The U.S. Radiologic Technologists Study (USRT) Cohort serves as a unique resource for assessing the health effects of chronic, low-to-medium dose exposure to ionizing radiation, and it also favorably serves as a general purpose cohort. Over the past four years, DCEG investigators have used the USRT cohort to study a number of different lifestyle factors in relation to various morbidity and mortality outcomes.
The USRT study has also been particularly useful in examining issues relating to the growing prevalence of obesity, including the nature of the relationship between body mass index (BMI) and all-cause mortality. REB investigators found that over a 15-year follow-up period, BMI appeared directly related to mortality in younger and middle-aged, but not older, participants, suggesting the importance of assessing whether other markers of body composition better explain mortality risks in older adults. Future analyses will explore the combined effects of smoking and obesity on mortality.
The USRT was the second large prospective study to report a significant but non-monotonic trend in increased risk associated with alcohol consumption. In an analysis of smoking, alcohol, and other factors and melanoma risk, no association with anthropometric and reproductive/hormonal factors was detected; however, investigators noted a positive association with alcohol intake (RR=2.1; 95% CI=0.9-4.8, for >14 drinks/week) and an inverse association with smoking of long duration (RR=0.6; 95% CI=0.3-1.3, =30 years; p(trend)=0.03).
The risk of breast cancer associated with age started smoking and cumulative tobacco exposure before and after first childbirth was investigated in this cohort. Smoking-related breast cancer risks differed by smoking during three reproductive time periods (p=0.003), with a statistically significant 3% increase per pack-year of smoking between menarche and first childbirth (RR=1.03; 95% CI=1.02-1.05) and no significant association for smoking after first childbirth. Also, the risk of breast cancer associated with physical activity is currently being studied.