Modifiable risk factors for dementia include smoking, lack of exercise, hearing loss, obesity, and high blood pressure, among others listed by the Lancet Commission on Dementia Prevention, Intervention, and Care. One of the more recent additions to their list is visual impairment, which one study (Varadaraj et al., 2021) concluded as having possibly led to up to 100,000 cases of dementia in the United States. Swenor et al. (2019) also found that visual impairment is a risk factor for cognitive decline. Researchers conclude that one of the top preventive actions that may reduce risk for Alzheimer’s and related dementias is getting vision problems corrected via eye exams, eyeglasses, and cataract surgery, especially since it is estimated that ninety percent of vision impairment is preventable or has yet to be treated.
Results of a poll conducted by the University of Michigan and AARP showed that eighteen percent of people ages 50 and older had not seen an optometrist or ophthalmologist in at least three years or were not sure when they’d had their last eye exam. The reasons given included not experiencing vision problems, the cost of an exam, or just not having gotten around to scheduling the appointment.
Varshini Varadaraj and her research team at John Hopkins Disability Health Research Center recently conducted a seven-year longitudinal study to investigate associations between vision and cognitive function. This research involved the use of data from the NIA-funded University of Michigan Health and Retirement Study (HRS), a longitudinal study tracking changes in health and economic circumstances for more than 20,000 older adult volunteers. The primary independent variables were three measures of visual function—visual acuity, contrast sensitivity, and stereo acuity—which were collected at the baseline visit. Visual acuity refers to how much a pattern must differ in size to be seen. Contrast sensitivity refers to how much a pattern must vary in contrast (i.e., brightness) to be seen, and stereo acuity is a measure of depth perception.
They found that poorer vision was associated with more rapid cognitive decline. Specifically, worse visual acuity and depth perception impairment were associated with greater declines in language and memory, whereas worse contrast sensitivity was associated with declines in language, memory, attention, and visuospatial ability. The patterns of cognitive decline differed by the type of vision measured.
One concern regarding vision problems is that they can add additional cognitive load to the brain and may be associated with shifts in brain function and structure like those seen in dementia. Also, when older adults with untreated vision impairments reduce their participation in their previous daily routines and social activities, the result is a loss of stimulation, not unlike that experienced by people with hearing impairment. Social interaction has been shown to be essential for maintaining brain health.