Changes in health behaviours and body mass index after a breast cancer diagnosis: results from a prospective cohort study.

The aim of the study was to describe changes in health behaviours and BMI after breast cancer diagnosis, depicting the potential influence of sociodemographic, clinical and psychological characteristics. A total of 428 breast cancer patients were prospectively followed for 3 years, since diagnosis. At the end of follow-up, women were classified regarding their adherence to recommendations for cancer prevention, prediagnosis and after 3 years, including not smoking, alcohol consumption up to one drink per day, intake of at least five portions per day of fruits and/or vegetables, physical activity and body mass index (BMI) less than 25.0 kg/m. To quantify associations between patients' characteristics and changes in adherence to each recommendation, age, education and cancer stage-adjusted odds ratio (OR) with 95% confidence intervals (CIs) were calculated. Among women adhering to each recommendation before diagnosis, 54.1% reduced their physical activity, 32.4% became overweight or obese and 6.1% reduced fruits and/or vegetables intake, but there were virtually no changes in alcohol consumption or smoking. Older and more educated participants were more likely to reduce their physical activity (OR=4.71, 95% CI: 1.17-18.99; OR=11.53, 95% CI: 2.20-60.53, respectively). Among participants not following each recommendation before diagnosis, 29.1% stopped smoking, 24.6% reduced alcohol consumption, 9.9% became physically active, 7.8% increased fruits and/or vegetables intake and 3.3% reduced their BMI to less than 25.0 kg/m. Older women were less likely to become physically active (OR=0.32, 95% CI: 0.14-0.75). Breast cancer patients showed some positive changes in their health behaviours after diagnosis. However, there is a large margin for improvement, which highlights the importance of health promotion interventions in this context.