Fran Lowry

November 18, 2010

November 18, 2010 (Phoenix, Arizona) — Age-related immunoglobulin (Ig)E levels have risen significantly in both males and females in the United States since the 1970s, researchers announced here at the American College of Allergy, Asthma & Immunology (ACAAI) 2010 Annual Scientific Meeting.

The finding might be the reason for the increase in allergic rhinitis, asthma, and allergies in general that are being seen today, said Zackary Jacobs, MD, from Children's Mercy Hospitals and Clinics, Kansas City, Missouri.

There have been no population studies quantifying total IgE since the late 1970s, when the Tucson Epidemiological Study was done. Because the prevalence of allergic disease is increasing, Dr. Jacobs and his team wanted to see if that increase was reflected in IgE levels.

To gauge the temporal trend of age-related total IgE, the researchers analyzed data from the National Health and Nutrition Survey (NHANES), a large cross-sectional database of the American population in 2005 and 2006. They then compared the results by age group with those of the earlier study.

They found that subjects in the NHANES group had higher levels of IgE than those in the Tucson study, and that the IgE levels did not fall as much in the NHANES study with increasing age as they did in the Tucson study.

"In the early years, in the 6 to 14 and 15 to 24 year age categories, the IgE levels were very similar in both the NHANES and the Tucson groups. But as the subjects got older, from the age of 25 on, IgE levels in NHANES subjects were significantly higher," he reported.

Another "interesting trend change" was that the IgE levels of people in NHANES remained high, Dr. Jacobs said.

IgE levels in the NHANES study and the Tucson Epidemiological Study

Age group (years)* NHANES, total IgE (kU/L) Tucson, total IgE (kU/L)
6–14 63.1 79.5
15–24 66.1 53.1
25–34 47.9 36.4
35–44 51.3 34.1
45–54 46.8 28.2
55–64 53.7 21.6
65–74 47.9 20.8
75+ 39.9 17.1
*P < .0001 for each age category

Dr. Jacobs noted that both groups were well-matched for age and sex. "Subjects in the Tucson group had higher IgE initially, but the NHANES subjects' IgE had a later peak and declined much less with age. The differences were statistically significant for each age group," he said.

"Obviously, this means that for whatever reason, people in the United States today have more IgE than they did 20 or 30 years ago. This is consistent with the idea that people have more allergies today than they did at that time," Dr. Jacobs told Medscape Medical News.

There could be many reasons for the increase in allergies, he continued. "People spend their whole careers trying to find out why, but we will need a lot of very strong studies, especially involving birth cohorts, [to determine] what is going on in the immune system to lead people to have more allergies. There are many different viewpoints and opinions."

Another reason for the finding could be differences in the methods used to determine IgE levels between the 2 studies, Dr. Jacobs suggested.

John J. Oppenheimer, MD, clinical associate professor at New Jersey Medical School in Newark, and chair of the ACAAI abstract review committee, called the study "interesting."

The findings "leave us with several potential conclusions. It could mean that the population of allergy sufferers is going up. We've certainly seen a rise in prevalence, and that might explain it."

Another possibility is, as Dr. Jacobs suggested, that the difference is due to changes in the way IgE is measured, Dr. Oppenheimer said.

"One must be sobered by the fact that these differences may be related to change in technique, because we use different measurements today than we did back then."

Dr. Jacobs has disclosed no relevant financial relationships. Dr. Oppenheimer reports being a consultant and doing research for AstraZeneca, Schering, Merck, Novartis, Glaxo, and Genentech.

American College of Allergy, Asthma & Immunology (ACAAI) 2010 Annual Scientific Meeting: Abstract 51. Presented November 15, 2010.