Adult alcohol consumption during the previous year is related to breast cancer risk, and breast tissue is particularly susceptible to carcinogens between menarche and first full-term pregnancy. In a study reported in Journal of the National Cancer Institute, Ying Liu, MD, PhD, of Washington University School of Medicine in St. Louis, and colleagues assessed the association between alcohol consumption between menarche and first pregnancy and risk for breast cancer and proliferative benign breast disease.1 They found that increased alcohol consumption before pregnancy was associated with increased risk for both breast cancer and benign breast disease.
Study Details
The study involved 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 benign breast disease or cancer in 1991 and were followed through June 30, 2001, were included in the analysis of proliferative benign breast disease risk.
Among the 91,005 women, 20.4% did not drink alcohol between menarche and first pregnancy and 3.8% reported moderate to high alcohol consumption (≥ 15 g/d, or at least approximately 1.3 drinks per day). Compared with nondrinkers, women who drank alcohol between menarche and first pregnancy were younger by 1 to 2 years at baseline and, after adjustment for age, were older at first pregnancy by 2 to 3 years and were more likely to have a first-degree family history of breast cancer (7% vs 5%).
Cumulative average alcohol consumption between menarche and pregnancy was moderately correlated with both current drinking at baseline and cumulative average drinking since first pregnancy.
Drinking Before Pregnancy
A total of 1,609 breast cancer cases between 1989 and 2009 were identified. Age-adjusted incidence rates were 197 cases per 100,000 person-years among women who had ≥ 15 g/d alcohol intake before first pregnancy and 144/100,000 person years among nondrinkers before first pregnancy.
After adjustment for age, questionnaire year, current body mass index, age at menarche, menopausal status, average body size between 5 and 10 years of age, family history of breast cancer in mother or sisters, postmenopausal hormone use, total duration of breast-feeding, and parity and age at first pregnancy, the cumulative average alcohol consumption between menarche and first pregnancy was associated with increased risk for breast cancer with a relative risk (RR) per 10 g/d intake (approximately 6 drinks/week) of 1.13 (95% confidence interval [CI] = 1.03–1.24; P = .01 for trend).
Relative risk was not significant for those with cumulative average intake of 0.1–4.9 g/d (1.08, 95% CI = 0.94–1.23) or 5.0–14.9 g/d (1.11, 95% CI = 0.94–1.32) and was significant for those with intake ≥ 15.0 g/d (1.41, 95% CI = 1.07–1.86).
After additional adjustment for drinking after first pregnancy, the relative risk for drinking before first pregnancy remained borderline significant (1.11 per 10 g/d intake, 95% CI = 1.00–1.23; P = .051 for trend); relative risk was not significant for those with cumulative average intake of 0.1–4.9 g/d (1.05, 95% CI = 0.90–1.22) or 5.0–14.9 g/d (1.07, 95% CI = 0.89–1.29) and was borderline significant for those with intake ≥ 15.0 g/d (1.34, 95% CI = 1.00–1.80).
Drinking After Pregnancy
Age-adjusted breast cancer incidence rates were 195/100,000 person-years for ≥ 15 g/d alcohol intake after first pregnancy and 138/100,000 person-years for nondrinking after first pregnancy.
The adjusted relative risk for breast cancer for alcohol intake after first pregnancy was 1.11 per 10 g/d intake (95% CI = 0.99–1.24; P = .06 for trend); relative risk was not significant for those with intake of 0.1–4.9 g/d (1.09, 95% CI = 0.93–1.28), 5.0–14.9 g/d (1.17, 95% CI = 0.95–1.43), or ≥ 15.0 g/d (1.30, 95% CI = 0.93–1.83). With additional adjustment for cumulative drinking before first pregnancy, the relative risk was 1.09 per 10 g/d (95% CI = 0.96–1.23; P = .20 for trend); relative risk was not significant for those with intake of 0.1–4.9 g/d (1.04, 95% CI = 0.86–1.26), 5.0–14.9 g/d (1.10, 95% CI = 0.87–1.40), or ≥ 15.0 g/d (1.21, 95% CI = 0.84–1.76).
Time Between Menarche and Pregnancy
Risk was greater among women with ≥ 10 years between menarche and first pregnancy (RR per 10 g/d 1.21, 95% CI = 1.08–1.36) compared with those with a duration of < 10 years (RR = 0.87, 95% CI = 0.69–1.10; P = .01 for interaction). Relative risk was 1.14 (95% CI = 0.97–1.34) among those with a duration of 10 to 14 years and 1.25 (95% CI = 1.06–1.48) among those with a duration of ≥ 15 years.
Analysis by estrogen receptor (ER) and progesterone receptor (PR) status showed that cumulative drinking before first pregnancy tended to be more strongly related to risk of ER-positive/PR-positive tumors (RR = 1.18 per 10 g/d intake, 95% CI = 1.03–1.34) compared with the risk for ER-positive/PR-negative tumors (RR = 0.86, 95% CI = 0.60–1.22) and ER-negative /PR-negative tumors (RR = 0.84, 95% CI = 0.60–1.16; P = .06 for heterogeneity).
Proliferative Benign Breast Disease
A total of 970 proliferative benign breast disease cases were confirmed by central histology review. The relative risk for benign breast disease per 10 g/d intake between menarche and first pregnancy was 1.16 (95% CI = 1.02–1.32), which was greater than risk associated with drinking after pregnancy (RR = 0.94, 95% CI = 0.79–1.11; P = .08 for heterogeneity).
Age-adjusted incidence rates were 298/100,000 person-years for ≥ 15 g/d intake and 271/100,000 person-years for nondrinkers. The association between alcohol consumption before first pregnancy and proliferative benign breast disease appeared to be restricted to women with longer duration between menarche and first pregnancy.
The investigators concluded: “[This study] provides evidence that alcohol consumption before first pregnancy was dose-dependently associated with increased risk of both proliferative [benign breast disease] and breast cancer, independent of drinking after first pregnancy. This increase in risk tended to be more pronounced among women with a longer time interval between menarche and first pregnancy compared with women with a shorter interval, consistent with breast cancer risk models…. Reducing alcohol consumption during this period may be an effective prevention strategy for breast cancer.” ■
Disclosure: The authors reported no potential conflicts of interest.
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