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Validity of Epidemiological Studies
Last July, introducing his office's latest report on secondhand smoke, then - U.S. Surgeon General Richard Carmona asserted that "there is no risk-free level of secondhand smoke exposure." In an effort to circumvent this capital obstacle, all secondhand smoke studies have estimated risk using a misleading marker of "lifetime exposure." Yet, instant exposures also vary uncontrollably over time, so lifetime summations of exposure could not be, and were not, measured. Typically, the studies asked 60--70 year-old self-declared nonsmokers to recall how many cigarettes, cigars or pipes might have been smoked in their presence during their lifetimes, how thick the smoke might have been in the rooms, whether the windows were open, and similar vagaries. Obtained mostly during brief phone interviews, answers were then recorded as precise measures of lifetime individual exposures. In reality, it is impossible to summarize accurately from momentary and vague recalls, and with an absurd expectation of precision, the total exposure to secondhand smoke over more than a half-century of a person's lifetime. No measure of cumulative lifetime secondhand smoke exposure was ever possible, so the epidemiologic studies estimated risk based not only on an improper marker of exposure, but also on exposure data that are illusory. In addition, results are not consistently reproducible. The majority of studies do not report a statistically significant change in risk from secondhand smoke exposure, few studies show a statistically insignificant increase in risk, and astoundingly some show a reduction of risk. It has been fashionable to ignore the weakness of "the science" on secondhand smoke, perhaps in the belief that claiming "the science is settled" will lead to policies and public attitudes that will reduce the prevalence of smoking. But such a Faustian bargain is an ominous precedent in public health and political ethics. A frank discussion is needed to restore straight thinking in the legitimate uses of "the science" of epidemiology -- uses that go well beyond secondhand smoke issues. Today, health rights command high priority on many agendas, as they should. It is not admissible to presume that people expect those rights to be served less than truthfully. Author: Gio Batta Gori, an epidemiologist and toxicologist, is a fellow of the Health Policy Center in Bethesda. He is a former deputy director of the National Cancer Institute's Division of Cancer Cause and Prevention, and he received the U.S. Public Health Service Superior Service Award in 1976 for his efforts to define less hazardous cigarettes. Gori's article "The Surgeon General's Doctored Opinion" will appear in the spring issue of the Cato Institute's Regulation Magazine.
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