PURPOSE: To illustrate the value of cohort studies to assess trends in chronic disease risk factors. METHODS: In collaboration with the American Registry of Radiologic Technologists and the University of Minnesota, the National Cancer Institute initiated a cohort study of cancer among radiologic technologists. More than 90,000 technologists who responded to a mailed questionnaire were grouped into ten birth cohorts from before 1920 through 1960 and later, and stratified by self-reported racial/ethnic groups. Trends in height, smoking, and reproductive factors were analyzed. RESULTS: Among the trends observed were that the proportion of young men (< 18 years) smoking generally fell in each birth cohort after 1925, whereas the proportion of young women smoking rose for those born after 1950. Among women born since 1940, the mean age at menarche for white women has remained at 12.5 years, but has declined among black and Asian/Pacific Islander women. Recent birth cohorts (since 1955) show among the highest mean ages at birth of first child (> 26 years), highest rates of nulliparity at age 25 (≥ 63 %), and lowest mean parity levels (≤ 1.7) compared with earlier cohorts. CONCLUSION: Analyses of large cohorts can clarify birth cohort trends in chronic disease risk factors.
Bibliographical noteFunding Information:
This research was supported in part by contracts NO1-CP-15673, NO1-CP-51016, NO2-CP-81005, and NO2-CP-81121 by the National Cancer Institute, National Institutes of Health, and U.S. Public Health Service. The authors gratefully acknowledge the thoughtful comments of Susan Devesa of the National Cancer Institute. We also thank Jerry Reid of the American Registry of Radiologic Technologists for continued support for this research effort, and Diane Kampa of the University of Minnesota for coordination of data collection.
- Body Height
- Chronic Disease
- Oral Contraceptives
- Risk Factors