Pre- and perinatal factors and incidence of breast cancer in the Black Women's Health Study

Investigating the Relationship between Birthweight and Breast Cancer from A Non-Linear and Mediation Perspective

Background

Epidemiological studies have shown a positive relationship between birthweight and breast cancer; however, inconsistent, sometimes even controversial, observations emerged. We re-explored the association between them in the UK Biobank cohort.

Methods

Relying on the UK Biobank cohort data of white British volunteers recruited between 2006 and 2010 (5,760 cases and 162,778 controls), we evaluated the causal mediation between birthweight and breast cancer, with age of menarche and age at menopause as two potential mediators under the traditional mediation analysis framework. The non-linear relationship between birthweight and breast cancer was also investigated by including the square of birthweight or discretized birthweight categories (<2.5, 2.5~4.0, or >4.0). Furthermore, we performed a stratification analysis in terms of the menopause status.

Results

Birthweight can indirectly influence breast cancer risk in adulthood via the path of age of menarche or age at menopause, and found statistical evidence supporting the existence of suggestive non-linear association between birthweight and breast cancer (β=0.062 and P=0.004 for the square of birthweight) although failing to discover a linear relationship (P=0.230). We also demonstrated such non-linear association seemed more pronounced and robust for premenopausal women compared with postmenopausal ones (27.5% vs. 19.5% increase in breast cancer risk).

Conclusion

This study provided an in-depth insight into the observed relationship between birthweight and breast cancer and revealed that non-linear impact and causal mediation commonly drive the connection between the two traits.

Review of mendelian randomization studies on age at natural menopause

Menopause marks the end of the reproductive phase of life. Based on epidemiological studies, abnormal age at natural menopause (ANM) is thought to contribute to a number of adverse outcomes, such as osteoporosis, cardiovascular disease, and cancer. However, the causality of these associations remains unclear. A powerful epidemiological method known as Mendelian randomization (MR) can be used to clarify the causality between ANM and other diseases or traits. The present review describes MR studies that included ANM as an exposure, outcome and mediator. The findings of MR analyses on ANM have revealed that higher body mass index, poor educational level, early age at menarche, early age at first live birth, early age at first sexual intercourse, and autoimmune thyroid disease appear to be involved in early ANM etiology. The etiology of late ANM appears to be influenced by higher free thyroxine 4 and methylene tetrahydrofolate reductase gene mutations. Furthermore, early ANM has been found to be causally associated with an increased risk of osteoporosis, fracture, type 2 diabetes mellitus, glycosylated hemoglobin, and the homeostasis model of insulin resistance level. In addition, late ANM has been found to be causally associated with an increased systolic blood pressure, higher risk of breast cancer, endometrial cancer, endometrioid ovarian carcinoma, lung cancer, longevity, airflow obstruction, and lower risk of Parkinson's disease. ANM is also a mediator for breast cancer caused by birth weight and childhood body size. However, due to the different instrumental variables used, some results of studies are inconsistent. Future studies with more valid genetic variants are needed for traits with discrepancies between MRs or between MR and other types of epidemiological studies.

Newborn metabolomic signatures of maternal per- and polyfluoroalkyl substance exposure and reduced length of gestation

Marginalized populations experience disproportionate rates of preterm birth and early term birth. Exposure to per- and polyfluoroalkyl substances (PFAS) has been reported to reduce length of gestation, but the underlying mechanisms are unknown. In the present study, we characterized the molecular signatures of prenatal PFAS exposure and gestational age at birth outcomes in the newborn dried blood spot metabolome among 267 African American dyads in Atlanta, Georgia between 2016 and 2020. Pregnant people with higher serum perfluorooctanoic acid and perfluorohexane sulfonic acid concentrations had increased odds of an early birth. After false discovery rate correction, the effect of prenatal PFAS exposure on reduced length of gestation was associated with 8 metabolomic pathways and 52 metabolites in newborn dried blood spots, which suggested perturbed tissue neogenesis, neuroendocrine function, and redox homeostasis. These mechanisms explain how prenatal PFAS exposure gives rise to the leading cause of infant death in the United States.

Association of birth weight with cancer risk: a dose-response meta-analysis and Mendelian randomization study

BACKGROUND

Several articles have shown that birth weight is associated with the risk of many types of cancers. However, the results are inconsistent, and whether the relationship has a causal effect remains unknown.

METHODS

We searched the PubMed and Embase libraries up to March 2021 and selected observational studies reporting the relationship between birth weight and adult-onset cancer risk. Dose-response meta-analysis and two-sample Mendelian randomization (MR) analysis were used to estimate the effect.

RESULT

In our dose-response meta-analysis, six cancers from 46 studies were found to have significant associations with birth weight. (Ovarian cancer: RR: 1.21, 95% CI 1.01-1.44; breast cancer: RR: 1.12, 95% CI 1.08-1.16; colorectal cancer: RR: 1.20, 95% CI 1.01-1.43; endometrial cancer: RR: 0.85, 95% CI 0.78-0.93; prostate cancer: RR: 1.27, 95% CI 1.01-1.61; testicular cancer: RR: 1.21, 95% CI 1.03-1.43). As birth weight increased, the slope of the dose-response curve of breast cancer increased continuously, and the curve of testicular cancer was U-shaped. In the MR study, seven cancers were included. Only invasive mucinous ovarian cancer was found to have a causal effect on birth weight (OR: 0.62; 95% CI 0.39-0.97), while other cancers did not.

CONCLUSIONS

Our findings suggest that birth weight are unlikely to have a casual effect on risk of cancers via the MR analysis, although the dose-response meta-analysis shows that there is a nonlinear relationship between birth weight and breast cancer and testicular cancer. More relevant researches are needed to further investigate their effect.

Exploring the association between birthweight and breast cancer using summary statistics from a perspective of genetic correlation, mediation, and causality

BACKGROUND

Previous studies demonstrated a positive relationship between birthweight and breast cancer; however, inconsistent, sometimes even controversial, observations also emerged, and the nature of such relationship remains unknown.

METHODS

Using summary statistics of birthweight and breast cancer, we assessed the fetal/maternal-specific genetic correlation between them via LDSC and prioritized fetal/maternal-specific pleiotropic genes through MAIUP. Relying on summary statistics we conducted Mendelian randomization (MR) to evaluate the fetal/maternal-specific origin of causal relationship between birthweight, age of menarche, age at menopause and breast cancer.

RESULTS

With summary statistics we identified a positive genetic correlation between fetal-specific birthweight and breast cancer (r_g = 0.123 and P = 0.013) as well as a negative but insignificant correlation between maternal-specific birthweight and breast cancer (r_g = - 0.068, P = 0.206); and detected 84 pleiotropic genes shared by fetal-specific birthweight and breast cancer, 49 shared by maternal-specific birthweight and breast cancer. We also revealed fetal-specific birthweight indirectly influenced breast cancer risk in adulthood via the path of age of menarche or age at menopause in terms of MR-based mediation analysis.

CONCLUSION

This study reveals that shared genetic foundation and causal mediation commonly drive the connection between the two traits, and that fetal/maternal-specific birthweight plays substantially distinct roles in such relationship. However, our work offers little supportive evidence for the fetal origins hypothesis of breast cancer originating in utero.

Perinatal factors, female breast cancer, and associated risk factors in Puerto Rico: evidence from the Atabey epidemiology of breast cancer study

PURPOSE

There is increasing evidence that exposures in utero and in infancy impact breast cancer risk. No previous studies have evaluated these associations among women in Puerto Rico.

METHODS

In a population-based case-control study of breast cancer epidemiology in the San Juan metropolitan area in Puerto Rico, we examined the association of early life factors with breast cancer risk and breast cancer risk factors. Both cases (n = 315) and controls (n = 348) completed interviewer-administered questionnaires, including self-reported birth country, birthweight, and history of having been breastfed. Comparisons of characteristics of those with and without the early life factors were made with t-tests or chi-squared tests; associations between early life factors and breast cancer risk were estimated with unconditional logistic regression adjusting for age, education, body mass index (BMI), age at menarche, parity, and menopausal status.

RESULTS

Women who had been breastfed tended to have higher adult body mass index (BMI), higher education, and lower parity (p < 0.05). Higher birthweight was associated with higher adult BMI and lower educational attainment (p < 0.05). Those born outside of Puerto Rico or the US were more likely to have higher educational attainment and earlier age at menarche than those born within Puerto Rico or the US (p < 0.05). We found no significant associations between any of the early life factors and breast cancer risk.

CONCLUSION

We did not find evidence of an association of early life factors with breast cancer risk among women in Puerto Rico.

Birth weight and the risk of overall breast cancer, premenopausal and postmenopausal breast cancer in adulthood: a dose-response meta-analysis of observational studies

IMPORTANCE

The effect of birth weight on breast cancer across different menopausal states remains unknown.

OBJECTIVE

The aim of this study was to systematically evaluate the association of birth weight with the risk of overall breast cancer (OBC) and premenopausal and postmenopausal breast cancer during adulthood. In parallel, the dose-response analyses were performed.

EVIDENCE REVIEW

Relevant studies were systematically searched from the PubMed, Embase, and the Cochrane Library databases from the inception to May 25, 2021, without language restrictions. All the results were pooled according to risk ratios (RRs).

FINDINGS

In total, 21 cohort studies comprising 1,139,032 participants were included. An increase in the birth weight was not associated with the risk of OBC and premenopausal and postmenopausal breast cancer. Compared with women having normal weight at birth, those with a high birth weight are likely to have an increased risk of invasive breast cancer (RR: 1.19, 95% confidence intervals: 1.03-1.38; I2: 28.6%). The dose-response analyses showed that the risk of premenopausal breast cancer increased significantly in unknown singleton status with birth weight over 2850 g (RR: 1.14 [1.02-1.30]). Similarly, postmenopausal breast cancer risk was increased in singleton births with birth weight over 3750 g (RR: 1.21 [1.00-1.47]).

CONCLUSIONS AND RELEVANCE

High weight at birth might be not significantly associated with the risk of OBC, premenopausal and postmenopausal breast cancer and ER+ and ER- breast cancer but is positively associated with the risk of invasive breast cancer, regardless of parity. Furthermore, with an increase in birth weight, the risk of postmenopausal breast cancer is likely to increase in the singleton births, whereas the risk of premenopausal breast cancer is likely to increase in unknown singleton status.

The Association Between High Birth Weight and Long-Term Outcomes-Implications for Assisted Reproductive Technologies: A Systematic Review and Meta-Analysis

Background: Studies have shown that the prevalence of children born with high birth weight or large for gestational age (LGA) is increasing. This is true for spontaneous pregnancies; however, children born after frozen embryo transfer (FET) as part of assisted reproductive technology (ART) also have an elevated risk. In recent years, the practice of FET has increased rapidly and while the perinatal and obstetric risks are well-studied, less is known about the long-term health consequences. Objective: The aim of this systematic review was to describe the association between high birth weight and LGA on long-term child outcomes. Data Sources: PubMed, Scopus, and Web of Science were searched up to January 2021. Exposure included high birth weight and LGA. Long-term outcome variables included malignancies, psychiatric disorders, cardiovascular disease, and diabetes. Study Selection: Original studies published in English or Scandinavian languages were included. Studies with a control group were included while studies published as abstracts and case reports were excluded. Data Extraction: The methodological quality, in terms of risk of bias, was assessed by pairs of reviewers. Robins-I (www.methods.cochrane.org) was used for risk of bias assessment in original articles. For systematic reviews, AMSTAR (www.amstar.ca) was used. For certainty of evidence, we used the GRADE system. The systematic review followed PRISMA guidelines. When possible, meta-analyses were performed. Results: The search included 11,767 articles out of which 173 met the inclusion criteria and were included in the qualitative analysis, while 63 were included in quantitative synthesis (meta-analyses). High birth weight and/or LGA was associated with low to moderately elevated risks for certain malignancies in childhood, breast cancer, several psychiatric disorders, hypertension in childhood, and type 1 and 2 diabetes. Conclusions: Although the increased risks for adverse outcome in offspring associated with high birth weight and LGA represent serious health effects in childhood and in adulthood, the size of these effects seems moderate. The identified risk association should, however, be taken into account in decisions concerning fresh and frozen ART cycles and is of general importance in view of the increasing prevalence in high birthweight babies.

Birth Weight and Incidence of Breast Cancer: Dose-Response Meta-analysis of Prospective Studies

BACKGROUND

Many studies have shown the association between birth weight and breast cancer (BC), but the evidence remains limited and inconsistent, especially in different menopause status. We sought to clarify the relationship and shape of the dose-response relation between birth weight and BC.

METHODS

The Web of Science, PubMed, and Embase databases were searched for prospective studies involving the relationship between birth weight and risk of BC published to November 2019. Random effects of generalized least squares regression models were used to estimate the quantitative dose-response association, and restricted cubic splines were used to model the association.

RESULTS

We included reports of 16 prospective studies describing 16,000 incident cases among 553,644 participants. We identified a modest-in-magnitude, but significant, association between birth weight and BC risk: risk increased by 2% (risk ratio, 1.02, 95% confidence interval, 1.01-1.03) and 9% (risk ratio, 1.09, 95% confidence interval, 1.04-1.15) with a per-500 g birth weight increment in all ages and premenopausal women, respectively. Our results showed a linear dose-response relationship between birth weight and BC risk (P_nonlinearity = .311) in premenopausal women, with statistical significance when birth weight was above about 3.5 kg. No significant association was found in postmenopausal women.

CONCLUSION

Higher birth weight has a relationship with increased risk of BC in premenopausal women, particularly when birth weight is above 3.5 kg.

Impact of maternal reproductive factors on cancer risks of offspring: A systematic review and meta-analysis of cohort studies

Background

A number of studies have reported on associations between reproductive factors, such as delivery methods, number of birth and breastfeeding, and incidence of cancer in children, but systematic reviews addressing this issue to date have important limitations, and no reviews have addressed the impact of reproductive factors on cancer over the full life course of offspring.

Methods

We performed a comprehensive search in MEDLINE, and Embase up to January 2020 and Web of Science up to 2018 July, including cohort studies reporting the association between maternal reproductive factors of age at birth, birth order, number of births, delivery methods, and breastfeeding duration and cancer in children. Teams of two reviewers independently extracted data and assessed risk of bias. We conducted random effects meta-analyses to estimate summary relative estimates, calculated absolute differences between those with and without risk factors, and used the GRADE approach to evaluate the certainty of evidence.

Results

For most exposures and most cancers, we found no suggestion of a causal relation. We found low to very low certainty evidence of the following very small possible impact: higher maternal age at birth with adult multiple myeloma and lifetime uterine cervix cancer incidence; lower maternal age at birth with childhood overall cancer mortality (RR = 1.15, 95% CI = 1.01–1.30; AR/10,000 = 1, 95% CI = 0 to 2), adult leukemia and lifetime uterine cervix cancer incidence; higher birth order with adult melanoma, cervix uteri, corpus uteri, thyroid cancer incidence, lifetime lung, corpus uteri, prostate, testis, sarcoma, thyroid cancer incidence; larger number of birth with childhood brain (RR = 1.27, 95% CI = 1.06–1.52; AR/10,000 = 1, 95% CI = 0 to 2), leukemia (RR = 2.11, 95% CI = 1.62–2.75; AR/10,000 = 9, 95% CI = 5 to 14), lymphoma (RR = 4.66, 95% CI = 1.40–15.57; AR/10,000 = 11, 95% CI = 1 to 44) incidence, adult stomach, corpus uteri cancer incidence and lung cancer mortality, lifetime stomach, lung, uterine cervix, uterine corpus, multiple myeloma, testis cancer incidence; Caesarean delivery with childhood kidney cancer incidence (RR = 1.25, 95% CI = 1.01–1.55; AR/10,000 = 0, 95% CI = 0 to 1); and breastfeeding with adult colorectal cancer incidence.

Conclusion

Very small impacts existed between a number of reproductive factors and cancer incidence and mortality in children and the certainty of evidence was low to very low primarily due to observational design.

Maternal and Infant Anthropometric Characteristics and Breast Cancer Incidence in the Daughter

The intrauterine and early life environments have been linked to the etiology of breast cancer in prior studies. We prospectively examined whether maternal and newborn anthropometric factors as reported by the mother are related to an increased incidence of adult breast cancer in the daughter. We used data from 35,133 mother-daughter dyads of the Nurses’ Health Study (NHS) II and the Nurses’ Mothers’ Cohort Study. In 2001, living mothers of NHS II participants who were free of cancer completed a questionnaire on their pregnancy with the nurse and their nurse daughter’s early life experience. During 403,786 years of follow-up, 865 daughters developed incident cases of invasive breast cancer. Nurses with a birthweight of ≥4000 g had a 32% greater risk for breast cancer (multivariable-adjusted hazard ratio (HR) = 1.32, 95% confidence interval (CI) = 1.02–1.71, p-trend = 0.09) compared with those with birthweights of 3000–3499 g. Higher birth length tended to increase risk of premenopausal breast cancer (p for trend = 0.05). We further noted a modest U-shaped relation between maternal weight gain during pregnancy and premenopausal breast cancer incidence in the daughter. Fetal growth may contribute to shaping later life risk for breast cancer, especially prior to menopause.

Severe acne and risk of breast cancer

PURPOSE

Hormonal imbalance early in life is thought to be associated with breast cancer risk. Severe acne may arise from hormonal imbalance and could serve as an indicator of increased breast cancer risk. We explored whether severe acne was associated with incident breast cancer.

METHODS

We used data from the Sister Study, a large (n = 50,884) prospective cohort of women who had a sister diagnosed with breast cancer, but who were free of breast cancer themselves at baseline. Participants completed a structured questionnaire that included demographics, lifestyle factors, and medical history, including any diagnosis of severe acne. Adjusted Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% confidence intervals (95% CIs) for the association of severe acne and breast cancer (invasive disease or ductal carcinoma in situ).

RESULTS

During an average of 8.4 years of follow-up, 3049 breast cancer cases were diagnosed. Ever being diagnosed with severe acne was associated with a higher risk of breast cancer (HR 1.23; 95% CI 0.98, 1.54), particularly in women who were diagnosed prior to age 18 years (HR 1.40; 95% CI 1.04, 1.90). Results were similar when limited to invasive cancers.

CONCLUSIONS

Our study supports a non-significant positive association between severe acne-a potential marker of hormonal imbalance-and breast cancer risk. These findings suggest that severe acne, when considered along with other risk factors, could help to identify women who may be at a higher risk of breast cancer.