Being visually impaired may increase the risk of dementia, according to a study in JAMA Ophthalmology of 1,061 postmenopausal women (average age 74) who were followed for up to seven years.
Women who scored 20/40 or worse on a vision exam at the start of the study (as measured while wearing any glasses or contacts they normally used) had a two- to nearly-six-fold higher risk of subsequently developing dementia, compared to women who had 20/20 vision.
The risk increased as vision worsened, with the highest dementia incidence seen in women with 20/100 vision or poorer. Impaired vision also increased the risk of mild cognitive impairment (MCI), a possible precursor to dementia.
The researchers controlled for some other factors that might contribute to cognitive decline, including age, hearing loss, and baseline cognitive performance; they did not control for socioeconomic status, however, which could well have influenced the results.
Also see Poor Vision Affects More Than Your Eyes.