Adverse Effects of Smoking on Respiratory Function in Young Adults Born Weighing Less Than 1000 Grams

OBJECTIVE: To determine whether active smoking has an adverse impact on respiratory function of young adults of extremely low birth weight (ELBW; birth weight <1000 g). METHODS: This was a cohort study of 60 consecutive ELBW survivors who were born during 1977-1980 at Royal Women's Hospital, Melbourne, Australia. Respiratory function was measured on 44 (73%) of the subjects at a mean age of 20.2 years (standard deviation: 1.0 year). Respiratory function had also been measured on 42 of the 44 subjects at 8 years of age. Respiratory function was compared between the 14 smokers and the 30 nonsmokers. RESULTS: Several respiratory function variables reflecting airflow (the forced expired volume in 1 second [FEV(1)]/forced vital capacity [FVC] ratio; flow rates at 75%, 50%, and 25% of vital capacity; and mid-expiratory flow from 25% to 75% of vital capacity) were significantly diminished in smokers. The proportion with a clinically important reduction in the FEV(1)/FVC ratio (<75%) was significantly higher in smokers (64%) than in nonsmokers (20%). There was a significantly larger decrease in the FEV(1)/FVC ratio between ages 8 and 20 years in the smokers (mean change: -8.2%; 95% confidence interval: -14.1% to -2.4%) CONCLUSIONS: Active smoking by young adult survivors of ELBW is associated with reduced respiratory function.