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In 1952 the Statistical Research Section, forerunner of the present Department of Epidemiology & Surveillance Research, began its first large prospective cohort study, the Hammond-Horn Study, to study the effect of cigarette smoking on death rates from cancer and other diseases. By using 22,000 ACS volunteers to recruit a cohort of 188,000 adult men and then to trace cohort members yearly through 1955, that study set the methodologic foundation for the two subsequent Cancer Prevention Studies (CPS-I and CPS-II). In contrast to the Hammond-Horn Study, both CPS-I and CPS-II were designed to address a wide range of potential exposures, in addition to tobacco use, that may be associated with cancer. CPS-I included approximately one million men and women recruited by 68,000 volunteers in 25 states. Participants were followed for 12 years, through 1972. CPS-I data continue to be analyzed today, often in collaboration with external investigators, or to compare with results from CPS-II, a separate and more contemporary cohort. CPS-II began in 1982 and encompassed 1.2 million subjects recruited by 77,000 volunteers in 50 states. In addition, mortality followup of all CPS-II cohort members remains active. Cancer incidence followup is being conducted currently in a sub-cohort.
Accomplishments
Early contributions from CPS-II primarily involved tobacco research. The increase in lung cancer risk among male and female smokers in CPS-II, compared to smokers in CPS-I, was highlighted by a 1989 U.S. Surgeon General's Report and a 1997 NCI Monograph. CPS-II provides the relative risk estimates from smoking used by the Centers for Disease Control and Prevention to estimate deaths attributable to smoking in the United States. More recently, CPS-II publications have contributed to our understanding of how various medications, medical conditions, familial, and environmental factors may affect cancer risk. CPS-II data stimulated research interest and funding regarding the potential of aspirin-like drugs to inhibit colorectal cancer. The relationship between postmenopausal hormone replacement in women and mortality from cancers of the colon, breast, and ovary has been examined in eight publications. A CPS-II publication on obesity and early mortality showed that the optimal range of body mass index remains constant throughout life, rather than increasing with age. Medical conditions associated with increased risk of various cancers include diabetes (pancreatic and colon cancer), infertility (ovarian), non-melanoma skin cancer (several), and hypertension or antihypertensive medications (renal cancer), but not spontaneous abortion (breast cancer). The department has made notable contributions to research on environmental factors such as air pollution. The 1995 analysis with Dr. Arden Pope and other air pollution researchers at Harvard found increased death rates from cardiopulmonary conditions among CPS II participants living in cities with higher particulate air pollution. Together with the Harvard Six Cities Study, this finding motivated EPA to propose more stringent limits on particulate air pollution.
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