Study objectives: To determine the risk of asthma among patients with occupationally induced rhinitis.
Design: Patients with confirmed occupational rhinitis were followed for asthma incidence through register linkage. Patients with other occupational diseases were used as a reference population.
Subjects: Patients entered into the Finnish Register of Occupational Diseases in from 1988 to 1999 for occupational rhinitis (n = 3,637) or other occupational disease (n = 31,457) were observed until December 31, 2000, through two national registers of individuals who were eligible for the reimbursement of asthma medication and the Population Register Center.
Methods: Incidence rates of asthma were calculated, and a log-linear model, adjusted for age, gender, and occupation, was used to estimate the relative risks (RRs) of asthma among those with occupational rhinitis compared to those with other occupational diseases.
Results: There were 420 and 972 incident cases of asthma, respectively, among those with occupational rhinitis and the reference population. The crude RR of asthma was 4.8 (95% confidence interval [CI], 4.3 to 5.4) for all patients with occupational rhinitis, 5.4 (95% CI, 4.8 to 6.2) for those with occupational rhinitis accepted for compensation, and 3.7 (95% CI, 3.1 to 4.5) for patients with unaccepted occupational rhinitis. The RR varied according to occupation and was the highest among farmers and wood workers, both groups having a sevenfold risk. The risk was especially high during the year following notification, but a roughly threefold risk persisted several years thereafter.
Conclusions: Patients with occupationally induced rhinitis have a high risk of asthma, but further studies are needed to establish the effect of preventive interventions.