By Nicole MacKee
Maintaining good vision may help ward off dementia in older people, US research published in JAMA Ophthalmology suggests.
A prospective longitudinal study of 2520 community- dwelling older adults (mean age 73 years) found that over eight years worsening visual acuity was associated with reduced cognitive functioning.
Participants with a mean decline in visual acuity of about one line on the Early Treatment Diabetic Retinopathy Study (ETDRS) chart had an associated decline in their Mini-Mental State Examination (MMSE) score of 0.83 (out of 30) over the study period. Participants with greater declines in visual acuity – about two lines on the ETDRS chart – showed an associated decline of 2.5 points on the MMSE.
The researchers said two hypotheses might explain the association: poor vision may reduce the ability to participate in activities that help to maintain wellbeing, or there may be a common cause such as inflammation or degeneration of the CNS. They found that visual acuity had a stronger influence on cognition than the reverse, suggesting that poor vision was likely to be adversely affecting cognitive function.
Professor Perminder Sachdev, Co-Director of the Centre for Healthy Brain Ageing at UNSW Sydney, said although this was an association study, which did not prove that poor vision caused cognitive decline, it did underline the importance of addressing vision impairment in ageing.
‘There is good evidence now that complex mental activity and social activity are important in preserving the brain and reducing the risk of dementia,’ Professor Sachdev told Medicine Today. ‘Someone with visual impairment is likely to have less input from the environment, so perhaps less cognitive activity and less social activity. So, older people with poor vision would not be able to participate in activities that help maintain their wellbeing and therefore their brain stimulation is reduced.’
Professor Sachdev agreed that degeneration of the CNS could also be a factor in the association.
‘The eye is an extension of the CNS, so that would need to be looked at as well,’ he said.
‘The message in this study is that older people with visual impairment should have it corrected as much as possible.’
JAMA Ophthalmol 2018; doi: 10.1001/jamaophthalmol.2018.2493.