Smoking increases the risk of all types of cancer, but the effect on the lungs is most significant. Approximately 90 percent of lung cancer deaths in men are caused by cancer, according to the National Cancer Institute. In addition to raising the risk of cancer, smoking also reduced the ability of the lungs to function. In particular, smoking reduces the vital capacity of the lungs, which is the amount of air the lungs can take in. This reduction in vital capacity has several important health effects.
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Decrease in Vital Capacity
Vital capacity is one measure used by doctors to gauge the maximum amount of air the lungs can hold. To measure vital capacity, a person exhales completely, then inhales until the lungs are completely full. The vital capacity is the volume of air inhaled. Studies have found that smoking reduces the vital capacity of the lungs, including one study published by the journal "Clinical Linguistics and Phonetics" in 2007. The study suggest that the reduction in vital capacity occur even in young people who have only been smoking for a short time.
Increased Forced Vital Capacity
The effects of smoking on vital capacity may not be so clear cut, however. One study, published in the September issue of the "New England Journal of Medicine" found that adolescent boys who smoked showed a slightly increased forced vital capacity, or FVC, although the difference was not statistically significant. Forced vital capacity is the maximum volume of air that could be expelled in one breath, in contrast to vital capacity, which is the maximum volume of air that can be inhaled.
Decreased Lung Function
The study in the New England Journal of Medicine showed that adolescent boys and girls who smoked showed decreased lung function by several other indicators, including forced expiratory volume in one second, or FEV1, and forced expiratory flow, or FEF. The study also shown that girls who smoked showed a decreased in the growth of lung capacity that normally occurs during adolescent years. Aside from the inconclusive result on forced vital capacity, the study clearly showed that smoking reduced lung function in adolescent boys and particularly in adolescent girls.