Incidence and remission of asthma: a retrospective study on the natural history of asthma in Italy.

BACKGROUND

The knowledge of the natural history of asthma from birth to adulthood could provide important clues for its cause and for the understanding of epidemiologic findings.

OBJECTIVE

This study is aimed at assessing the incidence and remission of asthma from birth to the age of 44 years by using data from 18,873 subjects involved in a large, nationally representative, cross-sectional study carried out in Italy from 1998 through 2000.

METHODS

The onset of asthma was defined as the age at the first attack, and remission was considered present when a subject was neither under treatment nor had experienced an asthma attack in the last 24 months. Person-years and survival techniques were used for the analysis.

RESULTS

The average annual incidence rate for the 1953 to 2000 period was 2.56/1000 persons per year. Incidence peaked in boys less than 10 years of age (4.38/1000 persons per year) and in women 30 years of age or older (3.1/1000 persons per year) and showed a generational increase (incident rate ratio = 2.63 and 95% CI = 2.20-3.12 for 1974-1979 vs 1953-1958 birth cohort). The overall remission rate was 45.8% (41.6% in women and 49.5% in men, P <.001). Asthmatic patients in remission had an earlier age at onset (7.8 vs 15.9 years, P <.001) and a shorter duration of the disease (5.6 vs 16.1 years, P <.001) than patients with current asthma. The probability of remission was strongly (P <.001) and inversely related to the age at onset (62.8% and 15.0% in the <10- and > or =20-years age-at-onset groups, respectively).

CONCLUSION

With respect to its natural history, asthma presents 2 different forms: early-onset asthma, which occurs early in childhood, affects mainly boys, and has a good prognosis, and late-onset asthma, which generally occurs during or after puberty, mainly affects women, and has a poor prognosis. The minority of patients with early-onset asthma who do not remit represents more than 35% of patients with current asthma in the general young adult population.