Visual impairment appears to be a risk factor for cognitive impairment, but more research is needed to confirm this, according to a study published in Ophthalmology. The study speculates that “it is possible that the additional cognitive resources allocated to sensory processing to overcome visual impairment may impair cognitive abilities for other tasks.”
The study, a systematic review and meta-analysis, examined the bidirectional relationship between sight and cognition, both prevalent age-related conditions with real impact on society. The literature has shown a 60% risk of cognitive impairment. Researchers searched the Pubmed, Embase, and Cochrane Central registries for observational studies published from inception through April 2020 in adults 40 years and older that reported objectively measured visual impairment and cognitive impairment using clinically validated cognitive screening tests or diagnostic ratings. A total of 40 studies were included (N = 47,913,570).
They examined the meta-analyzes of cross-sectional and longitudinal associations between visual impairment and cognitive impairment outcomes. Cognitive impairment was assessed using screening tests and clinically diagnosed dementia. They generated pooled odds ratios and a 95% confidence interval with random effect models and examined publication bias and heterogeneity using Eggers test, meta-regression and trim-and-fill methods.
The meta-analysis found that participants with visual impairments were more likely to have cognitive impairments and had significantly higher chances [OR (95%CI)] any cognitive impairment [cross-sectional: 2.38 (1.84-3.07); longitudinal: 1.66 (1.46-1.89)] and clinically diagnosed dementia [(cross-sectional: 2.43 (1.48-4.01); longitudinal: 2.09 (1.37-3.21)]compared to people without visual impairment. Differences in age, gender and duration of follow-up partly explained a significant heterogeneity.
“There was also evidence that people with [cognitive impairment]compared to cognitively intact people rather [visual impairment]Most of the articles (8/9, 89%) reported significantly positive associations. Meta-analyzes on this association could not be carried out due to insufficient data, ”the study says.
And these results were clinically relevant because “strategies for the early detection and treatment of visual and cognitive impairment in older people can minimize the individual clinical and health consequences,” according to the study.
The study had limitations, including the fact that the meta-analysis was only performed in English language publications, excluding relevant results in other language publications. Limited data also made some findings impossible, including determining the severity of visual impairment and the association between visual impairment and mild cognitive impairment. They also did not contain any studies examining the relationship between various eye pathologies and etiologies of cognitive impairment, and therefore could not determine the mechanisms involved. You also failed to consider other vision components that might help.
“Future prospective studies and randomized controlled trials are needed to investigate whether [cognitive impairment] predicts the risk of [visual impairment] and whether visually-sparing interventions are effective in preventing the progression of cognitive decline in cognitively impaired patients, ”researchers say.
Vu TA, Fenwick EK, Gan AT et al. The bidirectional relationship between seeing and cognizing: a systematic review and meta-analysis. Ophthalmol. Published online on December 14, 2020. doi: 10.1016 / j.ophtha.2020.12.010
This article originally appeared on Ophthalmology Advisor