Risk factors for chronic airflow limitation in the busselton community
Ryan G., James A., Knuiman M., Divitini M., Musk B.
Smoking and asthma both lead to chronic airflow limitation (CAL); the relative effect of each should be determined. AIM: To determine the risk conferred by asthma and cigarette smoking on the development of CAL in a community sample. METHODS: Subjects studied in both 1981 and 1995 health surveys in Busselton were identified. Information on respiratory symptoms, past illnesses and smoking was obtained by questionnaire and FEVi and FVC measured. CAL was defined as FEVi <80% predicted and a FEWFVC ratio <90% predicted in 1995. Predicted values were derived from the Busselton population. RESULTS: About 10% of 778 men and 7.2% of 1029 women who attended both surveys had CAL in 1995. After adjusting for level of lung function in 1981, using stepwise regression analysis, the associations between the presence of subject characteristics in 1981 and CAL in 1995 were, 1981 Characteristic Odds Ratio (95% Confidence interval) Men Women Age 1.06 (1.03-1.09) 1.04 (1.02-1.07) Asthma 4.84 (1.86-12.56) 3.77 (1.81-7.83) Cough and phlegm 3.06 (1.48-6.30) 2.92 (1.32-6.43) Smoking Never 1.00 1.00 Exsmoker 3.91 (1.46-10.50) 0.45 (0.19-1.12) light(<20/d) 9.58 (2.81-32.58) 2.57 (0.95-6.93) Heavy (>20/d) 16.97 (5.74-50.20) 5.05 (2.34-10.93) CONCLUSION: Asthma is a strong risk factor for CAL in this population with a similar level of effect to being a light smoker. Improvements in the treatment of asthma may reduce this risk.