July 17 (UPI) -- Researchers have discovered new risk genes for hay fever in the largest genetic study on this type of allergy.
Data on allergic rhinitis from 891,367 European participants in more than 30 studies were studied by researchers from the University of Copenhagen in Denmark and the Copenhagen Prospective Studies on Asthma in Childhood. The findings were published Monday in the journal Nature Genetics.
"The scope of the study has allowed us to learn more about the allergy, and it has only been possible with the help of many other research groups from around the world," co-author Dr. Klaus Bonnelykke, clinical research associate professor at University of Copenhagen, said in a press release. "The risk genes we have mapped can help us understand what causes hay fever. And in the longer term this will be helpful when it comes to developing drugs and better treatments for the allergy."
More than 400 million worldwide have hay fever, which is triggered by airborne allergens that include pollen, pet hair and dust mites. In the United States, 7.8 percent of people 18 and older have hay fever based on the National Health Interview Survey.
"Genes are very important, and twin studies show that in more than half of sufferers, the allergy is caused by genetics," said co-author Dr. Klaus Bonnelykke, also a clinical research associate professor at University of Copenhagen. "We can also see that a great many cases must be due to environmental factors, since the number of people with hay fever has increased over the past 100 years. ... It takes tens of thousands of years for genetic makeups to change."
Bonnelykke said he believes the rise is likely caused by an association between risk genes found in this study and environmental factors that trigger the allergy in those with risk genes.
The researchers found an overlap between risk genes for hay fever and ones for autoimmune diseases, including type 1 diabetes, rheumatoid arthritis and inflammatory bowel disease. Like allergies, autoimmune disease cases have risen sharply in recent years.
Researchers first compared the genome of 59,762 allergic rhinitis patients with 152,358 healthy controls. They found 41 significant risk genes, some of which had previously been described in other research.
Then, 20 previously unknown risk genes were confirmed from data of another 60,720 patients and 618,527 healthy controls.
"The higher the number of study participants, the more reliable conclusions we can draw," Dr. Marie Standl, head of a research group at the Institute of Epidemiology at Helmholtz Zentrum Munchen in Germany, said in a press release. "The identified risk genes can explain about 8 percent of all cases of allergic rhinitis."
Bonnelykke said understanding hay fever may be linked to finding out about autoimmune diseases.
"Our study helps identify genetic commonalities which may be a key to understanding why these illnesses are all on the rise," Bonnelykke said. "It seems there are some common factors in the western lifestyle that are causing these illnesses to become more widespread, but we haven't yet understood why. The genetic overlap we have observed seems to suggest that it is the same genes that trigger these illnesses, at least in part."