Effect of lifetime lactation on breast cancer risk: A Korean Women's Cohort Study

Abstract

The objective of our study was to examine the effect of lifetime lactation on breast cancer risk among premenopausal women. The data were from a prospective cohort study with a follow-up period of 6 years in Korea (1995Korea ( -2000 Although the protective effect of lactation on breast cancer has been discussed among researchers for more than 20 years, no study ever found a detrimental effect of breastfeeding on risk of breast cancer. For example, an inverse association between lifetime lactation and breast cancer risk among premenopausal women has been found in some case-control studies, 1-8 whereas other studies show no association. 9 -13 It is noteworthy that studies from the countries in which the prevalence of prolonged lactation is high, such as China 6,7 and Japan, 13,14 have consistently shown an association between lactation and a reduced risk of breast cancer. On the contrary, studies of Western populations, in which the duration of lactation is relatively short, have provided inconsistent results regarding the relation between breastfeeding and the risk of breast cancer. 10,11,15,16 These findings from case-control studies are also evident in cohort studies: Six cohort studies [17][18][19][20][21][22] to date have attempted to clarify the association between lifetime lactation and a reduced risk of breast cancer. Neither the first cohort study for premenopausal women in Norway 17 nor 2 studies from the Nurses' Health Study for U.S. women 18,19 showed the protective effect of lactation on breast cancer risk. However, the most recent nested casecontrol studies for an Iceland cohort 20 and a Connecticut cohort 21 reported a negative association between breastfeeding and breast cancer risk in both pre-and postmenopausal women. In particular, a significant reduction in breast cancer risk was observed among the women who had breastfed for more than 36 months in a Shanghai Textile Workers' cohort study, although a significant reduction in risk was not observed in women who had breastfed for fewer than 36 months. 22 Despite the several previous researches that uncovered the relationships between various aspects of lactation and breast cancer risk, gaps and inconsistencies remain. Given the finding that lactation is a potentially modifiable risk factor for breast cancer, which is a disease with great public health concerns for women of all ages and races, rigorous investigations are warranted to clarify the inconsistent conclusions from previous studies of lactation and breast cancer.Our study is the seventh reported cohort study to examine prospectively the relation between lactation and breast cancer. Our study used data gathering from 110,604 premenopausal Korean women to clarify the potential beneficial effect of lactation on the risk of breast cancer among premenopausal parous women. MATERIAL AND METHODSThe Korea Medical Insurance Corporation (KMIC) is the largest Korean insurance group that provides health insurance to government employees, teachers and their family members. Of the entire Korean populat...

An Example from the Rural Areas of Turkey: Women Breast Cancer Risk Levels and Application and Knowledge Regarding Early Diagnosis- Scan of Breast Cancer

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Breastfeeding in survivors of Hodgkin lymphoma treated with chest radiotherapy

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Breastfeeding and the Use of Human Milk

“…81,82 Maternal Health Benefits Important health benefits of breastfeeding and lactation are also described for mothers. 83 The benefits include decreased postpartum bleeding and more rapid uterine involution attributable to increased concentrations of oxytocin, 84 decreased menstrual blood loss and increased child spacing attributable to lactational amenorrhea, 85 earlier return to prepregnancy weight, 86 decreased risk of breast cancer, [87][88][89][90][91][92] decreased risk of ovarian cancer, 93 and possibly decreased risk of hip fractures and osteoporosis in the postmenopausal period. [94][95][96] …”