Are children of older fathers at risk for genetic disorders?

Noninvasive Prenatal Screening for Single-Gene Disorders

Single-gene disorders (SGDs), also known as monogenic disorders, are caused by pathogenic variants at individual loci. Prenatal cell-free DNA screening for SGDs has been investigated for decades. Detecting paternal and de novo variants may be somewhat straightforward, whereas detecting maternally inherited variants poses a significant challenge. Although commercially available in both high-risk and low-risk patients, many limitations exist. The use of SGDs is not supported by professional medical societies.

A Comprehensive Approach to Care of Women of Advanced Maternal Age

Advanced maternal age, historically defined as ages 35 years and older, is used to describe the later years in the female reproductive life span when rates of adverse pregnancy outcomes increase. The preconception period represents an opportunity to ensure the use of safe medications and optimize care for medical comorbidities. Routine prenatal care should be augmented with counseling on fetal aneuploidy with a detailed anatomic survey. Surveillance for preterm labor and preeclampsia is recommended. Growth assessment and antepartum testing for specific women are advised, particularly those ages 40 years and older and those with select medical problems. Despite an increased incidence of complications, most women of advanced maternal age will have normal pregnancies and will benefit from the compassionate care provided by midwives, advanced practice registered nurses (including nurse practitioners and clinical nurse specialists), and perinatal nurses.

Parental age and risk of genetic syndromes predisposing to nervous system tumors: nested case-control study

Purpose

Phacomatoses are genetic syndromes that are associated with increased risk of developing nervous system tumors. Phacomatoses are usually inherited, but many develop de novo, with unknown etiology. In this population-based study, we investigated the effect of parental age on the risk of phacomatoses in offspring.

Patients and methods

The study was a population-based nested case–control study. All individuals born and residing in Sweden between January 1960 and December 2010 were eligible for inclusion. Using the Patient Register, 4625 phacomatosis cases were identified and further classified as familial or nonfamilial. Ten matched controls per case were randomly selected from the eligible population. Data were analyzed using conditional logistic regression. Analyses were conducted for neurofibromatosis alone (n=2089) and other phacomatoses combined (n=2536).

Results

Compared with offspring of fathers aged 25–29 years, increased risk estimates of nonfamilial neurofibromatosis were found for offspring of fathers aged 35–39 years (odds ratio [OR]=1.43 [95% CI 1.16–1.74]) and ≥40 years (OR =1.74 [95% CI 1.38–2.19]). For other nonfamilial phacomatoses, the risk estimate for offspring of fathers aged ≥40 years was OR =1.23 (95% CI 1.01–1.50). Paternal age was not associated with familial phacomatoses, and no consistent association was observed with maternal age.

Conclusion

The findings show a consistent increase in risk of de novo occurrence of phacomatoses predisposing to nervous system tumors in offspring with increasing paternal age, most pronounced for neurofibromatosis, while maternal age did not seem to influence the risk. These findings suggest an increasing rate of new mutations in the NF1 and NF2 genes in spermatozoa of older fathers.

Is advanced paternal age a health risk for the offspring?

In this article we review the epidemiologic evidence for adverse health effects in offspring of fathers of advanced age. First the evidence regarding fetal survival is addressed, and afterward we review the evidence regarding morbidity in children with older fathers. The adverse conditions most consistently associated with increased paternal age are stillbirths, musculo-skeletal syndromes, cleft palate, acute lymphoblastic leukemia and retinoblastoma, and neurodevelopmental disorders in the autism spectrum and schizophrenia. Finally, we consider the public health impact of the increasing paternal age. We conclude that the adverse health effects in children that might be caused by the present increase in paternal age are severe but quantitatively of minor importance. However, identification of morbidities that are more frequent in offspring of older fathers, after having taken any maternal age effects and other confounding into account, may lead to a better understanding of the pathogenesis behind such conditions.

The Concept of Schizophrenia: From Unity to Diversity

After over 100 years of research without clarifying the aetiology of schizophrenia, a look at the current state of knowledge in epidemiology, genetics, precursors, psychopathology, and outcome seems worthwhile. The disease concept, created by Kraepelin and modified by Bleuler, has a varied history. Today, schizophrenia is considered a polygenic disorder with onset in early adulthood, characterized by irregular psychotic episodes and functional impairment, but incident cases occur at all ages with marked differences in symptoms and social outcome. Men’s and women’s lifetime risk is nearly the same. At young age, women fall ill a few years later and less severely than men, men more rarely and less severely later in life. The underlying protective effect of oestrogen is antagonized by genetic load. The illness course is heterogeneous and depressive mood the most frequent symptom. Depression and schizophrenia are functionally associated, and affective and nonaffective psychoses do not split neatly. Most social consequences occur at the prodromal stage. Neither schizophrenia as such nor its main symptom dimensions regularly show pronounced deterioration over time. Schizophrenia is neither a residual state of a neurodevelopmental disorder nor a progressing neurodegenerative process. It reflects multifactorial CNS instability, which leads to cognitive deficits and symptom exacerbations.

New genetic testing in prenatal diagnosis

Determining a genetic diagnosis prenatally permits patients to make informed reproductive decisions and to be counseled about possible fetal outcomes. Therefore, it is important for the provider to be aware of the spectrum of genetic conditions and to use appropriate testing modality to obtain specific diagnosis. This article reviews genetic techniques available for prenatal diagnosis such as preimplantation genetic testing, chromosomal microarray, non-invasive prenatal screening, and next-generation sequencing. Chromosomal microarray has emerged as the first diagnostic test for evaluation of multiple congenital anomalies and developmental delay as most of the next-generation sequencing methods do not detect copy-number variants (CNVs). Exome sequencing and whole genome sequencing are time-consuming, so if this needs to be done to obtain an accurate genetic diagnosis, allow sufficient time.

The participation of prospective fathers in preconception care

We present the data of male participants in the Coordinating Center of the Hungarian Preconception Service (HPS), Budapest, 1984–2010. One of main objectives of the HPS was the incorporation of male partners of female participants into the preparation of childbirth. The HPS is based on three steps: (I) Reproductive health check-up. (II) A 3-month preparation for conception with the major determinants of the development of new life such as sex, health and/or some diseases. Smoking and illicit drug use cessation and limitation of alcohol intake was suggested in the male participants (III) to achieve optimal conception and better protection of early pregnancy. Pregnant women usually visit prenatal care clinics between the 7th and 12th gestational week when it is too late to reduce the risk of congenital abnormalities. Male participation in HPS will help to enhance use of appropriate preconception methods at the appropriate time.

Ionizing radiation-induced mutant frequencies increase transiently in male germ cells of older mice

Spontaneous mutant frequency in the male germline increases with age, thereby increasing the risk of siring offspring with genetic disorders. In the present study we investigated the effect of age on ionizing radiation-induced male germline mutagenesis. lacI transgenic mice were treated with ionizing radiation at 4-, 15- and 26-month-old, and mutant frequencies were determined for pachytene spermatocytes and round spermatids at 15 days or 49 days after ionizing radiation treatment. Cells collected 15 days after treatment were derivatives of irradiated differentiating spermatogenic cells while cells collected 49 days later were derivatives of spermatogonial stem cells. The results showed that (1) spontaneous mutant frequency increased in spermatogenic cells recovered from nonirradiated old mice (26-months-old), particularly in the round spermatids; (2) mutant frequencies were significantly increased in round spermatids obtained from middle-aged mice (15-months-old) and old age mice (26-months-old) at 15 and 49 days after irradiation compared to the sham-treated old mice; and (3) pachytene spermatocytes obtained from 15- or 26-month-old mice displayed a significantly increased mutant frequency at 15 days post irradiation. This study indicates that age modulates the mutagenic response to ionizing radiation in the male germline.

Why do women not prefer much older men? a hypothesis based on alterations in male reproductive physiology related to increased age

Evolutionary Psychology studies suggest that women prefer slightly older or similarly aged partners, although to date few hypotheses have been put forth to explain this pattern of choice. Several recent studies have shown changes in male reproductive parameters as a result of increased age. In the current review of medical literature, we found evidence that much older men are more likely to be infertile, women with much older partners are more likely to experience problems during pregnancy, and children of much older men are more likely to have genetic abnormalities. Based on these findings, we suggest that reproducing with much older men does not represent the best reproductive option for women, which would explain the female preference for only slightly older or similarly-aged mates.

Could autism with mental retardation result from digenism and frequent de novo mutations?

The high concordance for autism symptoms in monozygotic twin-pairs compared to di-zygotic twins and/or non-twin sib-ships suggests a high genetic determinism in autism. Those results have hypothesized multi-factorial determinism in accordance with family studies and mathematical models. However, linkage and association or candidate gene strategies have failed to-date to identify clearly involved mechanisms. Mental retardation (MR) is known as frequently associated to autism. Multiplex XLMR pedigrees have been reported with only one mutated patient having autism and MR: different X-located MR genes have been shown to be involved (NLGN4, MECP2, OPHN1, ZNF674 and FRAXA) which does not suggest that they could be "autism genes". Tuberous sclerosis studies and report of numerous autosomal domains shown deleted in MR-autistic subjects suggest that several autosomal dominant (AD) genes could be also involved in MR with autism. Whereas multiplex AD-MR families are rare, AD de novo mutations could explain numerous sporadic situations of non-specific MR and of autism with MR, in accordance with twin studies. Finally, we hypothesize that in those autistic subjects with mendelian MR, the XL-MR or AD-MR gene (G1) would pave the way for a second Mendelian factor (G2) responsible for autism symptoms.

Statement on guidance for genetic counseling in advanced paternal age

In 1996, a practice guideline on genetic counseling for advanced paternal age was published. The current document updates the state of knowledge of advanced paternal age effects on single gene mutations, chromosome anomalies, and complex traits.

Characteristics, causes and evolutionary consequences of male-biased mutation

Mutation has traditionally been considered a random process, but this paradigm is challenged by recent evidence of divergence rate heterogeneity in different genomic regions. One facet of mutation rate variation is the propensity for genetic change to correlate with the number of germ cell divisions, reflecting the replication-dependent origin of many mutations. Haldane was the first to connect this association of replication and mutation to the difference in the number of cell divisions in oogenesis (low) and spermatogenesis (usually high), and the resulting sex difference in the rate of mutation. The concept of male-biased mutation has been thoroughly analysed in recent years using an evolutionary approach, in which sequence divergence of autosomes and/or sex chromosomes are compared to allow inference about the relative contribution of mothers and fathers in the accumulation of mutations. For instance, assuming that a neutral sequence is analysed, that rate heterogeneity owing to other factors is cancelled out by the investigation of many loci and that the effect of ancestral polymorphism is properly taken into account, the male-to-female mutation rate ratio, alpham, can be solved from the observed difference in rate of X and Y chromosome divergence. The male mutation bias is positively correlated with the relative excess of cell divisions in the male compared to the female germ line, as evidenced by a generation time effect: in mammals, alpham is estimated at approximately 4-6 in primates, approximately 3 in carnivores and approximately 2 in small rodents. Another life-history correlate is sexual selection: when there is intense sperm competition among males, increased sperm production will be associated with a larger number of mitotic cell divisions in spermatogenesis and hence an increase in alpham. Male-biased mutation has implications for important aspects of evolutionary biology such as mate choice in relation to mutation load, sexual selection and the maintenance of genetic diversity despite strong directional selection, the tendency for a disproportionate large role of the X (Z) chromosome in post-zygotic isolation, and the evolution of sex.

Parental age at delivery and incidence of breast cancer: a prospective cohort study

BACKGROUND

Studies on parental age at delivery in relation to breast cancer risk have had mixed results, but prospective data are limited. No study has explored the associations with subtypes of breast cancer defined by hormonal receptor status.

METHODS

109,773 women in the Nurses' Health Study were followed from 1976 to 2002. We used Cox proportional hazards model to examine the association between parental age at delivery and daughters' risk of breast cancer.

RESULTS

6,827 incident cases of invasive breast cancer occurred in this cohort during 2,581,098 person-years. Adjusting for other early life exposures and family history of breast cancer, the hazard ratio for breast cancer in women born to mothers aged 21-25, 26-30, 31-35, and > or =36 years was, respectively, 1.08 (95% CI: 0.99-1.18), 1.12 (95% CI: 1.03-1.23), 1.17 (95% CI: 1.06-1.29), and 1.12 (95% CI: 1.01-1.25), compared to women born to mothers aged < or =20 years (P for trend = 0.008). Similarly, advanced paternal age was associated with increased incidence of breast cancer (P for trend = 0.03), but the association disappeared when conditioning on maternal age. The positive association between maternal age and incidence of breast cancer was stronger for estrogen receptor-positive and progesterone receptor-positive tumors (P for trend = 0.003) than for tumors with both receptors negative (P for trend = 0.78), and was more consistent among postmenopausal women, women without a family history and women who were first born.

CONCLUSION

Our findings support a modest positive association between maternal age and daughter's risk of breast cancer, possibly mediated by hormonal factors.

Age-related decline in sperm deoxyribonucleic acid integrity in patients evaluated for male infertility

The purpose of this study was to analyze the relationship of male age and DNA integrity in men presenting for investigation of infertility. We found that men 45 years and older had significantly greater DNA fragmentation than younger men.

Paternal age as a risk factor for low birthweight

OBJECTIVES

We examined associations between paternal age and low birth-weight in the US urban population.

METHODS

Using a population-based sample of 4621 births, we used multiple logistic regression analysis to estimate associations between paternal age and low birthweight, controlling for maternal age, other demographic factors, and the child's gender.

RESULTS

When the child's gender and the mother's race/ethnicity, birthplace, parity, marital status, and health insurance type were controlled, teenaged fathers were 20% less likely and fathers older than 34 years were 90% more likely than fathers aged 20 to 34 years to have low-birthweight babies. The associations were significant when maternal age was also controlled. No racial/ethnic differences in associations between paternal age and low birthweight were found.

CONCLUSIONS

We identified paternal age as an independent risk factor for low birthweight in the US urban population, suggesting that more attention needs to be paid to paternal influences on birth outcomes and to the interactive effects of urban environments and individual risk factors on health.

Effect of paternal age on the frequency of cytogenetic abnormalities in human spermatozoa

Many surveys have been performed to find etiological relationships between pregnancy outcome and specific risk factors, such as exposure to chemicals and radiation or parental age. Advanced maternal age is a strong risk factor for trisomic pregnancies, albeit there are considerable variations among the different chromosomes. The definite incidence of the various structural and numerical chromosome aberrations in spontaneous abortions and liveborns is well known, as well as the rate of maternally and paternally derived rearrangements. Nevertheless studies have failed to assert an age-dependent risk for men fathering chromosomally abnormal children. New techniques using fluorescence in situ hybridization render it possible to analyze spermatozoa directly for numerical and, to some extent, for structural aberrations. This article compiles the findings of studies on human spermatozoa over the last few years.

The evolutionary role of erectile dysfunction

Biologic processes that affect the ability of an organism to reproduce are subject to heavy evolutionary pressure. Erectile dysfunction (ED), a common condition in elderly males, definitely affects the ability of the organism to reproduce, and therefore, it is expected to play a significant evolutionary role. Whereas oogenesis is limited to young females, spermatogenesis is a lifelong process. As a male gets older, the number of (pre-meiotic) mitotic cell divisions during spermatogenesis increases, as does the risk of de novo gene mutations. In this paper, I examine the hypothesis that ED, in addition to decrease in fertility, are two evolutionary safety mechanisms that reduce the probability of an ovum being fertilized with genetically altered sperm from an aged or sick male. This hypothesis is supported by the parallel rise in the occurrence of ED, infertility, and risk of congenital anomalies with age; by the occurrence of these three processes in the same medical conditions; and by the presence of a theory unifying the etiologies of three processes-the "free radical theory of aging". This hypothesis can predict the occurrence of congenital anomalies under conditions associated with ED and infertility but are presently not known to be associated with congenital anomalies.

Sperm concentration and normal sperm morphology decrease and follicle-stimulating hormone level increases with age

OBJECTIVE

To assess hormone levels, testicular volume, and semen characteristics of fertile men of various age groups.

PATIENTS AND METHODS

The records of 889 men who sought a vasectomy between September 1999 and March 2003 were reviewed. Patients were divided into five groups by age; we evaluated semen volume, sperm concentration, motility, morphology and complex sperm motion variables. Follicle-stimulating hormone (FSH), luteinizing hormone (LH), testosterone levels and both testicular volumes were compared.

RESULTS

There were no differences among the groups in the levels of LH, testosterone, or right and left testicular volumes. There were differences among the five groups in FSH levels, semen volume, sperm concentration and motility. Normal morphology according to the World Health Organisation criteria was significantly lower in patients aged > 45 years. From a linear regression analysis, semen volume, sperm concentration and motility decreased by 0.01 mL, 2.1%, and 0.27%, respectively, per year, and the FSH level increased by 0.27%.

CONCLUSIONS

Sperm concentration and motility decrease and FSH levels increase with age. Normal sperm morphology decreases from 45 years old. Thus, the ageing effect should be considered when proposing standard values for semen characteristics in routine semen analysis.

Association of paternal age at birth and the risk of breast cancer in offspring: a case control study

Background

Older paternal age may increase the germ cell mutation rate in the offspring. Maternal age may also mediate in utero exposure to pregnancy hormones in the offspring. To evaluate the association between paternal and maternal age at birth with the risk of breast cancer in female offspring, a case-control study was conducted in Korea.

Methods

Histologically confirmed breast cancer cases (n = 1,011) and controls (n = 1,011) with no present or previous history of cancer, matched on year of birth and menopausal status, were selected from several teaching hospitals and community in Seoul during 1995–2003. Information on paternal and maternal ages and other factors was collected by interviewed questionnaire. Odds ratio (OR) and 95% confidence interval (95% CI) were estimated by unconditional logistic regression model adjusting for family history of breast cancer in 1^st or 2^nd degree relatives, and lifetime estrogen exposure duration.

Results

The risk of breast cancer significantly increased as the paternal age increased (p for trend = 0.025). The association was stronger after controlling for maternal age; women whose fathers were aged ≥40 years at their birth had 1.6-fold increased risk of breast cancer compared with fathers aged <30 years. This association was profound in breast cancer cases in premenopausal women (OR = 1.9, 95% CI = 1.12–3.26, for paternal aged ≥40 vs. <30) (p for trend = 0.031). Although the risk of breast cancer increased as maternal age increased up to the intermediate, and then reduced; the risks in women whose mother were aged 25–29, 30–34, and ≥35 yrs at birth compared to women whose mothers were aged <25 years, were 1.2, 1.4, and 0.8, respectively, the trend was not significant (p for trend = 0.998).

Conclusion

These findings suggest that older paternal age increases the risk of breast cancer in their female offspring.

Male-driven evolution in closely related species of the mouse genus Mus

Recently, other researchers have found that closely related primate species had a lower male-to-female mutation rate ratio (alpha) than distantly related species. To determine if this is a general phenomenon affecting other mammalian orders, eleven species or subspecies of the rodent genus Mus and two outgroup species were compared. Intron sequences from a gene in the nonrecombining region of the Y chromosome Jarid1d (Smcy) and its X chromosomal gametolog, Jarid1c (Smcx), were analyzed in a phylogenetic context. The male-to-female mutation rate ratio for all thirteen taxa is approximately 2.5, which is similar to previous estimates in more distantly related rodents. However, when branches with lengths of more than 2.5% were removed from the analysis, the male-to-female mutation rate ratio dropped to 0.9. Thus, in closely related rodents, as in closely related primates, the male-to-female mutation rate ratio is lower than expected.