TOBACCO-SMOKE AND AGE AS RISK-FACTORS IN EMPHYSEMA - MORPHOMETRICAL STUDY ON THE RAT

During ageing, a progressive deterioration in the pulmonary function, which can be accelerated by exposure to tobacco smoke, takes place. Th e hypothesis that the initial age of exposure to tobacco smoke is a fa ctor of utmost importance in the development of emphysema is proposed. Eighty-six rats, aged nineteen months at the time of sacrifice, were used and were ordered into three groups: the first group consisted of unmanipulated animals; the second, of animals which had been exposed t o tobacco smoke from the age of twelve months to the age of nineteen m onths; and the third, of animals which had been exposed to tobacco smo ke from the age of nine months to the age of twelve months. The lungs of the animals were histologically processed for light microscopy and were studied morphometrically by computer. Eleven quantitative variabl es were quantified and ordered into three groups: variables related wi th alveolar enlargement; variables related with tissue loss; and varia bles related with the elastic fibre. The number of animals in which al veolar enlargement and tissue destruction concurred was counted, thus enabling the attributable and relative risks of developing emphysema t o be calculated in the two groups of manipulated animals. From the res ults it is clear that, when compared with the unmanipulated group, the two groups which had been exposed to tobacco smoke displayed an incre ase in the variables which quantified alveolar enlargement and a decre ase in those which measured tissue loss; these results were more signi ficant in the third group (p<0.001) than in the second (p<0.05); signi ficant differences were also found between these two groups of animals . The relative risk and attributable risks of developing emphysema wer e 2.41 and 28.15 respectively in the second group and 3.48 and 34.48 i n the third group. Our results lead us to propose that the risk of dev eloping emphysema exists in inverse proportion to the initial age of e xposure to tobacco smoke.