Changes in alcohol consumption, body weight and physical activity among breast cancer survivors and population-based unaffected women in a prospective study.

BACKGROUND: It is unclear whether a breast cancer diagnosis affects health behaviour changes that occur with ageing. We aimed to compare long-term changes of alcohol consumption, body weight, and physical activity in women with breast cancer and in age-matched unaffected women. METHODS: We used data from 1,925 women with breast cancer and 3,473 unaffected women aged 50-74 years enrolled in the population-based case-control study MARIE (Mamma Carcinoma Risk Factor Investigation) in 2002-2005, who also completed the follow-up in 2014-2016. Multinomial logistic regression was applied to estimate odds ratios (ORs) and 95 % confidence intervals (CIs) for the associations between breast cancer status and categories of change in alcohol consumption, weight and physical activity. RESULTS: After 11.6 years of follow-up, breast cancer survivors had significantly lower odds than unaffected women of increasing alcohol consumption from ≤10 to >10 g/day (adjusted OR 0.48, 95 % CI 0.35-0.65), but were more likely to experience a major weight change of ≥10 % compared to having stable weight (±<5 %) (OR for increase and decrease 1.32, 95 % CI 1.03-1.70 and 1.36, 95 % CI 1.05-1.77, resp.) and to decrease transport physical activity to below 2.5 h/week compared to maintaining the activity level (OR 1.61, 95 % CI 1.26-2.04). No significant group difference was found for changes in recreational physical activity. CONCLUSION: Our data indicate that some long-term health behaviour changes can be attributed to a breast cancer diagnosis rather than ageing, suggesting that long-term medical care of breast cancer survivors could pay greater attention to weight control and sufficient physical activity.