Visual Impairment, Eye Diseases, and Dementia Risk: A Systematic Review and Meta-Analysis
Kuźma E., Littlejohns TJ., Khawaja AP., Llewellyn DJ., Ukoumunne OC., Thiem U.
Background: Visual impairment and eye diseases have been associated with dementia, though with mixed findings and often in cross-sectional studies. Objective: To identify prospective studies investigating associations between visual impairment or common eye diseases and risk of all-cause dementia or key dementia subtypes. Methods: We searched Medline, PsycINFO, and Embase from inception to January 2020. We also conducted backward and forward citation searches of included studies and set up alerts to identify studies published after the search date. Random-effects meta-analysis was used to combine adjusted estimates across studies. Results: Thirty studies met our eligibility criteria. For visual impairment, pooled estimates indicated an increased risk of all-cause dementia (37,705 participants, 3,415 cases, risk ratio [RR] = 1.38, 95%confidence interval [CI]: 1.19–1.59, I2 = 28.6%). Pooled estimates also suggested an increased dementia risk associated with cataract (6,659 participants, 1,312 cases, hazard ratio [HR] = 1.17, 95%CI 1.00–1.38, I2 = 0.0%) and diabetic retinopathy (43,658 participants, 7,060 cases, HR = 1.34, 95%CI 1.11–1.61, I2 = 63.9%), respectively. There was no evidence of an association between glaucoma (175,357 participants, 44,144 cases, HR = 0.97, 95%CI 0.90–1.04, I2 = 51.5%) or age-related macular degeneration (7,800,692 participants, > 2,559 cases, HR = 1.15, 95%CI 0.88–1.50, I2 = 91.0%) and risk of dementia, respectively. Conclusion: As visual impairment, cataract, and diabetic retinopathy are associated with an increased likelihood of developing dementia, early diagnosis may help identify those at risk of dementia. Given most causes of visual impairment are treatable or preventable, the potential for dementia prevention warrants further investigation.