Iowa Women's Health Study: Epidemiology of Cancer in a Cohort of Older Women

Aaron R. Folsom, M.D., M.P.H.
University of Minnesota, School of Public Health, Minneapolis, Minn.
Funded since 1985
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Cancer is the second leading cause of death in postmenopausal women, and detailed epidemiological investigations are warranted to identify etiologic factors, including potentially modifiable risk factors. The Iowa Women's Health Study (IWHS) recruited a population-based cohort of 41,837 Iowa women, ages 55 to 69 years in 1986, to determine whether diet, body fat distribution, and other risk factors were related to cancer incidence. Exposure and lifestyle information was collected in a baseline mailed survey and four follow-up surveys. Cancer incidence and mortality have been ascertained since 1986 by linkage with the State Health Registry of Iowa, which is an NCI-funded Surveillance, Epidemiology, and End Results (SEER) Program, and the National Death Index.

The study has been extremely productive, with more than 90 publications. Because of the wealth of information on this large cohort of women, the investigators are extending follow-up for cancer incidence and mortality through 18 years. IWHS is expected to yield a total of at least 8,150 incident cancers and 11,000 deaths, and will allow the investigators to perform additional analyses in four broad areas to test hypotheses on:

• potential risk factors for uncommon cancers not yet studied in this cohort;
• unexamined potential risk factors for incident common cancers;
• risk factors for incident cancers examined in a limited fashion previously; and
• potential contributors to better survival of breast, colorectal, ovarian, or uterine cancer.

The investigators are expanding the existing nested case-control study of candidate genes for breast cancer to 432 cases and 332 controls. They are genotyping polymorphisms in DNA repair proteins to test the hypothesis that these are associated with risk of breast cancer.

This research project will provide new information on the risk and survival of cancer in older women, which could be valuable in the control of this major public health problem.