LAUSR

A relatively high healthy lifestyle index (HLI) score, representing a healthy diet, participation in moderate to vigorous physical exercise, no smoking, low to no alcohol intake, and a normal body mass index, has been associated with a reduced risk of invasive breast cancer. However, no study has shown an association between the HLI and the risk of ductal carcinoma in-situ of the breast (DCIS), which is considered to be a non-obligate precursor of invasive breast cancer. We evaluated this association in a prospective cohort of 132 230 postmenopausal women, aged 50-79 years, recruited between 1993 and 1998 across the United States and enrolled in the Women's Health Initiative study. The HLI score was created and categorized into quartiles. During an average follow-up of 15.4 years, 2035 DCIS cases were ascertained. Multivariable-adjusted Cox regression was used to estimate hazard ratios (HR) and 95% confidence intervals (CI) for the association of HLI with the risk of DCIS. Women in the highest HLI quartile had a lower DCIS risk than those in the lowest quartile (HR4 th QT  = 0.80, 95%CI, 0.70-0.92) and this association was stronger in women with a family history of breast cancer (HR4 th QT  = 0.70, 95% CI, 0.52-0.93), and for ER+/PR+ DCIS (HR4 th QT  = 0.66, 95%CI, 0.52-0.83). These findings suggest that there is an inverse association between HLI and risk of DCIS, and suggest that the adoption of a healthy lifestyle might lower the risk of DCIS. This article is protected by copyright. All rights reserved.