Physical activity and risk of cancer : a population based cohort study including prostate, testicular, colorectal, lung and breast cancer

The overall aim of this thesis was to elucidate any association between physical activity and the subsequent risk of some major types of cancer in the general adult population of Norway: prostate, testicular, colorectal, lung and breast cancer. • Another aim was to examine whether physical activity at work had a different association to these cancer types than physical activity in leisure time. • To investigate whether age, sex. body mass index and hormonal status (pre- and postmenopausal), on one side, and lifestyle-related factors such as smoking and dietary factors, on the other, strengthen or reduce these observed associations. • Could repeated assessments of physical activity induce stronger or weaker risk estimates? • If any associations between physical activity and risk of cancer were observed, then these associations were investigated to ascertain if these could indicate a causal relationship. • To study if changes in physical activity or sustained physical activity inlluence metabolic profiles to any large extent, which would support physical activity as a potent biological mediator of importance in reduction of risk for chronic diseases, e.g. cancer