Interaction between visual impairment and genetic risk of dementia and psychosis in older adults

Visual impairment (VI) is associated with dementia and other neuropsychiatric outcomes, but previous studies have not considered genetic sources of confounding or effect modification.

We analysed data from the Health and Retirement Study, an ongoing nationally representative survey of older US adults, a subset of whom underwent genetic testing from 2006 to 2012 (n = 13 465). Using discrete time proportional hazards models and generalised estimating equations, we measured the association between VI and dementia, depression and hallucinations adjusting for demographics and comorbidities, ancestry-specific principal components and polygenic risk scores (PRS) for Alzheimer's disease, major depressive disorder or schizophrenia. Effect modification was assessed using VI-PRS interaction terms and stratified analyses.

VI was associated with dementia, depression and hallucinations after adjusting polygenic risk and other confounders. There was no VI-PRS interaction for dementia or depression. However, the association between VI and hallucinations varied by genetic risk of schizophrenia. Within the bottom four quintiles of schizophrenia PRS, VI was not associated with hallucinations among White (OR 1.16, 95% CI: 0.87-1.55) or Black participants (OR 0.96, 95% CI: 0.49-1.89). In contrast, VI was strongly associated with hallucinations among White (OR 2.08, 95% CI: 1.17-3.71) and Black (OR 10.63, 95% CI: 1.74-65.03) participants in the top quintile of schizophrenia PRS.

The association between VI and neuropsychiatric outcomes is not explained by shared genetic risk factors, and there is a significant interaction between VI and polygenic risk of hallucinations in older adults.