Fertility History and Risk of Cognitive Impairment Among Older Parents in the United States

Association between parity and female mortality: the mediative role of depressive symptoms

STUDY QUESTION

Is parity associated with all-cause and cause-specific mortality among women in a nationally representative cohort of the US population, and does depression mediate this association?

SUMMARY ANSWER

Nulliparous women have a higher risk of all-cause and cause-specific mortality, with depression partially mediating the relationship between parity and women's all-cause and cause-specific mortality.

WHAT IS KNOWN ALREADY

Parity, a significant state in reproductive life, has enduring implications for women's health. There is also a complex relationship between depression, a prevalent mental and emotional disorder, and female fertility. Previous studies have elucidated the relationships between parity and depression, both of which are associated with mortality. However, findings from studies examining parity and women's mortality have been inconsistent. Moreover, few studies have investigated whether the effect of parity on mortality is mediated by depression.

STUDY DESIGN, SIZE, DURATION

We conducted a cross-sectional study using data from seven cycles of the National Health and Nutrition Examination Survey (NHANES) spanning 2005-2018.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The study cohort comprised adult women with available parity and survival follow-up data. Parity data were self-reported and sourced from the Reproductive Health Questionnaire. Depression scores were derived from the Patient Health Questionnaire 9, and cause-specific deaths were identified using the International Statistical Classification of Diseases, 10th Revision (ICD-10). Weighted multivariable Cox regression was applied to analyze the association between parity, depression, and mortality. Weighted linear regression was performed to examine the relationship between parity and depression. Mediation analyses were employed to determine whether and to what extent depression mediated the effect of parity on mortality.

MAIN RESULTS AND THE ROLE OF CHANCE

Our study ultimately encompassed 16 962 American women. Following multivariable adjustment, compared to nulliparous women, those with one to three live births exhibited a 17% and 33% reduction in all-cause and cancer mortality, respectively (all-cause mortality: HR = 0.83, 95% CI = 0.69-0.99, P = 0.040; cancer mortality: HR = 0.67, 95% CI = 0.45-0.99, P = 0.045). Women with more than four live births demonstrated lower all-cause mortality and mortality from other (not cancer or cardiovascular disease) diseases (all-cause mortality: HR = 0.73, 95% CI = 0.58-0.93, P = 0.011; other diseases mortality: HR = 0.66, 95% CI = 0.47-0.91, P = 0.013). No correlation was detected between parity and the risk of cardiovascular disease mortality among women. Furthermore, depression was found to partially mediate the impact of parity on all-cause mortality and mortality from other diseases in women.

LIMITATIONS, REASONS FOR CAUTION

Firstly, a single index of parity was used as an exposure factor, and other reproductive factors such as birth spacing, age at first birth, and mode of delivery were not taken into account. Secondly, despite accounting for important potentially confounders in our analysis, such as BMI, smoking status, and educational level, the influence of unmeasured confounders (e.g., social class, latent reproductive system diseases) on reproductive behavior or mortality cannot be dismissed. Thirdly, women's vulnerability to depression fluctuates across reproductive stages, and the effect of depression on female fertility varies over time. Due to data constraints, we were unable to obtain information on women's mental health status at different reproductive stages. Fourthly, due to the data accessibility limitations of NHANES, we were unable to specifically explore the relationship between parity and different specific types of cancer, a limitation that may obscure potential correlations. Additionally, despite our efforts to control for various confounding factors in subgroup analyses, the smaller sample sizes in some subgroups may limit the statistical power, affecting the ability to detect effects. Finally, studies exploring the association between parity and depression are cross-sectional designs, making it difficult to infer causality. These results should be interpreted with caution, and further research is warranted to corroborate our findings.

WIDER IMPLICATIONS OF THE FINDINGS

Our study underscores the elevated risk of all-cause and cause-specific mortality in nulliparous women and reveals that depression partially mediates the negative correlation between parity and women's all-cause mortality and mortality from other diseases. These results should be interpreted with caution, and further investigation is needed to support our findings.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the National Key Research and Development Program of China (2023YFC2705700), the Key Research & Developmental Program of Hubei Province (2022BCA042), and the Interdisciplinary Innovative Talents Foundation from Renmin Hospital of Wuhan University (JCRCWL-2022-001). The authors declare that they have no conflict of interest.

TRIAL REGISTRATION NUMBER

N/A.

Research Note: The Association Between Parity and Odds of Alzheimer's Disease and Dementias Status

While parity is a significant factor influencing parental health, its relationship with dementia remains underexplored. This research note advances the literature by conducting a well-powered analysis of associations between parity (i.e., number of children) and Alzheimer's disease and dementias (AD/D) status in large-scale population data. The data contain a large number of AD/D cases (37,228 women and 19,846 men), allowing a range (1-10) of parity associations to be estimated precisely. Using proxy (adult child's) reports of parental AD/D status, we find that both fathers and mothers with grand multiparity have decreased odds of AD/D status, and the effect sizes become larger as parity increases, with 30-40% reduction in AD/D status at parities above 7. The association is stronger for mothers than for fathers. This finding differs from much of the prior literature and likely suggests the impact of parity, as one of the important life course contexts, on people's cognitive function and risk of having AD/D. Finally, we include population projections that consider how large changes in parity distributions over time may contribute to small elevations in AD/D rates.

Higher Number of Children Is Associated With Increased Risk of Generalization Deficits in Older African American Women

OBJECTIVES

The objectives of this project were to: (1) examine the relationship between the number of biological children and hippocampal-dependent cognitive performance among older African American women and (2) determine the influence of socioeconomic status (i.e., age, education, marital status, median household income), if any, on this relationship.

METHODS

A total of 146 cognitively unimpaired African American women aged 60 and older were recruited from the greater Newark area and reported their number of biological children, marital status, educational level, and age. We retrieved median household income from census tract data based on the participants' addresses. Participants' cognitive performance was assessed using the Rey Auditory Verbal Learning Test (RAVLT) long delay recall and a Rutgers generalization task (Concurrent Discrimination and Transfer Task).

RESULTS

As the number of biological children a woman has had increases, the number of generalization errors also increased, indicating poorer hippocampal-dependent cognitive performance when controlling for age, education, marital status, and median household income. There was no significant relationship between the number of children and performance on a standardized neuropsychological measure of episodic memory (RAVLT), although education was a significant covariate.

DISCUSSION

Generalization tasks may better capture early changes in cognitive performance in older African American women who have had children than standardized neuropsychological assessments. This finding may be explained by the fluctuations in estrogen associated with having children. Future studies should explore how these findings can be applied to protecting cognitive function and preventing Alzheimer's disease in older African American women who have had children.

Sequencing of Births by Wantedness: Implications for Changes in Mid-Life Health Among Aging NLSY79 Women

OBJECTIVES

As life course frameworks highlight and gerontological studies confirm, the health implications of early birth timing (e.g., adolescent births) and unplanned births (e.g., unwanted or mistimed births) extend years after those births into mid and later life. Yet past research often overlooks the considerable diversity in sequencing and timing of unplanned births even within the same individual (e.g., having both wanted and unwanted births), which are likely fundamental for women's long-term health trajectories. We develop a holistic understanding of birth timing and wantedness to provide insight into when and how childbearing histories matter for aging women's health.

METHODS

We use sequence analysis with hierarchical cluster method and estimate regression models using the 1979 National Longitudinal Survey of Youth (N = 3,231) to examine how timing and patterning of births by wantedness are associated with changes in physical and mental health from ages 40 to 50.

RESULTS

We identify 7 clusters of childbearing sequences. Of those 7 clusters, respondents with sequences characterized by wanted births in their 20s and 30s had the smallest declines in health in mid-life, whereas respondents with sequences with mainly unwanted births at any age or with mainly mistimed births beginning in adolescence had the greatest health declines. Adjusting for social and economic variables accounted for some, but not all, health differences across childbearing clusters.

DISCUSSION

This project demonstrates the need for comprehensive life course perspectives on long-term health implications of birth wantedness and timing, recognizing diversity within and between individuals.

Gender differences in the association between parity and cognitive function: Evidence from the UK biobank

While much previous work linking fertility history with late-life cognition has focused on a narrow set of cognitive measures and/or has used modest sample sizes in the analysis, our paper expands the size and scope of these linkages by analyzing cognitive function across five domains and precisely estimating gendered patterns between men and women. Results point to important gendered associations between parity and cognition: having children is likely associated with better cognitive function for fathers in all five domains. However, mothers show worse cognitive function in some domains (i.e., numeric memory, prospective memory, and fluid intelligence) than childless women. We explore the possibility of confounding in these associations and rule out the effects of genetic cognitive ability on fertility. We also find that adding controls for educational attainment differ by gender-strengthening associations between parity and cognition for men and largely eliminating them for women. The findings support previous work done on how life course contexts may link to the risk of dementia or cognitive impairment, highlighting parity as potential protective or risk factors to parents' cognitive health. The use of five cognitive domains yields variations in results, giving implications on measure selection of cognitive function and calling for replicated work covering more cognitive domains.