Second-hand Smoke Study Sparks Controversy By Mike Wendling CNSNews.com London Bureau Chief May 16,

The Study A study about to be published in this week's British Medical Journal indicates that second-hand smoke doesn't increase the risk of heart disease or lung cancer, but the publication and the study's authors have come under attack by anti-smoking groups. Two American researchers analyzed data from an American Cancer Society survey that followed more than 118,000 Californians from 1960 until James E. Enstrom, of the University of California at Los Angeles and Geoffrey C. Kabat of the SUNY at Stony Brook concluded that "the results do not support a causal relation between environmental tobacco smoke (second-hand smoke) and tobacco related mortality, although they do not rule out a small effect." "The association between exposure to environmental tobacco smoke and coronary heart disease and lung cancer may be considerably weaker than generally believed," the researchers wrote. Study was funded from tobacco industry-related sources

Response (1) The data and design of the Enstrom and Kabat secondhand smoke study has been widely criticized. Even the British Medical Association, the publisher of the journal that printed the study, described the research as being "fundamentally flawed." The misuse of data and flawed methodology are two very significant faults in the study. Enstrom and Kabat did not gather original data for their study. Instead, it drew on data from the American Cancer Society's Cancer Prevention Study I (CPS-I), and used only a small subset (approximately 10%) of the total CPS-I data. Researchers at the American Cancer Society repeatedly warned Enstrom that the data from CPS-I could not be used to determine the health effects of secondhand smoke, and they spoke out against the study upon its release, stating that their data had been misused.

Response (2) The study used cohort methodology to look at the rate of mortality from heart disease and lung cancer in nonsmokers who were married to smokers, covering a time period from 1959 to A severe error in the study was the failure to establish a control group of nonsmokers who were unexposed to secondhand smoke. Other critical methodological flaws include not measuring for secondhand smoke exposure from any source other than the spouse, including the workplace (where smoking was extremely prevalent at the time); not taking into account either spouse's smoking status after 1972, though the study continued for 26 more years; and classifying the non-smoking spouse as still exposed to secondhand smoke in that 26 year period, during which time the "smoking spouse" could have quit smoking or died, not to mention that they could have divorced or separated.

Study and Responses Original Study 98/1057http://bmj.bmjjournals.com/cgi/content/full/326/73 98/1057 Rapid Responses #32297http://bmj.bmjjournals.com/cgi/eletters/326/7398/ 1057#32297