Multiparity, Brain Atrophy, and Cognitive Decline

Number of children and risk of dementia: a cohort study

BACKGROUND

Findings on the link between the number of children and dementia risk are inconsistent, mostly studied in females, suggesting pregnancy-related changes may be a key factor in this association.

METHODS

The Adult Changes in Thought Study is a cohort of adults aged ≥65 years from Kaiser Permanente Washington. The primary exposure was the number of children (0, 1, 2, 3 or ≥4), and the outcome was an incident dementia diagnosis. Cox proportional-hazards models were adjusted for demographic and early-life socioeconomic confounders. Models were then stratified by sex and by birth year <1928 versus ≥1928.

RESULTS

Among 4668 participants (average age at enrolment 74.1±SD 6.3 years; 59% female), 967 (21%) had 0 children, 484 (10%) had one child, 1240 (27%) had two children, 968 (21%) had three children and 1009 (22%) had four or more children. We found no association between the number of children and dementia overall or after stratification by birth cohort. When stratified by sex and adjusting for confounders, having ≥4 children compared with two children was associated with a higher rate of dementia in males (HR=1.31, 95% CI 1.01 to 1.71).

CONCLUSIONS

The number of children was not consistently associated with the risk of dementia. We observed a greater risk of dementia only among males who had ≥4 children, with the lower bound of the 95% CI marginally exceeding 1. These findings suggest that the number of children may influence the risk of dementia through other than pregnancy-related pathways.

Pregnancy as a window of opportunity for dementia prevention: a narrative review

Dementia is a debilitating condition with a disproportionate impact on women. While sex differences in longevity contribute to the disparity, the role of the female sex as a biological variable in disease progression is not yet fully elucidated. Metabolic dysfunctions are drivers of dementia etiology, and cardiometabolic diseases are among the most influential modifiable risk factors. Pregnancy is a time of enhanced vulnerability for metabolic disorders. Many dementia risk factors, such as hypertension or blood glucose dysregulation, often emerge for the first time in pregnancy. While such cardiometabolic complications in pregnancy pose a risk to the health trajectory of a woman, increasing her odds of developing type 2 diabetes or chronic hypertension, it is not fully understood how this relates to her risk for dementia. Furthermore, structural and functional changes in the maternal brain have been reported during pregnancy suggesting it is a time of neuroplasticity for the mother. Therefore, pregnancy may be a window of opportunity to optimize metabolic health and support the maternal brain. Healthy dietary patterns are known to reduce the risk of cardiometabolic diseases and have been linked to dementia prevention, yet interventions targeting cognitive function in late life have largely been unsuccessful. Earlier interventions are needed to address the underlying metabolic dysfunctions and potentially reduce the risk of dementia, and pregnancy offers an ideal opportunity to intervene. This review discusses current evidence regarding maternal brain health and the potential window of opportunity in pregnancy to use diet to address neurological health disparities for women.

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.

Exploring the parity paradox: Differential effects on neuroplasticity and inflammation by APOEe4 genotype at middle age

Female sex and Apolipoprotein E (APOE) ε4 genotype are top non-modifiable risk factors for Alzheimer's disease (AD). Although female-unique experiences like parity (pregnancy and motherhood) have positive effects on neuroplasticity at middle age, previous pregnancy may also contribute to AD risk. To explore these seemingly paradoxical long-term effects of parity, we investigated the impact of parity with APOEε4 genotype by examining behavioural and neural biomarkers of brain health in middle-aged female rats. Our findings show that primiparous (parous one time) hAPOEε4 rats display increased use of a non-spatial cognitive strategy and exhibit decreased number and recruitment of new-born neurons in the ventral dentate gyrus of the hippocampus in response to spatial working memory retrieval. Furthermore, primiparity and hAPOEε4 genotype synergistically modulate inflammatory markers in the ventral hippocampus. Collectively, these findings demonstrate that previous parity in hAPOEε4 rats confers an added risk to present with reduced activity and engagement of the hippocampus as well as elevated pro-inflammatory signaling, and underscore the importance of considering female-specific factors and genotype in health research.

Guidelines for assessing maternal cardiovascular physiology during pregnancy and postpartum

Maternal mortality rates are at an all-time high across the world and are set to increase in subsequent years. Cardiovascular disease is the leading cause of death during pregnancy and postpartum, especially in the United States. Therefore, understanding the physiological changes in the cardiovascular system during normal pregnancy is necessary to understand disease-related pathology. Significant systemic and cardiovascular physiological changes occur during pregnancy that are essential for supporting the maternal-fetal dyad. The physiological impact of pregnancy on the cardiovascular system has been examined in both experimental animal models and in humans. However, there is a continued need in this field of study to provide increased rigor and reproducibility. Therefore, these guidelines aim to provide information regarding best practices and recommendations to accurately and rigorously measure cardiovascular physiology during normal and cardiovascular disease-complicated pregnancies in human and animal models.

Longitudinal associations of reproductive factors and exogeneous estrogens with neuroimaging biomarkers of Alzheimer's disease and cerebrovascular disease

INTRODUCTION

Female-specific reproductive factors and exogeneous estrogen use are associated with cognition in later life. However, the underlying mechanisms are not understood. The present study aimed to investigate the effect of reproductive factors on neuroimaging biomarkers of Alzheimer's disease (AD) and cerebrovascular pathologies.

METHODS

We evaluated 389 females (median age of 71.7 years) enrolled in the Mayo Clinic Study of Aging with reproductive history data and longitudinal magnetic resonance imaging (MRI) scans. We used linear mixed effect models to examine the associations between reproductive factors and changes in neuroimaging measures.

RESULTS

Ever hormonal contraception (HC) use was longitudinally associated with higher fractional anisotropy across the corpus callosum, lower white matter hyperintensity (WMH) volume, and greater cortical thickness in an AD meta-region of interest (ROI). The initiation of menopausal hormone therapy (MHT) > 5 years post menopause was associated with higher WMH volume.

DISCUSSION

HC use and initiation of MHT >5 years post menopause were generally associated with neuroimaging biomarkers of cerebrovascular pathologies.

HIGHLIGHTS

Hormonal contraception use was associated with better brain white matter (WM) integrity. Initiation of menopausal hormone therapy >5 years post menopause was associated with worsening brain WM integrity. Hormonal contraception use was associated with greater cortical thickness. Ages at menarche and menopause and number of pregnancies were not associated with imaging measures. There were few associations between reproductive factors or exogenous estrogens and amyloid or tau PET.

Adolescent stress accelerates postpartum novelty recognition impairment in 5xFAD mice

Pregnancy and the postpartum period induce physiological changes that can influence women's cognitive functions. Alzheimer's disease (AD) has a higher prevalence in women and is exacerbated by early life stress. In the present study, we found that late adolescent social isolation combined with the experience of pregnancy and delivery accelerates the onset of cognitive deficits in 5xFAD dams, particularly affecting their ability to recognize novelty. These cognitive deficits manifested as early as 16 weeks, earlier than the usual timeline for these mice, and were closely associated with increased levels of corticosterone, suggesting dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis. Notably, the presence of β-amyloid plaques in brain regions associated with novelty recognition did not significantly contribute to these deficits. This highlights the potential role of stress and HPA axis dysregulation in the development of cognitive impairments related to AD, and underscores the need for further investigation.

Effects of reproductive experience on cost-benefit decision making in female rats

Many individuals undergo mating and/or other aspects of reproductive experience at some point in their lives, and pregnancy and childbirth in particular are associated with alterations in the prevalence of several psychiatric disorders. Research in rodents shows that maternal experience affects spatial learning and other aspects of hippocampal function. In contrast, there has been little work in animal models concerning how reproductive experience affects cost-benefit decision making, despite the relevance of this aspect of cognition for psychiatric disorders. To begin to address this issue, reproductively experienced (RE) and reproductively naïve (RN) female Long-Evans rats were tested across multiple tasks that assess different forms of cost-benefit decision making. In a risky decision-making task, in which rats chose between a small, safe food reward and a large food reward accompanied by variable probabilities of punishment, RE females chose the large risky reward significantly more frequently than RN females (greater risk taking). In an intertemporal choice task, in which rats chose between a small, immediate food reward and a large food reward delivered after a variable delay period, RE females chose the large reward less frequently than RN females. Together, these results show distinct effects of reproductive experience on different forms of cost-benefit decision making in female rats, and highlight reproductive status as a variable that could influence aspects of cognition relevant for psychiatric disorders.

Parity and Risk of Dementia in Women: The Atherosclerosis Risk in Communities Study

Objective: Reproductive factors, including parity, may contribute to dementia risk, due to hormonal, physiological, social, and demographic factors. We hypothesized that higher parity would be associated with increased dementia risk. Materials and Methods: We utilized data from the Atherosclerosis Risk in Communities (ARIC) community-based cohort study. Participants were recruited in 1987-1989 and followed through 2017. Participants, all born between 1921 and 1945, were from four U.S. communities in Forsyth County, NC; Jackson, MS; Minneapolis, MN; and Washington County, MD. We included all female participants seen at ARIC visit three or five for whom parity and dementia outcomes were available (N = 7,921). The primary exposure was self-reported number of live births. Our primary outcome was dementia, diagnosed via neurocognitive assessments, informant interviews, and expert adjudication. We created Cox proportional hazards models to evaluate the association between parity and incident dementia, adjusting for demographic factors, education level, apolipoprotein E allele status, and vascular risk factors. We tested for interactions by race and birth cohort. Results: The adjusted hazard ratio was 0.82 (95% confidence intervals [CI] 0.69-0.99) for dementia in women with 0-1 births and 0.85 (95% CI 0.72-0.99) for women with 5+ births, compared to women with 2 births (reference group). This association was present in women born from 1924 to 1934, but not in women born in 1935 or later (p-interaction <0.001). Conclusion: We found an inverted U-shaped association of parity with dementia risk. This effect was modified by birth cohort, suggesting that the association may depend on demographic and sociocultural factors.

Comparison of the clinical value of MRI and plasma markers for cognitive impairment in patients aged ≥75 years: a retrospective study

Background

Dementia has become the main cause of disability in older adults aged ≥75 years. Cerebral small vessel disease (CSVD) is involved in cognitive impairment (CI) and dementia and is a cause of vascular CI (VCI), which is manageable and its onset and progression can be delayed. Simple and effective markers will be beneficial to the early detection and intervention of CI. The aim of this study is to investigate the clinical application value of plasma amyloid β1-42 (Aβ42), phosphorylated tau 181 (p-tau181) and conventional structural magnetic resonance imaging (MRI) parameters for cognitive impairment (CI) in patients aged ≥75 years.

Methods

We retrospectively selected patients who visited the Affiliated Hospital of Xuzhou Medical University and were clinically diagnosed with or without cognitive dysfunction between May 2018 and November 2021. Plasma indicators (Aβ42 and p-tau181) and conventional structural MRI parameters were collected and analyzed. Multivariate logistic regression and receiver operator characteristic (ROC) curve were used to evaluate the diagnostic value.

Results

One hundred and eighty-four subjects were included, including 54 cases in CI group and 130 cases in noncognitive impairment (NCI) groups, respectively. Univariate logistic regression analysis revealed that the percentages of Aβ42+_, P-tau 181+, and Aβ42+/P-tau181+ showed no significant difference between the groups of CI and NCI (all P > 0.05). Multivariate logistic regression analysis showed that moderate/severe periventricular WMH (PVWMH) (OR 2.857, (1.365-5.983), P = 0.005), lateral ventricle body index (LVBI) (OR 0.413, (0.243-0.700), P = 0.001), and cortical atrophy (OR 1.304, (1.079-1.575), P = 0.006) were factors associated with CI. The combined model including PVWMH, LVBI, and cortical atrophy to detect CI and NCI showed an area under the ROC curve (AUROC) is 0.782, with the sensitivity and specificity 68.5% and 78.5%, respectively.

Conclusion

For individuals ≥75 years, plasma Aβ42 and P-tau181 might not be associated with cognitive impairment, and MRI parameters, including PVWMH, LVBI and cortical atrophy, are related to CI. The cognitive statuses of people over 75 years old were used as the endpoint event in this study. Therefore, it can be considered that these MRI markers might have more important clinical significance for early assessment and dynamic observation, but more studies are still needed to verify this hypothesis.

Walking for Cognitive Health: Previous Parity Moderates the Relationship Between Self-Reported Walking and Cognition

BACKGROUND

Older females show greater cognitive gains from physical activity (PA) than males, which may be related to long-term consequences of female-specific reproductive events (eg, pregnancy) on cognitive health.

METHODS

To determine whether previous parity could moderate the relationship between PA and cognitive decline in older women, we conducted secondary analyses of data from the Health, Aging, and Body Composition Study. We tested whether the association between average PA over 10 years and cognition (Modified Mini-Mental State Examination [3MS]) and executive functioning (digit symbol substitution test [DSST]) over 10 years varied by previous parity (nulliparity, low parity, medium parity, and grand multiparity). An analysis of covariance was performed with cognition (average and change over 10 years) as the dependent variables, parity as a categorical predictor, average PA as a continuous predictor, and a set of relevant covariates.

RESULTS

Significant interactions were found between PA and parity group for all 4 comparisons: average 3MS (p = .014), average DSST (p = .032), change in 3MS (p = .016), and change in DSST (p = .017). Simple slope analyses indicated the positive relationship between PA and average 3MS and DSST was only significant in the nulliparity and grand multiparity groups, and the positive relationship between PA and change in 3MS and DSST was only significant in the grand multiparity group.

CONCLUSION

The findings suggest the relationship between self-reported walking and cognitive performance was strongest in the groups at risk for cognitive decline and dementia, the nulliparous and grand multiparous groups.

Retinal Venule Coverage by Pericytes Decreases in Multiparous Mice in a Time-Dependent Manner Post-Delivery

Structural changes in the retinal vasculature have been linked to increased cardiovascular risks and also change as a function of age. Because multiparity has been associated with poorer cardiovascular health scores, we hypothesized that changes in retinal vascular caliber would be observed in multiparous, compared to nulliparous, females and retired breeder males. Age-matched nulliparous (n = 6) and multiparous (n = 11, retired breeder females with 4 ± 1 litters), and male breeder (n = 7) SMA-GFP reporter mice were included for assessment of retinal vascular structure. Multiparous females had higher body mass, heart weight, and kidney weight compared to nulliparous mice, with lower kidney and higher brain weight compared to male breeders. There was no difference in number of retinal arterioles or venules, or arteriole or venule diameter among groups; however, venous pericyte density (number per venule area) decreased in multiparous vs. nulliparous mice and was negatively associated with the time since last litter and with age. Our results suggest that the time elapsed since delivery is an important factor to be considered in multiparity studies. Taken together, changes in vascular structure and potentially function, are time- and age-dependent. Ongoing and future work will determine whether structural changes are associated with functional consequences at the blood-retinal barrier.

Associations Between Parity and Cognition: Race/Ethnic Differences

BACKGROUND

Race/ethnicity is associated with differences in reproductive history and cognition individually, yet it remains an understudied factor in the relationship between parity and later-life cognition.

OBJECTIVE

To evaluate if the association between parity and cognition differs between racial/ethnic groups.

METHODS

Participants included 778 older, postmenopausal women from the Health and Nutrition Examination Survey (Latina: n = 178, Non-Latino Black [NLB]: n = 169, Non-Latino White [NLW]: n = 431) who self-reported at least one birth. Cognitive outcomes included working memory, learning memory, and verbal fluency. Covariates included age, education, cardiovascular and other reproductive health factors, adult socioeconomic status (SES) and depressive symptoms. We fit a series of linear models to examine a) whether parity was associated with cognitive functioning, b) if this association varied by race/ethnicity through parity by race/ethnicity interactions, and c) individual parity with cognition associations stratified by race/ethnicity.

RESULTS

In the full sample, parity was significantly negatively associated with Digit Symbol Substitution Test (DSST) performance (b = -0.70, p = 0.024) but not Animal Fluency or word-list learning and memory. Tests of race/ethnicity-by-parity interactions were not statistically significant (ps > 0.05). However, stratified analyses by race/ethnicity showed a differential effect of parity on DSST performance, such that parity was significantly negatively associated with DSST performance (b = -1.66, p = 0.007) among Latinas but not in NLWs (b = -0.16, p = 0.74) or NLBs (b = -0.81, p = 0.191).

CONCLUSION

Among Latina, but not NLB or NLW women, greater parity was associated with worse processing speed/executive functioning later in life. Further research is needed to understand the mechanisms driving racial/ethnic differences.

The expectant brain-pregnancy leads to changes in brain morphology in the early postpartum period

There is growing evidence that pregnancy may have a significant impact on the maternal brain, causing changes in its structure. To investigate the patterns of these changes, we compared nulliparous women (n = 40) with a group of primiparous women (n = 40) and multiparous mothers (n = 37) within 1-4 days postpartum, using voxel-based and surface-based morphometry (SBM). Compared with the nulliparous women, the young mothers showed decreases in gray matter volume in the bilateral hippocampus/amygdala, the orbitofrontal/subgenual prefrontal area, the right superior temporal gyrus and insula, and the cerebellum. These pregnancy-related changes in brain structure did not predict the quality of mother-infant attachment at either 3 or 12 weeks postpartum nor were they more pronounced among the multiparous women. SBM analyses showed significant cortical thinning especially in the frontal and parietal cortices, with the parietal cortical thinning likely potentiated by multiple pregnancies. We conclude that, compared with the brain of nulliparous women, the maternal brain shows widespread morphological changes shortly after childbirth. Also, the experience of pregnancy alone may not be the underlying cause of the adaptations for mothering. As regards the exact biological function of the changes in brain morphology, longitudinal research will be needed to draw any definitive conclusions.

Associations of Parity With Change in Global Cognition and Incident Cognitive Impairment in Older Women

Background

The evidence of the association between parity and risk of mild cognitive impairment (MCI) or dementia is mixed, and the relationship between parity and longitudinal cognitive changes is less clear. We investigated these issues in a large population of older women who were carefully monitored for development of MCI and probable dementia.

Methods

Using the Women’s Health Initiative Memory Study, 7,100 postmenopausal women (mean age 70.1 ± 3.8 years) with information on baseline parity (defined as the number of term pregnancies), measures of global cognition (Modified Mini-Mental State Examination score) from 1996–2007, and cognitive impairment (centrally adjudicated diagnoses of MCI and dementia) from 1996–2016 were included. Multivariable linear mixed-effects models were used to analyze the rate of changes in global cognition. Cox regression models were used to evaluate the risk of MCI/dementia across parity groups.

Results

Over an average of 10.5 years, 465 new cases of MCI/dementia were identified. Compared with nulliparous women, those with a parity of 1–3 and ≥4 had a lower MCI/dementia risk. The HRs were 0.75 (0.56–0.99) and 0.71 (0.53–0.96), respectively (P < 0.01). Similarly, a parity of 1–3 and ≥4 was related to slower cognitive decline (β = 0.164, 0.292, respectively, P < 0.05).

Conclusion

Higher parity attenuated the future risk for MCI/dementia and slowed the rates of cognitive decline in elderly women. Future studies are needed to determine how parity affects late-life cognitive function in women.

Endogenous and Exogenous Estrogen Exposures: How Women's Reproductive Health Can Drive Brain Aging and Inform Alzheimer's Prevention

After advanced age, female sex is the major risk factor for late-onset Alzheimer's disease (AD), the most common cause of dementia affecting over 24 million people worldwide. The prevalence of AD is higher in women than in men, with postmenopausal women accounting for over 60% of all those affected. While most research has focused on gender-combined risk, emerging data indicate sex and gender differences in AD pathophysiology, onset, and progression, which may help account for the higher prevalence in women. Notably, AD-related brain changes develop during a 10-20 year prodromal phase originating in midlife, thus proximate with the hormonal transitions of endocrine aging characteristic of the menopause transition in women. Preclinical evidence for neuroprotective effects of gonadal sex steroid hormones, especially 17β-estradiol, strongly argue for associations between female fertility, reproductive history, and AD risk. The level of gonadal hormones to which the female brain is exposed changes considerably across the lifespan, with relevance to AD risk. However, the neurobiological consequences of hormonal fluctuations, as well as that of hormone therapies, are yet to be fully understood. Epidemiological studies have yielded contrasting results of protective, deleterious and null effects of estrogen exposure on dementia risk. In contrast, brain imaging studies provide encouraging evidence for positive associations between greater cumulative lifetime estrogen exposure and lower AD risk in women, whereas estrogen deprivation is associated with negative consequences on brain structure, function, and biochemistry. Herein, we review the existing literature and evaluate the strength of observed associations between female-specific reproductive health factors and AD risk in women, with a focus on the role of endogenous and exogenous estrogen exposures as a key underlying mechanism. Chief among these variables are reproductive lifespan, menopause status, type of menopause (spontaneous vs. induced), number of pregnancies, and exposure to hormonal therapy, including hormonal contraceptives, hormonal therapy for menopause, and anti-estrogen treatment. As aging is the greatest risk factor for AD followed by female sex, understanding sex-specific biological pathways through which reproductive history modulates brain aging is crucial to inform preventative and therapeutic strategies for AD.

A Lifecourse Perspective on Female Sex-Specific Risk Factors for Later Life Cognition

PURPOSE OF REVIEW

The prevalence of Alzheimer's disease and related dementias is greater in women compared to men. We provide a review of female sex-specific risk factors across the lifecourse for cognition in older adulthood, highlighting areas that need further study.

RECENT FINDINGS

Pregnancy may affect late-life cognition, with adverse pregnancy outcomes associated with an increased risk of cognitive decline but parity providing a protective effect. Cumulative estrogen exposure, influenced by age of menarche, menopause, and exogenous estrogen use, may modify a woman's risk for dementia. Menopause transition-associated symptoms may impact cognitive health at the time of the symptoms, but long-term effects remain unknown. As compared to natural menopause, surgical menopause seems to increase the risk for cognitive impairment. Studies that have assessed the association between women's reproductive health and cognition have produced conflicting results. Future studies that address these inconsistencies among diverse populations are needed to better care for women throughout their lives.