Physical activity and breast cancer. Risk, survival and perceived energy

Sammanfattning: Background: Physical activity and avoidance of sedentariness do enhance health in women with breast cancer, and could even reduce the risk of developing the disease. One aim of this thesis was to elucidate the association between sedentariness and breast cancer risk in women as a whole, and then separately for those younger than 55 years old and those 55 years or older. Two additional aims were regarding physical activity and its role after diagnosis: to describe the perception of energy, stress, nausea and pain after a single exercise session during chemotherapy, and to elucidate the association between physical activity level and survival in women under 55 years old or 55 years or over at diagnosis. Methods: Studies I and IV were prospective population-based cohort studies, based on data from 29 524 women included in the Melanoma Inquiry of Southern Sweden (MISS) cohort study 1990-92. In Study I, questions about occupation and established risk factors were used and data were linked to the Swedish Cancer Register and the Cause of Death Register. Study IV included women with breast cancer after the first MISS questionnaire who responded to a post-diagnosis follow-up questionnaire. Questions about physical activity and other risk factors were used and linked to the Swedish Cancer Register, the Cause of Death Register and the Swedish Population Register. Studies II and III were based on selfreported data regarding energy, stress, nausea and pain in 57 women with breast cancer who performed exercise during chemotherapy in the “Phys-Can" (Physical training and Cancer) study. Changes from before to immediately after, and 3 hours after a single exercise session were analysed at different time points during a course of chemotherapy. Results: Sedentariness was associated with breast cancer risk especially among women younger than 55 years old at diagnosis. After breast cancer diagnosis, energy and nausea improved immediately after a single exercise session performed within the first week after chemotherapy infusion. This was true for both endurance and resistance exercise. Energy level increased after an exercise session throughout the chemotherapy course, and stress was reduced at the beginning of the course. Furthermore, the energy increase was larger when the energy level before the session was lower. Physical activity level after breast cancer diagnosis was associated with survival in a dose-response manner among women at 55 years or older at diagnosis. In conclusion we have found that avoidance of occupational sedentariness is associated with reduced breast cancer risk in younger women. After diagnosis physical activity is healthenhancing: one single exercise session during chemotherapy improves energy with a higher increase when the level is low before the session, and furthermore, even a rather small dose of physical activity compared to no physical activity is associated with improved survival, especially in older women.