Investigating the Link Between lifestyle and Postmenopausal Breast Cancer: Findings from the EPIC Study
Background: Understanding the impact of lifestyle on breast cancer risk is crucial for prevention efforts. This study, utilizing data from the European Prospective Inquiry into Cancer and Nutrition (EPIC), aimed too determine if changes in lifestyle habits are associated with the advancement of postmenopausal breast cancer.
Methods: Researchers analyzed data from 125,746 women participating in the EPIC study. A Healthy Lifestyle index (HLI) – ranging from 0 to 16 – was calculated for each participant based on four factors: smoking status, alcohol consumption, body mass index (BMI), and physical activity. HLI scores were assessed at two time points, separated by a median of 10 years (Interquartile Range: 5.2-12.0 years). over a median follow-up of nearly 4 years (IQR: 2.9-8.4 years) after the second assessment, 2,175 women were diagnosed with breast cancer. Cox proportional hazards models were used to evaluate the relationship between changes in the HLI and breast cancer risk, considering both overall risk and risk based on estrogen receptor (ER) status. Individual components of the HLI were also examined. To address the possibility that early signs of health issues might influence lifestyle choices (reverse causation), sensitivity analyses were conducted by delaying the start of the follow-up period by 1 to 3 years.
Results: An increase of one unit in the overall HLI score, indicating a healthier lifestyle, did not demonstrate a critically important association with the overall risk of postmenopausal breast cancer. However, analysis of individual HLI components revealed a statistically significant inverse association between BMI and breast cancer risk. Specifically, a one-unit increase in the BMI score – representing a move towards a healthier weight – was linked to a 6.4% reduction in overall breast cancer risk (HR = 0.936; 95% CI 0.880-0.996) and a 7% reduction in ER-positive breast cancer risk (HR = 0.930; 95% CI 0.865-1.000).
Conclusions: This study suggests that overall lifestyle changes, as measured by the HLI, during mid-adulthood are not strongly associated with postmenopausal breast cancer risk. Though, maintaining a healthy BMI appears to be a possibly critically important factor in breast cancer prevention. Future research should focus on larger, more diverse populations and investigate lifestyle factors earlier in life to gain a more thorough understanding of the relationship between lifestyle and breast cancer development.
