Incidence of asthma and its determinants among adults in Spain

The objective was to measure the incidence of asthma and its determinants i n Spain, where the prevalence of asthma is low to medium. A follow-up of su bjects participating in the European Community Respiratory Health Survey (E CRHS) was conducted in 1998-1999 (n = 1,640, 85% of those eligible). Subjec ts were ran om selected from the general population and were 20 to 44 yr ol d in 1991-1993. Time of follow-up was on average 6.75 yr (range, 5.3 to 7.9 yr). Asthma was defined as reporting ever having had asthma. The incidence of asthma was 5.53 (95% confidence interval, 4.28-7.16) per 1,000 person-y ears (6.88 in females, 4.04 in males). Incidence was highest in subjects wh o at the baseline survey had bronchial hyperresponsiveness (incidence rate ratio [IRR], 3.85), in those with positive IgE against timothy grass (IRR, 3.16), and in females (IRR, 1.80). These results persisted after adjusting for respiratory symptoms at baseline. There was no significant association (p < 0.2) with high total serum IgE, atopy defined by reactivity to any all ergen, smoking, occupational exposure, or maternal asthma. A sensitivity an alysis using four definitions of population at risk yielded incidence rates varying from 5.53 to 1.50. In this population of subjects without self-rep orted asthma or asthma-type symptoms at baseline, bronchial hyperresponsive ness and IgE reactivity to grass appeared as the main determinants of new a sthma.