NEW YORK, Apr 20 (Reuters Health) -- Even after they kick the habit, ex-smokers still show changes in lung density similar to those found in current smokers, Japanese researchers report.

Their study findings suggest that smoking makes the lungs more susceptible to the effects of aging -- and this negative effect remains even after a smoker quits. The investigators used a detailed imaging technique called high-resolution computed tomography to look for structural changes over 5 years in the lungs of 83 men and women. They found that while normal aging caused air spaces in the lungs to become larger, smoking worsened these changes. Dr. Kenzo Soejima and colleagues at Keio University in Tokyo, Japan, report the findings in the April issue of the American Journal of Respiratory and Critical Care Medicine. The structural changes seen in this study are important causes of lung deterioration, study co-author Dr. Kazuhiro Yamaguchi told Reuters Health. In smokers, Yamaguchi noted, structural abnormalities begin in the upper part of the lungs, but eventually occur elsewhere in the lung. Normal aging typically affects only the lower part of the lungs. Among the people studied, 36 had never smoked, 35 were current smokers, and 12 were ex-smokers. To track changes in their lung structure, the researchers took images of the volunteers' upper, middle, and lower lungs while they inhaled and exhaled. Pulmonary function tests were used to gauge their breathing capacity. At the end of 5 years, Soejima's team found that although subjects' pulmonary function showed no changes, there were definite changes in lung density. Air space abnormalities in the upper lungs grew worse each year among smokers and ex-smokers. Nonsmokers also showed changes, but in the lower part of the lungs -- suggesting that in people who do not smoke, the upper lungs are less affected by aging. It is ``extremely difficult'' to know why people who had stopped smoking still showed lung abnormalities similar to smokers', the researchers write. One possibility, they note, is that years of smoking made air spaces in the lungs more susceptible to the aging process.

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