Association between number of children and mortality of mothers: results of a 37-year follow-up study

The Trade-Off between Female Fertility and Longevity during the Epidemiological Transition in the Netherlands

Several hypotheses have been put forward to explain the relationship between women's fertility and their post-reproductive longevity. In this study, we focus on the disposable soma theory, which posits that a negative relationship between women's fertility and longevity can be understood as an evolutionary trade-off between reproduction and survival. We examine the relationship between fertility and longevity during the epidemiological transition in the Netherlands. This period of rapid decline in mortality from infectious diseases offers a good opportunity to study the relationship between fertility and longevity, using registry data from 6,359 women born in The Netherlands between 1850 and 1910. We hypothesize that an initially negative relationship between women's fertility and their longevity gradually turns less negative during the epidemiological transition, because of decreasing costs of higher parities. An initially inversed U-shaped association between fertility and longevity changes to zero during the epidemiological transition. This does suggest a diminishing environmental pressure on fertility. However, we find no evidence of an initial linear trade-off between fertility and post-reproductive survival.

Grand multiparity and reproductive cancer in the Jerusalem Perinatal Study Cohort

OBJECTIVES

Grand multiparity is associated with reduced mortality from reproductive cancers. We aimed to separate the components of mortality, by measuring incidence of and survival after reproductive cancer onset in grand multiparous compared to other parous women.

STUDY DESIGN

We linked data from the population-based Jerusalem Perinatal Study Cohort, which included women aged 13-55 who delivered 1964-1976, with Israel's National Cancer Registry. We compared breast and gynecologic cancer risk and all-cause survival following a cancer diagnosis, among grand multiparae (GMPs = parity 5+, n = 8,246) versus women with parity 1-4 (n = 19,703), adjusting for reproductive and demographic variables.

RESULTS

Grand multiparae were at significantly lower risk of breast cancer than others (adjusted hazard ratio (HRadj) = 0.62, 95 % confidence interval (CI) 0.54-0.71), after controlling for age at first birth, education, and other covariates. This reduction was greater among GMPs whose first birth occurred after age 30 (p-interaction = 0.0001) and for cancer occurring before age 50 years (p = 0.002). In contrast, GMPs were at greater risk of death than women with parity <5, following a breast cancer diagnosis (HRadj = 1.69, CI 1.39-2.1). Ovarian, uterine, and cervical cancer incidence did not differ between the groups, but survival was reduced for GMPs with uterine cancer (HRadj = 2.48, CI 1.22-5.03).

CONCLUSION

Reduced reproductive cancer mortality reported among GMPs masks two opposing phenomena: decreased breast cancer risk and poorer survival after breast and uterine cancers. The latter unfavorable outcome suggests that tumors in GMPs may be particularly aggressive, having perhaps escaped protective mechanisms conferred by parity. This finding calls for heightened clinical attention in this group.

Low dose radiation and circulatory diseases: a brief narrative review

Exposure to high doses of ionizing radiation is associated with damage to the heart and coronary arteries. However, only recently have studies with high-quality individual dosimetry data allowed this risk to be estimated while adjusting for concomitant chemotherapy. An association between lower dose exposures and late-occurring circulatory disease has only recently been suspected in the Japanese atomic bomb survivors and in various occupationally exposed cohorts and is still controversial. Excess relative risks per unit dose in moderate- and low-dose epidemiological studies are variable, possibly resulting from confounding and effect-modification by well known (but unobserved) risk factors. Here, we summarize the evidence for a causal association between moderate- and low-level radiation exposure (whether at high or low dose rates) and circulatory disease.

Reproductive factors and risk of mortality in the European Prospective Investigation into Cancer and Nutrition; a cohort study

BACKGROUND

Reproductive events are associated with important physiologic changes, yet little is known about how reproductive factors influence long-term health in women. Our objective was to assess the relation of reproductive characteristics with all-cause and cause-specific mortality risk.

METHODS

The analysis was performed within the European Investigation into Cancer and Nutrition prospective cohort study, which enrolled >500,000 women and men from 1992 to 2000, who were residing in a given town/geographic area in 10 European countries. The current analysis included 322,972 eligible women aged 25-70 years with 99 % complete follow-up for vital status. We assessed reproductive characteristics reported at the study baseline including parity, age at the first birth, breastfeeding, infertility, oral contraceptive use, age at menarche and menopause, total ovulatory years, and history of oophorectomy/hysterectomy. Hazard ratios (HRs) and 95 % confidence intervals (CIs) for mortality were determined using Cox proportional hazards regression models adjusted for menopausal status, body mass index, physical activity, education level, and smoking status/intensity and duration.

RESULTS

During a mean follow-up of 12.9 years, 14,383 deaths occurred. The HR (95 % CI) for risk of all-cause mortality was lower in parous versus nulliparous women (0.80; 0.76-0.84), in women who had ever versus never breastfed (0.92; 0.87-0.97), in ever versus never users of oral contraceptives (among non-smokers; 0.90; 0.86-0.95), and in women reporting a later age at menarche (≥15 years versus <12; 0.90; 0.85-0.96; P for trend = 0.038).

CONCLUSIONS

Childbirth, breastfeeding, oral contraceptive use, and a later age at menarche were associated with better health outcomes. These findings may contribute to the development of improved strategies to promote better long-term health in women.

Parity and Cardiovascular Disease Mortality: a Dose-Response Meta-Analysis of Cohort Studies

Parity has been shown to inversely associate with cardiovascular disease (CVD) mortality, but the evidence of epidemiological studies is still controversial. Therefore, we quantitatively assessed the relationship between parity and CVD mortality by summarizing the evidence from prospective studies. We searched MEDLINE (PubMed), EMBASE and ISI Web of Science databases for relevant prospective studies of parity and CVD mortality through the end of March 2015. Fixed- or random-effects models were used to estimate summary relative risks (RRs) and 95% confidence intervals (CIs). Heterogeneity among studies was assessed using the I² statistics. All statistical tests were two-sided. Ten prospective studies were included with a total of 994,810 participants and 16,601 CVD events. A borderline significant inverse association was observed while comparing parity with nulliparous, with summarized RR = 0.79 (95% CI: 0.60–1.06; I² = 90.9%, P < 0.001). In dose-response analysis, we observed a significant nonlinear association between parity number and CVD mortality. The greatest risk reduction appeared when the parity number reached four. The findings of this meta-analysis suggests that ever parity is inversely related to CVD mortality. Furthermore, there is a statistically significant nonlinear inverse association between parity number and CVD mortality.

Natural fertility and longevity

Much empirical work suggests an association between fertility patterns and longevity. I review this association, focusing on natural fertility populations and emphasizing the role of both the timing and the intensity of fertility. Overall, it appears that although age at last reproduction routinely correlates with post-reproductive longevity, suggesting a slower rate of senescence among late fertile women, the same is not true for age at first reproduction and parity. I discuss some of the conceptual and methodologic issues, as well as the sources of the biases, that have been a persistent feature of this body of research. I conclude by suggesting avenues of research that could be initiated or pursued in the area.

Immune Sensitization and Mortality in Wait-Listed Kidney Transplant Candidates

Cardiovascular mortality is the leading cause of death in ESRD. Whereas innate and adaptive immunity have established roles in cardiovascular disease, the role of humoral immunity is unknown. We conducted a retrospective cohort study in first-time adult kidney transplant candidates (N=161,308) using data from the Scientific Registry of Transplant Recipients and the Centers for Medicare and Medicaid Services to evaluate whether anti-human leukocyte antigen antibodies, measured as panel reactive antibodies (PRAs), are related to mortality in ESRD. Relationships between time-varying PRAs and all-cause or cardiovascular mortality were assessed using Cox proportional hazards models. The analysis was repeated in subcohorts of candidates at lower risk for significant comorbidities, activated on the waiting list after 2007, or unsensitized at activation. Competing risks analyses were also conducted. Fully adjusted models showed increased hazard ratios (HRs [95% confidence intervals]) for all-cause mortality (HR, 1.02 [95% CI, 0.99 to 1.06]; HR, 1.11 [95% CI,1.07 to 1.16]; and HR,1.21 [95% CI,1.15 to 1.27]) and cardiovascular mortality (HR, 1.05 [95% CI,1.00 to 1.10]; HR,1.11 [95% CI,1.05 to 1.18]; and HR,1.21 [95% CI,1.12 to 1.31]) in PRA 1%-19%, PRA 20%-79%, and PRA 80%-100% categories compared with PRA 0%, respectively. Associations between PRA and the study outcomes were accentuated in competing risks models and in lower-risk patients and persisted in other subcohorts. Our findings suggest that PRA is an independent predictor of mortality in wait-listed kidney transplant candidates. The mechanisms by which PRA confers an incremental mortality risk in sensitized patients, and the role of transplantation in modifying this risk, warrant further study.

Association between number of live births and markers of subclinical atherosclerosis: The Dallas Heart Study

AIMS

Higher parity has been associated with increased maternal risk of cardiovascular disease, but the mechanism is not well delineated. Whether the number of live births is associated with coronary and aortic subclinical atherosclerosis has not been fully evaluated.

METHODS AND RESULTS

Women from the Dallas Heart Study, a multiethnic population-based cohort of subjects aged 30-65 years, were included if they had data on self-reported live births and coronary artery calcium (CAC) measured by computed tomography or aortic wall thickness (AWT) by MRI. Coronary artery calcium was positive if >10 Agatston units, and aortic wall thickness if greater than the 75(th) percentile reference point for age and gender. Among the 1644 women included in the study, the mean age was 45 years and 55% were Black. Sequential multivariable models were done adjusting for age, race, traditional cardiovascular risk factors, body mass index, income, education, hormone replacement therapy, oral contraceptives, and physical activity. Using women with 2-3 live births as the reference, those with four or more live births had an increased prevalence of elevated coronary artery calcium (odds ratio (OR) 2.2, 95% confidence interval (CI) 1.28-3.65) and aortic wall thickness (OR 1.6, 95% CI 1.04-2.41). Women with 0-1 live births also had increased coronary artery calcium (OR 1.9, 95% CI 1.16-3.03) and aortic wall thickness (OR 1.5, 95% CI 1.05-2.09) after multivariable adjustment.

CONCLUSION

The number of live births is associated with subclinical coronary and aortic atherosclerosis, with an apparent U-shaped relationship. Further studies are needed to confirm this association and explore the biological underpinnings of these findings.

Influence of late-age births on maternal longevity

PURPOSE

To examine the association between the mother's age at last birth and maternal long-term survival.

METHODS

Data from three national censuses (1972, 1983, and 1995) and national birth and death records (1972-2009) were used to examine the association between age at last birth and mortality while accounting for potential confounders, such as parity. Age-adjusted mortality rates and Cox proportional hazard models were used in the analysis.

RESULTS

A total of 887 women who delivered their last child after 45 years of age were identified from among 178,507 women (1,592,379 person-years). Age-adjusted mortality rates from 55 years of age were highest for childless women (9.2 per 1000) and decreased linearly (P < .001) for parous women with increased age at last birth (5.2 per 1000 for women aged ≥45 years at last birth). In models adjusted for age at first birth and parity, mortality risks were lowest among parous women with late-age births (≥45 years) compared with parous women with their last births before 35 years of age (hazard ratio, 0.58; 95% confidence interval, 0.40-0.86).

CONCLUSIONS

This study provides new empirical evidence that late-age births are associated with maternal longevity, although a direct causal relation cannot be established with the information available.

Determinants of exceptional human longevity: new ideas and findings

Studies of centenarians are useful in identifying factors leading to long life and avoidance of fatal diseases. In this article we consider several approaches to study effects of early-life and midlife conditions on survival to advanced ages: use of non-biological relatives as controls, the within-family analysis, as well as a sampling of controls from the same population universe as centenarians. These approaches are illustrated using data on American centenarians, their relatives and unrelated shorter-lived controls obtained from the online genealogies. The within-family analysis revealed that young maternal age at person's birth is associated with higher chances of exceptional longevity. Comparison of centenarians and their shorter-lived peers (died at age 65 and sampled from the same pool of online genealogies) confirmed that birth timing in the second half of the calendar year predicts survival to age 100. Parental longevity as well as some childhood and midlife characteristics also proved to be significant predictors of exceptional longevity.