The Ecological Relationship Between the Trends of Asthma and Invasive Pneumococcal Disease in Rochester, Minnesota

Abstract

A previous study reported asthmatic patients have increased risk of invasive pneumococcal disease (IPD). However, it is unknown whether the rising trend of asthma incidence results in an impact on the trend of IPD incidence at a population level (i.e., ecological relationship). We assessed the trend of IPD incidence in relation to the previously reported trend of asthma incidence between 1964 and 1983 in Rochester, Minnesota. The study subjects were Rochester, Minnesota residents between 1964 and 1983. We used a population-based computer-linked medical diagnosis system to identify all individuals with diagnoses potentially including IPD. All records were reviewed using explicit predetermined criteria. IPD incidence was calculated in an interval of every five years due to a small number of incidence cases of IPD per year. All asthmatic individuals were similarly (i.e., predetermined criteria) identified by a previous study between 1964 and 1983. The age- and sex- adjusted annual IPD incidence was calculated using the 2000 total U.S. population. Between 1964 to 1983, overall asthma incidence rates increased from 183 per 100,000 in 1964 to 284 per 100,000 in 1983. During the same study period, IPD incidence increased from 10.0 per 100,000 (95% CI: 6.1-13.9) between 1964 and 1968 to 15.9 per 100,000 (95% CI: 11.8-20.0) between 1979 and 1983. The increased incidence of IPD during our study period may correspond with the previously observed rise in asthma incidence in Rochester, Minnesota reflecting the relationship between asthma and IPD at an individual level. Further analyses are underway to clarify this ecological relationship.