Study strengthens smoking, Hodgkin's disease link

Last Updated: 2002-12-10 (Reuters Health)

By Alison McCook

NEW YORK (Reuters Health) - People who smoke appear to be almost twice as likely to develop Hodgkin's disease, a type of cancer that strikes a component of the body's immune defenses, new research reports.

And the risk appears to increase with the amount that people smoke and how long they have maintained the habit, according to Dr. Nathaniel C. Briggs of Meharry Medical College in Nashville, Tennessee and his colleagues.

"Overall, men who were current smokers had a significant, nearly twofold increase in risk of Hodgkin's disease, with risk increasing linearly with increasing years of smoking and number of packs-per-day of cigarettes smoked," Briggs told Reuters Health.

But, encouragingly, abandoning the habit makes a difference, he added. "The good news is that, among former smokers, the risk of Hodgkin's disease decreased linearly with increasing time since cessation of smoking," Briggs said.

Hodgkin's disease is a cancer of the lymphatic system, which is part of the body's immune defenses. It is more common in men than in women, and it usually strikes people between the ages of 15 and 34 or after age 55.

Previous research has investigated whether cigarette smoke increases the risk of this type of cancer, but studies have produced mixed results. Briggs attributed the murky picture of the relationship between cigarettes and the disease painted by these studies to a number of factors, including the fact that they included only small numbers of people, and failed to distinguish between past and present smokers.

In the current study, Briggs and his colleagues collected detailed information on the smoking histories of a relatively large sample of men: 343 between the ages of 32 and 60 with Hodgkin's disease, and almost 2,000 others who were free of the cancer. The disease-free men were discovered by randomly dialing telephone numbers, until the investigators were able to match people of the same age and background to the Hodgkin's patients.

During interviews, the authors classified men as smokers if they said they had ever smoked at least a half-a-pack of cigarettes per week for at least a year during their lives. Current smokers were those who said they had smoked within 2 years before the interviews. Smokers provided information about how much they smoked, when they started, and, if and when they had quit.

Briggs and his team discovered that current smokers were almost twice as likely as people who had never smoked to develop Hodgkin's disease. In people who smoked at least two packs each day or had maintained the habit for at least 30 years, the risk rose to 2.5 times that of someone who had never smoked, according to the report in the American Journal of Epidemiology.

However, people who had stopped smoking at least 10 years before had a lower risk of the cancer than both current smokers and those who had kicked the habit more recently.

The link between smoking and Hodgkin's appeared strongest for one type of the disease, known as mixed cellularity, the most aggressive and common form diagnosed in patients 50 years or older. "Men who currently smoked two or more packs-per-day of cigarettes had a significant, greater than sevenfold increase in risk for mixed cellularity Hodgkin's disease," Briggs told Reuters Health in an interview.

Although the means by which cigarettes could increase the risk of the cancer remain unknown, Briggs noted that certain ingredients of tobacco and cigarette smoke have been implicated as risk factors for Hodgkin's. Alternatively, he suggested that smoking could also decrease the functioning of certain immune system cells, indirectly leading to the cancer.

SOURCE: American Journal of Epidemiology 2002;156:1011-1020.

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U.S. National Cancer Institue

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