How Does the Co-Occurrence of Visual Impairment, Dementia Affect Disability Risk?

Older adults with dementia and self-reported visual impairment (VI) may be at high risk for disability, while the co-occurrence of the 2 conditions may potentiate this risk, according to a study published in JAMA Ophthalmology.

VI is estimated to affect around 1 in 11 US adults aged 65 and older and is associated with an increased risk of falls, social isolation, loss of independence, disability, and dementia. As the population of older Americans increases, the number of individuals affected by VI and blindness is projected to more than double by 2050, authors write. Currently, VI and dementia co-occur in around 4% of older adults in the United States.

In this cross-sectional analysis of a nationally representative cohort study, researchers collected data from the National Health and Aging Trends Study (NHATS). The survey is conducted annually among Medicare beneficiaries aged 65 and older. Data from 7124 participants who completed the study in 2015 were included in the analysis. Using multivariable Poisson regression, investigators modeled the independent associations and interaction between dementia and self-reported VI.

“Respondents were classified as having self-reported VI if they were blind or could not see across the street and/or read newspaper print, even with glasses,” while dementia was determined using the validated NHATS classification, the researchers note.

Three functional activity scales measured the conditions’ impact on self-care (eating, dressing, toileting, bathing), mobility (going outside, getting around inside, getting out of bed), and household activities (doing laundry, shopping for groceries, etc). Participants rated ease of performance for each activity on a scale of 1 to 4, with 4 indicating the ability to independently complete the activity and 1 denoting a need for assistance to complete the activity.

After adjusting for sociodemographic and medical factors, the researchers found “self-reported VI was more common among those who had dementia, were older, female, nonwhite, less educated, had lower incomes, a history of cataract surgery, depressive symptoms, more medical comorbidities, or required a proxy respondent.”

Among the 8.6% (95% CI, 7.8%-9.3%) of participants with self-reported VI, data showed the condition was associated with a 14.7% decrease in mobility score (functional scale scores for no VI vs VI: 10.82 vs 9.23, respectively), a 9.5% decrease in self-care score (14.54 vs 13.16), and a 15.2% reduction in household activity score (18.23 vs 15.45).

In addition, 8.3% (95% CI, 7.8%-8.9%) of participants had possible dementia. In this cohort, the condition was associated with decreases of 27.8% in mobility score (10.82 for no dementia vs 7.81 for probable dementia), 22.9% in self-care score (14.54 vs 11.20, respectively), and 34.7% in household activity score (18.23 vs 11.90).

For individuals reporting both VI and probable dementia, data revealed:

• A decrease of 50.1% in mobility score (10.82 for no VI and no dementia vs 5.40 for VI and probable dementia)
• A decrease of 42.4% in self-care score (14.54 vs 8.38, respectively)
• A decrease of 52.4% in household activity score (18.23 vs 8.68)

These results suggest that “when dementia and self-reported VI occur together, the capacity to carry out mobility, self-care, and household activities is decreased to a greater degree than would be expected based on the independent associations of these 2 health conditions,” the researchers said. Because of this, they note this population may benefit from interventions aiming to maximize vision and cognition, while promoting functioning and independence.

The investigators also point out survey data are prone to recall bias, and this may be exacerbated in participants with cognitive impairment. “Additional investigations are needed using objectively measured visual function to determine the association between disability and changes in vision and cognitive function over time,” they conclude.

Reference

Patel N, Stagg BC, Swenor BK, Zhou Y, Talwar N, Ehrlich JR. Association of co-occurring dementia and self-reported visual impairment with activity limitations in older adults [published online May 14, 2020]. JAMA Ophthalmol. doi: 10.1001/jamaophthalmol.2020.1562