Parental age effects and Rett syndrome

Rett syndrome (RTT) is a progressive neurodevelopmental disorder, and pathogenic Methyl-CpG-binding Protein 2 (MECP2) variants are identified in >95% of individuals with typical RTT. Most of RTT-causing variants in MECP2 are de novo and usually on the paternally inherited X chromosome. While paternal age has been reported to be associated with increased risk of genetic disorders, it is unknown whether parental age contributes to the risk of the development of RTT. Clinical data including parental age, RTT diagnostic status, and clinical severity are collected from 1226 participants with RTT and confirmed MECP2 variants. Statistical analyses are performed using Student t-test, single factor analysis of variance (ANOVA), and multi-factor regression. No significant difference is observed in parental ages of RTT probands compared to that of the general population. A small increase in parental ages is observed in participants with missense variants compared to those with nonsense variants. When we evaluate the association between clinical severity and parental ages by multiple regression analysis, there is no clear association between clinical severity and parental ages. Advanced parental ages do not appear to be a risk factor for RTT, and do not contribute to the clinical severity in individuals with RTT.

Early-life telomeres are influenced by environments acting at multiple temporal and spatial scales

An individual's telomere length early in life may reflect or contribute to key life-history processes sensitive to environmental variation. Yet, the relative importance of genetic and environmental factors in shaping early-life telomere length is not well understood as it requires samples collected from multiple generations with known developmental histories. We used a confirmed pedigree and conducted an animal model analysis of telomere lengths obtained from nestling house sparrows (Passer domesticus) sampled over a span of 22 years. We found significant additive genetic variation for early-life telomere length, but it comprised a small proportion (9%) of the total biological variation. Three sources of environmental variation were important: among cohorts, among-breeding attempts within years, and among nestmates. The magnitude of variation among breeding attempts and among nestmates also differed by cohort, suggesting that interactive effects of environmental factors across time or spatial scales were important, yet we were unable to identify the specific causes of these interactions. The mean amount of precipitation during the breeding season positively predicted telomere length, but neither weather during a given breeding attempt nor date in the breeding season contributed to an offspring's telomere length. At the level of individual nestlings, offspring sex, size and mass at 10 days of age also did not predict telomere length. Environmental effects appear especially important in shaping early-life telomere length in some species, and more focus on how environmental factors that interact across scales may help to explain some of the variation observed among studies.

An Observational Case-Control Study on Parental Age and Childhood Renal Tumors

Despite excellent outcomes, many open questions remain about Wilms tumor (WT). Influences and risk factors for tumorigenesis, as well as tumor aggressiveness and recurrence, are not fully understood. Parental age plays a role in various childhood diseases and is also discussed as a risk factor for childhood cancer. We analyzed both maternal and paternal age at birth as risk factors for the occurrence of Wilms and non-Wilms tumors in children and investigated whether older maternal or paternal age is associated with a higher tumor incidence. During 1990 and 2019 we collected data from 3991 patients from the multicenter studies SIOP9/GPO, SIOP 93-01/GPOH, and SIOP 2001/GPOH, of whom maternal and paternal age was available in 2277 cases. Data from the Federal Statistical Office containing live births in Germany from 1990-2019 served as a comparative database. For maternal age at birth, the control data yielded 22,451,412 cases and for paternal age yielded 19,046,314 cases. Comparing maternal and paternal ages of the study patients with those of the control data, we confirmed that higher parental age is not correlated with the incidence of renal tumors in childhood. Mean ages of fathers and mothers in patients and the control cohort increased between 1991 and 2019 (fathers: 30.28 vs. 34.04; mothers: 27.68 vs. 29.79 in the patient group and 31.29 vs. 34.23 and 28.88 vs. 32.67 in the control group, respectively) without higher numbers of patients with kidney cancer over time. No influence was found for the subtype of cancer nor for syndromes. In addition, overall survival of patients is independent of the year of diagnosis and the age of the parents but depends on histology type and stage in WT.

Parental age at birth and biomarkers of fecundity in young Danish men

BACKGROUND

High parental age is associated with adverse birth and genetic outcomes, but little is known about fecundity in male offspring.

OBJECTIVES

We investigated if high parental age at birth was associated with biomarkers of male fecundity in a large population-based sample of young men.

MATERIALS AND METHODS

We conducted a study of 1057 men from the Fetal Programming of Semen Quality (FEPOS) cohort, a sub-cohort of sons born 1998-2000 into the Danish National Birth Cohort. Semen characteristics and reproductive hormone concentrations were measured in samples provided by the men 2017-2019. Testis volume was determined by self-measurement. Data on the parental age was drawn from registers. Adjusted relative difference in percentage with 95% confidence intervals were estimated for each outcome according to pre-specified maternal and paternal age groups (< 30 (reference), 30-34 and ≥ 35) as well as for combinations of parental age groups, using multivariable negative binomial regression models.

RESULTS

We did not observe consistent associations between parental age and biomarkers of fecundity, although sons of mothers ≥ 35 years had lower sperm concentration (-15% (95% CI: -30, 3)) and total sperm count (-10% (95% CI: -25, 9)). The analysis with parental age combinations showed lower sperm concentration with high age of the parents (both ≥ 35 years: -27%, 95% CI: -40, -19) when compared to the reference where both parents were below 30 years.

DISCUSSION AND CONCLUSION

We found no strong association between higher parental age and biomarkers of fecundity in young men. However, we cannot exclude poorer semen characteristics in sons born by older mothers or with high age of both parents.

Associations between accelerated parental biologic age, autism spectrum disorder, social traits, and developmental and cognitive outcomes in their children

Parental age is a known risk factor for autism spectrum disorder (ASD), however, studies to identify the biologic changes underpinning this association are limited. In recent years, "epigenetic clock" algorithms have been developed to estimate biologic age and to evaluate how the epigenetic aging impacts health and disease. In this study, we examined the relationship between parental epigenetic aging and their child's prospective risk of ASD and autism related quantitative traits in the Early Autism Risk Longitudinal Investigation study. Estimates of epigenetic age were computed using three robust clock algorithms and DNA methylation measures from the Infinium HumanMethylation450k platform for maternal blood and paternal blood specimens collected during pregnancy. Epigenetic age acceleration was defined as the residual of regressing chronological age on epigenetic age while accounting for cell type proportions. Multinomial logistic regression and linear regression models were completed adjusting for potential confounders for both maternal epigenetic age acceleration (n = 163) and paternal epigenetic age acceleration (n = 80). We found accelerated epigenetic aging in mothers estimated by Hannum's clock was significantly associated with lower cognitive ability and function in offspring at 12 months, as measured by Mullen Scales of Early Learning scores (β = -1.66, 95% CI: -3.28, -0.04 for a one-unit increase). We also observed a marginal association between accelerated maternal epigenetic aging by Horvath's clock and increased odds of ASD in offspring at 36 months of age (aOR = 1.12, 95% CI: 0.99, 1.26). By contrast, fathers accelerated aging was marginally associated with decreased ASD risk in their offspring (aOR = 0.83, 95% CI: 0.68, 1.01). Our findings suggest epigenetic aging could play a role in parental age risks on child brain development.

Causes and consequences of variation in development time in a field cricket

Variation in development time can affect life-history traits that contribute to fitness. In Gryllus vocalis, a non-diapausing cricket with variable development time, we used a path analysis approach to determine the causative relationships between parental age, offspring development time and offspring life-history traits. Our best-supported path model included both the effects of parental age and offspring development time on offspring morphological traits. This result suggests that offspring traits are influenced by both variation in acquisition of resources and trade-offs between traits. We found that crickets with longer development times became larger adults with better phenoloxidase-based immunity. This is consistent with the hypothesis that crickets must make a trade-off between developing quickly to avoid predation before reproduction and attaining better immunity and a larger adult body size that provides advantages in male-male competition, mate choice and female fecundity. Slower-developing crickets were also more likely to be short-winged (unable to disperse by flight). Parental age has opposing direct and indirect effects on the body size of daughters, but when both the direct and indirect effects of parental age are taken into account, younger parents had smaller sons and daughters. This pattern may be attributable to a parental trade-off between the number and size of eggs produced with younger parents producing more eggs with fewer resources per egg. The relationships between variables in the life-history traits of sons and daughters were similar, suggesting that parental age and development time had similar causative effects on male and female life-history traits.

Parental age and autism severity in the Rhode Island Consortium for Autism Research and Treatment (RI-CART) study

Advanced parental age at offspring birth has been associated with autism spectrum disorder (ASD). The objective of the current study was to investigate associations between parental age at birth and autism severity. The Rhode Island Consortium for Autism Research and Treatment (RI-CART) study represents a community-based sample with a range of autism severity, including participants with and without ASD. This study involved participants (n = 1178) enrolled in RI-CART with available mother and father ages at birth. Primary data points included the age of mother and father at the participant's birth and results from the Autism Diagnostic Observation Schedule - Second Edition (ADOS-2). Mothers were 1.7 years older at the time of birth of the child with ASD, as compared to mothers of offspring without ASD. Fathers of children with ASD were 1.6 years older at the time of birth than fathers of children without ASD. The age of both parents at offspring birth displayed a positive, statistically significant association with overall ASD severity and the severity of restricted/repetitive behaviors. This finding was driven by the association between parental age and the severity of compulsions or rituals. Intelligence and adaptive functioning did not moderate the relationship between parental age and ASD severity. This study extends prior research to show that advanced parental age at birth is associated with the severity as well as the presence of ASD in offspring.

The role of sperm and oocyte in fetal programming: Is Lamarck making a comeback?

Compelling evidence has shown that parental experiences and age at conception may potentially shape the future health of the next generation(s). Certain factors may affect both the female and, strikingly, the male gametes potentially causing the transmission of acquired traits, which was strongly defended by Jean-Baptiste Lamarck. Neurodevelopmental psychiatric disorders, trinucleotide repeat-associated diseases, cardiovascular pathologies, diabetes, obesity and cancer in the offspring, among others, have now been associated with events occurring at the preconception level. The potential implications of a (trans)generational inheritance of parental disease and exposure effects should be taken into account in counselling and public policy. Further research into how exactly gametes apparently deliver more than DNA to a new generation is warranted.

Parental Age and the Risk of ADHD in Offspring: A Systematic Review and Meta-Analysis

Evidence has suggested that parental age at birth is a risk factor of offspring attention deficit/hyperactivity disorder (ADHD). We conducted a meta-analysis of observational studies investigating the association between parental age and offspring ADHD. We conducted a systematic search that followed the recommended guidelines for performing meta-analyses on PUBMED, EMBASE, and Web of Science up to 8 April 2021. We calculated pooled risk estimates from individual age with and without adjusting for possible confounding factors. Dose–response analysis for parental age and ADHD risk was performed. Eleven studies were selected in this meta-analysis, which included 111,101 cases and 4,417,148 participants. Compared with the reference points, the lowest parental age category was associated with an increased risk of ADHD in the offspring, with adjusted odds ratios (ORs) of 1.49 (95% confidence intervals (95%CI) 1.19–1.87) and 1.75 (95%CI 1.31–2.36) for the mother and father, respectively. The highest parental age was statistically insignificant, with adjusted ORs of 1.11 (95%CI 0.79–1.55) and 0.93 (95%CI 0.70–1.23) for mother and father separately. Dose–response analysis indicated a non-linear relationship of parental age with offspring ADHD, with the lowest ADHD risk at 31–35 years old. The results of this meta-analysis support an association between young parental age and the risk of ADHD. More high-quality studies are needed to establish whether the association with parental age is causal.

Parental Risk Factors and Child Birth Data in a Matched Year and Sex Group Cleft Population: A Case-Control Study

(1) Background: The etiology of orofacial cleft (OC) is not completely known but several genetic and environmental risk factors have been identified. Moreover, a knowledge gap still persists regarding neonatal characteristics. This study evaluated the effect of parental age and mothers’ body mass index on the risk of having an OC child, in a matched year and sex group (cleft/healthy control). Additionally, birth data were analyzed between groups. (2) Methods: 266 individuals born between 1995 to 2015 were evaluated: 133 OC individuals (85 males/48 females) and 133 control (85 males/48 females). A logistic model was used for the independent variables. ANOVA or Kruskal-Wallis tests were used for comparison between the OC phenotypes. (3) Results: Regarding statistically significant parental related factors, the probability of having a cleft child decreases for each maternal year increase (odds ratio = 0.903) and increases for each body mass index unit (kg/m²) increase (odds ratio = 1.14). On the child data birth, for each mass unit (kg) increase, the probability of having a cleft child decrease (odds ratio = 0.435). (4) Conclusions: In this study, only maternal body mass index and maternal age found statistical differences in the risk of having a cleft child. In the children’s initial data, the cleft group found a higher risk of having a lower birth weight but no relation was found regarding length and head circumference.

Parental Effects on Epigenetic Programming in Gametes and Embryos of Dairy Cows

The bovine represents an important agriculture species and dairy breeds have experienced intense genetic selection over the last decades. The selection of breeders focused initially on milk production, but now includes feed efficiency, health, and fertility, although these traits show lower heritability. The non-genetic paternal and maternal effects on the next generation represent a new research topic that is part of epigenetics. The evidence for embryo programming from both parents is increasing. Both oocytes and spermatozoa carry methylation marks, histones modifications, small RNAs, and chromatin state variations. These epigenetic modifications may remain active in the early zygote and influence the embryonic period and beyond. In this paper, we review parental non-genetic effects retained in gametes on early embryo development of dairy cows, with emphasis on parental age (around puberty), the metabolism of the mother at the time of conception and in vitro culture (IVC) conditions. In our recent findings, transcriptomic signatures and DNA methylation patterns of blastocysts and gametes originating from various parental and IVC conditions revealed surprisingly similar results. Embryos from all these experiments displayed a metabolic signature that could be described as an "economy" mode where protein synthesis is reduced, mitochondria are considered less functional. In the absence of any significant phenotype, these results indicated a possible similar adaptation of the embryo to younger parental age, post-partum metabolic status and IVC conditions mediated by epigenetic factors.

Parental Age at Conception and the Relationship with Severity of Autism Symptoms

BACKGROUND

Previous research has examined the relationship between advanced parental age at conception and the incidence of autism, and has noted strong relationships between advanced parental age and other developmental disabilities.

AIM

The purpose of this study was to confirm that and extend that knowledge to the association between advanced parental age and severity of autism symptoms as measured by a parental report of ASD symptom severity.

METHODS

The current study included 252 participants between the ages of 2-17 years and their parents.

RESULTS

Child's gender and paternal age were found to be significant predictors of autism severity with males and children with older fathers at conception showing the highest severity. Interestingly, maternal age was not found to be a significant predictor of autism risk or severity of symptoms in this sample.

CONCLUSION

Possible explanations for these findings are discussed, as well as future directions for research in this area.

The Association Between Parental Age and Autism-Related Outcomes in Children at High Familial Risk for Autism

Advanced parental age is a well-replicated risk factor for autism spectrum disorder (ASD), a neurodevelopmental condition with a complex and not well-defined etiology. We sought to determine parental age associations with ASD-related outcomes in subjects at high familial risk for ASD. A total of 397 younger siblings of a child with ASD, drawn from existing prospective high familial risk cohorts, were included in these analyses. Overall, we did not observe significant associations of advanced parental age with clinical ASD diagnosis, Social Responsiveness Scale, or Vineland Adaptive Behavior Scales scores. Instead, increased odds of ASD were found with paternal age < 30 years (adjusted odds ratio [AOR] = 2.83 and 95% confidence intervals [CI] = 1.14-7.02). Likewise, younger age (<30 years) for both parents was associated with decreases in Mullen Scales of Early Learning early learning composite (MSEL-ELC) scores (adjusted β = -9.62, 95% CI = -17.1 to -2.15). We also found significant increases in cognitive functioning based on MSEL-ELC scores with increasing paternal age (adjusted β associated with a 10-year increase in paternal age = 5.51, 95% CI = 0.70-10.3). Results suggest the potential for a different relationship between parental age and ASD-related outcomes in families with elevated ASD risk than has been observed in general population samples. Autism Res 2020, 13: 998-1010. © 2020 International Society for Autism Research, Wiley Periodicals, Inc. LAY SUMMARY: Previous work suggests that older parents have a greater likelihood of having a child with autism. We investigated this relationship in the younger siblings of families who already had a child with autism. In this setting, we found a higher likelihood of autism, as well as poorer cognitive scores, in the siblings with younger fathers, and higher cognitive scores in the siblings with older parents. These results suggest that parental age associations may differ based on children's familial risk for autism.

Levels of Heterochiasmy During Arabidopsis Development as Reported by Fluorescent Tagged Lines

Crossing over, the exchange of DNA between the chromosomes during meiosis, contributes significantly to genetic variation. The rate of crossovers (CO) varies depending upon the taxon, population, age, external conditions, and also, sometimes, between the sexes, a phenomenon called heterochiasmy. In the model plant Arabidopsis thaliana, the male rate of all crossover events (mCO) is typically nearly double the female rate (fCO). A previous, PCR-based genotyping study has reported that the disparity decreases with increasing parental age, because fCO rises while mCO remains stable. We revisited this topic using a fluorescent tagged lines approach to examine how heterochiasmy responded to parental age in eight genomic intervals distributed across the organism’s five chromosomes. We determined recombination frequency for, on average, more than 2000 seeds, for each interval, for each of four age groups, to estimate sex-specific CO rates. mCO did not change with age, as reported previously, but, here, fCO did not rise, and thus the levels of heterochiasmy were unchanged. We can see no methodological reason to doubt that our results reflect the underlying biology of the accessions we studied. The lack of response to age could perhaps be due to previously reported variation in CO rate among accessions of Arabidopsis.

The deteriorating soma and the indispensable germline: gamete senescence and offspring fitness

The idea that there is an impenetrable barrier that separates the germline and soma has shaped much thinking in evolutionary biology and in many other disciplines. However, recent research has revealed that the so-called 'Weismann Barrier' is leaky, and that information is transferred from soma to germline. Moreover, the germline itself is now known to age, and to be influenced by an age-related deterioration of the soma that houses and protects it. This could reduce the likelihood of successful reproduction by old individuals, but also lead to long-term deleterious consequences for any offspring that they do produce (including a shortened lifespan). Here, we review the evidence from a diverse and multidisciplinary literature for senescence in the germline and its consequences; we also examine the underlying mechanisms responsible, emphasizing changes in mutation rate, telomere loss, and impaired mitochondrial function in gametes. We consider the effect on life-history evolution, particularly reproductive scheduling and mate choice. Throughout, we draw attention to unresolved issues, new questions to consider, and areas where more research is needed. We also highlight the need for a more comparative approach that would reveal the diversity of processes that organisms have evolved to slow or halt age-related germline deterioration.

Parental Age and Differential Estimates of Risk for Neuropsychiatric Disorders: Findings From the Danish Birth Cohort

OBJECTIVE

Parental age at birth has been shown to affect the rates of a range of neurodevelopmental disorders, but the understanding of the mechanisms through which it mediates different outcomes is still lacking. A population-based cohort was used to assess differential effects of parental age on estimates of risk across pediatric-onset neuropsychiatric disorders: autism spectrum disorder (ASD), attention-deficit/hyperactivity disorder (ADHD), obsessive-compulsive disorder (OCD), and Tourette's disorder/chronic tic disorder (TD/CT).

METHOD

The study cohort included all singleton births in Denmark from 1980 through 2007 with full information on parental ages (N = 1,490,745) and was followed through December 31, 2013. Cases of ASD, ADHD, OCD, and TD/CT were identified in the Danish Psychiatric Central Register and the National Patient Register. Associations with parental age were modeled using a stratified Cox regression, allowing for changes in baseline diagnostic rates across time.

RESULTS

Younger parental age was significantly associated with increased estimates of risk for ADHD and TD/CT, whereas older parental age was associated with ASD and OCD. Except for OCD, no evidence for differential effects of parental ages on male versus female offspring was observed.

CONCLUSION

This study provides novel evidence for the association between age at parenthood and TD/CT and OCD and for the first time shows in a population-based sample that parental age confers differential risk rates for pediatric-onset psychiatric disorders. These results are consistent with a model of shared and unshared risk architecture for pediatric-onset neuropsychiatric conditions, highlighting unique contributions of maternal and paternal ages.

Mother's age at delivery and daughters' risk of preeclampsia

BACKGROUND

Some cardiovascular disease risk factors are associated with both risk of preeclampsia and having been born to a younger or older mother. We examined whether mother's age at delivery predicts a primiparous daughter's risk of preeclampsia.

METHODS

The analysis included 39 803 Sister Study participants (designated as "daughters") born between 1930 and 1974. Using log-binomial regression, we estimated relative risks (RR) of preeclampsia in the first pregnancy ending in birth ("primiparous preeclampsia") associated with mother's age at the daughter's birth. Models included: number of older full and maternal half-siblings, income level growing up, daughter's age at delivery, race/ethnicity, and 5-year birth cohort. We examined self-reported relative weight at age 10 (heavier than peers versus not) as a potential effect measure modifier.

RESULTS

Overall, 6.2% of daughters reported preeclampsia. Compared with those who had been born to 20-24-year old mothers, daughters of teenage mothers had a relative risk of 1.20 (95% confidence interval (CI) 1.01, 1.43) and daughters of mothers ≥25 had a ~10% lower risk. Relative weight at age 10 modified the association, with an inverse association between mother's age at delivery and preeclampsia seen only among daughters with low/normal childhood relative weight. In this subset, results were consistent across strata of daughter's age at menarche and age at first birth.

CONCLUSIONS

These findings, based on self-reported data, require replication. Nevertheless, as women increasingly delay childbearing, they provide some reassurance that having been born to an older mother is not, per se, a risk factor for primiparous preeclampsia.

Paternal and maternal age as risk factors for schizophrenia: a case-control study

OBJECTIVE

Advanced parental age might constitute a generic risk factor for mental and somatic disorders. The current study tested whether this concerns also patients with schizophrenia.

METHODS

A total of 231 schizophrenic, 56 other severe mental disorders patients and 204 controls were diagnosed according to DSM-IV-TR. Data were tested with ANOVA models including relative risk and odds ratios.

RESULTS

Patients with schizophrenia manifested higher paternal (32.55 ± 6.35 vs. 29.42 ± 6.07, p < .001) and maternal age (27.66 ± 5.57 vs. 25.46 ± 4.52, p < .001). Patients with other mental disorders had higher paternal (33.29 ± 8.35; p = .001) but not maternal age (26.69 ± 5.89; p = .296) compared to controls. There was no difference between the two patient groups concerning either paternal or maternal age (p > .05). There seems to be a higher risk for the development of schizophrenia in offspring with paternal age above 25 years and maternal age above 22 years at delivery.

CONCLUSIONS

The current study provides further support for the suggestion that advanced paternal age constitutes a risk factor (in a non-dose dependent and gender-independent way) for the development of schizophrenia but also for other mental disorders. In contrast, advanced maternal age characterises schizophrenia specifically. The higher risk is evident after 25 years of paternal and 22 years of maternal age, respectively.

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.

Parental age and attention-deficit/hyperactivity disorder (ADHD)

Background

Previous studies have suggested that young mothers more often have children with ADHD. We used sibling comparisons to examine the nature of this association and to investigate if this association is explained by early environment or genetic and socioeconomic factors.

Methods

A large population-based cohort including all singletons born in Denmark from 1 January 1991 through 31 December 2005 was followed from birth until 30 April 2011. Data were available for 94% ( N  = 943 785) of the population. Offspring ADHD was identified by an ICD-10 diagnosis of Hyperkinetic Disorder (HKD). We used sibling-matched Cox regression to control for genetic and socioeconomic factors.

Results

In the population cohort we found that children born by parents aged 20 years or younger had more than twice the risk of being diagnosed with ADHD compared with children with parents between 26 and 30 years of age. When comparing full siblings the associations were attenuated, but we found a trend of increased risk of ADHD with decreasing maternal age, which was not seen for paternal age.

Conclusions

Sibling comparisons suggested that the associations between both maternal and paternal age and ADHD are partly explained by common genetic and socioeconomic factors. The trend of increased risk of ADHD with decreasing maternal age, but not with paternal age, may be linked to pregnancy or early-life environmental factors. Even though only a smaller part of the association can be attributed to environmental factors, there is a public health interest to support young parents through their first years of parenthood.

Offspring telomere length in the long lived Alpine swift is negatively related to the age of their biological father and foster mother

A growing body of studies is showing that offspring telomere length (TL) can be influenced by the age of their parents. Such a relationship might be explained by variation in TL at conception (gamete effect) and/or by alteration of early growth conditions in species providing parental care. In a long-lived bird with bi-parental care, the Alpine swift (Apus melba), we exchanged an uneven number of 2 to 4-day-old nestlings between pairs as part of a brood size manipulation. Nestling TL was measured at 50 days after hatching, which allowed investigation of the influence of the age of both their biological and foster parents on offspring TL, after controlling for the manipulation. Nestling TL was negatively related to the age of their biological father and foster mother. Nestling TL did not differ between enlarged and reduced broods. These findings suggest that offspring from older males were fertilized by gametes with shorter telomeres, presumably due to a greater cell division history or a longer accumulation of damage, and that older females may have provided poorer parental care to their offspring.

Male-biased sex allocation in ageing parents; a longitudinal study in a long-lived seabird

Optimal sex allocation is frequency-dependent, but senescence may cause behaviour at old age to be suboptimal. We investigated whether sex allocation changes with parental age, using 16 years of data comprising more than 2500 molecularly sexed offspring of more than 600 known-age parents in common terns (Sterna hirundo), slightly sexually size-dimorphic seabirds. We decomposed parental age effects into within-individual change and sex allocation-associated selective (dis)appearance. Individual parents did not differ consistently in sex allocation, but offspring sex ratios at fledging changed from female- to male-biased as parents aged. Sex ratios at hatching were not related to parental age, suggesting sons to outperform daughters after hatching in broods of old parents. Our results call for the integration of sex allocation theory with theory on ageing and demography, as a change in sex allocation with age per se will cause the age structure of a population to affect the frequency-dependent benefits and the age-specific strength of selection on sex allocation.

Parental Age and Risk of Pediatric Cancer in the Offspring: A Population-Based Record-Linkage Study in California

Linking birth records and cancer registry data from California, we conducted a population-based study with 23,419 cases and 87,593 matched controls born during 1978-2009 to investigate the relationship of parental age to risk of pediatric cancer. Compared with children born to mothers aged 20-24 years, those born to mothers in older age groups had a 13%-36% higher risk of pediatric cancer; the odds ratio for each 5-year increase in maternal age was 1.06 (95% confidence interval (CI): 1.04, 1.09). For cancer diagnosed in children in age groups 0-14 years and 15-19 years, the odds ratios for each 5-year increase in maternal age were 1.05 (95% CI: 1.02, 1.07) and 1.14 (95% CI: 1.09, 1.19), respectively. Having an older father also conferred an increased risk, with an odds ratio for each 5-year increase of 1.03 (95% CI: 1.02, 1.05) for cancer diagnosed at ages 0-19 years and 1.03 (95% CI: 1.02, 1.05) for cancer diagnosed at ages 0-14 years. While advancing maternal age increased risk of leukemia and central nervous system tumors, older paternal age was not associated with risk of either type. Both maternal and paternal older ages were associated with risk of lymphoma. In this large, population-based record-linkage study, advancing parental age, especially advancing maternal age, was associated with higher pediatric cancer risk, with variations across types of cancer.

Parental Age and Offspring Psychopathology in the Philadelphia Neurodevelopmental Cohort

OBJECTIVE

Increasing evidence implicates advanced paternal age at offspring birth in neuropsychiatric disorders. Advanced maternal age has also been associated with schizophrenia and other neurodevelopmental disorders, whereas younger maternal age has been linked with behavioral disorders. Few studies have considered the specificity of the associations with respect to comorbidity. In addition, most prior studies have been conducted in clinical samples or registries that may reflect more severe forms of psychopathology. The aim of this research is to examine the independent and joint associations of maternal and paternal age with specific subtypes of psychopathology in offspring in a pediatric sample of adolescents with emergent psychiatric syndromes.

METHOD

A total of 8,725 youths (aged 8-21 years) from the Philadelphia Neurodevelopmental Cohort were included in the analyses. Logistic regression models with parental age predicting offspring psychopathology were adjusted for sociodemographic factors and comorbid disorders.

RESULTS

We found that younger parental ages were generally associated with increased rates of offspring psychopathology. After controlling for sociodemographic characteristics and comorbidity, both younger maternal and paternal ages were associated with behavior syndromes and psychosis in youth, whereas advanced paternal age was associated with pervasive developmental disorders/autism spectrum disorder (PDD/ASD).

CONCLUSION

These findings suggest that both younger and older parental age at birth are associated with specific forms of psychopathology in offspring. The persistence of the influence of parental age after control for demographic factors and an index of social environment suggests that additional explanations for these findings should be examined in future studies.

Aging parasites produce offspring with poor fitness prospects

Senescing individuals have poor survival prospects and low fecundity. They can also produce offspring with reduced survival and reproductive success. We tested the effect of parental age on the performance of descendants in the nematode Heligmosomoides polygyrus, an intestinal parasite of rodents. We found that offspring of senescing worms had reduced within-host survival and reduced egg shedding over the first month post-infection compared with offspring produced by young parents. These results suggest that declining offspring quality is a component of senescence in parasitic nematodes and might have evolutionary consequences for the optimal schedule of age-dependent investment into reproductive effort.

Examining genotypic variation in autism spectrum disorder and its relationship to parental age and phenotype

Background

Previous studies on genetic testing of chromosomal abnormalities in individuals diagnosed with autism spectrum disorder (ASD) found that ~80% have negative genetic test results (NGTRs) and ~20% have positive genetic test results (PGTRs), of which ~7% were probable de novo mutations (PDNMs). Research suggests that parental age is a risk factor for an ASD diagnosis. This study examined genotypic variation in ASD and its relationship to parental age and phenotype.

Methods

Phenotype was derived from detailed clinical information, and genotype was derived from high-resolution blood chromosome and blood whole-genome copy number variant genetic testing on a consecutive cohort (born: 1983–2009) of subjects diagnosed with ASD (N=218).

Results

Among the subjects examined, 80.3% had NGTRs and 19.7% had PGTRs, of which 6.9% had PDNMs. NGTR subjects were born more recently (the risk of PDNMs decreasing by 12% per more recent birth year) and tended to have an increased male–female ratio compared to PDNM subjects. PDNM subjects had significantly increased mean parental age and paternal age at subject’s birth (the risk of a PDNM increasing by 7%–8% per year of parental or paternal age) compared to NGTR subjects. PGTR and NGTR subjects showed significant improvements in speech/language/communication with increasing age. PGTR subjects showed significant improvements in sociability, a core feature of an ASD diagnosis, with increasing age, whereas NGTR subjects showed significant worsening in sociability with increasing age.

Conclusion

This study helps to elucidate different phenotypic ASD subtypes and may even indicate the need for differential diagnostic classifications.

Parental age influences developmental stability of the progeny in Drosophila

The stochastic nature of biochemical processes is a source of variability that influences developmental stability. Developmental instability (DI) is often estimated through fluctuating asymmetry (FA), a parameter that deals with within-individual variation in bilateral structures. A relevant goal is to shed light on how environment, physiology and genotype relate to DI, thus providing a more comprehensive view of organismal development. Using Drosophila melanogaster isogenic lines, we investigated the effect of parental age, parental diet and offspring heterozygosity on DI. In this work, we have uncovered a clear relationship between parental age and offspring asymmetry. We show that asymmetry of the progeny increases concomitantly with parental age. Moreover, we demonstrate that enriching the diet of parents mitigates the effect of age on offspring symmetry. We show as well that increasing the heterozygosity of the progeny eliminates the effect of parental age on offspring symmetry. Taken together, our results suggest that diet, genotype and age of the parents interact to determine offspring DI in wild populations. These findings provide us with an avenue to understand the mechanisms underlying DI.

Parental age and the risk of attention-deficit/hyperactivity disorder: a nationwide, population-based cohort study

OBJECTIVE

An increasing number of studies has shown an association between parental age and psychiatric disorders. However, there are inconsistent results regarding whether age at parenthood is associated with attention-deficit/hyperactivity disorder (ADHD). The aim of this study is to examine whether low or advanced parental age is associated with ADHD.

METHOD

In this nested case-control study, we identified 10,409 individuals with ADHD born in Finland during 1991 to 2005 and diagnosed with ADHD between 1995 and 2011, along with 39,125 controls matched on sex, date, and place of birth, from nationwide population-based registers. Conditional logistic regression was used to examine the association between parental age and ADHD in offspring, adjusting for potential confounding due to parental psychiatric history, maternal socioeconomic status, marital status, maternal smoking during pregnancy, number of previous births, and birth weight for gestational age.

RESULTS

Fathers younger than 20 years had a 1.5-fold (odds ratio [OR] = 1.55, 95% CI = 1.11-2.18, p = .01) increased risk of having offspring with ADHD as compared to fathers aged 25 to 29 years. Mothers of the same age group had a 1.4-fold (OR = 1.41, 95% CI = 1.15-1.72, p =.0009) increased risk. Advanced maternal age was inversely associated with ADHD (OR = 0.79, 95% CI = 0.64-0.97, p = .02).

CONCLUSION

ADHD was associated with young fathers or mothers at the time of birth. Health professionals working with young parents should be aware of the increased risk of ADHD in offspring. This will improve early detection; however, for the development of preventive measures and appropriate interventions, more information on the developmental pathways is needed.

Parental age and the risk of bipolar disorders

OBJECTIVES

Studies on the association between parental age and bipolar disorder (BPD) are scarce and with inconsistent findings. The aim of this study was to examine the association of parental age and age difference between parents with risk of BPD in offspring.

METHODS

This nested case-control study identified 1,861 cases of individuals with BPD born in Finland during 1983-1998 and diagnosed by the end of 2008, and 3,643 sex- and date of birth-matched controls from nationwide population-based registers. Conditional logistic regression was used to examine the association adjusting for potential confounding due to age of the other parent, parental psychiatric history, educational level, and place of birth.

RESULTS

A U-shaped association of unadjusted odds ratios (ORs) for BPD risk was seen in different paternal age categories, with the odds increasing at both ends of the age spectrum. In the adjusted analyses, offspring of fathers aged ≥ 50 years had a 2.8-fold increased odds [OR = 2.84, 95% confidence interval (CI): 1.32-6.12] of BPD as compared to those with fathers aged 30-34 years. The odds were increased 1.3-fold (OR = 1.35, CI: 1.06-1.72) in fathers aged 20-24 years. No significant association was found between maternal age and BPD in the adjusted analyses. Age difference between parents was not associated with BPD.

CONCLUSIONS

The increased risk of BPD in offspring of the youngest and oldest fathers in the study suggests the involvement of different biological and psychosocial factors at the two ends of the paternal age spectrum. These findings may be significant in the context of advancing parental age in recent times.

Parental age and the risk of autism spectrum disorders: findings from a Swedish population-based cohort

BACKGROUND

The objectives of this study were to examine the independent and dependent associations of maternal and paternal age and risk of offspring autism spectrum disorders (ASD), with and without intellectual disability (ID).

METHODS

The sample consisted of 417 303 Swedish children born 1984-2003. ASD case status (N = 4746) was ascertained using national and regional registers. Smoothing splines in generalized additive models were used to estimate associations of parental age with ASD.

RESULTS

Whereas advancing parental age increased the risk of child ASD, maternal age effects were non-linear and paternal age effects were linear. Compared with mothers at the median age 29 years, those <29 had similar risk, whereas risk increased after age 30, with an odds ratio (OR) of 1.75 [95% (CI): 1.63-1.89] at ages 40-45. For fathers, compared with the median age of 32 years, the OR for ages 55-59 was 1.39 (1.29-1.50). The risk of ASD was greater for older mothers as compared with older fathers. For example, mothers aged 40-45 (≥97.2th percentile) had an estimated 18.63 (95% CI: 17.25-20.01) ASD cases per 1000 births, whereas fathers aged 55-59 (≥99.7th percentile) had 16.35 (95% CI: 15.11-17.58) ASD cases per 1000 births. In analyses stratified by co-parental age, increased risk due to advancing paternal age was evident only with mothers ≤35 years. In contrast, advancing maternal age increased risk regardless of paternal age. Advancing parental age was more strongly associated with ASD with ID, compared with ASD without ID.

CONCLUSIONS

We confirm prior findings that advancing parental age increases risk of ASD, particularly for ASD with ID, in a manner dependent on co-parental age. Although recent attention has emphasized the effects of older fathers on ASD risk, an increase of n years in maternal age has greater implications for ASD risk than a similar increase in paternal age.

Parental age effects on cortical morphology in offspring

The age at which a parent has a child impacts the child's cognition and risk for mental illness. It appears that this risk is curvilinear, with both age extremes associated with lower intelligence and increased prevalence of some neuropsychiatric disorders. Little is known of the neural mechanisms underpinning this phenomenon. We extracted lobar volumes, surface areas, and cortical thickness from 489 neuroanatomic magnetic resonance images acquired on 171 youth. Using linear mixed model regression, we determined the association between parental age and offspring's neuroanatomy, adjusting for offspring's age, sex, intelligence, and parental socioeconomic class. For gray matter volumes, quadratic paternal and maternal age terms contributed significantly (maternal quadratic age effect: t = -2.2, P = 0.03; paternal quadratic age effect: t = -2.4, P = 0.02) delineating an inverted "U" relationship between parental age and gray matter volume. Cortical volume increased with both advancing paternal and maternal age until around the early 30s after which it fell. Paternal age effects were more pronounced on cortical surface area, whereas maternal age impacted more on cortical thickness. There were no significant effects of parental age on white matter volumes. These parental age effects on cerebral morphology may form part of the link between parental age extremes and suboptimal neurocognitive outcomes.

Advanced parental age at birth is associated with poorer social functioning in adolescent males: shedding light on a core symptom of schizophrenia and autism

BACKGROUND

Evidence indicates an association between older parents at birth and increased risk for schizophrenia and autism. Patients with schizophrenia and autism and their first-degree relatives have impaired social functioning; hence, impaired social functioning is probably an intermediate phenotype of the illness. This study tested the hypothesis that advanced father's age at birth would be associated with poorer social functioning in the general population. To test this hypothesis, we examined the association between parental age at birth and the social functioning of their adolescent male offspring in a population-based study.

METHODS

Subjects were 403486, 16- to 17-year-old Israeli-born male adolescents assessed by the Israeli Draft Board. The effect of parental age on social functioning was assessed in analyses controlling for cognitive functioning, the other parent's age, parental socioeconomic status, birth order, and year of draft board assessment.

RESULTS

Compared with offspring of parents aged 25-29 years, the prevalence of poor social functioning was increased both in offspring of fathers younger than 20 years (odds ratio [OR] = 1.27, 95% confidence interval [CI] = 1.08-1.49) and in offspring of fathers 45 years old (OR = 1.52, 95% CI = 1.43-1.61). Male adolescent children of mothers aged 40 years and above were 1.15 (95% CI = 1.07-1.24) times more likely to have poor social functioning.

CONCLUSIONS

These modest associations between parental age and poor social functioning in the general population parallel the associations between parental age and risk for schizophrenia and autism and suggest that the risk pathways between advanced parental age and schizophrenia and autism might, at least partially, include mildly deleterious effects on social functioning.

Positive experiences of teenage motherhood: a qualitative study

BACKGROUND

Teenage pregnancy is seen as a cause for concern in the United Kingdom (UK). However, there has been little research from primary care looking at teenage motherhood and its implications.

AIM

To investigate the experiences of teenage mothers in relation to their role as mothers and their expectations of their futures.

DESIGN OF STUDY

Qualitative study.

SETTING

East Devon, England.

METHOD

Nine women who had conceived their first child while still a teenager agreed to participate. Semi-structured interviews were undertaken, audiotaped, transcribed, and analysed using interpretative phenomenological analysis.

RESULTS

The women expressed positive attitudes to being mothers and described how it had affected their lives. For some, motherhood had been the impetus to change direction and consider a career, because they had someone else for whom they were responsible. They recognised that they were still young enough to enter further education or other aspects of employment as their children grew up.

CONCLUSIONS

For the women in this study, having been a teenage mother did not mean that their life and future were all over. Motherhood and bringing up children were valued in their own right. The women were realistic about their futures, often making plans to develop their careers.