Study links secondhand smoke to heart disease.

Regular exposure to secondhand smoke -- either at home or at work -- appears to increase the risk of heart disease, a 10-year study of more than 32,000 women showed.

The results of the study, published in the May 20 American Heart Association journal Circulation, support the conclusion that secondhand smoke is dangerous, an opinion held by proponents of smoke-free policies at work and in public locations. The results also could prove useful in lawsuits against the tobacco industry, such as the first class action alleging harm to flight attendants from workplace exposure to secondhand smoke, which went to trial in Florida last month. (Broin v. Philip Morris Cos., Inc, No. 91-49738 (Fla., Dade County Cir. Ct. filed Oct. 31, 1991).)

Researchers at Harvard Medical School and Brigham and Women's Hospital in Boston began the study in 1982. They tracked the health of 32,046 nurses, 36 to 61 years old, every 2 years for 10 years. The women said they had never smoked before entering the study, remained nonsmokers throughout the study, and had not been diagnosed with heart disease, cancer, or stroke when the study began.

This study differs from previous ones on secondhand smoke effects in two significant ways, said Ichiro Kawachi, a medical doctor and assistant professor at the Harvard School of Public Health and the study's lead author.

"First, the study asked about the workplace specifically," Kawachi said. "Other studies focused on exposure at the home. This one points out that exposure can be just as bad at work."

Second, the study took into account cardiovascular risk factors such as high fat diet, lack of exercise, and high blood cholesterol. Critics of previous studies linking secondhand smoke to heart disease said these studies had not considered these risk factors. The nurses' study was "adjusted for the full range of confounding factors," Kawachi said.

The Harvard researchers found 152 new cases of heart disease -- 127 nonfatal and 25 fatal -- by the time the study concluded in 1992. The researchers observed that nonsmoking women who were regularly exposed to secondhand smoke had a 91 percent higher risk of heart disease, which, according to Kawachi, is nearly double the risk of those not exposed. Nurses occasionally exposed to a secondhand smoke environment had a 58 percent higher risk of heart disease than colleagues who were not exposed.

Although the study's results were based on data obtained from women only, Kawachi said past research indicates that the effects of tobacco products are similar in both men and women and that the conclusions apply to both sexes.

The authors acknowledged, however, that the study has limitations. For example, the nurses themselves assessed the amount of exposure to secondhand smoke to which they were subjected. And the nurses identified the amount of exposure only at the beginning of the study. Kawachi said that over the 10 years, the nurses' exposure would most likely decrease because of work environments becoming smoke-free. Thus, women who identified themselves and were categorized as "regularly" exposed to secondhand smoke may have actually been exposed only "occasionally" or not at all by the end of the study.

Stanton Glantz, a medical professor at the University of California, San Francisco, said the limitations of the study do not discredit the results. Glantz, a researcher on the effects of secondhand smoke exposure, was not involved in the nurses' study.

"It is a very fine study," said Glantz. "It is an important contribution to earlier research. "He said that because of the connection of secondhand smoke hazards to the workplace, the study could help plaintiffs hold employers responsible for injuries caused by exposure. Glantz, who has served as an expert witness in hearings that focus on secondhand smoke in the workplace, said the study will be equally valuable in lawsuits filed against the tobacco industry.

The Florida lawsuit, which went to trial last month, involves about 60,000 nonsmoking flight attendants who claim to have received on-the-job illnessess by working on flights that allowed smoking before the government banned it. This first-ever class action suit against several tobacco companies sets out to prove that the flight attendants' illnesses were caused by secondhand smoke exposure.

According to Miami attorney Stanley Rosenblatt, who represents the flight attendants, the study "definitely strengthens the cause-and-effect relationship between secondhand smoke and heart disease. Therefore, it is very helpful to us." (John Schwartz, Secondhand Smoke Linked to Increased Heart Attack Rate, Wash. Post, May 20, 1997, at A2.)

While no single study is likely to sway a jury, Kawachi said, the nurses' study adds to a growing body of evidence that can support the cases of those claiming illness from secondhand smoke exposure.