Do sons reduce parental mortality?

Impact of fertility on the longevity of older rural Chinese women: an analysis of a longitudinal survey

Background

This study evaluates the impact of fertility during the childbearing period on the longevity of older rural Chinese women and verifies whether any trade-off exists between women’s longevity and their number of children to provide empirical evidence for improving health intervention policies and formulating active fertility policies in low-fertility countries.

Methods

Based on the data of the deaths of 1623 older adults aged 65 and above during 2014–2018 in the Chinese Longitudinal Healthy Longevity Survey, this study explores the relationship between the number of children born and older rural women’s longevity using the ordinary least squares method. Furthermore, the impact of fertility on the longevity of men and women in rural and urban areas, along with other reproductive behaviours on older rural women’s longevity, were analysed.

Results

There was a significant negative correlation between the number of children born and women’s longevity (β = − 0.555, p < 0.05). Additionally, their longevity exhibited a decreasing trend with having birthed more sons and an increasing trend with more daughters. Age at first and last births had a significant positive relationship with rural women’s longevity; however, the effect of fertility on the longevity of older rural and urban men and older urban women was not significant.

Conclusions

It is confirmed that there is a trade-off between fertility and longevity for rural women in China. Future research should focus on compensating for the decline in female longevity caused by the number of children born and promote the concept of a healthy pregnancy, scientific nurture, and gender equality in fertility.

Son or Daughter Care in Relation to Self-Reported Health Outcomes for Older Adults in China

OBJECTIVES

Parental care in China is traditionally provided by sons. In recent decades-partly due to the One-Child Policy but also economic development and urbanization-significant changes have occurred with more and more parents receiving care from daughters. We investigate the disparities in outcomes of eldercare provided by son(s) and daughter(s).

METHODS

Our study compares the self-reported health (SRH) status of parents who receive eldercare from daughters and sons in China, analyzing the harmonized 2013, 2015, and 2018 waves of CHARLS with random-effects logistic estimates.

RESULTS

Our results show that the SRH status of parents who receive care from their sons is greater than those cared for by their daughters. This disparity is greater in rural areas, for mothers, and poorer families.

DISCUSSION

The One-Child Policy was more effective in urban areas, reducing both the availability of sons and cultural son preference. Higher levels of education received by girls in urban settings increases their employability and thus their ability to materially care for their parents. However, traditional norms and gender differences in social economic statuses still persist in rural areas, leading to higher SRH status of those cared for by sons, especially amongst those who are heavily dependent on their children: mothers or parents with less wealth.

The Influence of Female Reproductive Factors on Longevity: A Systematized Narrative Review of Epidemiological Studies

Purpose: This systematized review presents a synthesis of epidemiological studies that examine the association between female reproductive factors and longevity indicators. Methods: A comprehensive literature search was conducted using four bibliographic databases: OVID Medline, Web of Science, PubMed, and Google Scholar, including English language articles published until March 2022. Results from the search strategy yielded 306 articles, 37 of which were included for review based on eligibility criteria. Results were identified within the following nine themes: endogenous androgens and estrogens, age at first childbirth, age at last childbirth, parity, reproductive lifespan, menopause-related factors, hormone therapy use, age at menarche, and offspring gender. Results: Evidence that links reproductive factors and long lifespan is limited. Several female reproductive factors are shown to be significantly associated with longevity, yet findings remain inconclusive. The most consistent association was between parity (fertility and fecundity) and increased female lifespan. Age at first birth and parity were consistently associated with increased longevity. Associations between age at menarche and menopause, premature menopause, reproductive lifespan, offspring gender and longevity are inconclusive. Conclusion: There is not enough evidence to consider sex a longevity predictor. To understand the mechanisms that predict longevity outcomes, it is imperative to consider sex-specific within-population differences.

Healthy Ageing and Biomarkers Cohort Study (HABCS): a cohort profile

PURPOSE

The Chinese Longitudinal Healthy Longevity Survey Biomarkers Cohort (Healthy Ageing and Biomarkers Cohort Study (HABCS)) was established to investigate the determinants of healthy aging and mortality among the oldest old in China. Besides collecting health status, behavioural and sociodemographic circumstances, the present study also gathers comprehensive data for the elderly by simultaneously collecting, detecting, analysing blood and urine, respectively.

PARTICIPANTS

HABCS is a community-based longitudinal multiwave study of older men and women aged 65 or above. Baseline survey and the follow-up surveys with replacement for deceased elderly were conducted in eight longevity areas in China, which cover the northern, middle and southern parts of China. Between 2008 and 2017, 6333 participants were included in HABCS, comprising 1385 centenarians, 1350 nonagenarians, 1294 octogenarians, 1577 younger elderly (aged 65-79).

FINDINGS TO DATE

We have found that higher baseline levels of (1) total cholesterol, (2) low-density lipoprotein cholesterol (LDL-C) and (3) superoxide dismutase activity were associated with greater cognitive decline. While (4) higher LDL-C level was associated with lower risk of all-cause mortality. There was a reverse association between (5) plasma vitamin D and cognitive impairment in cross-sectional and prospective study.

FUTURE PLANS

We are currently exploring the relationships between various biomarkers and different outcomes such as cognitive function and mortality. This longitudinal cohort study will be continued in the future.

Maternal longevity and offspring sex in wild ungulates

In species with sexual size dimorphism, the offspring of the larger sex usually have greater energy requirements and may lead to greater fitness costs for parents. The effects of offspring sex on maternal longevity, however, have only been tested in humans. Human studies produced mixed results and considerable debate mainly owing to the difficulty of distinguishing the effects of sexual dimorphism from sociocultural factors. To advance this debate, we examined how the relative number of sons influenced maternal longevity in four species of free-living ungulates (Soay sheep Ovis aries; bighorn sheep, Ovis canadensis; red deer, Cervus elaphus; mountain goat, Oreamnos americanus), with high male-biased sexual size dimorphism but without complicating sociocultural variables. We found no evidence for a higher cumulative cost of sons than of daughters on maternal longevity. For a given number of offspring, most females with many sons in all four populations lived longer than females with few sons. The higher cost of sons over daughters on maternal lifespan reported by some human studies may be the exception rather than the rule in long-lived iteroparous species.

Offspring sex and parental health and mortality

Increased mortality has been observed in mothers and fathers with male offspring but little is known regarding specific diseases. In a register linkage we linked women born 1925–1954 having survived to age 50 (n = 661,031) to offspring and fathers (n = 691,124). Three approaches were used: 1) number of total boy and girl offspring, 2) sex of the first and second offspring and 3) proportion of boys to total number of offspring. A sub-cohort (n = 50,736 mothers, n = 44,794 fathers) from survey data was analysed for risk factors. Mothers had increased risk of total and cardiovascular mortality that was consistent across approaches: cardiovascular mortality of 1.07 (95% CI: 1.03–1.11) per boy (approach 2), 1.04 (1.01–1.07) if the first offspring was a boy, and 1.06 (1.01–1.10) if the first two offspring were boys (approach 3). We found that sex of offspring was not associated with total or cardiovascular mortality in fathers. For other diseases or risk factors no robust associations were seen in mothers or fathers. Increased cardiovascular risk in mothers having male offspring suggests a maternal disease specific mechanism. The lack of consistent associations on measured risk factors could suggest other biological pathways than those studied play a role in generating this additional cardiovascular risk.

Payback time? Influence of having children on mortality in old age

BACKGROUND

It is known that parents have lower mortality than childless individuals. Support from adult children to ageing parents may be of importance for parental health and longevity. The aim of this study was to estimate the association between having a child and the risk of death, and to examine whether the association increased at older ages when health starts to deteriorate and the need of support from a family member increases.

METHODS

In this nationwide study, all men and women (born between 1911 and 1925 and residing in Sweden), as well as their children, were identified in population registers and followed over time. Age-specific death risks were calculated for each calendar year for individuals having at least one child and for individuals without children. Adjusted risk differences and risk ratios were estimated.

RESULTS

Men and women having at least one child experienced lower death risks than childless men and women. At 60 years of age, the difference in life expectancy was 2 years for men and 1.5 years for women. The absolute differences in death risks increased with parents' age and were somewhat larger for men than for women. The association persisted when the potential confounding effect of having a partner was taken into account. The gender of the child did not matter for the association between parenthood and mortality.

CONCLUSIONS

Having children is associated with increased longevity, particularly in an absolute sense in old age. That the association increased with parents' age and was somewhat stronger for the non-married may suggest that social support is a possible explanation.

Older Parents Benefit More in Health Outcome From Daughters' Than Sons' Emotional Care in China

OBJECTIVE

To examine whether older parents in China would benefit more from daughters' care than from sons' emotional care.

METHOD

Analysis of the unique data sets of the Chinese Longitudinal Healthy Longevity Survey conducted in 2002, 2005, and 2008-2009 in 22 provinces.

RESULTS

As compared with having son(s), having daughter(s) is significantly more beneficial at older ages in China, with regard to maintaining higher cognitive capacity and reducing mortality risk. Such daughter advantages in providing emotional care to older parents are more profound among the oldest-old aged 80+ as compared with the young-old aged 65 to 79 and surprisingly more profound in rural areas as compared with urban areas, even though son preference is much more common among rural residents.

DISCUSSION

We describe how educational campaigns aimed at informing the public about the benefits of daughter(s) for older parents' health outcome could help promote gender equality and reduce traditional son preference, especially in rural China.

The effects of China's universal two-child policy

In October, 2015, China's one-child policy was replaced by a universal two-child policy. The effects of the new policy are inevitably speculative, but predictions can be made based on recent trends. The population increase will be relatively small, peaking at 1·45 billion in 2029 (compared with a peak of 1·4 billion in 2023 if the one-child policy continued). The new policy will allow almost all Chinese people to have their preferred number of children. The benefits of the new policy include: a large reduction in abortions of unapproved pregnancies, virtual elimination of the problem of unregistered children, and a more normal sex ratio. All of these effects should improve health outcomes. Effects of the new policy on the shrinking workforce and rapid population ageing will not be evident for two decades. In the meantime, more sound policy actions are needed to meet the social, health, and care needs of the elderly population.

Older parents enjoy better filial piety and care from daughters than sons in China

This study analyzes the unique datasets of the Chinese Longitudinal Healthy Longevity Survey using logistic regression and controlling for various covariates. Our analyses clearly demonstrate that disabled older parents are more satisfied with care provided by daughters than sons and that older parents enjoy greater filial piety from and better relationships with daughters than sons. The daughter-advantages of enjoying greater filial piety from and better relationships with children are stronger among the oldest-old aged 80+ than the young-old aged 65-79, and surprisingly more profound in rural areas than urban areas, while son-preference is much more prevalent among rural residents. We also discuss why China's rigorous fertility policy until October-2015 and much less-developed pension system in rural areas substantially contribute to sustaining traditional son-preference and a high sex ratio at birth (SRB) when fertility is low. We recommend China take integrative public health policy actions of informing the public that having daughter(s) is beneficial for old age care, developing the rural pension system and implementing the universal two-child policy as soon as possible. We believe that these policy actions would help to reduce son-preference, bring down the high SRB, and enable more future elderly parents to enjoy better care from their children and healthier lives.

Fertility History, Children's Gender, and Post-Reproductive Survival in a Longevous Population

The question of whether mothers' fertility history influences their post-reproductive survival has been addressed frequently in the scientific literature. Using data from Villagrande Strisaili, Sardinia, where longevity is higher than anywhere else in Europe, we analyzed the relationship between the fertility pattern of mothers who survived past age 50 (n = 539) and their post-reproductive lifespan. We find that, after adjustment for potential confounders (mothers' birth cohort, survival of spouse), the mothers who on average delivered their children later displayed a reduced mortality risk (‒2.9 percent for each additional year), supporting previously reported findings. We also find that a male-skewed offspring ratio was associated with decreased mortality risk of mothers, with longer survival of mothers who delivered their sons above age 35 (p = 0.005), a result not found for daughters. So far, no biological explanation has been suggested for the positive effect of delivering sons later in life. We conjecture that in our dataset stronger nonbiological factors such as gender-specific sociocultural and economic factors may have masked the negative effect reported in other populations, for which a biological explanation was proposed.

A trade-off between having many sons and shorter maternal post-reproductive survival in pre-industrial Finland

A bias in reproduction towards sons, which are energetically more costly than daughters, has been suggested to shorten parental lifespan, but previous results have been mixed. Reproductive costs should be most evident in low rather than high resource settings, and are not expected to be severe in men, because women pay higher direct costs of reproduction. We, therefore, used demographic data from pre-industrial Finland to investigate whether the number of sons and daughters born affected their parents' post-reproductive survival and whether this was related to parent's resource availability. Irrespective of access to resources, mothers, but not fathers, with many sons suffered from reduced post-reproductive survival, and this association decreased as mothers aged. Our results provide evidence that Finnish mothers traded long post-reproductive lifespan for giving birth to many sons.