Smoking & Cancer (Contd.)

The Seventh International Cancer Congress in London this week heard the sobering results of a sweeping study of the effects of smoking on the death rate from cancer and other diseases. Author of the report: Statistician Harold F. Dorn of the U.S. National Institutes of Health. Dorn's project was begun in 1954 as a check on the disturbing findings from the American Cancer Society's famed Hammond & Horn survey of 188,000 U.S. males. Researcher Dorn threw his statistical net even wider: it covered 198,000 men (and a sprinkling of women) holding Government life insurance as a result of military service between 1917 and 1940.

All these cases were followed through the mountainous files of the Veterans Administration. The Dorn-VA technique: whenever a claim was filed to collect insurance, investigators double-checked both the primary cause of death and other contributory diseases with the physician who signed the death certificate, and (if possible) with the results of post-mortem examinations. Where the Hammond-Horn study had been attacked by the tobacco industry as statistically unsound because of the investigators' bias, the Dorn-VA investigation could not be assailed on the same ground, although even before formal publication it was criticized by industry spokesmen ("It cannot possibly establish the cause or causes of any diseases"). The findings, startlingly similar to those of the American Cancer Society:

P: Men who smoke two packs of cigarettes or more a day have the biggest death rate in the age groups covered (30-to-80, but largely concentrated on 50-to-70). The rate: twice that for nonsmokers.

P: Those who smoke cigars or pipes as well as cigarettes have a lower death rate in proportion to the smaller number of cigarettes smoked.

P: Cigars or pipes alone cause only a negligible increase in the death rate.

P: Cigarette smokers improve their chances of living longer if they quit smoking. Those who stopped "prior to the start of the survey" have a death rate 1.4 times that of nonsmokers, whereas for all cigarette smokers (any amount) the rate is 1.66 times that of nonsmokers.

P: In absolute numbers, the increase in early deaths among heavy cigarette smokers is mainly from heart and artery disease. But the cause of death that shows by far the greatest proportionate jump is lung cancer: it is six times as common among all smokers as among nonsmokers, 9.35 times as common among cigarette smokers.

Britain's Dr. Percy Stocks took up the question of lung cancer and air pollution, reporting on a study of more than 2,000 men who died of lung cancer in smoggy Merseyside areas (centered at Liverpool) and clear-aired North Wales. Among nonsmokers the hazard of smoggy air was clear: 2.3 times as much lung cancer in smoke-palled belts as in cleaner areas. But to the identity of the cancer-causing substance in polluted air, Dr. Stocks had no clue. In smoggy areas, the death rates were almost identical for light smokers (less than a pack a day) and nonsmokers. But among men who smoked more than a pack a day, the death rate rose, paradoxically, far faster in rural, smog-free areas. Explanation? Dr. Stocks had none.

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