Alcohol intake between menarche and first pregnancy: a prospective study of breast cancer risk

Abstract

Background: Adult alcohol consumption during the previous year is related to breast cancer risk. Breast tissue is particularly susceptible to carcinogens between menarche and first full-term pregnancy. No study has characterized the contribution of alcohol consumption during this interval to risks of proliferative benign breast disease (BBD) and breast cancer.

Methods: We used data from 91,005 parous women in the Nurses' Health Study II who had no cancer history, completed questions on early alcohol consumption in 1989, and were followed through June 30, 2009, to analyze breast cancer risk. A subset of 60,093 women who had no history of BBD or cancer in 1991 and were followed through June 30, 2001, were included in the analysis of proliferative BBD. Relative risks (RRs) were estimated using Cox proportional hazard regression.

Results: We identified 1609 breast cancer cases and 970 proliferative BBD cases confirmed by central histology review. Alcohol consumption between menarche and first pregnancy, adjusted for drinking after first pregnancy, was associated with risks of breast cancer (RR = 1.11 per 10 g/day intake; 95% confidence interval [CI] = 1.00 to 1.23) and proliferative BBD (RR = 1.16 per 10 g/day intake; 95% CI = 1.02 to 1.32). Drinking after first pregnancy had a similar risk for breast cancer (RR = 1.09 per 10 g/day intake; 95% CI = 0.96 to 1.23) but not for BBD. The association between drinking before first pregnancy and breast neoplasia appeared to be stronger with longer menarche to first pregnancy intervals.

Conclusions: Alcohol consumption before first pregnancy was consistently associated with increased risks of proliferative BBD and breast cancer.

Figure 1.

Relative risks (RRs) of breast cancer (solid diamonds) and proliferative benign breast disease (solid circles) per 10g/day alcohol consumption between menarche and first pregnancy, according to the length of duration between these events, among parous women participating in the Nurses’ Health Study II. The releative risks were adjusted for cumulative alcohol consumption after first pregnancy and other breast cancer risk factors including age (continuous), questionnaire year (continuous), current body mass index (quintiles), age at menarche (<12, 12, 13, or ≥14 years), menopausal status (premenopausal, postmenopausal, or unknown), average body size between ages 5 and 10 years (somatotype pictogram 1, 1.5–2, 2.5–3, 3.5–4.5, ≥5, or unknown), family history of breast cancer in mother or sister(s) (yes or no), postmenopausal hormone use (never use, ever use, or unknown), total duration of breastfeeding (0, 0.1–11 months, ≥12 months, or unknown), and parity and age at first pregnancy (nulliparous; 1–2 pregnancies, age at first pregnancy <25 years; 1–2 pregnancies, age at first pregnancy 25–29 years; 1–2 pregnancies, age at first pregnancy ≥30 years; ≥3 pregnancies, age at first pregnancy <25 years; ≥3 pregnancies, age at first pregnancy 25–29 years; ≥3 pregnancies, age at first pregnancy ≥30 years, or unknown).