Mahyar Etminan
A first-ever epidemiological study of a class of osteoporosis drugs has revealed a statistical connection between long-term use and a higher risk of developing age-related macular degeneration (AMD).
Published in May in the American Journal of Ophthalmology, the study by Assistant Professor Mahyar Etminan showed that use of oral bisphosphonates nearly doubles the risk of developing AMD. Since the annual risk of developing AMD is 5 per cent to 10 per cent, that means users of oral bisphosphonates – including Fosamax, Actonel and Didronel – might face a heightened risk of 10 per cent to 20 per cent.
Dr. Etminan and ophthalmology resident Zaid Mammo, with support from the Foundation Fighting Blindness, decided to take a close look at oral bisphosphonates because they are known to promote inflammation and other inflammatory ocular conditions, such as uveitis. He looked for a connection between that family of drugs and the neovascular or “wet” form of AMD, which is the least common type but also the most potentially harmful because it can lead to blindness.
Using anonymized health records of nearly 7,800 AMD patients in British Columbia, Dr. Etminan and Dr. Mammo (the lead author), compared them to approximately one million controls, examining patterns of bisphosphonate use between the two groups.
Despite the finding, Dr. Etminan, a pharmacological epidemiologist in the Department of Ophthalmology and Visual Science, cautions that it’s too soon for people to stop using the drugs or to avoid taking them, because this is the first study to show a link. Other large-scale studies using other patient databases need to be done before drawing firm conclusions.
Even if the finding is validated, Dr. Etminan points out that the elevated risk for AMD from bisphosphonates is small, so a careful weighing of risks and benefits – in consultation with a physician – would be necessary.
Nevertheless, Dr. Etminan says many users of oral bisphosphonates are taking the drug only because of bone thinning, not because they have experienced a traumatic fracture, and for them the benefits are generally smaller – perhaps small enough not to warrant the elevated risk of developing AMD.
“The data is compelling enough to look into this further,” he says.