Researchers from Loughborough University in England have uncovered a link between visual processing speed and dementia that could predict the onset of the disease up to 12 years before clinical diagnosis.
In the prospective cohort study published in Scientific Reports, the researchers assessed cognition, physical functioning and eye health of 8,623 participants aged 48–92 years between 2004 and 2011.
Participants underwent a Visual Sensitivity Test (VST) to assess visual processing speed and reaction time where they were asked to press a button upon detecting a triangle emerging from a field of moving dots.
Follow-up assessments found individuals with lower VST scores had a higher probability of a future dementia diagnosis.
The researchers suggest that visual issues may be an early indicator of cognitive decline as the toxic amyloid plaques associated with Alzheimer’s disease may first affect areas of the brain associated with vision, with parts of the brain associated with memory becoming damaged as the disease progresses.
Therefore, vision tests may find deficits before memory tests do.
Moreover, visual processing such as the ability to see outlines of objects (contrast sensitivity) and to discern between certain colours (the ability to see the blue-green spectrum is affected early in dementia), are also implicated in Alzheimer’s.
Another early sign of Alzheimer’s is a deficit in the “inhibitory control” of eye movements, where distracting stimuli appear to hold attention more readily. People with Alzheimer’s are said to have an issue ignoring distracting stimuli, which may show up as eye-movement-control issues.
“As the VST was significantly associated with more dementia risk factors, it could be integrated into the screening process for dementia risk and early diagnoses alongside other cognitive tests,” the study authors said.
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