Incidence of asthma in twelve thousand Finnish adults born in 1966.

Asthma prevalence is increasing in many countries. Some recent articles, however, claim that this tendency is drawing to an end. Hence, the incidence of persistent asthma was drawn from a birth cohort study in Finland.A cohort of 6107 men and 5839 women was followed from 1981 to 2004. The participants were members of the Northern Finland Birth Cohort 1966 Study (NFBC-66). The single-year birth cohort was followed from the age of 15 to 38 years by means of a complete register held by the national Social Insurance Institute (SII) in Finland. Within the register data, an incident case of asthma was defined by the received right for reimbursement for asthma medication from the SII.Over a 23-year follow-up period, persistent asthma occurred in 466 study participants of whom 54% were women. The incidence of persistent asthma increased from the rate of 10 cases per 10 000 person-years at the age of 15-20 years to 21 cases per 10 000 person-years at the age of 36-38 years. In females, a peak of incidence rate was found between the age of 31 and 35 years, up to 27 cases per 10 000 person-years.The follow-up of a population-based birth cohort among young working aged Finns shows the increasing incidence rate of persistent asthma. In recent years, however, a decline in new cases of asthma occurred in females aged between 36 and 38 years.