Parental age and offspring mortality: Negative effects of reproductive ageing may be counterbalanced by secular increases in longevity

Parental age at conception on mouse lemur's offspring longevity: Sex-specific maternal effects

Parental age at conception often influences offspring's longevity, a phenomenon referred as the "Lansing effect" described in large variety of organisms. But, the majority of the results refer to the survival of juveniles, mainly explained by an inadequate parental care by the elderly parents, mostly the mothers. Studies on the effect of parental age on offspring's longevity in adulthood remain few, except in humans for whom effects of parental age vary according to statistical models or socioeconomic environments. In a small primate in which the longevity reaches up to 13 years, we investigated the effects of parental age at conception on the longevity of offspring (N = 278) issued from parents with known longevity. None of the postnatal parameters (body mass at 30 and 60 days after birth, size and composition of the litter) influenced offspring's longevity. Mothers' age at conception negatively affected offspring's longevity in males but not in females. By contrast, fathers' age at conception did not influence offspring's longevity. Finally, the longevity of female offspring was significantly positively related to the longevity of both parents. Compared with current studies, the surprisingly minor effect of fathers 'age was related to the high seasonal reproduction and the particular telomere biology of mouse lemurs.

What have we learned about mortality patterns over the past 25 years?

In this paper, I examine progress in the field of mortality over the past 25 years. I argue that we have been most successful in taking advantage of an increasingly data-rich environment to improve aggregate mortality models and test pre-existing theories. Less progress has been made in relating our estimates of mortality risk at the individual level to broader mortality patterns at the population level while appropriately accounting for contextual differences and compositional change. Overall, I find that the field of mortality continues to be highly visible in demographic journals, including Population Studies. However much of what is published today in field journals could just as easily appear in neighbouring disciplinary journals, as disciplinary boundaries are shrinking.

A Nation-Wide Swedish Cohort Study on Early Maternal Age at First Childbirth and Risk for Offspring Deaths, Accidents, and Suicide Attempts

In a sample of over one million Swedish first-born offspring, we examined associations between early maternal age at first childbirth (MAFC; i.e., < 20 and 20-24 vs 25-29 years) and offspring non-accidental deaths, accidental deaths, deaths by suicide, non-fatal accidents, and suicide attempts. We included year of birth and several maternal and paternal characteristics as covariates and conducted maternal cousin comparisons to adjust for unmeasured confounding. Early MAFC (e.g., teenage childbearing) was associated with all outcomes, with the most pronounced risk elevation for accidental deaths [Hazard Ratio (HR) < 20 2.50, 95% confidence interval (CI) 2.23, 2.80], suicides (HR < 20 2.08, 95% CI 1.79, 2.41), and suicide attempts (HR < 20 2.85, 95% CI 2.71, 3.00). Adjusting for covariates and comparing cousins greatly attenuated associations (e.g., accidental deaths HR < 20 1.61, 95% CI 1.22, 2.11; suicides HR < 20 1.01, 95% CI 0.69, 1.47; and suicide attempts HR < 20 1.35, 95% CI 1.19, 1.52). A similar pattern emerged for non-accidental deaths and non-fatal accidents. Therefore, results indicated maternal background factors may be largely responsible for observed associations.

Under-5 mortality and morbidity outcomes of fertility postponement in Turkey: explanations by observed and unobserved characteristics

This paper investigates the association between advanced maternal age and under-5 mortality and morbidity in Turkey, and is the first such study in the country to use a sibling comparison model to analyze this phenomenon. The study is based on data obtained from the 2013 Turkey Demographic and Health Survey, and analyzes the association of advanced maternal age with: (1) under-five mortality, using Cox proportional hazard models and their stratified versions to compare sibling groups born to the same mother in the 1978-2013 period, and (2) under-five morbidity; specifically, being born with low birth weight, stunting, underweight, and wasting based on between- and within-sibling groups models for the 2008-2013 period. Overall, our findings suggest that the hazard of under-5 mortality increases as maternal age increases. We conclude that period effects have failed to reverse the impeding effects of advanced maternal age on child mortality. Between-sibling group models indicate a positive but close to null association between advanced maternal age and child morbidity in general, although these positive associations vanish once we apply within-sibling group models. This result can be partially attributed to our controlling for unobserved characteristics specific to sibling groups, in addition to other methodological differences.

The other face of advanced paternal age: a scoping review of its terminological, social, public health, psychological, ethical and regulatory aspects

BACKGROUND

There is a global tendency for parents to conceive children later in life. The maternal dimension of the postponement transition has been thoroughly studied, but interest in the paternal side is more recent. For the moment, most literature reviews on the topic have focused on the consequences of advanced paternal age (APA) on fertility, pregnancy and the health of the child.

OBJECTIVE AND RATIONALE

The present review seeks to move the focus away from the biological and medical dimensions of APA and synthesise the knowledge of the other face of APA.

SEARCH METHODS

We used the scoping review methodology. Searches of interdisciplinary articles databases were performed with keywords pertaining to APA and its dimensions outside of biology and medicine. We included scientific articles, original research, essays, commentaries and editorials in the sample. The final sample of 177 documents was analysed with qualitative thematic analysis.

OUTCOMES

We identified six themes highlighting the interdisciplinary nature of APA research. The 'terminological aspects' highlight the lack of consensus on the definition of APA and the strategies developed to offer alternatives. The 'social aspects' focus on the postponement transition towards reproducing later in life and its cultural dimensions. The 'public health aspects' refer to attempts to analyse APA as a problem with wider health and economic implications. The 'psychological aspects' focus on the consequences of APA and older fatherhood on psychological characteristics of the child. The 'ethical aspects' reflect on issues of APA emerging at the intersection of parental autonomy, children's welfare and social responsibility. The 'regulatory aspects' group different suggestions to collectively approach the implications of APA. Our results show that the field of APA is still in the making and that evidence is lacking to fully address the issues of APA. The review suggests promising avenues of research such as introducing the voice of fathers of advanced age into the research agenda.

WIDER IMPLICATIONS

The results of this review will be useful for developing policies and preconception health interventions that consider and include prospective fathers of advanced age.

Associations of parental age with offspring all-cause and cause-specific adult mortality

People are having children later in life. The consequences for offspring adult survival have been little studied due to the need for long follow-up linked to parental data and most research has considered offspring survival only in early life. We used Swedish registry data to examine all-cause and cause-specific adult mortality (293,470 deaths among 5,204,433 people, followed up to a maximum of 80 years old) in relation to parental age. For most common causes of death adult survival was improved in the offspring of older parents (HR for all-cause survival was 0.96 (95% CI: 0.96, 0.97) and 0.98 (0.97, 0.98) per five years of maternal and paternal age, respectively). The childhood environment provided by older parents may more than compensate for any physiological disadvantages. Within-family analyses suggested stronger benefits of advanced parental age. This emphasises the importance of secular trends; a parent's later children were born into a wealthier, healthier world. Sibling-comparison analyses can best assess individual family planning choices, but our results suggested a vulnerability to selection bias when there is extensive censoring. We consider the numerous causal and non-causal mechanisms which can link parental age and offspring survival, and the difficulty of separating them with currently available data.

Maternal age alters offspring lifespan, fitness, and lifespan extension under caloric restriction

Maternal age has a negative effect on offspring lifespan in a range of taxa and is hypothesized to influence the evolution of aging. However, the mechanisms of maternal age effects are unknown, and it remains unclear if maternal age alters offspring response to therapeutic interventions to aging. Here, we evaluate maternal age effects on offspring lifespan, reproduction, and the response to caloric restriction, and investigate maternal investment as a source of maternal age effects using the rotifer, Brachionus manjavacas, an aquatic invertebrate. We found that offspring lifespan and fecundity decline with increasing maternal age. Caloric restriction increases lifespan in all offspring, but the magnitude of lifespan extension is greater in the offspring from older mothers. The trade-off between reproduction and lifespan extension under low food conditions expected by life history theory is observed in young-mother offspring, but not in old-mother offspring. Age-related changes in maternal resource allocation to reproduction do not drive changes in offspring fitness or plasticity under caloric restriction in B. manjavacas. Our results suggest that the declines in reproduction in old-mother offspring negate the evolutionary fitness benefits of lifespan extension under caloric restriction.