Daily patterns of asthma in New York City and New Orleans: an epidemiologic investigation.

Examination of records of daily visits to emergency rooms for asthma covering 25 years from New Orleans and 9 years from New York City reveals a distinct day-of-the-week pattern in New York City whereas no such pattern is discernible in New Orleans. The difference in daily patterns of asthma attacks in the populations from the two cities strongly suggests a different environmental etiologic agent acting on these two populations. It is proposed herein that in New York susceptible individuals are exposed to some agents or factors triggering attacks which are present in the home environment where most of their time is spent on weekends, while in New Orleans, homes are not as sealed off from the outside air, because of the warmer climate, so that the agent triggering attacks is as common outdoors as indoors, and thus there is little difference between weekend and weekday exposure.