Does having children extend life span? A genealogical study of parity and longevity in the Amish

The CFTR Met 470 allele is associated with lower birth rates in fertile men from a population isolate

Although little is known about the role of the cystic fibrosis transmembrane regulator (CFTR) gene in reproductive physiology, numerous variants in this gene have been implicated in etiology of male infertility due to congenital bilateral absence of the vas deferens (CBAVD). Here, we studied the fertility effects of three CBAVD–associated CFTR polymorphisms, the (TG)m and polyT repeat polymorphisms in intron 8 and Met470Val in exon 10, in healthy men of European descent. Homozygosity for the Met470 allele was associated with lower birth rates, defined as the number of births per year of marriage (P = 0.0029). The Met470Val locus explained 4.36% of the phenotypic variance in birth rate, and men homozygous for the Met470 allele had 0.56 fewer children on average compared to Val470 carrier men. The derived Val470 allele occurs at high frequencies in non-African populations (allele frequency  = 0.51 in HapMap CEU), whereas it is very rare in African population (Fst  = 0.43 between HapMap CEU and YRI). In addition, haplotypes bearing Val470 show a lack of genetic diversity and are thus longer than haplotypes bearing Met470 (measured by an integrated haplotype score [iHS] of −1.93 in HapMap CEU). The fraction of SNPs in the HapMap Phase2 data set with more extreme Fst and iHS measures is 0.003, consistent with a selective sweep outside of Africa. The fertility advantage conferred by Val470 relative to Met470 may provide a selective mechanism for these population genetic observations.

Cystic fibrosis (CF) is the most common lethal recessive disorder in European-derived populations and is characterized by clinical heterogeneity that involves multiple organ systems. Over 1,600 disease-causing mutations have been identified in the cystic fibrosis transmembrane regulator (CFTR) gene, but our understanding of genotype–phenotype correlations is incomplete. Male infertility is a common feature in CF patients; but, curiously, CF–causing mutations are also found in infertile men who do not exhibit any other CF–related complications. In addition, three common polymorphisms in CFTR have been associated with infertility in otherwise healthy men. We studied these three polymorphisms in fertile men and show that one, called Met470Val, is associated with variation in male fertility and shows a signature of positive selection. We suggest that the Val470 allele has risen to high frequencies in European populations due a fertility advantage but that other genetic and, possibly, environmental factors have tempered the magnitude of these effects during human evolution.

PedHunter 2.0 and its usage to characterize the founder structure of the Old Order Amish of Lancaster County

BACKGROUND

Because they are a closed founder population, the Old Order Amish (OOA) of Lancaster County have been the subject of many medical genetics studies. We constructed four versions of Anabaptist Genealogy Database (AGDB) using three sources of genealogies and multiple updates. In addition, we developed PedHunter, a suite of query software that can solve pedigree-related problems automatically and systematically.

METHODS

We report on how we have used new features in PedHunter to quantify the number and expected genetic contribution of founders to the OOA. The queries and utility of PedHunter programs are illustrated by examples using AGDB in this paper. For example, we calculated the number of founders expected to be contributing genetic material to the present-day living OOA and estimated the mean relative founder representation for each founder. New features in PedHunter also include pedigree trimming and pedigree renumbering, which should prove useful for studying large pedigrees.

RESULTS

With PedHunter version 2.0 querying AGDB version 4.0, we identified 34,160 presumed living OOA individuals and connected them into a 14-generation pedigree descending from 554 founders (332 females and 222 males) after trimming. From the analysis of cumulative mean relative founder representation, 128 founders (78 females and 50 males) accounted for over 95% of the mean relative founder contribution among living OOA descendants.

DISCUSSION/CONCLUSIONS

The OOA are a closed founder population in which a modest number of founders account for the genetic variation present in the current OOA population. Improvements to the PedHunter software will be useful in future studies of both the OOA and other populations with large and computerized genealogies.

Female fertility and longevity

Does bearing children shorten a woman's life expectancy? Pleiotropic theories of aging predict that it should, and in particular, the Disposable Soma theory predicts unequivocally that this effect should be inescapable. But many demographic studies, historic and current, have found no such effect. In this context,the Caerphilly cohort study stands apart as the sole test that corroborates the theory. Why has this study found an effect that others fail to see? Their analysis is based on Poisson regression, a statistical technique that is accurate only if the underlying data are Poisson distributed.But the distribution of the number of children born to women in the Caerphilly data based departs strongly from Poisson at the high end. This makes the result overly sensitive to a handful of women with 15 children or more who lived before 1700. When these five women are removed from a database of more than 2,900, the Poisson regression no longer shows a significant result. Bilinear regression relating life span to fertility and date of birth results in a small positive coefficient for fertility, in agreement with the main trend of reported results.

Familial aggregation of survival and late female reproduction

Women giving birth at advanced reproductive ages in natural fertility conditions have been shown to have superior postmenopausal longevity. It is unknown whether improved survival is more likely among relatives of late-fertile women. This study compares survival past age 50 of men with and without a late-fertile sister in two populations: Utahns born in 1800-1869 identified from the Utah Population Database and Québec residents born in 1670-1750 identified from the Programme de recherche en démographie historique. Male survival was greater for those with, rather than without, a sister reproducing after age 45, particularly among men with at least three sisters (Utah rate ratio [RR] = .801, 95% CI = 0.687-0.940; Quebec RR = .786, 95% CI = 0.664-0.931). Survival of wives was unaffected by whether their husbands had a late-fertile sister, suggesting a weak influence of unmeasured socioenvironmental factors. These results support the hypothesis that late female fertility and slow somatic aging may be promoted by the same genetic variants.

Lifespan is unrelated to investment in reproduction in populations of mammals and birds in captivity

We examined the relationship between number of offspring produced to a certain age and subsequent longevity in captive zoo populations of 18 species of mammal and 12 species of bird. The age cut-offs in each analysis were set to include 50%, 75% and 90% of the offspring produced in each of the population samples. Only one of 68 regressions was significant, and its slope was positive. In addition, we examined the relationship between age at first reproduction up to a certain age and longevity after that age, generally 5 years (3-8), among 17 species of mammal and 12 species of bird. Only one of these regressions had a significantly positive slope, indicating that early reproduction rarely reduces lifespan. Overall, we found no evidence that producing offspring in a zoo environment influences the age at death. Thus, although trade-offs might apply in natural populations under resource limitation, neither pregnancy, growth of the foetus and lactation in mammals, nor egg production in birds, reduces lifespan in the absence of such stress. If genetically based or other intrinsic antagonistic pleiotropy underlies the evolution of senescence, it was not evident in our analyses.

Early childbearing, marital status, and women's health and mortality after age 50

This article examines the relationship between a woman's childbearing history and her later health and mortality, with primary focus on whether the association between them is due to early and later socioeconomic status. Data are drawn from the Health and Retirement Study birth cohort of 1931-1941. Results indicate that, conditional on reaching midlife and controlling for early and later socioeconomic status, a first birth before age 20 is associated with a higher hazard of dying. In addition, having an early birth is associated with a higher prevalence of reported heart disease, lung disease, and cancer in 1994. Being unmarried at the time of the first birth is associated with earlier mortality, but this association disappears when midlife socioeconomic status is controlled. The number of children ever born does not significantly affect mortality but is associated with prevalence of diabetes.

Does reproduction decrease longevity in human beings?

According to the disposable soma theory, a cost for reproduction could exist in human beings and other species and, thus, longevity could decrease when women have a higher number of children. The purpose of this article is to review the evidence in populations living or not living under natural fertility conditions, i.e. when fertility is near its biological maximum. The results indicate that in natural fertility conditions longevity does not decrease when the number of children increases but, in modern populations, mortality could slightly increase when women have more than ca 5 children. Complete data for these modern cohorts will tell us, one day, whether these results are still observed when the variable of interest is longevity and not only mortality.

[Factors influencing pulmonary function in Tunisian women aged 45 years and more]

INTRODUCTION

The aim of this study was to analyse the factors influencing pulmonary function and inspiratory muscle strength in healthy Tunisian women aged >or=45 years and in particular to determine the effect of parity.

METHODS

A medical questionnaire together with an evaluation of sporting activity score and 2 levels for schooling and socio-economic status was administered. Parity was introduced as numeric, as dichotomous (G1:<or=3; G2: >or=4) and in 3 classes (C1:<2; C2:=3-4; C3: > 4). Plethysmography with measurement of airway conductance and maximal inspiratory pressure was performed.

RESULTS

108 women were included. According to the ascending multiple linear regression, and in decreasing order, the following influencing factors are noted: Age and height, parity, weight and daily activity, schooling level, and finally leisure activity, body mass index, and physical activity. With high parity, and especially in women aged >or=60 years, there was a decrease in inspiratory muscle strength and an obstructive tendency, without associated restrictive component. Parity effects are age independent.

CONCLUSIONS

Factors influencing the pulmonary function of healthy Tunisian women aged >or=45 years are multiple. Lung function declines with increasing parity.