Fertility history and cause-specific mortality: A register-based analysis of complete cohorts of Norwegian women and men

Age at first birth and risk of later-life cardiovascular disease: a systematic review of the literature, its limitation, and recommendations for future research

Background

Cardiovascular disease (CVD) is the principal contributor to the burden of disease and mortality worldwide. Previous studies observed associations between early age at first birth (AFB) and all-cause mortality. AFB may be associated with CVD both through physiological and sociobiological pathways. In this paper, we review the literature on AFB and CVD events and mortality. Additionally, we provide an overview of limitations of the current research and recommendations for future research.

Methods

PubMed and Web of Science databases were searched for observational studies published between 1980-June 2016, investigating associations between AFB and CVD events and mortality. Data were extracted using a pre-defined list.

Results

A total of 20 publications, reporting on 33 associations, were included in the review. Ten studies observed a positive association between early AFB and CVD while two studies observed a positive association between later AFB and CVD. Substantial methodological limitations were observed related to: operationalization of exposure categories, choice of reference category, sample size, follow-up time and possibly over adjustment.

Conclusions

Early AFB is possibly related to CVD. More work, in particular from large cohort studies starting before reproductive age is reached, is needed to better investigate this relationship, and to ascertain causal pathways that may explain observed associations.

Electronic supplementary material

The online version of this article (doi:10.1186/s12889-017-4519-x) contains supplementary material, which is available to authorized users.

Fertility history and use of antidepressant medication in late mid-life: a register-based analysis of Norwegian women and men

OBJECTIVES

Life course influences on later life depression may include parenting trajectories. We investigate associations between number and timing of births and use of antidepressant medication in late mid-life using data on the whole Norwegian population.

METHODS

We estimated logistic regression models to analyse variations in the purchase of antidepressants between 2004 and 2008 by timing of births and number of children among women and men aged 45-73, using Norwegian population register data. We controlled for age, education, marital and partnership status, and (in some models) family background shared among siblings.

RESULTS

Mothers and fathers of two or more children were generally less likely to purchase antidepressants than the childless. Mothers who started childbearing before age 22 were an exception, although according to sibling models they were not more likely to purchase antidepressants. All models showed that women who became mothers before age 26 and had only one child had higher odds of medication purchase than the childless. Older age at first birth was generally associated with lower risks of antidepressant purchase.

CONCLUSION

This analysis of high-quality data for a national population indicates that early motherhood, childlessness and low parity are associated with higher usage of antidepressants in late mid-life. Our data did not allow identification of mediating pathways, and we lacked information on early mental and physical health and some other potentially important confounders not shared between siblings. Furthermore purchase of antidepressants is not a perfect indicator of depression. Those concerns aside, the results suggest complex effects of fertility on depression that merit further investigation.

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.

Number of children and later-life mortality among Finns born 1938-50

We investigated the association between number of offspring and later-life mortality of Finnish men and women born 1938-50, and whether the association was explained by living conditions in own childhood and adulthood, chronic conditions, fertility timing, and unobserved characteristics common to siblings. We used a longitudinal 1950 census sample to estimate mortality at ages 50-72. Relative to parents of two children, all-cause mortality is highest among childless men and women, and elevated among those with one child, independently of observed confounders. Fixed-effect models, which control for unobserved characteristics shared by siblings, clearly support these findings among men. Cardiovascular mortality is higher among men with no, one, or at least four children than among those with two. Living conditions in adulthood contribute to the association between the number of children and mortality to a greater extent than childhood background, and chronic conditions contribute to the excess mortality of the childless.

Association of Women's Reproductive History With Long-term Mortality and Effect of Socioeconomic Factors

OBJECTIVE

To assess the effects of socioeconomic factors on the association between parity and long-term maternal mortality.

METHODS

This was a population-based cohort study of mothers with births registered in the Medical Birth Registry of Norway during the period 1967-2009. We estimated age-specific (40-69 years) cardiovascular and noncardiovascular mortality ratios by number of births using Cox proportional hazard models. To assess effect modification by mothers' attained education, we stratified on low (less than 11 years) and high (11 years or greater) educational level. We further evaluated fathers' mortality by number of births using the same analytical approach.

RESULTS

Mothers with low education had higher mortality (cardiovascular: hazard ratio 2.62, 95% confidence interval [CI] 2.34-2.93, noncardiovascular: hazard ratio 1.67, 95% CI 1.62-1.73). Among mothers with low education, cardiovascular mortality increased linearly with each additional birth above one (P trend=.02). In contrast, among mothers with high education, cardiovascular mortality declined with added births (P trend=.045). For noncardiovascular mortality there was no association among mothers with low education, whereas mortality declined with increasing number of births among mothers with high education (P trend<.01). Father's mortality showed similar associations with number of births when stratified on maternal education.

CONCLUSION

Women's long-term mortality rose with number of births only for cardiovascular causes of death and only among mothers with low education. Partners of women with low education had similar increasing risk with increasing number of births. Maternal educational level is a strong modifier of the association between parity and long-term mortality.

LEVEL OF EVIDENCE

II.

Reproductive factors and risk of mortality in the European Prospective Investigation into Cancer and Nutrition; a cohort study

BACKGROUND

Reproductive events are associated with important physiologic changes, yet little is known about how reproductive factors influence long-term health in women. Our objective was to assess the relation of reproductive characteristics with all-cause and cause-specific mortality risk.

METHODS

The analysis was performed within the European Investigation into Cancer and Nutrition prospective cohort study, which enrolled >500,000 women and men from 1992 to 2000, who were residing in a given town/geographic area in 10 European countries. The current analysis included 322,972 eligible women aged 25-70 years with 99 % complete follow-up for vital status. We assessed reproductive characteristics reported at the study baseline including parity, age at the first birth, breastfeeding, infertility, oral contraceptive use, age at menarche and menopause, total ovulatory years, and history of oophorectomy/hysterectomy. Hazard ratios (HRs) and 95 % confidence intervals (CIs) for mortality were determined using Cox proportional hazards regression models adjusted for menopausal status, body mass index, physical activity, education level, and smoking status/intensity and duration.

RESULTS

During a mean follow-up of 12.9 years, 14,383 deaths occurred. The HR (95 % CI) for risk of all-cause mortality was lower in parous versus nulliparous women (0.80; 0.76-0.84), in women who had ever versus never breastfed (0.92; 0.87-0.97), in ever versus never users of oral contraceptives (among non-smokers; 0.90; 0.86-0.95), and in women reporting a later age at menarche (≥15 years versus <12; 0.90; 0.85-0.96; P for trend = 0.038).

CONCLUSIONS

Childbirth, breastfeeding, oral contraceptive use, and a later age at menarche were associated with better health outcomes. These findings may contribute to the development of improved strategies to promote better long-term health in women.

The more the merrier? Fertility and food insecurity among older Senegalese women

The number of children women have is a critical determinant of their future wellbeing. Often, adult children confer some protection against adverse conditions in their older ages. In many sub-Saharan African societies, it is expected that older women who typically have had many children, will benefit from their investment in children. Yet it is unclear if this is really the case. Using data from the 10 per cent micro-sample of the 2002 Senegalese Population and Housing Census, this study investigates the effect of the childbearing histories of older women (aged 60–85) on the likelihood that their households experienced food insecurity in the past year. Women who had had no children and those who had ever had two or more, were not significantly different from those who had had five or more – only those who had had one child were adversely affected. Based on principles of intergenerational altruism and moral obligation, I expected that food insecurity would decrease with increases in the number of surviving children. This pattern was generally found. However, among women in the bottom 40 per cent of the wealth distribution, the relationship was, at best, weak with respect to all of the fertility variables (children ever had, living, co-resident). The benefits of high fertility seem to accrue to relatively richer women – those in the top 60 per cent of the wealth distribution. Yet among these richer women, having fewer than three children and co-resident adult children were significant risk factors of food insecurity.

Is being childless detrimental to a woman's health and well-being across her life course?

BACKGROUND

Childlessness is a growing phenomenon. Previous research examining health and well-being differentials between women with and without children has produced conflicting results. Most of this research has been conducted in the United States or parts of Europe. There has been limited research in Australia that has examined the health and well-being of women with and without children across the life course. The aim of the current study was to examine the association between motherhood status and general physical and mental health and well-being over a 10-year time period.

METHODS

Using 10 waves of data from the Household, Income and Labour Dynamics in Australia study, longitudinal linear mixed models with time varying variables (both dependent and independent) were constructed to assess the effect of childlessness on health and well-being based on the Short Form-36 Health Survey Version 1 (n=52,381 observations).

FINDINGS

Findings suggest that childless women experience poorer physical and mental health and well-being during the peak reproductive years; however, this trend is reversed for women aged 65 years or more. Although never-married, childless women experienced better health and well-being compared with mothers, this was not the case for childless women who were divorced, separated, or widowed or in a relationship.

CONCLUSION

The findings support the notion that whether or not a woman has children does have consequences for her health and well-being; however, this differs across the life course.

Someone to live for: effects of partner and dependent children on preventable death in a population wide sample from Northern Ireland

How to allocate resources between somatic maintenance and reproduction in a manner that maximizes inclusive fitness is a fundamental challenge for all organisms. Life history theory predicts that effort put into somatic maintenance (health) should vary with sex, mating and parenting status because men and women have different costs of reproduction, and because life transitions such as family formation alter the fitness payoffs from investing in current versus future reproduction. However, few tests of how such life history parameters influence behaviours closely linked to survival exist. Here we examine whether specific forms of preventable death (accidents/suicides, alcohol-related causes, and other preventable diseases) are predicted by marital status and dependent offspring in a modern developed context; that of Northern Ireland. We predict that men, non-partnered individuals and individuals who do not have dependent offspring will be at higher risk of preventable death. Running survival analyses on the entire adult population (aged 16-59, n = 927,134) controlling for socioeconomic position (SEP) and other potential confounds, we find that being single (compared to cohabiting/married) increases risk of accidental/suicide death for men (but not for women), whereas having dependent children is associated with lower risk of preventable mortality for women but less so for men. We also find that the protective effect of partners is larger for men with low SEP than for high SEP men. Findings support life history predictions and suggest that individuals respond to variation in fitness costs linked to their mating and parenting status.

The impact of children's sex composition on parents' mortality

BACKGROUND

This study explores the relationship between children's sex composition and parents' mortality in a contemporary western society. It improves on earlier research by using a larger and more representative dataset - constructed from registers and encompassing the entire Norwegian population.

METHODS

The analysis is based on discrete-time hazard models, estimated for the years 1980-2008 for women and men born after 1935.

RESULTS

When operationalising sex composition as the "number of boys", coefficients are insignificant in all specifications. However, when considering the three categories "only boys", "only girls" and "mixed sex", I find a small but significant disadvantage of having only girls, compared to having at least one child of each sex, for mothers of two or more children. Having only daughters is associated with a mortality disadvantage compared to having only sons for mothers of two children, but a mortality advantage among mothers with four children. Among women who gave birth to their first child as teenagers, those who have only sons have relatively high mortality. I also find an excess mortality both for mothers of only girls and mothers of only boys in the period 1980-1989.

CONCLUSION

These results lend some support to the notion that there is a larger benefit of the first son or daughter than the later children of the same sex, and especially in the earliest decade of the study period.

Effectiveness of population-based service screening with mammography for women ages 40 to 49 years with a high or low risk of breast cancer: socioeconomic status, parity, and age at birth of first child

BACKGROUND

Invitation to mammography screening of women aged 40 to 49 years is a matter of debate in many countries and a cost-effective alternative in countries without screening among women aged 40 to 49 years could be inviting those at higher risk. The relative effectiveness of mammography screening was estimated for subgroups based on the breast cancer risk factors parity, age at time of birth of first child, and socioeconomic status (SES).

METHODS

The SCReening of Young Women (SCRY) database consists of all women aged 40 to 49 years in Sweden between 1986 and 2005 and was split into a study and control group. The study group consisted of women residing in areas in which women aged 40 to 49 years were invited to screening and the control group of women in areas in which women aged 40 to 49 years were not invited to screening. Rate ratio (RR) estimates were calculated for 2 exposures: invitation and attendance.

RESULTS

There were striking similarities noted in the RR pattern for women invited to and attending screening and no statistically significant difference or trend in the RR was noted by risk group. The RR estimates increased by increasing parity for parity of 0 to 2 and ranged from 0.55 (95% confidence interval [95% CI], 0.38-0.79) to 0.79 (95% CI, 0.65-0.95) for attending women. The RR for women with high SES was lower than that for women with low SES (RR, 0.72 [95% CI, 0.60-0.86] and RR, 0.79 [95% CI, 0.63-0.99], respectively). For women aged 20 to 24 years at the time of the birth of their first child, the RR was 0.73 (95% CI, 0.58-0.91) and estimates for other ages were similar.

CONCLUSIONS

There was no statistically significant difference noted in the relative effectiveness of mammography screening by parity, age at the time of birth of the first child, or SES.

The association between grandparenthood and mortality

Few studies have so far enquired into the relationship between being a grandparent and health and mortality outcomes, and the majority of these have looked exclusively at grandparents who take over parenting responsibility for their grandchildren. This study aims to fill this gap in the knowledge of how family structure is linked to mortality by focusing on whether being a grandparent in itself is associated with mortality. Norwegian parents in the age groups 40-73 are analysed using register data that encompass the entire population. The analysis is based on discrete-time hazard models, estimated for the years 1980-2008. I find a mortality disadvantage of being a grandfather, which is particularly strong for those who become grandfathers at an early age. Controlling for characteristics of the middle generation such as sex, education and marital status does not remove the association. For men the mortality disadvantage is not influenced by the number of grandchildren or the number of sets of grandchildren. For women there is significantly higher mortality only for those who become grandmothers in their thirties or forties, who are married or who have many children. Becoming a grandmother after age 50 is associated with significantly lower mortality. At least part of these associations are likely due to selection effects, however they may also to some extent be caused by the individuals' relationship with grandchildren, and children who have become parents themselves.

Cardiovascular mortality after pre-eclampsia in one child mothers: prospective, population based cohort study

OBJECTIVE

To assess the association of pre-eclampsia with later cardiovascular death in mothers according to their lifetime number of pregnancies, and particularly after only one child.

DESIGN

Prospective, population based cohort study.

SETTING

Medical Birth Registry of Norway.

PARTICIPANTS

We followed 836,147 Norwegian women with a first singleton birth between 1967 and 2002 for cardiovascular mortality through linkage to the national Cause of Death Registry. About 23,000 women died by 2009, of whom 3891 died from cardiovascular causes. Associations between pre-eclampsia and cardiovascular death were assessed by hazard ratios, estimated by Cox regression analyses. Hazard ratios were adjusted for maternal education (three categories), maternal age at first birth, and year of first birth

RESULTS

The rate of cardiovascular mortality among women with preterm pre-eclampsia was 9.2% after having only one child, falling to 1.1% for those with two or more children. With term pre-eclampsia, the rates were 2.8% and 1.1%, respectively. Women with pre-eclampsia in their first pregnancy had higher rates of cardiovascular death than those who did not have the condition at first birth (adjusted hazard ratio 1.6 (95% confidence interval 1.4 to 2.0) after term pre-eclampsia; 3.7 (2.7 to 4.8) after preterm pre-eclampsia). Among women with only one lifetime pregnancy, the increase in risk of cardiovascular death was higher than for those with two or more children (3.4 (2.6 to 4.6) after term pre-eclampsia; 9.4 (6.5 to 13.7) after preterm pre-eclampsia). The risk of cardiovascular death was only moderately elevated among women with pre-eclamptic first pregnancies who went on to have additional children (1.5 (1.2 to 2.0) after term pre-eclampsia; 2.4 (1.5 to 3.9) after preterm pre-eclampsia). There was little evidence of additional risk after recurrent pre-eclampsia. All cause mortality for women with two or more lifetime births, who had pre-eclampsia in first pregnancy, was not elevated, even with preterm pre-eclampsia in first pregnancy (1.1 (0.87 to 1.14)).

CONCLUSIONS

Cardiovascular death in women with pre-eclampsia in their first pregnancy is concentrated mainly in women with no additional births. This association might be due to health problems that discourage or prevent further pregnancies rather than to pre-eclampsia itself. As a screening criterion for cardiovascular disease risk, pre-eclampsia is a strong predictor primarily among women with only one child-particularly with preterm pre-eclampsia.

Childbearing history and late-life mortality: the Dubbo study of Australian elderly

OBJECTIVE

to examine the association of parity with mortality in later life.

DESIGN

a longitudinal, community-based study.

SETTING

semi-rural town of Dubbo, NSW, Australia.

SUBJECTS

a total of 1,571 women and 1,233 men 60 years and older first examined in 1988-89.

OUTCOME MEASURES

all-cause and cause-specific mortality rates analysed over 16-year follow-up. Hazard ratios obtained from proportional hazards models employing conventional predictors, potential confounders and measure of parity.

RESULTS

increasing parity in women was weakly associated with overweight, diabetes and hypertension. All-cause mortality fell progressively with increasing parity in women (hazard ratio and 95% confidence intervals): childless, 1.00; 1 child, 1.03 (0.75-1.43); 2 children, 0.83 (0.61-1.11); 3 children, 0.80 (0.60-1.08); 4 children, 0.91 (0.66-1.25); 5 children, 0.70 (0.49-1.01); 6+ children, 0.60 (0.43-0.85) (trend for parity P<0.002). This result was similar whether or not hypertension, diabetes and overweight were included in multivariate models adjusting for social variables and other confounders. The reduction in all-cause mortality was accompanied by a parallel reduction in deaths from cancer and respiratory conditions, while coronary heart disease mortality increased 60-111% in all parous women.

CONCLUSION

there was increased all-cause mortality in later life in childless women, accompanied by reduced mortality as parity increased. Underlying mechanisms are unclear but findings may have public health importance.

Exceptional longevity is associated with decreased reproduction

A number of leading theories of aging, namely The Antagonistic Pleiotropy Theory (Williams, 1957), The Disposable Soma Theory (Kirkwood, 1977) and most recently The Reproductive-Cell Cycle Theory (Bowen and Atwood, 2004, 2010) suggest a tradeoff between longevity and reproduction. While there has been an abundance of data linking longevity with reduced fertility in lower life forms, human data have been conflicting. We assessed this tradeoff in a cohort of genetically and socially homogenous Ashkenazi Jewish centenarians (average age ~100 years). As compared with an Ashkenazi cohort without exceptional longevity, our centenarians had fewer children (2.01 vs 2.53, p<0.0001), were older at first childbirth (28.0 vs 25.6, p<0.0001), and at last childbirth (32.4 vs 30.3, p<0.0001). The smaller number of children was observed for male and female centenarians alike. The lower number of children in both genders together with the pattern of delayed reproductive maturity is suggestive of constitutional factors that might enhance human life span at the expense of reduced reproductive ability.

Estimating Mortality Differences in Developed Countries From Survey Information on Maternal and Paternal Orphanhood

In general, the use of indirect methods is limited to developing countries. Developed countries are usually assumed to have no need to apply such methods because detailed demographic data exist. However, the potentialities of demographic analysis with direct methods are limited to the characteristics of available macro data on births, deaths, and migration. For instance, in many Western countries, official population statistics do not permit the estimation of mortality by socioeconomic status (SES) or migration background, or for estimating the relationship between parity and mortality. In order to overcome these shortcomings, I modify and extend the so-called orphanhood method for indirect estimation of adult mortality from survey information on maternal and paternal survival to allow its application to populations of developed countries. The method is demonstrated and tested with data from two independent Italian cross-sectional surveys by estimating overall and SES-specific life expectancy. The empirical applications reveal that the proposed method can be used successfully for estimating levels and trends of mortality differences in developed countries and thus offers new prospects for the analysis of mortality.

[Social living conditions and health among mothers in Germany : findings from a population sample]

This paper reports findings from a population sample of mothers with underage children living in Germany (n=3,129). The objective of the study was to analyze whether social and familiar living conditions are associated with enhanced health risks for mothers. The sample is representative with respect to German federal states, school education, marital status, age of mothers, and number of children. Health problems were assessed in terms of physical disabilities and discomforts, anxiety and depression, and self-rated health. About 27% of mothers perceived physical disabilities and discomfort, 21% reported high levels of anxiety, and 22% high levels of depression. About 6% assessed their health as poor or very poor. Particularly single motherhood, unemployment, sole responsibility for household and family as well as low income and low school education increased the risk of poor health. The findings suggest that for specific subgroups of mothers parenting may be a vulnerable phase of life reflecting the need for a life stage orientation in health inequality research.

An examination of the health and wellbeing of childless women: a cross-sectional exploratory study in Victoria, Australia

Background

Childlessness among Australian women is increasing. Despite this, little is known about the physical and mental health and wellbeing of childless women, particularly during the reproductive years. The aims of this exploratory study were to: 1) describe the physical and mental health and wellbeing and lifestyle behaviours of childless women who are currently within the latter part of their reproductive years (30 - 45 years of age); and 2) compare the physical and mental health and wellbeing and lifestyle behaviours of these childless women to Australian population norms.

Methods

A convenience sample of 50 women aged between 30 and 45 years were recruited to participate in a computer assisted telephone interview. The SF-36 Health Survey v2 and lifestyle indicators were collected in regards to women's health and wellbeing. Data were analysed using descriptive statistics, t-tests for independent sample means and 95% confidence intervals for the difference between two independent proportions.

Results

Childless women in this study reported statistically significant poorer general health, vitality, social functioning and mental health when compared to the adult female population of Australia. With the exception of vegetable consumption, lifestyle behaviours were similar for the childless sample compared to the adult female population in Australia.

Conclusions

Childless women may be at a greater risk of experiencing poor physical and mental health when compared to the Australian population. A woman's health and wellbeing during her reproductive years may have longer term health consequences and as such the health and wellbeing of childless women requires further investigation to identify and address implications for the provision of health (and other social) services for this growing population group.

The associations between nationality, fertility history and diabetes-related mortality: a retrospective cohort study in the Brussels-Capital Region (2001-2005)

BACKGROUND

The relationship between women's parity and diabetes mortality has been investigated in several studies, with mixed results. This study aims to establish if parity and age at first birth are associated with diabetes-related mortality and if these factors contribute to variations in diabetes-related mortality among women with different nationalities.

METHODS

Data of the 2001 census are linked to registration records of all deaths and emigrations (period 2001-2005). The study population comprises all female inhabitants of the Brussels-Capital Region aged 45-74 of either Belgian or North African nationality (n = 108 296). Age-standardized mortality rates (direct standardization) and mortality rate ratios (Poisson's regression) are computed.

RESULTS

Both parity and age at first birth are associated with diabetes-related mortality. Highest risks of dying from diabetes are observed among grandmultiparous women and teenage mothers. Differences in diabetes-related mortality according to nationality are observed. Age-standardized diabetes mortality rates are higher in North African [ASMR = 417.4/100,000; 95% confidence interval (CI) 227.2-607.7] than in Belgian women (ASMR = 184.0/100,000; 95% CI 157.3-210.8). Taking parity, age at first birth and education into account, these differences largely disappear.

CONCLUSIONS

Reproductive factors are associated with diabetes-related mortality and play an important part in the higher diabetes-related mortality of North African compared with Belgian women.