Cataracts confer increased risk of vascular dementia

People with cataracts may be at elevated risk of vascular dementia and reduced total brain volumes by way of vascular and non-Alzheimer’s disease (AD) mechanisms, according to a study.

Researchers conducted a cohort and two-sample bidirectional Mendelian randomization (MR) analysis to explore potentially causal associations between visual acuity, eye conditions (specifically cataracts and myopia), neuroimaging outcomes, and AD and related dementias (ADRDs). They used data from the UK Biobank and summary statistics from previously published genome-wide association studies on cataract, myopia, and AD.

A total of 304,953 participants (mean age 62.1 years, 53.72 percent women) without dementia at baseline were included in the analysis, with 14,295 (4.69 percent) having cataracts and 2,754 (3.86 percent) having worse than 20/40 vision. These participants underwent genotyping and reported on eye conditions, with a subset completing visual acuity examinations (n=69,852–71,429) or brain imaging (n=36,591–36,855).

Cataracts were associated with an 18-percent increased risk of ADRD (hazard ratio [HR], 1.18, 95 percent confidence interval [CI], 1.07–1.29), while myopia was associated with a 35-percent risk increase (HR, 1.35, 95 percent CI, 1.06–1.70).

In MR analyses, cataracts appeared to be causally associated with vascular dementia (inverse variance-weighted odds ratio [OR], 1.92, 95 percent CI, 1.26–2.92) but not with dementia (OR, 1.21, 95 percent CI, 0.98–1.50). No link was established between myopia and dementia.

Additionally, there was no potential for reverse causality, with AD having no association with cataracts (inverse variance–weighted OR, 0.99, 95 percent CI, 0.96–1.01).

Genetic predisposition for cataracts correlated with smaller total brain (β, −597.43 mm3) and gray matter (β, −375.17 mm3) volumes but not the other brain regions.

These results lend support to the hypothesis that cataract extraction may reduce the risk for dementia, according to the investigators.