Research indicates that dementia and age-related macular degeneration may have a common cause
TUESDAY, May 12 (HealthDay News) -- Seniors who perform poorly on tests of language, memory and concentration are more likely to be suffering from the early stages of age-related macular degeneration, a major cause of vision loss, a new study suggests.
The finding stems from a look at the association between cognitive function decline and the onset of age-related macular degeneration (AMD) among approximately 2,000 Australian seniors between the ages of 69 and 97.
"We found that those who have memory impairment were more likely to have early stages of macular degeneration independent of the effects of age, education and vascular risk factors," said study co-author Dr. Tien Yin Wong, a professor in the department of ophthalmology within the Centre for Eye Research Australia at the University of Melbourne.
Wong and his colleagues published the findings in the May issue of the Archives of Ophthalmology.
Age-related macular degeneration is the leading cause of vision loss among the elderly. The researchers note that prior research has suggested that Alzheimer's disease and AMD share similar developmental pathways in terms of protein build-up and brain and eye changes.
The authors' current observations are drawn from an analysis of retinal photographs taken of study participants (more than 80 percent white and all enrolled in a larger cardiovascular health study), from which a diagnosis of early-stage AMD was made.
Those diagnoses were lined up against results of cognitive function and neuropsychological tests designed to assess each subject's abilities in terms of concentration, language, memory and orientation skills. Most were also tested for dementia and cardiovascular risk factors.
The researchers determined that nearly 16 percent of the participants had early AMD, while 135 and 86 patients were diagnosed with dementia or Alzheimer's disease, respectively.
Having dementia and/or Alzheimer's was not linked to an increased likelihood for early AMD. However, the authors found that an AMD diagnosis was associated with having poorer scores on cognitive testing -- a trend deemed small but "significant."
"Our study suggests that there may be common links in the cause and risk factors for both conditions," Wong said. "They further raise the possibility that preventive and treatment strategies targeted at one condition may be useful for another." They did not suggest that having AMD causes dementia.
Dr. Demetrios Vavvas, a specialist in AMD at the Massachusetts Eye and Ear Infirmary in Boston, agreed that "there's probably something common between the two problems."
"As a retinal physician I'm already alert that these people are older, and they might have cognitive decline," he noted. "So certainly there may be a common pathogenesis between these two diseases."
"To say there is a mild correlation between these two diseases is along expected lines from what we know from previous studies," said Vavvas. "But I don't think this changes my day-to-day clinical approach to our patients."
The same issue of the journal included two additional Australian studies -- one from the University of Sydney and the other from the Centre for Eye Research -- that indicate that AMD risk can be reduced by avoiding trans fats and by regularly consuming fish, nuts, olive oil and other foods containing omega-3 fatty acids.
For additional information and resources on macular degeneration, visit the National Eye Institute.
SOURCES: Tien Yin Wong, M.D., Ph.D., professor, department of ophthalmology, Centre for Eye Research Australia, The University of Melbourne, Victoria, Australia; Demetrios Vavvas, M.D., Ph.D., vitreoretinal surgeon, Massachusetts Eye and Ear Infirmary, Boston, and principal investigator, angiogenesis laboratory, Harvard Medical School, Boston; May 2009 Archives of Ophthalmology
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