Incidence of new-onset wheeze: a prospective study in a large middle-aged general population

Wheeze is a very common respiratory symptom, which is associated with several factors and diseases. Studies on incidence of new-onset wheeze in general adult populations are rare. The present prospective study aimed to investigate the incidence rate of new-onset wheeze, and predictors for wheeze, in a general, middle-aged population.

Individuals, born 1943-1973, who had participated in a previous Swedish study in 1993 (n = 15,813), were mailed a new respiratory questionnaire in 2003. The questionnaire, which included items about respiratory symptoms, atopy, and smoking was answered by 11,463 (72%). Incidence rates of new-onset wheeze were calculated. Cox regression analyses were performed with incident wheeze as an event and person-years under observation as dependent variable.

Among those free of wheeze at baseline (n = 8885), there were 378 new cases of wheeze during the study period (1993-2003). The incidence rate was 4.3/1000 person-years. The adjusted risk was increased in relation to smoking (HR 2.1;95% CI 1.7-2.7), ex-smoking (HR 1.4;95% CI 1.1-1.9), young age (HR 1.7;95% CI 1.3-2.2), chronic bronchitis (HR 2.3;95% CI 0.96-5.7), and rhinitis (HR 1.8;95% CI 1.4-2.2) at baseline, and body mass index ≥30 (HR 1.9;95% CI 1.5-2.6) at follow-up.

This is a unique study that presents an incidence rate for new-onset wheeze in a middle-aged, general population sample previously free of adult wheeze. The results indicate that new-onset wheeze is quite common in this age group. Health care staff should bear this in mind since new-onset wheeze could be one of the earliest symptoms of severe respiratory disease. Special attention should be paid to patients with a smoking history, chronic bronchitis, rhinitis or obesity.