A new study by the University of South Australia (UniSA) has found that millions of older people with poor vision are at risk of being misdiagnosed with mild cognitive impairments.
The study, published in Scientific Reports, demonstrates the negative consequences of visual impairments on cognitive test performance, as conditions that are synchronous with ageing, including visual decline, are easily overlooked when interpreting cognitive test scores.
People with AMD are already experiencing multiple issues due to vision loss and an inaccurate cognitive assessment is an additional burden they don’t need
Therefore, cognitive tests that rely on vision-dependent tasks could be skewing results in up to a quarter of people aged over 50 who have undiagnosed visual problems such as cataracts or age-related macular degeneration (AMD).
UniSA researchers recruited 24 participants with normal vision to complete two cognitive tests – one involving vision-dependent reactive tasks and the other based of verbal fluency. Participants were required to wear goggles to simulate AMD.
The results showed that performance on the reaction time task significantly decreased (p < 0.001) in the simulated AMD condition, by as much as 25 percentile ranks. In contrast, performance on the verbal fluency test were not statistically different between the simulated and normal vision conditions (p = 0.78).
Anne Macnamara, UniSA PhD candidate who led the study, says the results are a reminder that visual impairments – which, worldwide, affect approximately 200 million people over the age of 50 – unfairly affect cognitive scores when tests involve visual abilities.
“A mistaken score in cognitive tests could have devastating ramifications, leading to unnecessary changes to a person’s living, working, financial or social circumstances,” said Ms Macnamara.
“For example, if a mistaken score contributed to a diagnosis of mild cognitive impairment, it could trigger psychological problems including depression and anxiety.
“People with AMD are already experiencing multiple issues due to vision loss and an inaccurate cognitive assessment is an additional burden they don’t need.”
UniSA researchers noted that reduced vision is underestimated in up to 50% of older adults, and that this figure is expected to increase in line with an ageing population. Therefore, it is critical that neuro-degenerative researchers control for vision when assessing people’s cognition.
Researchers say the incorporation of simple precautionary measures to make allowances for the potential impact of AMD, could help combat this major concern. Such measures include screening participants with mobile vision charts prior to participation, or administering vision-friendly variation of standard cognitive assessments.
As well as this, Ms Macnamara acknowledged that, “mobile apps can now be used to overlay simulated visual impairments onto test materials when piloting their stimuli.”
The study paper concluded that, “While the true impact of AMD on cognitive test scores remains to be established, it is clear that not controlling for vision can adversely affect the results and can have broader implications for the health of visually impaired people.”
The full study report is available here.
