Changes in body mass index and alcohol and tobacco consumption among breast cancer survivors and cancer-free women: A prospective study in the Danish Diet, Cancer and Health Cohort

Background. A breast cancer diagnosis has been suggested as a teachable moment when a woman is more open to making healthier lifestyle changes. Little is known about the health behaviour changes women with breast cancer initiate compared to those made by other women. Material and methods. We examined changes in body mass index (BMI) and tobacco and alcohol consumption among women with a diagnosis of breast cancer and among cancer-free women. We used data from 23 420 women aged 50-64 years who participated in the Diet, Cancer and Health cohort, of whom 449 were diagnosed with breast cancer between baseline (1993-1997) and follow-up (2000-2002), and 22 971 remained cancer-free. We used multiple linear regression analysis to examine differences in BMI and alcohol and tobacco consumption between the two groups and to examine whether demographic and prognostic factors were associated with behavioural changes in women with breast cancer. Results. There were no significant differences in changes in BMI, alcohol and tobacco consumption between the two groups. Only in sub-analyses among women who lost weight between baseline and follow-up, women with breast cancer lost more weight than cancer-free women (β = 0.2; CI 0.1; 0.4), but residual confounding from stage cannot be excluded. Among the women with breast cancer we found no significant changes in BMI, alcohol and tobacco consumption by level of education, marital status, chemotherapy, hormone therapy or radiation. Conclusion. Women with breast cancer did not reduce their BMI, or modify their alcohol use or tobacco consumption compared with cancer-free women. This study indicates that guidelines and interventions to change health behaviour are needed after a cancer diagnosis.