Investigating the Association of Lactation History and Postmenopausal Breast Cancer Risk in the Women's Health Initiative

Breastfeeding Mode and Risk of Breast Cancer: A Dose-Response Meta-Analysis

BACKGROUND

Breastfeeding reduces women's risk of breast cancer. Since exclusive breastfeeding has a stronger hormonal effect, it could theoretically result in a greater reduction in breast cancer risk than any breastfeeding mode. No meta-analysis has examined breast cancer risk by breastfeeding mode. Research aim: The authors conducted a meta-analysis for breast cancer risk in parous women who breastfed exclusively or in any mode versus parous women who formula fed their infants, and they estimated the summary dose-response association by the accumulated duration of any breastfeeding mode.

METHODS

A systematic review of studies published between 2005 and 2015 analyzing breastfeeding and breast cancer risk in women was conducted in PubMed and EBSCOhost. A meta-analysis ( n = 65 studies) with fixed effects (or random effects, if heterogeneity existed) was carried out stratified by breastfeeding mode and menopausal and parity status. A summary dose-response association was estimated using the generalized least-squares method.

RESULTS

The summary relative risk (SRR) for breast cancer in parous women who breastfed exclusively was 0.72, 95% confidence interval (CI) [0.58, 0.90], versus parous women who had never breastfed. For parous women who breastfed in any mode, the SRR was lower in both premenopausal women (0.86, 95% CI [0.80, 0.93]) and postmenopausal women (0.89, 95% CI [0.83, 0.95]). There was no heterogeneity or publication bias. There is weak evidence of a difference between exclusive and any breastfeeding mode ( p = .08). The summary dose-response curve was nonlinear ( p < .001).

CONCLUSION

Exclusive breastfeeding among parous women reduces the risk of breast cancer compared with parous women who do not breastfeed exclusively.

High Expression of the Newly Found Long Noncoding RNA Z38 Promotes Cell Proliferation and Oncogenic Activity in Breast Cancer

The aberrant expression of long noncoding RNAs (lncRNAs) has great impacts on cancer origination and progression. In the current study, a newly found lncRNA Z38, which was identified through combining experiments of suppression subtractive hybridization (SSH) and reverse dot-blotting, was found to have high expression in breast cancer. More importantly, inhibiting Z38 expression by gene silencing greatly suppressed breast cancer cell proliferation and tumorigenesis, and treatment with Z38 siRNAs significantly induced cell apoptosis and inhibited tumor growth. In conclusion, the newly found lncRNA Z38, which plays important roles in breast cancer, may act as a candidate biomarker and therapeutic target in carcinomas.

Associations between the number of natural teeth in postmenopausal women and duration of lactation: The 2010-2012 Korea National Health and Nutrition Examination Survey

OBJECTIVES

Lactation is reported to be associated with changes in maternal calcium homeostasis. The relationship between lactation and long-term oral health remains to be revealed. This study was aimed to evaluate the relationship between lactation and the number of natural teeth in postmenopausal women using nationally representative data.

METHODS

The data from the Korea National Health and Nutrition Examination Survey between 2010 and 2012 were used, and the analysis in this study was confined to 4211 respondents over 19 years old who had gone through menopause and had no missing values for the reproductive factors and outcome variables. The total number of natural teeth was then calculated after excluding third molars. Multiple logistic regression analyses were used to assess the associations of the number of natural teeth and lactation.

RESULTS

As the duration of total lactation increased, the number of natural teeth decreased. Average duration of lactation per child showed similar trends. The association between the total duration of lactation and the number of natural teeth showed an inverse relationship with a beta value of -0.0181 per day after adjustment, and the beta value of the average duration of lactation per child was -0.0287 after the adjustment. The odds ratios of the percentage of individuals with the number of teeth ≤ 27 tended to increase with increased duration of lactation. Adjusted odds ratios and 95% confidence intervals were 1.830 (1.009, 3.320); 1.142 (0.765, 1.704); 1.159 (0.807, 1.664); and 0.857 (0.563, 1.306) for lactation period of ≥ 25 months, 13-24 months, 7-12 months, ≤ 6 months, and no lactation, respectively.

CONCLUSIONS

This study investigated the relationship between the number of teeth and the total duration of lactation or an average duration of lactation per child using nationally representative data. Total duration of lactation and average duration of lactation per child were inversely related to the number of natural teeth. Lactation may be considered to be an independent risk indicator for tooth loss in Korean postmenopausal women.