified by objective measures and cognitive impairment (eOR 1.56, 95 %CI, 1.12-2.18). The observed suggestive level of evidence for the relationship between eye disease and dementia (as well as dementia subtypes) suggests that policy and interventions to aid in the prevention and management of eye disease may also aid in the prevention of dementia syndrome. Where the level of evidence is weak, further studies are needed with stronger methodological approaches.