Being breastfed in infancy and breast cancer incidence in adult life: results from the two nurses' health studies

Breastfeeding in infancy and mortality in middle and late adulthood: A prospective cohort study and meta-analysis

BACKGROUND

Breastfeeding in infancy is associated with a lower risk of mortality among children, but the impact on mortality in middle and late adulthood remains unknown.

OBJECTIVES

To assess the association between breastfeeding in infancy and mortality in middle and late adulthood.

METHODS

We included 383,627 participants aged 40-73 from the UK Biobank (2006-2010) and followed up until 2021. Hazard ratios (HRs) and 95% confidence intervals (CIs) for all-cause and cause-specific mortality according to breastfeeding in infancy were estimated with Cox proportional hazards regression models. We further did a meta-analysis, including results from our present study and three other cohort studies (PROSPERO; number CRD42022348925).

RESULTS

During a total of 4732,751 person-years of follow-up, 25,581 deaths were identified. Breastfeeding in infancy was associated with lower risks of mortality in middle and late adulthood, with adjusted HRs (95% CIs) of 0.95 (0.93-0.98) for all-cause mortality; 0.91 (0.87-0.96) for cardiovascular mortality and 0.94 (0.874-0.999) for respiratory mortality. Specifically, the association with mortality seemed to attenuate with age - stronger in middle-aged adults than in older adults. A similar association between breastfeeding in infancy and all-cause mortality was found in the meta-analysis.

CONCLUSION

Breastfeeding in infancy is associated with a lower risk of mortality - even decades later - in middle and late adulthood.

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.

Breast Cancer and Nutrition: A Paradigm for Prevention in 3D Across the Life Course

Breast cancer, the most common cancer in women worldwide, has recognized reproductive and anthropometric risk factors including age at menarche and adult height. Yet the age when a woman attains her adult height or experiences menarche for example is simply the timing of the major life event at the end of a long trail of exposures that began in utero. The objective of this article is to investigate through a review of the literature the role of nutrition in breast cancer prevention through three dimensions (D). Each D offers a different lens. The First D identifies windows/ages of exposures or conditions that convey vulnerability or protection from breast cancer. The Second D addresses the intensity and duration of the exposure; and the (Third D) examines the pace, i.e., how rapid or slow the young woman experiences her growth and development. Birthweight illustrative of the First D reveals a strong signal across the life course on BC risk, but the risk group varies from low to high birthweight. Stressful life events like being a pubertal aged girl living in a household with an unemployed father during the Great Depression or high levels of environmental contaminants exposure are representative of the Second D. Height velocity at specific ages and weight loss in postmenopausal years are illustrative of anthropometric trajectories that reveal an adaptive biosystem that provides a contextual state to interact with the other two Ds. This article presents a new paradigm of nutrition and breast cancer prevention through the lens of three very different dimensions. It is the premise of this article that all three dimensions are essential tasks to tease apart the life course and identify windows for preventive strategies.

Adult cancer risk in women who were breastfed as infants: large UK prospective study

There are known short-term benefits in breastfed infants versus bottle-fed infants in terms of lower risks of infection and obesity in infancy and childhood, but the long-term effect on the risk of adult cancers is unclear. In a cohort of 1 in 4 UK women born in 1935-1950 we report the incidence of adult cancers in relation to having been breastfed in infancy. In median year 2001 (interquartile range 2000-2003) 548,741 women without prior cancer reported whether they had been breastfed. There was 81% agreement between women's report of having been breastfed and information on breastfeeding recorded when they were 2 years old. Participants were followed by record-linkage to national cancer registration, hospital admission and death databases. Cox regression yielded adjusted relative risks (RRs) and 95% confidence intervals (CI) by having been breastfed or not for eight cancer sites with > 2000 incident cases and for related conditions, where appropriate. Of the eight cancers examined here one association was highly statistically significant: an increase in colorectal cancer incidence among women who had been breastfed versus not (RR 1.18, 95% CI 1.12-1.24, n = 8651). To investigate further the findings for colorectal cancer, we studied eight other gastro-intestinal conditions, and found increased risks in women who had been breastfed versus not for benign colorectal polyps (RR 1.09, 95% CI 1.05-1.13, n = 17,677) and for appendicitis (RR 1.19, 95% CI 1.07-1.31, n = 2108). The greater risks of adult colorectal cancer, colorectal polyps and appendicitis associated with having been breastfed in infancy suggest possible long-term effects of infant feeding practices on the gastrointestinal tract. Further studies are required to clarify this novel association.

Infectious Agents in Bovine Red Meat and Milk and Their Potential Role in Cancer and Other Chronic Diseases

Red meat and dairy products have frequently been suggested to represent risk factors for certain cancers, chronic neurodegenerative diseases, and autoimmune and cardiovascular disorders. This review summarizes the evidence and investigates the possible involvement of infectious factors in these diseases. The isolation of small circular single-stranded DNA molecules from serum and dairy products of Eurasian Aurochs (Bos taurus)-derived cattle, obviously persisting as episomes in infected cells, provides the basis for further investigations. Gene expression of these agents in human cells has been demonstrated, and frequent infection of humans is implicated by the detection of antibodies in a high percentage of healthy individuals. Epidemiological observations suggest their relationship to the development multiple sclerosis, to heterophile antibodies, and to N-glycolylneuraminic acid (Neu5Gc) containing cell surface receptors.

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

PURPOSE

The purpose of the study was to investigate the association between pre- or perinatal factors and breast cancer risk among African American women.

METHODS

Participants in the Black Women's Health Study, a prospective cohort of 59,000 African American women, reported birth weight, preterm birth, twin or triplet status, maternal age at birth, birth order, and having been breastfed during infancy at various times during follow-up from 1997 to 2015. Numbers of incident cases ranged from 312 for breastfed analyses to 1,583 for twin or triplet analyses. Using multivariable Cox proportional hazards regression, we estimated hazard ratios (HRs) and 95% confidence intervals (CIs) for associations between each factor and breast cancer risk overall and by estrogen receptor (ER) status.

RESULTS

Compared to birth weights of 5 lbs. 8 oz.-8 lbs. 13 oz., low (< 5 lbs. 8 oz.) and high (> 8 lbs. 13 oz.) birth weights were associated with increased breast cancer risk; HRs (95% CI) were 1.19 (0.98-1.44) and 1.26 (0.97-1.63), respectively. Associations were similar by ER status. Having been born to a mother aged ≥ 35 years versus < 20 years was associated with risk of ER+ (HR 1.59, 95% CI 1.10-2.29), but not ER- breast cancer. Other perinatal factors were not associated with breast cancer.

CONCLUSION

African American women with a low or high birth weight or born to older mothers may have increased breast cancer risk. Trends towards delayed child birth and higher birth weights, coupled with disproportionately high rates of low birth weight among African Americans, may contribute to increases in breast cancer incidence.

Reproductive factors and the risk of triple-negative breast cancer in white women and African-American women: a pooled analysis

BACKGROUND

Early age at menarche, nulliparity, late age at first completed pregnancy, and never having breastfed, are established breast cancer risk factors. However, among breast cancer subtypes, it remains unclear whether all of these are risk factors for triple-negative breast cancer (TNBC).

METHODS

We evaluated the associations of these reproductive factors with TNBC, in 2658 patients with breast cancer (including 554 with TNBC) and 2448 controls aged 20-64 years, who participated in one of the three population-based case-control studies: the Women's Contraceptive and Reproductive Experiences Study, the Women's Breast Carcinoma in situ Study, or the Women's Learning the Influence of Family and Environment Study. We used multivariable polychotomous unconditional logistic regression methods to conduct case-control comparisons among breast cancer subtypes defined by estrogen receptor, progesterone receptor, and human epidermal growth factor receptor-2 expression status.

RESULTS

TNBC risk decreased with increasing duration of breastfeeding (P trend = 0.006), but age at menarche, age at first completed pregnancy, and nulliparity were not associated with risk of TNBC. Parous women who breastfed for at least one year had a 31% lower risk of TNBC than parous women who had never breastfed (odds ratio, OR = 0.69; 95% confidence interval, CI = 0.50-0.96). The association between breastfeeding and risk of TNBC was modified by age and race. Parous African-American women aged 20-44 years who breastfed for 6 months or longer had an 82% lower risk of TNBC than their counterparts who had never breastfed (OR = 0.18, 95% CI = 0.07-0.46).

CONCLUSIONS

Our data indicate that breastfeeding decreases the risk of TNBC, especially for younger African-American women.

Exposures in early life: associations with DNA promoter methylation in breast tumors

There is evidence that epigenetic changes occur early in breast carcinogenesis. We hypothesized that early-life exposures associated with breast cancer would be associated with epigenetic alterations in breast tumors. In particular, we examined DNA methylation patterns in breast tumors in association with several early-life exposures in a population-based case-control study. Promoter methylation of E-cadherin, p16 and RAR-β2 genes was assessed in archived tumor blocks from 803 cases with real-time methylation-specific PCR. Unconditional logistic regression was used for case-case comparisons of those with and without promoter methylation. We found no differences in the prevalence of DNA methylation of the individual genes by age at menarche, age at first live birth and weight at age 20. In case-case comparisons of premenopausal breast cancer, lower birth weight was associated with increased likelihood of E-cadherin promoter methylation (OR = 2.79, 95% CI, 1.15-6.82, for ⩽2.5 v. 2.6-2.9 kg); higher adult height with RAR-β2 methylation (OR = 3.34, 95% CI, 1.19-9.39, for ⩾1.65 v. <1.60 m); and not having been breastfed with p16 methylation (OR = 2.75, 95% CI, 1.14-6.62). Among postmenopausal breast cancers, birth order was associated with increased likelihood of p16 promoter methylation. Being other than first in the birth order was inversely associated with likelihood of ⩾1 of the three genes being methylated for premenopausal breast cancers, but positively associated with methylation in postmenopausal women. These results suggest that there may be alterations in methylation associated with early-life exposures that persist into adulthood and affect breast cancer risk.

Being breastfed in infancy and adult breast cancer risk among Japanese women

OBJECTIVE

Being breastfed in infancy has been hypothesized to influence subsequent breast cancer risk. In a hospital-based case-control study, we investigated the relationship between having been breastfed and breast cancer risk, both overall and separately among female subjects with different birth years.

METHODS

The study subjects included 571 cases and 2,155 controls admitted to a single hospital in Miyagi Prefecture, Japan, between 1997 and 2005. History of having been breastfed was assessed with a self-administered questionnaire. Odds ratios (ORs) and 95% confidence interval (CI) were estimated using logistic regression.

RESULTS

After adjustment for known risk factors, no association for having been breastfed was observed overall (OR = 1.20; 95% CI: 0.82-1.76). Analysis stratified according to birth year (<1950, ≥1950) demonstrated heterogeneity in the association for having been breastfed between the two birth-year groups (p for interaction = 0.0006); having been breastfed was significantly associated with a decreased risk among subjects who were born before 1950 (OR = 0.59; 95% CI: 0.35-0.99), whereas no such risk reduction was observed for subjects born after 1950 (OR = 1.60; 95% CI: 0.88-2.90).

CONCLUSION

Although having been breastfed is not related to overall risk, birth year may modify the association between having been breastfed in infancy and breast cancer risk. In Japan, sociodemographic changes have occurred since the end of World War II. The use of standard formula supplement began to spread around 1950. The difference of breast cancer risk between birth-year groups may be attributable to these environmental changes.

Association of Birth Weight with Health and Long-Term Survival up to Middle and Old Ages in China

This study is based on an unique dataset of birth records of 11,693 persons born in Beijing, China from 1921-54 and from clinical examinations (May 2003-April 2005) of 2,085 tracked surviving cohort members (aged 50-82) to diagnose seven major chronic diseases. Data were analyzed using the extended Fixed Attribute Dynamics (FAD) method and multivariate regressions. The results of our FAD analysis have shown that, as compared to the persons with low birth weight (<2,500 g), the probability of survival from age 0 to ages 50-56, 63-67 and 68-82 for persons with higher birth weight (2,500-2,999 g, 3,000-3499 g, or ≥3,500 g) was 16-31, 62-104, and 52-108% higher respectively. These estimates display similar patterns for both genders, with somewhat stronger effects in men. Of the 27 estimates of the Odds Ratio of Survival in the FAD analysis, 21 are statistically significant. Controlling for 14 confounding factors, multivariate binary logistic regressions have demonstrated that the risk of having cardiovascular disease and diabetes is negatively associated birth weight; ordinal logit regressions have shown that the number of major chronic diseases at ages 50-82 is significantly associated with birth weight: the lower the birth weight, the higher the risk of having more chronic diseases. We conclude that low birth weight is negatively associated with 1) long-term survival probability from age 0 to ages 50-82, and 2) overall health at middle and old ages. Further research is needed to understand the mechanisms of these effects.

Pregnancy-related factors and the risk of breast carcinoma in situ and invasive breast cancer among postmenopausal women in the California Teachers Study cohort

Introduction

Although pregnancy-related factors such as nulliparity and late age at first full-term pregnancy are well-established risk factors for invasive breast cancer, the roles of these factors in the natural history of breast cancer development remain unclear.

Methods

Among 52,464 postmenopausal women participating in the California Teachers Study (CTS), 624 were diagnosed with breast carcinoma in situ (CIS) and 2,828 with invasive breast cancer between 1995 and 2007. Multivariable Cox proportional hazards regression methods were used to estimate relative risks associated with parity, age at first full-term pregnancy, breastfeeding, nausea or vomiting during pregnancy, and preeclampsia.

Results

Compared with never-pregnant women, an increasing number of full-term pregnancies was associated with greater risk reduction for both breast CIS and invasive breast cancer (both P trend < 0.01). Women having four or more full-term pregnancies had a 31% lower breast CIS risk (RR = 0.69, 95% CI = 0.51 to 0.93) and 18% lower invasive breast cancer risk (RR = 0.82, 95% CI = 0.72 to 0.94). Parous women whose first full-term pregnancy occurred at age 35 years or later had a 118% greater risk for breast CIS (RR = 2.18, 95% CI = 1.36 to 3.49) and 27% greater risk for invasive breast cancer (RR = 1.27, 95% CI = 0.99 to 1.65) than those whose first full-term pregnancy occurred before age 21 years. Furthermore, parity was negatively associated with the risk of estrogen receptor-positive (ER+) or ER+/progesterone receptor-positive (PR+) while age at first full-term pregnancy was positively associated with the risk of ER+ or ER+/PR+ invasive breast cancer. Neither of these factors was statistically significantly associated with the risk of ER-negative (ER-) or ER-/PR- invasive breast cancer, tests for heterogeneity between subtypes did not reach statistical significance. No clear associations were detected for other pregnancy-related factors.

Conclusions

These results provide some epidemiologic evidence that parity and age at first full-term pregnancy are involved in the development of breast cancer among postmenopausal women. The role of these factors in risk of in situ versus invasive, and hormone receptor-positive versus -negative breast cancer merits further exploration.

Through the Looking Glass at Early-Life Exposures and Breast Cancer Risk

The global increase in the proportion of women diagnosed with breast cancer, inadequate access to screening and high cost of treatment for breast cancer argue strongly for a greater focus on preventive strategies. But at what age is it appropriate to begin targeting preventive approaches? The recognized role of perinatal nutrition in neurologic development and the relation of maternal nutritional status to birthweight and subsequent risk of hypertension, diabetes, and cardiovascular disease identify pregnancy and early childhood as potential phases for prevention. This review examines indicators of hormonal and nutritional exposures in early life and breast cancer risk through the lens of the life course paradigm integrated with maternal and child health research and methodology. Compared to women who were normal birthweight (2500-3999 g), women who weighed>or=4,000 g at birth have a 20 percent to 5-fold increased risk of premenopausal breast cancer. Women born preterm and likely to be small- or large-for-date also have an increased risk. Birth length is directly associated with risk and has a larger magnitude of effect than birthweight. Prior preeclamptics and their daughters have a lower risk of breast cancer than comparable normotensives. An association between infant feeding practices and breast cancer is unclear without improved exposure assessment and analysis. Rapid childhood and pubertal linear growth increases breast cancer risk, while greater body fat over the same periods reduces risk. Growth data thus far have not been calculated in Z-scores from reference growth curves for comparison across studies. Events and secular trends influencing birth cohorts may not be adequately addressed, thereby limiting the interpretation and implications of the findings. Research in nonhuman primates may help uncover underlying mechanisms.

Breast cancer in young women and its impact on reproductive function

BACKGROUND

Breast cancer is the most common cancer in women in developed countries, and 12% of breast cancer occurs in women 20-34 years. Survival from breast cancer has significantly improved, and the potential late effects of treatment and the impact on quality of life have become increasingly important. Young women constitute a minority of breast cancer patients, but commonly have distinct concerns and issues compared with older women, including queries regarding fertility, contraception and pregnancy. Further, they are more likely than older women to have questions regarding potential side effects of therapy and risk of relapse or a new primary. In addition, many will have symptoms associated with treatment and they present a management challenge. Reproductive medicine specialists and gynaecologists commonly see these women either shortly after initial diagnosis or following adjuvant therapy and should be aware of current management of breast cancer, the options for women at increased genetic risk, the prognosis of patients with early stage breast cancer and how adjuvant systemic treatments may impact reproductive function.

METHODS

No systematic literature search was done. The review focuses on the current management of breast cancer in young women and the impact of treatment on reproductive function and subsequent management. With reference to key studies and meta-analyses, we highlight controversies and current unanswered questions regarding patient management.

RESULTS

Chemotherapy for breast cancer is likely to negatively impact on reproductive function. A number of interventions are available which may increase the likelihood of future successful pregnancy, but the relative safety of these interventions is not well established. For those who do conceive following breast cancer, there is no good evidence that pregnancy is detrimental to survival. We review current treatment; effects on reproductive function; preservation of fertility; contraception; pregnancy; breastfeeding and management of menopausal symptoms following breast cancer.

CONCLUSION

This paper provides an update on the management of breast cancer in young women and is targeted at reproductive medicine specialists and gynaecologists.

Exposure to breast milk in infancy and risk of breast cancer

Early life exposures, such as being breastfed in infancy, may influence the risk of breast cancer in adulthood. We evaluated the risk of breast cancer in relation to ever having been breastfed in infancy among 9,442 women who participated in a population-based, case-control study. Cases were identified through cancer registries in three states (Massachusetts, New Hampshire, and Wisconsin); controls were identified through statewide drivers' license lists or medicare lists. Data on known and suspected risk factors were obtained through telephone interview. We used unconditional logistic regression to assess the relation of breast cancer with ever having been breastfed and with breastfeeding duration (available for only 19% of breastfed women) in premenopausal women (1,986 cases and 1,760 controls) and postmenopausal women (2,600 cases and 2,493 controls). We found no evidence that ever having been breastfed in infancy was associated with breast cancer risk in either premenopausal women (odds ratio [OR] = 0.96; 95% confidence interval [CI] = 0.83-1.10) or postmenopausal women (OR = 0.98; 95% CI = 0.87-1.10). The association did not differ according to breast cancer stage, mother's history of breast cancer, or any other reproductive factor assessed. Likewise, we found no association between breastfeeding duration and risk of breast cancer. Our results did not support the hypothesis that exposure to breast milk in infancy influences the risk of adult breast cancer.

Perinatal factors and adult-onset lupus

OBJECTIVE

Some evidence suggests that perinatal factors, including birth weight and breastfeeding, may influence the occurrence of autoimmune rheumatic diseases. However, few studies have investigated these factors in patients with systemic lupus erythematosus (SLE). Therefore, we evaluated the role of birth weight, being breastfed, and preterm birth on the incidence of SLE in participants in the Nurses' Health Study (NHS) and the Nurses' Health Study II (NHSII).

METHODS

We studied 87,411 NHS participants and 98,413 NHSII participants without SLE at baseline who provided information on perinatal exposures. Among these women, during 26 (NHS) and 14 (NHSII) years of followup, 222 incident SLE cases were confirmed (136 NHS and 86 NHSII) by medical record review using American College of Rheumatology criteria. We used stratified Cox models to estimate the association of perinatal factors with SLE, adjusting for race, early passive cigarette smoke exposure, and parents' occupation. A random-effects meta-analysis was used to compute combined estimates across the 2 cohorts.

RESULTS

After adjustment for multiple potential confounders, high birth weight (> or =10 pounds) was associated with increased rates of SLE compared with normal birth weight (7-8.5 pounds; rate ratio [RR] 2.7, 95% confidence interval [95% CI] 1.2-5.9), as was being born > or =2 weeks preterm (RR 1.9, 95% CI 1.2-3.0); however, being breastfed was not (RR 0.8, 95% CI 0.6-1.1).

CONCLUSION

Birth weight > or =10 pounds and preterm birth were both positively associated with incident SLE among women.

Effects of birth order and maternal age on breast cancer risk: modification by whether women had been breast-fed

BACKGROUND

Early life risk factors for breast cancer have been investigated in relation to hormonal, nutritional, infectious, and genetic hypotheses. Recent studies have also considered potential health effects associated with exposure to environmental contaminants in breastmilk.

METHODS

We analyzed data from a population-based case-control study of women living in Wisconsin. Cases (n = 2016) had an incident diagnosis of invasive breast cancer in 2002-2006 reported to the statewide tumor registry. Controls (n = 1960) of similar ages were randomly selected from driver's license lists. Risk-factor information was collected during structured telephone interviews. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated from multivariable logistic regression.

RESULTS

In multivariable models, maternal age and birth order were not associated with breast cancer risk in the full study population. The odds ratio for breast cancer risk associated with having been breast-fed in infancy was 0.83 (95% CI = 0.72-0.96). In analyses restricted to breast-fed women, maternal age associations with breast cancer were null (P = 0.2). Increasing maternal age was negatively associated with breast cancer risk among women who were not breast-fed; the odds ratio for breast cancer associated with each 5-year increase in maternal age was 0.90 (0.82-1.00). Higher birth order was inversely associated with breast cancer risk among breast-fed women (for women with 3 or more older siblings compared with first-born women, OR = 0.58 [CI = 0.39-0.86]) but not among nonbreast-fed women (1.13 [0.81-1.57]).

CONCLUSION

These findings suggest that early life risk factor associations for breast cancer may differ according to breast-feeding status in infancy.

Infant feeding and the incidence of endometrial cancer

Biological mechanisms could support both an inverse and a direct association between exposure to breast milk in infancy and the risk of cancer. Having been breast-fed has been investigated in relation to the risk of breast and other cancer sites, and conflicting results have been reported. The association between infant feeding and the risk of endometrial cancer has not been explored. From 1976 to 2004, we followed 74,757 cancer-free participants in the Nurses' Health Study who had not undergone hysterectomy. Information on infant feeding was self-reported by study participants. A total of 708 incident cases of endometrial cancer were diagnosed during follow-up. After adjusting for age, family history of endometrial cancer, birth weight, premature birth, and birth order, the incidence of endometrial cancer was not associated with ever having been breast-fed (hazards ratio, 0.94; 95% confidence interval, 0.79-1.11) or duration of having been breast-fed [hazards ratio (95% confidence interval): 1.11 (0.80-1.54), 0.84 (0.62-1.13), 1.02 (0.79-1.31), respectively, for < or =3, 4-8, and > or =9 months of having been breastfed; P for trend = 0.88]. There was no significant effect modification by menopausal status, anthropometric factors (somatotype at age 5 or 10 years, body mass index at age 18 years, or current body mass index), or by other early-life exposures (birth weight, premature birth or exposure to parental smoking in childhood). Additional adjustment for adulthood risk factors of endometrial cancer did not materially change the results. Having been breast-fed was not associated with the incidence of endometrial cancer in this cohort, but statistical power for analyses restricted to premenopausal women was limited.

Perinatal exposures and breast cancer risk in the Western New York Exposures and Breast Cancer (WEB) Study

BACKGROUND

There is increasing evidence that early life exposures, such as birth weight, infant feeding practices, birth rank and maternal age at delivery may play a role in breast carcinogenesis.

METHODS

We conducted a case-control study of women aged 35-80 in Western New York (Western New York Exposure and Breast Cancer Study, the WEB Study, 1996-2001). The study included 845 women diagnosed with primary, incident, histologically confirmed breast cancer, and 1538 controls frequency-matched to cases on age, race, and county of residence. We conducted extensive in-person interviews including self-reported birth weight, history of having been breastfed, birth rank, and maternal age at delivery.

RESULTS

Birth weight was significantly associated with pre- but not post-menopausal breast cancer risk. Compared to women whose birth weight was 5.5-7 pounds, we found an increased risk associated with a birth weight greater than 8.5 pounds (OR 1.84, 95%CI: 1.12-3.02). Risk was also increased for pre- but not post-menopausal women who had not been breastfed (OR 1.78, 95%CI: 1.21-2.60). Birth order and maternal age at delivery were not significantly associated with breast cancer risk.

CONCLUSIONS

Our findings are consistent with other studies showing breast cancer risk associated with birth weight for pre- but not post-menopausal breast cancer. As we found in an earlier study, having been breastfed was associated with decreased risk. These findings add to the accumulating evidence that early life events impact women's subsequent breast cancer risk.

Early life factors and incidence of proliferative benign breast disease

Proliferative benign breast disease is a marker of increased breast cancer risk, yet little is known about its etiology. Most studies of benign breast disease have focused only on risk factors in adulthood, despite growing evidence that factors in early life influence breast cancer risk. We explored the relations of several early life factors with incidence of proliferative benign breast disease among 71,896 premenopausal women in the Nurses' Health Study II who recalled their body fatness at young ages, physical activity in adolescence, birthweight, and history of being breastfed. Between 1991 and 1997, 901 of these women were identified as having proliferative benign breast disease from a centralized pathology review. Relative risks (RR) and 95% confidence intervals (95% CI) were estimated from Cox proportional hazards models. Greater childhood body fatness (ages 5-10) was associated with decreased risk of proliferative benign breast disease; the multivariate RR (95% CI) for the most overweight compared with the most lean was 0.61 (0.44-0.86; P(trend) < 0.0001) and remained significant after adjustment for current body mass index. Body mass index at age 18 was also inversely associated with incidence of proliferative benign breast disease, with a multivariate RR (95% CI) of 0.67 (0.52-0.88) for those who were > or =25 kg/m(2) compared with those who were <19 kg/m(2) (P(trend) = 0.001). There were no clear associations for physical activity in adolescence, birthweight, or being breastfed. These results indicate that premenopausal women who were heavier at young ages have lower incidence of proliferative benign breast disease, consistent with previous findings for breast cancer.

Epidemiology and the causes of breast cancer

This article describes the characteristics of 3 dominant features of breast cancer epidemiology. These characteristics include the association of disease risk with childbearing, its relationship to ovarian activity and its international variation (particularly as the latter differs in the years before and after menopause). Equivocal tests of one hypothesis that reconciled some of these features through variations in levels of the fractions of estrogen are described. Other hypotheses with a similar objective are needed. The 3 known causes of human breast cancer, ionizing radiation, exogenous ovarian hormones and beverage alcohol, offer some preventive possibilities but do little to explain the epidemiologic features of the majority of cases of the disease that occur in their absence.

Breast-feeding and cancer: the Boyd Orr cohort and a systematic review with meta-analysis

BACKGROUND

Having been breast-fed has been suggested to influence cancer risk in adulthood. We investigated associations between breast-feeding during infancy and adult cancer incidence and mortality in a cohort study and meta-analyses of published studies.

METHODS

The Boyd Orr cohort consisted of 4999 subjects who were originally surveyed in 1937-39, when they were 0-19 years of age. Cancer outcomes from 1948 through 2003 were available for 4379 (88%) subjects, and 3844 had complete data on all covariates. Associations of breast-feeding with cancer were investigated using proportional hazards models. We also identified 14 studies on infant feeding and cancer published from 1966 through July 2005, of which 10 could be combined with the Boyd Orr cohort results in a meta-analysis of breast cancer using random-effect models.

RESULTS

In the Boyd Orr cohort, ever having been breast-fed, compared with never having been breast-fed, was not associated with the incidence of all cancers (hazard ratio [HR] = 1.07, 95% confidence interval [CI] = 0.89 to 1.28) or of any individual cancer type examined (prostate HR = 1.43, 95% CI = 0.58 to 3.52; breast HR = 1.62, 95% CI = 0.89 to 2.94; colorectal HR = 0.86, 95% CI = 0.45 to 1.63; gastric HR = 1.22, 95% CI = 0.47 to 3.15). In the meta-analysis, there was also no association between breast-feeding and breast cancer (regardless of menopausal status) (relative risk [RR] = 0.94, 95% CI = 0.85 to 1.04). However, breast-fed women had a reduced risk of premenopausal breast cancer (RR = 0.88, 95% CI = 0.79 to 0.98) but not of postmenopausal breast cancer (RR = 1.00, 95% CI = 0.86 to 1.16).

CONCLUSION

Ever having been breast-fed was not associated with overall breast cancer risk, although the meta-analysis revealed a reduced risk of premenopausal breast cancer in women who had been breast-fed.

Prenatal and perinatal correlates of adult mammographic breast density

BACKGROUND

Adult mammographic percent density is one of the strongest known risk factors for breast cancer. In utero exposure to high levels of endogenous estrogens (or other pregnancy hormones) has been hypothesized to increase breast cancer risk in later life. We examined the hypothesis that those factors associated with higher levels of estrogen during pregnancy or shortly after birth are associated with higher mammographic breast density in adulthood.

METHODS

We analyzed data on 1,893 women from 360 families in the Minnesota Breast Cancer Family Study who had screening mammograms, risk factor data, over age 40, and no history of breast cancer. Prenatal and perinatal risk factor data were ascertained using a mailed questionnaire. Mammographic percent density and dense area were estimated from the mediolateral oblique view using Cumulus, a computer-assisted thresholding program. Linear mixed effects models incorporating familial correlation were used to assess the association of risk factors with percent density, adjusting for age, weight, and other breast cancer risk factors, all at time of mammography.

RESULTS

The mean age at mammography was 60.4 years (range, 40-91 years), and 76% were postmenopausal. Among postmenopausal women, there was a positive association of birthweight with percent density (P trend <0.01), with an adjusted mean percent density of 17.1% for <2.95 kg versus 21.0% for > or = 3.75 kg. There were suggestive positive associations with gestational age (mean percent density of 16.7% for preterm birth, 20.2% for term birth, and 23.0% for late birth; P trend = 0.07), maternal eclampsia/preeclampsia (mean percent density of 19.9% for no and 14.6% for yes; P = 0.16), and being breast-fed as an infant (mean percent density of 18.2% for never and 20.0% for ever; P = 0.08). There was no association of percent density with maternal age, birth order, maternal use of alcohol or cigarettes, or neonatal jaundice. Except for being breast-fed, these associations showed similar but attenuated trends among premenopausal women, although none were statistically significant. The results for dense area paralleled the percent density results. The associations of gestational age and being breast-fed as an infant with percent density attenuated when included in the same model as birthweight.

CONCLUSIONS

Birthweight was positively associated with mammographic breast density and dense area among postmenopausal women and more weakly among premenopausal women, suggesting that it may be a marker of this early life exposure. These results offer some support to the hypothesis that pregnancy estrogens or other pregnancy changes may play a role in breast cancer etiology, and suggest that these factors may act in part through long-term effects on breast density.

Could associations between breastfeeding and insulin-like growth factors underlie associations of breastfeeding with adult chronic disease? The Avon Longitudinal Study of Parents and Children

OBJECTIVE

The influence of infant feeding method (breast/formula) on growth factor levels could underlie associations of breastfeeding with childhood growth and risk factors for cardiovascular disease. We investigated associations of having been breastfed with serum IGF-I and IGFBP-3 in childhood.

METHODS

Prospective birth cohort study (subsample of the Avon Longitudinal Study of Parents and Children, UK) based on 871 children born in 1991/1992 who underwent clinical follow-up and blood tests at age 7-8 years. A total of 488 (56%) children had complete data.

RESULTS

In children with complete data, the age- and sex-standardized IGF-I levels of those who were partially or exclusively breastfed were 6.1 and 13.8 ng/ml higher, respectively, than those who were never breastfed (increase in IGF-I levels per category of breastfeeding exclusivity: 7.1 ng/ml; 95% CI: 0.3-13.9; P = 0.04). In models also controlling for birthweight, gestational age, mother's age, and socioeconomic and dietary factors, the breastfeeding-IGF-I association was attenuated (regression coefficient: 3.3 ng/ml; -4.2-10.7; P = 0.4); further adjustment for IGFBP-3 made little difference (regression coefficient: 4.1 ng/ml; -2.8-10.9; P = 0.2). There was little evidence for an association between breastfeeding and IGFBP-3 or the molar ratio IGF-I/IGFBP-3.

CONCLUSIONS

The positive association between breastfeeding and IGF-I could be due to residual confounding or to chance. Nevertheless, the magnitude of the fully adjusted effect estimate and the novelty of the association suggest that larger studies should now be conducted to confirm or refute the hypothesis that variations in IGF-I by infant feeding mode explain associations of breastfeeding with health in later life.

Common risk factors of breast and ovarian cancer: recent view

Clinicians, epidemiologists, and public health specialists tend to examine breast and ovarian cancer separately. Although this seems fairly rational and expected, both malignancies are estrogen related and thus share many risk factors. In this review, we investigate the common familial, reproductive, anthropometric, nutritional, and lifestyle risk factors of breast and ovarian cancer. We believe that the parallel examination of the two cancer types could significantly contribute to an improved prevention of "gynecological cancer" as a whole.

Breastfeeding and breast cancer: a case-control study in Southern Brazil

To investigate the relationship between breastfeeding and breast cancer in Southern Brazil, a case-control design was employed, with two age-matched control groups. A total of 250 cases of breast cancer were identified in women from 20 to 60 years of age, with 1,020 hospital and community controls. The main study variables were occurrence of breastfeeding and duration of breastfeeding. A multivariate conditional logistic regression analysis was employed. According to the results, breastfeeding did not have a protective effect against breast cancer. The odds ratio (OR) for women who breastfed was 0.9 (95% CI: 0.8-1.2) compared to women who did not breastfeed. For women who breastfed for six months or less, the OR was 1.0 (95% CI: 0.6-1.8). In pre-menopausal women who breastfed for more than 25 months, the OR was 0.95 (95% CI: 0.5-3.5), and in post-menopausal women OR was 1.27 (95% CI: 0.5-3.1), compared to women who had not breastfeed.

Associations of adult measures of childhood growth with breast cancer: findings from the British Women's Heart and Health Study

Since the two components of adult height - leg length and trunk length - are poorly correlated with each other and appear to be influenced by different early life factors, examining their separate influence on breast cancer may provide additional insights into the mechanisms responsible for the positive association between adult height and breast cancer. In a cross-sectional study of 4286 women aged 60-79 years, in whom there were 170 cases of breast cancer, we found total height, leg length and trunk length were all modestly positively and linearly associated with breast cancer. The magnitudes of the associations of leg and trunk length were similar: fully adjusted odds ratio (95% confidence interval) of breast cancer for a one standard deviation (s.d.) increase in leg length 1.17 (0.98, 1.39) and for a 1 s.d. increase in trunk length 1.19 (0.99, 1.41). Self-reported birth weight (available on 33% of the sample) was positively and linearly associated with breast cancer: fully adjusted odds ratio of breast cancer for a 1 s.d. increase in birth weight 1.30 (0.93, 1.80). These associations were all independent of each other and other potential confounding factors and are likely to reflect different mechanisms by which factors operating prenatally and prepubertally influence breast cancer risk.

Early life predictors of chronic disease

Many chronic diseases may have their seeds early in life. Observations from the Dutch famine have taught us that the intrauterine environment is an important determinant of adult health. Birth weight has been related to cardiovascular disease (CVD), hypertension, diabetes, and cancer. Critical phases for adult obesity development include time periods between conception and adolescence. A life course approach to chronic disease prevention includes the study of maternal diet during pregnancy, intrauterine exposures, postnatal growth, and the adolescent period.

Exposures in childhood, adolescence and early adulthood and breast cancer risk: a systematic review of the literature

A growing body of work indicates that exposures over the life course have important roles to play in the aetiology of breast cancer. This review synthesises the literature that has been published in the area of early life events and female breast cancer risk. The review finds some evidence, primarily from cohort studies on the relationship between birthweight and breast cancer, to suggest that in utero events are related to breast cancer risk in adulthood. Strong evidence to support a positive association between height and breast cancer exists. Postulated mechanisms for this relationship include the role of early diet in subsequent disease risk, and the influence of endogenous growth factors mediating the relationship. There is some evidence to suggest that leg length is the component of height which is generating the observed associations between height and breast cancer. There is no consistent pattern of association between relative weight in childhood or adolescence and risk of breast cancer. The evidence to suggest an association between physical activity in early life and breast cancer risk is convincing from case-control studies, but is not fully substantiated by the results of three cohort studies. There are inconsistent results regarding the association between smoking at a young age and breast cancer risk. There is little evidence for an association between passive smoking in early life and breast cancer risk. No clear association between early drinking and breast cancer risk exists. These results are discussed in relation to possible underlying mechanisms and health promotion strategies which could reduce breast cancer risk.

General introduction to the importance of genomics in food biotechnology and nutrition

Knowledge of the human genome and other genomes, the selection of health-beneficial components, information and communication technology (ICT)-driven plant cultivation and small-scale processes will together change the agrofoods business from a rather low-tech to a high-tech (functional) foods business. ICT will provide consumers with information that in combination with their private genetic passport may be used to select those functional foods that are most beneficial for them.