Breast cancer and breastfeeding: collaborative reanalysis of individual data from 47 epidemiological studies in 30 countries, including 50 302 women with breast cancer and 96 973 women without the disease

The connection between breast cancer and estrogen has been recognized for more than 100 years, since George Beatson demonstrated that bilateral oophorectomy resulted in the remission of breast cancer in premenopausal women.1 Subsequent evidence has implicated both endogenous and exogenous estrogen in the pathogenesis of breast cancer. In this article, we review the relation between estrogen and the risk of breast cancer. Estrogen and Breast Carcinogenesis Experimental data strongly suggest that estrogens have a role in the development and growth of breast cancer.2 Although the exact mechanisms remain to be fully elucidated, the alkylation of cellular molecules and the generation . . .

Estrogen and the Risk of Breast Cancer

Aim: To evaluate the effect of breastfeeding on long-term (breast carcinoma ovarian carcinoma osteoporosis and type 2 diabetes mellitus) and short-term (lactational amenorrhoea postpartum depression postpartum weight change) maternal health outcomes. Methods: A systematic literature search was conducted in PubMed Cochrane Library and CABI databases. Outcome estimates of odds ratios or relative risks or standardised mean differences were pooled. In cases of heterogeneity subgroup analysis and meta-regression were explored. Results: Breastfeeding >12 months was associated with reduced risk of breast and ovarian carcinoma by 26% and 37% respectively. No conclusive evidence of an association between breastfeeding and bone mineral density was found. Breastfeeding was associated with 32% lower risk of type 2 diabetes. Exclusive breastfeeding and predominant breastfeeding were associated with longer duration of amenorrhoea. Shorter duration of breastfeeding was associated with higher risk of postpartum depression. Evidence suggesting an association of breastfeeding with postpartum weight change was lacking. Conclusion: This review supports the hypothesis that breastfeeding is protective against breast and ovarian carcinoma and exclusive breastfeeding and predominant breastfeeding increase the duration of lactational amenorrhoea. There is evidence that breastfeeding reduces the risk of type 2 diabetes. However an association between breastfeeding and bone mineral density or maternal depression or postpartum weight change was not evident. ©2015 The Authors. Open Access.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/apa.13102

Breastfeeding and maternal health outcomes: a systematic review and meta-analysis

https://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(10)60550-8.pdf

Diabetes in sub-Saharan Africa

The premise that bones grow and remodel throughout life to adapt to their mechanical environment is often called Wolff's law. Wolff's law, however, is not always true, and in fact comprises a variety of different processes that are best considered separately. Here we review the molecular and physiological mechanisms by which bone senses, transduces, and responds to mechanical loads, and the effects of aging processes on the relationship (if any) between cortical bone form and mechanical function. Experimental and comparative evidence suggests that cortical bone is primarily responsive to strain prior to sexual maturity, both in terms of the rate of new bone growth (modeling) as well as rates of turnover (Haversian remodeling). Rates of modeling and Haversian remodeling, however, vary greatly at different skeletal sites. In addition, there is no simple relationship between the orientation of loads in long bone diaphyses and their cross-sectional geometry. In combination, these data caution against assuming without testing adaptationist views about form-function relationships in order to infer adult activity patterns from skeletal features such as cross-sectional geometry, cortical bones density, and musculo-skeletal stress markers. Efforts to infer function from shape in the human skeleton should be based on biomechanical and developmental models that are experimentally tested and validated.

/pdf/the-aging-of-wolff-s-law-ontogeny-and-responses-to-25ufbu7nqc.pdf

The Aging of Wolff’s “Law”: Ontogeny and Responses to Mechanical Loading in Cortical Bone

We investigated the relation between lifetime physical activity and bone mineral density (BMD) in South African women using data collected in a case-control study of breast cancer in relation to BMD. Subjects (n = 144) were of black African or mixed ancestral origin, and <60 years of age (mean age 42.6 +/- 8.9 years). Cases had newly diagnosed breast cancer (n = 62) and controls were referred for conditions unrelated to BMD or breast cancer (n = 82). Physical activity data consisting of household, occupational and leisure-time activity, and activity for transport, were collected via questionnaire at 4 life stages (epochs), viz. 14-21, 22-34, 35-50, and 50+ years of age. Total energy (MET hrs) and peak strain scores were calculated. Lumbar spine and total proximal femur BMD were measured using dual-energy x-ray absorptiometry. BMD measures were similar between groups, therefore data were combined. BMD measures were unrelated to total lifetime physical activity. However, the major determinants of total proximal femur BMD included age, transport activity including walking and bicycling between the ages of 14 and 21 years, and current weight (adjusted r2 = 0.33, P < 0.0001). The major determinants of lumbar spine BMD included age, household energy expenditure between the ages of 14 and 21 years, and current weight (adjusted r2 = 0.23, P < 0.0001). Total peak bone strain score for activities between 14-21 years of age was also significantly correlated with lumbar spine BMD ( r = 0.18, P < 0.05). Intraclass correlation coefficients to assess tracking of activity through epochs 1, 2, and 3 were high for total energy expenditure (0.96; 95%CI: 0.94-0.97), household (0.98; 95%CI: 0.97-0.99) and occupational activity (0.78; 95%CI: 0.71-0.84) and activity for transport (0.92; 95%CI: 0.89-0.94). These data suggest that walking or activities resulting in impact loading at a young age are associated with higher BMD in later years. In addition, our findings suggest tracking of physical activity over time.

Bone Mineral Density and Lifetime Physical Activity in South African Women

BACKGROUND

A number of epidemiologic studies have reported a reduced risk of breast carcinoma among women who have lactated but others have not. The current study presents data regarding lactation and breast carcinoma risk from a hospital-based case–control study of black and colored South African women.



METHODS

Incident breast carcinoma cases treated between January 1994 and October 1997 (n = 446) at 2 major hospitals in Cape Town and hospital patients admitted for conditions unrelated to breast carcinoma (controls, n = 1471) were queried regarding the duration of breast-feeding each liveborn child and breast carcinoma risk factors. Multivariate logistic regression models were used to calculate odds ratios (ORs) for various categories of lactation compared with a reference category of never having breast-fed among women who had had at least one full term live birth.



RESULTS

Approximately 83% of cases and 85% of controls had ever breast-fed (OR = 0.9; 95% confidence interval [95% CI], 0.7–1.3). Among all subjects, the ORs for those who lactated for <3 years were near or at unity. Beyond 3 years, ORs extending up to ≥7 years were less than unity, but the 95% CIs included 1.0 (OR for duration of ≥7 years = 0.7; 95% CI, 0.4–1.3). ORs did not vary by menopausal status. Breast carcinoma risk was not found to be related to the duration of breast-feeding the first child, the number of children breast-fed, or the patient's age at first lactation.



CONCLUSIONS

The results of the current study suggest lactation has little or no protective effect on breast carcinoma risk. Cancer 1999;86:982–9. © 1999 American Cancer Society.

Lactation and breast carcinoma risk in a South African population.

Risk factors for breast cancer in South African women.

Although Depo-Provera is one of the most widely used reversible methods of contraception the influence of unopposed progestogen on the risk of breast cancer has not been addressed. An ongoing case-control study in South Africas Western Cape is investigating the relationship between injectable progestogen contraceptives (IPCs) and breast cancer. Enrolled to date have been the 122 cases of invasive breast cancer diagnosed in the previous 6 months among Colored and Black women under 55 years of age at the areas 2 tertiary care hospitals and 389 hospital controls matched for age race and area of residence. This phase of the study sought to describe the patterns of use of IPCs among controls. 280 controls (72%) reported ever-use of IPCs; 73 (19%) were current users 117 (30%) had used this method for 5 or more years and 232 (61%) had initiated use a decade or more ago. These findings indicate the broader study will have sufficient power to document or rule out increased breast cancer risks of the order of 1.5-fold even for 5 or more years of exposure that occurred as much as a decade earlier.

A case control study of breast cancer risk and exposure to injectable progestogen contraceptives : Methods and patterns of use among controls

We investigated the relation between lifetime physical activity and bone mineral density (BMD) in South African women using data collected in a case- control studyof breast cancer in relation to BMD. Subjects (n = 144) were of black African or mixed an- cestral origin, and <60 years of age (mean age 42.6 ± 8.9 years). Cases had newly diagnosed breast cancer (n = 62) and controls were referred for condi- tions unrelated to BMD or breast cancer (n = 82). Physical activity data consisting of household, occupa- tional and leisure-time activity, and activity for trans- port, were collected via questionnaire at 4 life stages (epochs), viz. 14-21, 22-34, 35-50, and 50+ years of age. Total energy(MET hrs) and peak strain scores were calculated. Lumbar spine and total proximal femur BMD were measured using dual-energyx-rayabsorp- tiometry. BMD measures were similar between groups, therefore data were combined. BMD measures were unrelated to total lifetime physical activity. However, the major determinants of total proximal femur BMD included age, transport activityincluding walking and bicycling between the ages of 14 and 21 years, and current weight (adjusted r 2 = 0.33, P < 0.0001). The major determinants of lumbar spine BMD included age, household energyexpenditure between the ages of 14 and 21 years, and current weight (adjusted r 2 = 0.23, P < 0.0001). Total peak bone strain score for activities between 14-21 years of age was also significantly cor- related with lumbar spine BMD (r = 0.18, P < 0.05). Intraclass correlation coefficients to assess tracking of activitythrough epochs 1, 2, and 3 were high for total energyexpenditure (0.96; 95 %CI: 0.94-0.97), household (0.98; 95%CI: 0.97-0.99) and occupational activity (0.78; 95%CI: 0.71-0.84) and activityfor transport (0.92; 95%CI: 0.89-0.94). These data suggest that walking or activities resulting in impact loading at a young age are associated with higher BMD in later years. In addition, our findings suggest tracking of physical activity over time.

Bone Mineral Density and Lifetime Physical Activity in

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