Asthma Prevalence
A total of 4,581 participants were seen in the CHS clinics during the year 6 follow-up examination from May 1993 to June 1994. Four percent of all CHS participants reported current (definite) asthma that had been confirmed by a physician (Table 1 ). An additional 4% reported at least one attack of wheezing with dyspnea or chest tightness during the previous year (probable asthma), and an additional 11% reported wheezing brought on by various exposures (possible asthma). Not included in the “definite asthma” category are 145 participants who reported a history of asthma but stated that they do not still have asthma. Some of these participants with “past asthma,” however, reported asthma symptoms during the previous 12 months, and are included in our possible or probable asthma categories (n = 32 and 16, respectively). Ninety-seven participants with past asthma (but no asthma symptoms) were included in the “no asthma” category.
About 8% of those with definite asthma and 8% of those with no asthma had CHF, and they were excluded from subsequent analyses. Those with asthma were somewhat more likely to be current or former smokers, and have more pack-years of smoking when compared with those without asthma. To eliminate the possibility that reported asthma symptoms and lung function abnormalities were due to smoking-related lung disease, we excluded current smokers as well as former smokers who reported> 10 pack-years of smoking from further analyses, leaving a total of 2,527 participants. See Table 2 for their demographics. Those with probable or definite asthma were more likely to be female, black, and older when compared with those who did not have asthma.