FOLLOW-UP EVALUATION OF A PREVALENCE STUDY FOR CHRONIC-BRONCHITIS AND CHRONIC AIRWAY-OBSTRUCTION

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Abstract
Follow-up of a prevalence study of respiratory symptoms and chronic airway obstruction was performed after a 6 to 7 yr interval. One hundred fifteen of 117 subjects (98%) originally labeled abnormal (chronic bronchitis or asthma by history, or ratio of 1-s forced expiratory volume to forced vital capacity < 60%), and 111 of a random sample of 116 subjects (95%) originally labeled normal were traced. Nineteen patients were dead, 14 abnormal subjects and 5 normal (P < 0.05), with mortality increasing with severity of the original spirometric abnormality. Knowledge of the presence of chronic bronchitis after the original study had no effect on subjects'' smoking habits, although chronic bronchitis was significantly less prevalent at follow-up among those who did stop smoking (P < 0.01). Eighty-eight of the originally labeled abnormal subjects and 91 of the random normal sample could be retested by spirometry. Subjects with lower initial ratios of 1-s forced expiratory volume to forced vital capacity tended to lose more 1-s forced expiratory volume and forced vital capacity. Early identification of respiratory symptoms and spirometric abnormalities may identify persons at increased risk of death who could benefit from appropriate therapy.