Median age at onset of asthma and allergic rhinitis in Tecumseh, Michigan.

The ages at which allergies are likely to first become manifest is a subject of epidemiologic interest. The distribution of the onset ages reported in a population survey provides a distorted picture because it is a function of the age distribution of the population at the time of survey, and hence does not represent generational experience. A lifetable method is presented which transforms the raw cross-sectional data to a longitudinal basis. The information on onset age of asthma and allergic rhinitis collected in the 1962-1965 cycle of the Tecumseh Community Health Study is used to illustrate the method. The resultant distributions have median onset ages for the respective allergies which are considerably higher than those based on the onset frequency distributions of enumerated data.