| Background and objective. Psychological stress is an increasing public health problem and may play a role in the etiology of hormone-dependent cancers by impairing the body's synthesis of and sensitivity towards sex steroid hormones. The objective of the dissertation is to address a potential relation between perceived stress and risk of primary breast, endometrial, colorectal, and prostate cancers as well as to address if perceived stress affects endogenous levels of sex steroid hormones.; Material and methods. The 12,698 men and women who participated in the longitudinal Copenhagen City Heart Study were asked about their stress level in 1981-83. The participants were followed in a cancer registry until year 2000 and first-time incidence of primary hormone-dependent cancers were identified. Less than 0.1% was lost to follow-up. Causal diagrams were used to visualize the assumed causal model and Cox proportional hazard models were used to analyze data. Plasma levels of sex steroid hormones were assayed in a sub-sample of postmenopausal women.; Results. A one-unit change in perceived stress measured on a seven-point stress scale was consistently associated with lower risk of breast (hazard ratio: 0.92; 95% confidence intervals: 0.85-0.99), endometrial (0.88; 0.76-1.01), and colon cancer (0.89; 0.81-0.99) in a linear dose-response manner in women. Some sub-groups were more sensitive to the effect of stress than others, especially those women who received hormone therapy. However, no differences in endogenous sex steroid hormones were observed among postmenopausal women with varying stress levels. There were no evidence of a relation between perceived stress and risk of colorectal (0.99; 0.90-1.09) or prostate cancer (0.99; 0.90-1.09) in men.; Discussion. We found perceived stress to be associated with a lower risk of hormone-dependent cancers in women. However, it is important to emphasize that stress is not a healthy response and that the total burden of disease attributable to perceived stress most likely may exceed the few cases of hormone-dependent cancers that may be prevented by stress. |
