The Cognitive Toolbox: Do the Eyes Have It?

Better visual function may improve social interactions and facilitate cognitive stimulation whereas sensory impairment may lead to social isolation and depression, which exacerbate risk of dementia.

RESEARCH UPDATE

Cataract surgery may have a salutary effect on the trajectory of cognitive decline, according to an investigative team from the University of Manchester in Manchester, UK.¹ This study was part of the European Union Horizon 2020 SENSE-Cog multi-phase research program, which aims to promote well-being in older adults with sensory and cognitive impairments.

The relationship between sensory impairment and cognitive performance has been hypothesized to be either associated with age-related degeneration of the central nervous system; a neurobiological domino effect (“cascade hypothesis”) mediated by compromised self-efficacy, social isolation, or depression; or simply poorer cognitive test performance due to sensory impairment.

Maharani and colleagues¹ decided to explore the issue by looking at the impact of cataract surgery on cognitive outcomes in older adults. The results of their findings supports the cascade hypothesis, whereby cataract surgery putatively may allow for better visual input, thereby resulting  in a slower rate of cognitive decline via several potential mechanisms, including neurobiological mechanisms.

They reviewed longitudinal data from 7 “waves” of survey data over the course of 13 years (2002 to 2015) from the English Longitudinal Study of Ageing (ELSA). ELSA collects information on demographics, socioeconomics, health, and social participation of persons age 50 years and older.

A total of 2068 participants who had had cataract surgery between waves 2 and 6 and 3636 who did not have cataract surgery until wave 7 formed the active and control groups, respectively. 

In the treatment group, cataract surgery was associated with significantly improved memory (P<.001), and, although cognitive decline persisted with aging, the decline in episodic memory scores was slower after cataract surgery (P<.001) when social determinants, behavioral risk factors, depression score, and chronic conditions were controlled for.

The slope of cognitive decline in the control group before cataract surgery was gentler than that in the treatment group (P<.001) , and the rate of memory decline postsurgery was similar to that of the control group. 

Female sex, higher educational attainment, higher income and regular, moderate physical exercise were associated with higher memory scores whereas depression and chronic disease were negatively associated. In response to these findings, the study authors pointed to research showing that better vision may help facilitate physical activity, which in turn improves cognitive function.^2,3

They added that better visual function may improve social interactions and facilitate cognitive stimulation whereas sensory impairment may lead to social isolation and depression, which exacerbate risk of dementia.

The bottom line

Cataract surgery was found to be associated with a slower rate of cognitive decline. This finding has important implications when identifying people at risk for cognitive decline and formulating interventions. The authors noted that further research is warranted and recommended that it focus on how treatment or prevention of vision impairment might lower the risk of dementia.

References:

1. Maharani A, Dawes P, Nazroo J, et al; SENSE-Cog WP1 group. Cataract surgery and age-related cognitive decline: A 13-year follow-up of the English Longitudinal Study of Ageing. PLoS One. 2018;11;13:e0204833.

2. Salive ME, Guralnik J, Glynn RJ, et al. Association of visual impairment with mobility and physical function. J Am Geriatr Soc. 1994;42:287-292.

3. Weuve J, Kang JH, Manson JE, et al F. Physical activity, including walking, and cognitive function in older women. JAMA. 2004;292(12): 1454-1461.