During 14 years (945,764 person-years) of follow-up, we documented 1,179 cases of invasive breast cancer among 90,628 premenopausal women in the cohort. The age range of women in 1991 was 26–46 years. Ages at breast cancer diagnosis ranged from 26 to 56 years. We had information on estrogen receptor (ER)/progesterone receptor (PR) status for 916 (78%) cases. Of these, 597 were ER and PR positive (ER+/PR+), and 196 were ER and PR negative (ER−/PR−). Because of the small number of mixed ER/PR status tumors, we did not include these cases in our analysis by ER/PR status.
shows the characteristics of the cohort in 1991 by quintile of energy-adjusted acrylamide intake. The mean acrylamide intake was 10.8 μg/day in the lowest quintile and 37.8 μg/day in the highest quintile. The major food contributors to acrylamide intake were French fries (23%), coffee (15%), cold breakfast cereal (12%), potato chips (9%), and other potatoes (baked, roasted, mashed; 5%). Those in the highest quintile of acrylamide consumption were more likely to be current smokers and were less likely to exercise than those in the lowest quintile.
Age-standardized Characteristics of the Nurses' Health Study II Cohort in 1991a
Intake of acrylamide was not associated with risk of premenopausal breast cancer (). The multivariable relative risk of breast cancer was 0.92 (95% confidence interval (CI): 0.76, 1.11) in the highest quintile of intake compared with the lowest quintile. The P value for a linear trend across quintiles was 0.61. No association was found for ER+/PR+ or ER−/PR− cancers.
Relative Risk (95% Confidence Intervals) of Breast Cancer by Quintile of Calorie-adjusted Acrylamide Intake, Nurses' Health Study II, 1991–2005
Because tobacco use is a major source of acrylamide exposure, we examined the association among never smokers, former smokers, and current smokers separately (). There was no indication of increased risk of breast cancer for higher acrylamide intakes in any of these groups.
We found no significant differences in the association between dietary acrylamide intake and breast cancer risk when we stratified the population by age, body mass index, alcohol intake, glycemic index, or glycemic load (data not shown).
We repeated the analysis measuring acrylamide exposure relative to body weight (i.e., μg/kg of body weight/day), as this is the exposure measurement used in toxicology studies, and again found similar results. The relative risk for the highest versus the lowest quintile of acrylamide by body weight was 1.00 (95% CI: 0.82, 1.22), with a P value for linear trend of 0.95. Baseline acrylamide intake through diet was also not associated with breast cancer risk. The relative risks relative to the lowest quintile of baseline acrylamide intake were 0.96 (95% CI: 0.79, 1.15) for quintile 2, 1.05 (95% CI: 0.88, 1.26) for quintile 3, 1.01 (95% CI: 0.84, 1.21) for quintile 4, and 1.03 (95% CI: 0.86, 1.24) for quintile 5 (Ptrend = 0.62).
shows the association between consumption of the major acrylamide-contributing foods and premenopausal breast cancer risk. We examined all individual foods that contributed at least 2% to the total estimated acrylamide intake in our population, and none was positively associated with breast cancer risk. We also examined several food groups that are major sources of acrylamide: all potatoes (French fries, potato chips, and baked/mashed/roasted potatoes), breads (white and dark bread, English muffins/bagels/rolls, tortillas, pancakes, pizza, and crackers), and baked goods (cookies, brownies, donuts, cake, pie, and sweet rolls). None of these food groups was associated with breast cancer risk.
Relative Risk (95% Confidence Intervals) of Breast Cancer by Intake of High-Acrylamide Foods, Nurses' Health Study II, 1991–2005