A history of allergies may reduce a person’s risk of developing age-related macular degeneration (AMD). That is the message of a European study led by a German scientist, Dr. Sascha Fauser, at the University Hospital of Cologne.
The study involved over 3,800 Europeans, who were part of a European genetics database. Half had AMD, and about a 1/3 of those had severe late stage AMD; the remaining participants were people were a matched group of similar ages and demographics who did not have AMD. All participants were asked about their history of allergies to common substances including pollen, drugs, and various foods.
Intriguingly, the study found that people with a history of allergies of any type (pollen, drug, food) were unlikely to have AMD, and even more unlikely to have severe AMD, than those who had no history of allergies.
This finding was unexpected. Allergies are due to a reaction of the immune system, and AMD is also at least partly caused by an immune response. However, the part of the immune system responsible for allergies is different from the part that is thought to increase the risk of AMD. Consequently, the reason for a correlation between allergies and risk of AMD is not immediately obvious; in fact, the researchers characterized the connection as “counterintuitive”.
For the present, this finding is an unexpected and unexplained correlation between allergy and AMD, and it’s too early to conclude that allergy (or the biological mechanisms responsible for allergic reactions) causes the risk of AMD to go down. The authors themselves note, “Another explanation could be that allergy itself is not protective against AMD, but that the susceptibility for allergy and the protection against AMD share a common cause.” Basic research in laboratory models will be necessary to sort this out. If researchers can understand why people with a history of allergies are less likely to have AMD, they may be directed towards previously unsuspected ways of preventing AMD.
This research was published in the early online portion of the journal, Investigative Ophthalmology & Vision Science, and will appear in a later print version of the journal.