Chronic respiratory disease among workers in a pulp mill: a ten-year follow-up study

A 10-year follow-up study was carried out on 659 men aged 18 to 64 years when first surveyed by questionnaire and simple spirometry in 1967, to determine the effect of smoking habits on respiratory symptoms and ventilatory function. Symptoms tended to increase during the follow-up period, and were most marked among the men who continued to smoke. The remission rates of respiratory symptoms were high in all the smoking groups, however, and cough and phlegm actually diminished during the ten years in the men who stopped smoking after the first survey. The follow-up survey in 1977 showed a prevalence of 6 to 8 percent for severe airways obstruction in the ex-smokers and smokers, but only 2 percent in the life-long non-smokers. The average decreased in one second forced expiratory volume (FEV1) was 44 ml/year in the total series, 37 ml/year in the life-ling nonsmokers and 49 ml/year in the continuous smokers (P less than 0.001). The men who had stopped smoking before the first survey resembled the non-smokers, whereas those who had stopped during the follow-up period resembled the continuous smokers in respect to the decrease in FEV.