Associations of Age and Birth Cohort with Total and Specific IgE Antibody Levels

Abstract

Background. Total and antigen-specific IgE levels vary greatly with age; however, it is unclear whether they are more closely related to patient age or birth cohort. Objective. To determine whether birth cohort or age was more strongly correlated with total and specific IgE levels. Methods. We retrospectively examined the medical records of 5136 asthma patients who were treated at the Niigata Allergic Disease Research Institute Outpatient Clinic during the period from 1997 to 2005. The subjects were divided into four birth cohorts based on their year of birth: the first cohort was born in 1935 or earlier, the second in 1936–1955, the third in 1956–1975, and the fourth in 1976 or later. Their total IgE level and mite-, cedar-, and Candida albicans (Candida)-specific IgE levels were measured using the CAP RAST fluoroenzyme immunoassay test. Results. Univariate analysis revealed that total IgE level and mite-, cedar-, and Candida-specific IgE levels significantly decreased (p < .001) with advancing age. In addition, there were significantly higher IgE levels in later birth cohorts (p < .01). On multivariate analysis, there were associations of total IgE level and mite- and cedar-specific IgE levels with both age and birth cohort. However, there was no significant association between Candida-specific IgE antibody level and either age or birth cohort. Conclusions. The associations of total and specific IgE levels with age and birth cohort were different. Thus, in comparing the results of IgE antibody testing done in different years, even for patients of the same age, the possibility of a birth cohort effect on IgE levels should be considered.