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No association between POAG, Alzheimer's disease, researchers find
Primary open-angle glaucoma is modestly associated with the development of vascular dementia, according to a study recently published in the
Keenan and colleagues found no association between POAG and Alzheimer's disease in investigating the risk between the diseases.
"We have previously examined the potential association between age-related macular degeneration (AMD) and Alzheimer’s disease using record linkage," the researchers reported. "Similarly, the main purpose of the current study was to use record linkage to determine whether individuals admitted to hospital with POAG were significantly more or less likely than others to develop Alzheimer’s disease in subsequent years. In addition, the risk of developing vascular dementia in subsequent years was examined, given ongoing interest in potential links between POAG and vascular disease."
Researchers utilized the English National Health Service's database of hospital episode statistics for their data. This included 87,658 POAG patients, 251,703 Alzheimer's disease patients, 217,301 vascular dementia patients and a reference group of more than 2.5 million participants.
Researchers calculated rate ratios to determine risk levels.
"These data provide evidence that there is no positive association between POAG and Alzheimer’s disease," the authors concluded. "However, a weakly positive association was found between POAG and vascular dementia. Vascular risk factors may be responsible for this relationship, particularly in the context of [normal tension glaucoma]. People with dementia in England are substantially less likely to receive a subsequent hospital diagnosis of POAG. Any potential deficit in glaucoma care for these vulnerable individuals needs to be examined and addressed in the near future."
Disclosure: The authors have no relevant financial disclosures.
Perspective
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Primary open-angle glaucoma is an elevation in intraocular pressure. No, it is a decrease in ocular perfusion pressure … or an increase in trans-lamina cribrosa pressure differential … or is it the most common neurodegenerative disease we encounter? Perhaps it is all of the above.
Through a record linkage study of a large English National Health Service data set, Keenan et al. demonstrate that a diagnosis of POAG slightly increases the subsequent risk of hospitalization for vascular dementia, but not for Alzheimer’s disease (AD). Conversely, a diagnosis of dementia significantly decreases the likelihood of a subsequent diagnosis of POAG.
Whether this represents an underdiagnosis due to a deficit in eye care for the population with dementia (a tragedy that must be addressed, if proven) or a secondary vascular/neuroprotective effect of medications prescribed for the treatment of dementia remains to be determined.
Despite past disappointments, including the phase 3 memantine trial, the search for commonalities in pathophysiology and treatment for dementia/AD (Wostyn) and POAG (McKinnon) seems likely to continue.
References:
McKinnon SJ. Front Biosci. 2003;8:s1140-1156.
Wostyn P, et al. Med Hypotheses. 2010;74(6):973-977. doi: 10.1016/j.mehy.2009.12.019.