Abstract
PurposeWhether an unfavorable lifestyle not only affects breast cancer risk, but also influences age at onset of breast cancer and survival, is under debate.MethodsIn a population-based cohort, the Energy Balance and Breast Cancer Aspects throughout life (EBBA-Life) study, a total of 17,145 women were included. During follow-up, 574 women developed invasive breast cancer. Breast cancer cases were followed for an additional 9.1 years. Detailed medical records were obtained. Cox’s proportional hazard regression models were used to study the association between pre-diagnostic lifestyle factors (weight, physical activity, alcohol use, smoking, and hypertension), breast cancer risk, age at diagnosis, and survival.ResultsAt study entry, 34.3% of the participating women were overweight and 30.7% were physically inactive. Mean age at breast cancer diagnosis was 58.0 years, and 78.9% of the tumors were estrogen receptor positive. Among menopausal women who did not use hormone therapy and had an unfavorable lifestyle (3–5 unfavorable factors), compared with women who had a favorable lifestyle, we observed a twofold higher risk for postmenopausal breast cancer (hazard ratio [HR] 2.13, 95% confidence interval [CI] 1.23–3.69), and they were 3.4 years younger at diagnosis (64.8 versus 68.2 years, P = 0.032). Breast cancer patients with an unfavorable lifestyle, compared with patients with a favorable lifestyle, had almost a two times higher overall mortality risk (HR 1.96, 95% CI 1.01–3.80).ConclusionsOur study supports a healthy lifestyle improving breast cancer prevention, postponing onset of disease, and extending life expectancy among breast cancer patients.
Highlights
A global increase in breast cancer incidence has been observed, with incidence rates being almost fourfold higher in the developed than in the less-developed countries, emphasizing that large differences in lifestyle may have an important role to play [1]
Life expectancy for women who have survived breast cancer has been observed to be shorter compared with women in the general population [3], but whether lifestyle factors play a key role in relation to breast cancer survival remains ambiguous
To study the importance of the variation in lifestyle factors independently and in combination, we identified five different modifiable lifestyle-related factors associated with breast cancer development, and categorized each of them into favorable versus unfavorable based on international categorization (WCRF/AICRF, World Health Organization) [36, 37]: 1. Body composition favorable—Body Mass Index (BMI) < 25 kg/m2 versus unfavorable—BMI ≥ 25 kg/m2
Summary
A global increase in breast cancer incidence has been observed, with incidence rates being almost fourfold higher in the developed than in the less-developed countries, emphasizing that large differences in lifestyle may have an important role to play [1]. A physically active lifestyle compared with a sedentary lifestyle has been observed to reduce both pre- and postmenopausal breast cancer risk overall [8, 9]. The most consistent dietary risk factor for breast cancer is alcohol [10, 11]. Alcohol intake has been associated with higher estradiol levels and higher mammographic density [12], and both pre- and postmenopausal breast cancer risk [13, 14]. Recent meta-analysis observed a positive association between hypertension and breast cancer risk [15, 16]. Tobacco smoking possesses potential mammary carcinogens [18], and recently tobacco use showed an increased risk for ER-positive breast cancer [19]
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