Visual Impairment May Be Early Dementia Risk Factor

Visual impairment may be a risk factor for dementia, according to a study published in JAMA Ophthalmology.

In a prospective, longitudinal cohort study of 1061 women between the ages of 66 and 84, researchers compared the likelihood of incident dementia or mild cognitive impairment (MCI) among women with and without baseline visual impairment. Data showed women with baseline objective visual impairment were more likely to develop dementia after an average follow-up of 3.8 years.

The study began in 2000 and is the first prospective analysis based on standardized, objective, visual acuity measurement and adjudicated cognitive assessment. Postmenopausal women were selected for participation if they were concurrently enrolled in the Women’s Health Initiative (WHI) Sight Examination Study (enrollment 2000-2002) and WHI Memory Study (enrollment 1996-1998, ongoing). Any patients exhibiting dementia or MCI before the baseline eye exam were excluded.

Visual impairment was objectively measured via vision tests and categorized based on 3 thresholds: visual acuity worse than 20/40, 20/80, or 20/100. Participants also self-reported visual impairment through their survey responses. The researchers used cognitive testing, clinical assessment, and centralized review and adjudication to determine cognitive impairment (ie, probable dementia or MCI). Data were adjusted for confounding factors such as demographics, systemic comorbidities, hearing impairment, educational level, physical activity, smoking, and hormone therapy.

The average participant age was 74, and of the 1061 women included, 206 (19.4%) had self-reported visual impairment while 183 (17.2%) had objective visual impairment. The researchers note self-reported visual impairment was not associated with any risk of dementia or MCI. However, data showed “visual impairment was associated with an even higher likelihood of dementia when combined with self-reported hearing loss.”

The researchers found women with visual acuity of 20/100 or worse at baseline (HR, 5.66; 95% CI, 1.75-18.37) were at the greatest risk for developing dementia. When it comes to the risk of developing MCI, this group also had the greatest risk (HR, 6.43; 95% CI, 1.66-24.85).

“Objectively measured visual impairment was associated with a 2- to more than 5-fold higher risk of subsequent dementia, with stronger [hazard ratios] at higher visual impairment thresholds,” the researchers found.

Women with 20/80 visual acuity or worse had an HR of 5.2 of developing dementia (95% CI, 1.94-13.95) while women with 20/40 visual acuity or worse exhibited an HR of 2.14 (95% CI, 1.08-4.21). Similarly, greater HRs of MCI were observed in participants with greater objective visual impairment.

Although there is no underlying mechanism specifically associating visual and cognitive impairment, the researchers note the relationship between visual and cognitive function is likely bidirectional and multifactorial.

The results suggest interventions to improve visual acuity in older adults may be beneficial. “Older adults who undergo cataract surgery have been suggested to have lower risk of new-onset dementia, and other studies have suggested improved cognitive scores after cataract surgery,” the researchers said.

Future research should be conducted to evaluate the effect of ophthalmic interventions on dementia incidence and/or cognitive trajectories among patients with dementia, they conclude.

Reference

Tran EM, Stefanick ML, Henderson VW, et al. Association of visual impairment with risk of incident dementia in a Women’s Health Initiative population [published online April 16, 2020]. JAMA Ophthalmol. doi: 10.1001/jamaophthalmol.2020.0959.