Differential effects of completed and incomplete pregnancies on the risk of Alzheimer disease

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.

Apolipoprotein E polymorphisms and female fertility in a transgenic mouse model of Alzheimer's disease

Apolipoprotein E (APOE) is a major cholesterol carrier responsible for lipid transport and injury repair in the brain. The human APOE gene (h-APOE) has 3 naturally occurring alleles: ε3, the common allele; ε4, which increases Alzheimer's disease (AD) risk up to 15-fold; and ε2, the rare allele which protects against AD. Although APOE4 has negative effects on neurocognition in old age, its persistence in the population suggests a survival advantage. We investigated the relationship between APOE genotypes and fertility in EFAD mice, a transgenic mouse model expressing h-APOE. We show that APOE4 transgenic mice had the highest level of reproductive performance, followed by APOE3 and APOE2. Intriguingly, APOE3 pregnancies had more fetal resorptions and reduced fetal weights relative to APOE4 pregnancies. In conclusion, APOE genotypes impact fertility and pregnancy outcomes in female mice, in concordance with findings in human populations. These mouse models may help elucidate how h-APOE4 promotes reproductive fitness at the cost of AD in later life.

Pregnancy-induced oxidative stress and inflammation are not associated with impaired maternal neuronal activity or memory function

Pregnancy is associated with neural and behavioral plasticity, systemic inflammation, and oxidative stress, yet the impact of inflammation and oxidative stress on maternal neural and behavioral plasticity during pregnancy is unclear. We hypothesized that healthy pregnancy transiently reduces learning and memory and these deficits are associated with pregnancy-induced elevations in inflammation and oxidative stress. Cognitive performance was tested with novel object recognition (recollective memory), Morris water maze (spatial memory), and open field (anxiety-like) behavior tasks in female Sprague-Dawley rats of varying reproductive states [nonpregnant (nulliparous), pregnant (near term), and 1-2 mo after pregnancy (primiparous); n = 7 or 8/group]. Plasma and CA1 proinflammatory cytokines were measured with a MILLIPLEX magnetic bead assay. Plasma oxidative stress was measured via advanced oxidation protein products (AOPP) assay. CA1 markers of oxidative stress, neuronal activity, and apoptosis were quantified via Western blot analysis. Our results demonstrate that CA1 oxidative stress-associated markers were elevated in pregnant compared with nulliparous rats (P ≤ 0.017) but there were equivalent levels in pregnant and primiparous rats. In contrast, reproductive state did not impact CA1 inflammatory cytokines, neuronal activity, or apoptosis. Likewise, there was no effect of reproductive state on recollective or spatial memory. Even so, spatial learning was impaired (P ≤ 0.007) whereas anxiety-like behavior (P ≤ 0.034) was reduced in primiparous rats. Overall, our data suggest that maternal hippocampal CA1 is protected from systemic inflammation but vulnerable to peripartum oxidative stress. Peripartum oxidative stress elevations, such as in pregnancy complications, may contribute to peripartum neural and behavioral plasticity.NEW & NOTEWORTHY Healthy pregnancy is associated with elevated maternal systemic and brain oxidative stress. During postpregnancy, brain oxidative stress remains elevated whereas systemic oxidative stress is resolved. This sustained maternal brain oxidative stress is associated with learning impairments and decreased anxiety-like behavior during the postpregnancy period.

Parental status and markers of brain and cellular age: A 3D convolutional network and classification study

Recent research shows prominent effects of pregnancy and the parenthood transition on structural brain characteristics in humans. Here, we present a comprehensive study of how parental status and number of children born/fathered links to markers of brain and cellular ageing in 36,323 UK Biobank participants (age range 44.57-82.06 years; 52% female). To assess global effects of parenting on the brain, we trained a 3D convolutional neural network on T1-weighted magnetic resonance images, and estimated brain age in a held-out test set. To investigate regional specificity, we extracted cortical and subcortical volumes using FreeSurfer, and ran hierarchical clustering to group regional volumes based on covariance. Leukocyte telomere length (LTL) derived from DNA was used as a marker of cellular ageing. We employed linear regression models to assess relationships between number of children, brain age, regional brain volumes, and LTL, and included interaction terms to probe sex differences in associations. Lastly, we used the brain measures and LTL as features in binary classification models, to determine if markers of brain and cellular ageing could predict parental status. The results showed associations between a greater number of children born/fathered and younger brain age in both females and males, with stronger effects observed in females. Volume-based analyses showed maternal effects in striatal and limbic regions, which were not evident in fathers. We found no evidence for associations between number of children and LTL. Classification of parental status showed an Area under the ROC Curve (AUC) of 0.57 for the brain age model, while the models using regional brain volumes and LTL as predictors showed AUCs of 0.52. Our findings align with previous population-based studies of middle- and older-aged parents, revealing subtle but significant associations between parental experience and neuroimaging-based surrogate markers of brain health. The findings further corroborate results from longitudinal cohort studies following parents across pregnancy and postpartum, potentially indicating that the parenthood transition is associated with long-term influences on brain health.

Sexual Dimorphism in Age-Dependent Neurodegeneration After Mild Head Trauma in Drosophila : Unveiling the Adverse Impact of Female Reproductive Signaling

Environmental insults, including mild head trauma, significantly increase the risk of neurodegeneration. However, it remains challenging to establish a causative connection between early-life exposure to mild head trauma and late-life emergence of neurodegenerative deficits, nor do we know how sex and age compound the outcome. Using a Drosophila model, we demonstrate that exposure to mild head trauma causes neurodegenerative conditions that emerge late in life and disproportionately affect females. Increasing age-at-injury further exacerbates this effect in a sexually dimorphic manner. We further identify Sex Peptide (SP) signaling as a key factor in female susceptibility to post-injury brain deficits. RNA sequencing highlights a reduction in innate immune defense transcripts specifically in mated females during late life. Our findings establish a causal relationship between early head trauma and late-life neurodegeneration, emphasizing sex differences in injury response and the impact of age-at-injury. Finally, our findings reveal that reproductive signaling adversely impacts female response to mild head insults and elevates vulnerability to late-life neurodegeneration.

Association between Female Reproductive Factors and Risk of Dementia

Women have an over 50% greater risk of dementia than men, which is a main topic of much research. This review aims to investigate the impact of a woman's reproductive history on dementia risk. The consequences of stillbirth are long-term health and psychosocial problems for women. Because of the awareness of an endangered pregnancy, many parents experience deep anxiety and stress in subsequent pregnancies. There are contradictory conclusions from research about abortion and the risk of dementia correlation. When it comes to the late age of first birth, which is said to be above 35 years old, it was observed that older mothers have a decreased risk of dementia compared to those who gave birth in their 20s; however, being a child of the older mother is connected with a higher risk of developing dementia. Using hormonal contraception can result in decreased risk of dementia as estrogen stimulates microglia-related Aβ removal and reduces tau hyperphosphorylation. The influence of postmenopausal hormonal therapy and the duration of the reproductive period on developing dementia remains unclear. Although female disorders like endometriosis and polycystic ovary syndrome are reported to increase the risk of dementia, the research on this topic is very limited, especially when it comes to endometriosis, and needs further investigation. Interestingly, there is no conclusion on whether hypertensive disorders of pregnancy increase the risk of dementia, but most articles seem to confirm this theory.

Women and the risk of Alzheimer's disease

Purpose of the review

This review will elucidate reasons to explain why women may be at greater risk for Alzheimer's disease.

Recent findings

Potential mechanisms to explain sex and gender differences in Alzheimer dementia include: differences in risk associated with the apolipoprotein E 4 allele; telomere shortening- which is linked with neurodegeneration, higher incidence of depression and insomnia in women as psychiatric co-morbidities which are linked with an increased Alzheimer disease risk, disorders of pregnancy including gestational hypertension and preeclampsia and psychosocial factors such as educational level which may contribute to differences in cognitive reserve.

Summary

The sex and gender differences in Alzheimer's disease can be explained by biological and psychosocial factors.

Cellular and molecular signatures of motherhood in the adult and ageing rat brain

Pregnancy is marked by robust changes, including brain changes to volume, structure, connectivity and neuroplasticity. Although some brain changes are restricted to pregnancy and the postpartum, others are long-lasting. Few studies have examined possible mechanisms of these changes or the effects of multiple pregnancies. We characterized various cellular and molecular signatures of parity (nulliparous, primiparous, biparous) in the rat hippocampus. We investigated density of neural stems cells (Sox2), microglia (Iba-1) and levels of a synaptic protein (PSD-95), cell signalling pathways, neuroinflammation, and the tryptophan-kynurenine (TRP-KYN) pathway, one week after weaning their pups from the last pregnancy (age of dam: seven months) and in middle-age (age of dam: 13 months). Parity increased PSD-95 levels in both age groups and prevented the age-related decrease in neural stem cell density observed in nulliparous rats. Biparity increased cell signalling phosphoproteins (pp70S6K, S6RP) and number of microglia in the dentate gyrus, regardless of age. Parity resulted in transient changes to the TRP-KYN system. Thus, previous parity has lasting effects on synaptic plasticity with fewer lasting effects on inflammation and cell signalling phosphoproteins in the whole hippocampus.

Cognitive impairment and the associated factors among women with a history of pregnancy complications in rural southwestern Uganda

BACKGROUND

Worldwide, there is a growing concern about the rising number of people with declining cognitive functioning. However, findings on this phenomenon are inconclusive. Our study aimed to assess the prevalence of cognitive impairment and the associated factors in women with a history of pregnancy complications in rural southwestern Uganda.

METHODS

This was a cross-sectional study carried out among women above 40 years of age in the greater Kabale district of southwestern Uganda between March and April 2022. Study participants were identified using a consecutive sampling method. Predictor variables included pregnancy complications and other social demographic factors that were assessed by semi-structured interviews while cognitive functioning as an outcome variable was assessed by Montreal Cognitive Assessment (MoCA-B) tool. Data were analyzed using STATA at a 95% Confidence level. Logistic regression analyses were selected for statistical modelling while odds ratios were calculated to assess the strength of associations between the predictor and outcome variables.

RESULTS

In total, 75% (212/280) of participants had some form of cognitive impairment, with 45% (123/280) falling into mild CI, 31% (86/280) moderate CI and 4% (10/280) severe CI. Twenty-three percent (68/280) of participants fell into category of normal cognitive functioning. Participants with >65 years of age had higher odds of developing cognitive impairment (OR = 2.94; 95%CI: 0.96-9.04, p = 0.06) than those with < 65 years of age. Protective factors to cognitive impairment include delivering from a health facility (OR = 0.31,95% CI:0.16-0.60, p = < .001), primary and post primary levels of education (OR = 0.05; 95% CI: 0.02-0.13, p<0.001, OR = 0.04; 95%CI: 0.02-0.23, p<0.001) respectively.

CONCLUSION

Results from this study show a high prevalence of cognitive impairment among women with a history of pregnancy complications in rural southwestern Uganda. Interventions geared toward preventing cognitive impairment among females with a history of pregnancy complications should be emphasized.

Sex and gender differences in Alzheimer's disease, Parkinson's disease, and Amyotrophic Lateral Sclerosis: a narrative review

Neurodegenerative diseases (NDs), including Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS), exhibit high phenotypic variability and they are very common in the general population. These diseases are associated with poor prognosis and a significant burden on patients and their caregivers. Although increasing evidence suggests that biological sex is an important factor for the development and phenotypical expression of some NDs, the role of sex and gender in the diagnosis and prognosis of NDs has been poorly explored. Current knowledge relating to sex- and gender-related differences in the epidemiology, clinical features, biomarkers, and treatment of AD, PD, and ALS will be summarized in this narrative review. The cumulative evidence hitherto collected suggests that sex and gender are factors to be considered in explaining the heterogeneity of these NDs. Clarifying the role of sex and gender in AD, PD, and ALS is a key topic in precision medicine, which will facilitate sex-specific prevention and treatment strategies to be implemented in the near future.

Beyond sex differences: short- and long-term effects of pregnancy on the brain

Growing attention has been directed to the inclusion of females in neuroscience studies, and to the importance of studying sex as a biological variable. However, how female-specific factors such as menopause and pregnancy, affect the brain remains understudied. In this review, we use pregnancy as a case in point of a female-unique experience that can alter neuroplasticity, neuroinflammation, and cognition. We examine studies in both humans and rodents indicating that pregnancy can modify neural function in the short term, as well as alter the trajectory of brain aging. Furthermore, we discuss the influence of maternal age, fetal sex, number of pregnancies, and presence of pregnancy complications on brain health outcomes. We conclude by encouraging the scientific community to prioritize researching female health by recognizing and including factors such as pregnancy history in research.

Lactation attenuates pro-oxidant reactions in the maternal brain

Reactive oxygen species (ROS) are intimately linked to bioenergetics and redox biology, contributing to cellular functioning and physiological signaling, but also acting as toxic agents during oxidative stress. Hence, the balance between pro-oxidant reactions and the activity of antioxidant defenses sustains a basal oxidative status, controls the increase of redox signaling, and mediates potential pathological events during oxidative stress. Maternal experience, especially during nursing, requires high energetic demands and expenditure to ensure the well-being of the offspring. The mother must adapt from satisfying her own needs to additionally fulfilling those of her descendants. Oxidative stress has been proposed as one of the reproductive trade-off hallmarks. However, the oxidative shielding hypothesis has also been proposed in the context of reproduction. The reproductive experience induces a wide range of well-documented changes in the female brain, which potentially lead to protection against the enhanced oxidative activity. To date, the metabolic and cellular mechanisms that underlie lactation-induced neuroprotection against oxidants are unknown. The neuroendocrine changes in the brain of the lactating dam promote diminished propensity to excitotoxic brain injury and stress, as well as enhanced neuroprotection and plasticity. In addition to review studies on the oxidant balance due to motherhood, we included new data from our laboratory, addressing the importance of measuring pro-oxidant reactions in separated brain regions. The hippocampus of lactating rats exhibits lower levels of pro-oxidant reactions than that of virgin rats, supporting the oxidative shielding hypothesis in lactation.

Drosophila melanogaster as a model to study age and sex differences in brain injury and neurodegeneration after mild head trauma

Repetitive physical insults to the head, including those that elicit mild traumatic brain injury (mTBI), are a known risk factor for a variety of neurodegenerative conditions including Alzheimer's disease (AD), Parkinson's disease (PD), and chronic traumatic encephalopathy (CTE). Although most individuals who sustain mTBI typically achieve a seemingly full recovery within a few weeks, a subset experience delayed-onset symptoms later in life. As most mTBI research has focused on the acute phase of injury, there is an incomplete understanding of mechanisms related to the late-life emergence of neurodegeneration after early exposure to mild head trauma. The recent adoption of Drosophila-based brain injury models provides several unique advantages over existing preclinical animal models, including a tractable framework amenable to high-throughput assays and short relative lifespan conducive to lifelong mechanistic investigation. The use of flies also provides an opportunity to investigate important risk factors associated with neurodegenerative conditions, specifically age and sex. In this review, we survey current literature that examines age and sex as contributing factors to head trauma-mediated neurodegeneration in humans and preclinical models, including mammalian and Drosophila models. We discuss similarities and disparities between human and fly in aging, sex differences, and pathophysiology. Finally, we highlight Drosophila as an effective tool for investigating mechanisms underlying head trauma-induced neurodegeneration and for identifying therapeutic targets for treatment and recovery.

Associations between parenthood and dementia in men and women: biology or confounding?

BACKGROUND

High parity and extremes of age at first birth have been linked with increased dementia risk in women, with exposure to pregnancy-associated physiological changes proposed as an explanation. However, confounding by socioeconomic and lifestyle factors could also produce such associations, whereby men would share similar patterns of association. We investigated whether these associations hold for both sexes.

METHODS

In a cohort study including all women (N = 2,222,638) and men (N = 2,141,002) ≥ 40 years of age in 1994-2017 in Denmark, we used Cox regression to evaluate associations between number of children, age at first birth, and dementia risk separately for women and men.

RESULTS

During follow-up, 81,413 women and 53,568 men (median age at diagnosis, 83.3 and 80.3 years, respectively) developed dementia. Compared with having one child, having two or more children was associated with modest decreases in overall dementia risk in both sexes (hazard ratio [HR] range 0.82-0.91, P_{difference men vs. women} = 0.07). Although the associations between childlessness and overall dementia risk differed statistically for men and women, the association magnitudes differed only slightly (HR_men 1.04, 95% confidence interval [CI] 1.01-1.06; HR_women 0.99, 95% CI 0.97-1.01; P = 0.002). Associations between age at becoming a parent and overall dementia were also similar for women and men, with the exception of older (≥ 40 years) first-time parents (HR_men 1.00, 95% CI 0.96-1.05; HR_women 0.92, 95% CI 0.86-0.98; P = 0.01). With few exceptions, sub-analyses by dementia subtype and timing of onset also revealed similar patterns and effect magnitudes for women and men.

CONCLUSIONS

Associations between number of children, age at becoming a parent, and dementia risk were similar for both sexes. Lifestyle and socioeconomic factors are more likely to explain the observed associations than normal pregnancy-related physiological changes.

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.

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 mediating role of socioeconomic status on the relationship between pregnancy history and later-life cognition

OBJECTIVE

The association of pregnancy with later-life cognition is not well understood. We examined whether full-term and incomplete pregnancies were associated with cognition in a sample of postmenopausal women, and whether socioeconomic status (SES) factors mediated these relationships.

METHODS

A total of 1016 cognitively normal women from the National Health and Nutrition Examination Survey (NHANES) were examined. Cognitive measures included the Digit Symbol Substitution Test (DSST), Animal Fluency (AF) and the Consortium to Establish a Registry for Alzheimer's Disease (CERAD) Word Learning (CERAD-WL) and Delayed Recall (CERAD-DR) tasks. Analyses examined the relationship between the number of term and incomplete pregnancies with cognitive performance, as well as the mediating effects of education and the federal income-to-poverty ratio (PIR).

RESULTS

A greater number of term pregnancies was associated with worse performance on the DSST (β = -0.09, 95% confidence interval [CI]: -0.12, -0.06), AF (β = -0.03, 95% CI: -0.07, 0.00) and CERAD-DR (β = -0.04, 95% CI: -0.08, -0.01). More incomplete pregnancies were associated with better CERAD-DR performance (β = 0.07, 95% CI: 0.01, 0.13), and 28% (95% CI: 0.17, 0.42) of the association of term pregnancies with the DSST was mediated by the PIR.

CONCLUSIONS

A higher number of term pregnancies was associated with worse cognitive performance, whereas a higher number of incomplete pregnancies was associated with better cognitive performance. Results indicate the necessity to consider SES factors when studying the relationship between pregnancy and cognition.

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.

Reproductive factors and the risk of incident dementia: A cohort study of UK Biobank participants

BACKGROUND

Women's reproductive factors have been associated with the risk of dementia; however, these findings remain uncertain. This study aimed to examine the risk of incident all-cause dementia associated with reproductive factors in women and the number of children in both sexes and whether the associations vary by age, socioeconomic status (SES), smoking status, and body mass index (BMI) in the UK Biobank.

METHODS AND FINDINGS

A total of 273,240 women and 228,957 men without prevalent dementia from the UK Biobank were included in the analyses. Cox proportional hazard regressions estimated hazard ratios (HRs) for reproductive factors with incident all-cause dementia. Multiple adjusted models included age at study entry, SES, ethnicity, smoking status, systolic blood pressure, BMI, history of diabetes mellitus, total cholesterol, antihypertensive drugs, and lipid-lowering drugs. Over a median of 11.8 years follow-up, 1,866 dementia cases were recorded in women and 2,202 in men. Multiple adjusted HRs ((95% confidence intervals (CIs)), p-value) for dementia were 1.20 (1.08, 1.34) (p = 0.016) for menarche <12 years and 1.19 (1.07, 1.34) (p = 0.024) for menarche >14 years compared to 13 years; 0.85 (0.74, 0.98) (p = 0.026) for ever been pregnant; 1.43 (1.26, 1.62) (p < 0.001) for age at first live birth <21 compared to 25 to 26 years; 0.82 (0.71, 0.94) (p = 0.006) for each abortion; 1.32 (1.15, 1.51) (p = 0.008) for natural menopause at <47 compared to 50 years; 1.12 (1.01, 1.25) (p = 0.039) for hysterectomy; 2.35 (1.06, 5.23) (p = 0.037) for hysterectomy with previous oophorectomy; and 0.80 (0.72, 0.88) (p < 0.001) for oral contraceptive pills use. The U-shaped associations between the number of children and the risk of dementia were similar for both sexes: Compared with those with 2 children, for those without children, the multiple adjusted HR ((95% CIs), p-value) was 1.18 (1.04, 1.33) (p = 0.027) for women and 1.10 (0.98, 1.23) (p = 0.164) for men, and the women-to-men ratio of HRs was 1.09 (0.92, 1.28) (p = 0.403); for those with 4 or more children, the HR was 1.14 (0.98, 1.33) (p = 0.132) for women and 1.26 (1.10, 1.45) (p = 0.003) for men, and the women-to-men ratio of HRs was 0.93 (0.76, 1.14) (p = 0.530). There was evidence that hysterectomy (HR, 1.31 (1.09, 1.59), p = 0.013) and oophorectomy (HR, 1.39 (1.08, 1.78), p = 0.002) were associated with a higher risk of dementia among women of relatively lower SES only. Limitations of the study include potential residual confounding and self-reported measures of reproductive factors, as well as the limited representativeness of the UK Biobank population.

CONCLUSIONS

In this study, we observed that some reproductive events related to shorter cumulative endogenous estrogen exposure in women were associated with higher dementia risk, and there was a similar association between the number of children and dementia risk between women and men.

Effects of Reproductive Factors on Lauren Intestinal-Type Gastric Cancers in Females: A Multicenter Retrospective Study in South Korea

Background/Aims

Gastric cancers (GCs), particularly the Lauren intestinal type, show a male predominance. The aim of this study was to investigate the effects of reproductive factors on GCs in females, according to Lauren classification.

Methods

Medical records of 1,849 males and 424 females who underwent radical gastrectomy or endoscopic resection for GCs between 2010 and 2018 were reviewed. The incidences of intestinal-type GCs were compared between males and groups of females stratified according to postmenopausal period. Associations between reproductive factors in females and intestinaltype GCs were analyzed using multivariate models.

Results

The proportions of intestinal-type GCs were significantly lower in premenopausal (19%), less than 10 years postmenopausal (30.4%), and 10 to 19 years postmenopausal females (44.1%) than in males (61.0%) (p<0.05 for all). Females ≥20 years postmenopause had a proportion of intestinal-type GCs similar to that in males (60.6% vs 61.0%; p=0.948). Multivariate analysis revealed that age (odds ratio [OR], 1.075; 95% confidence interval [CI], 1.039 to 1.113; p<0.001) and parity ≥3 (OR, 1.775; 95% CI, 1.012 to 3.114; p=0.045) were positively associated with an increased risk of intestinal-type GCs in postmenopausal females, while long fertility duration (OR, 1.147; 95% CI, 1.043 to 1.261; p=0.005) was positively associated with an increased risk of intestinal-type GCs in premenopausal females.

Conclusions

There were no significant differences in the proportions of intestinal-type GCs between males and females ≥20 years postmenopause, suggesting that female reproductive factors play a role in the prevention of intestinal-type GC.

Recent Neuroscience Advances in Human Parenting

The transition to parenthood entails brain adaptations to the demands of caring for a newborn. This chapter reviews recent neuroscience findings on human parenting, focusing on neuroimaging studies. First, we describe the brain circuits underlying human maternal behavior, which comprise ancient subcortical circuits and more sophisticated cortical regions. Then, we present the short-term and long-term functional and structural brain adaptations that characterize the transition to motherhood, discuss the long-term effects of parenthood on the brain, and propose several underlying neural mechanisms. We also review neuroimaging findings in biological fathers and alloparents (such as other relatives or adoptive parents), who engage in parenting without directly experiencing pregnancy or childbirth. Finally, we describe perinatal mental illnesses and discuss the neural responses associated with such disorders. To date, studies indicate that parenthood is a period of enhanced brain plasticity within brain areas critical for cognitive and social processing and that both parenting experience and gestational-related factors can prime such plasticity.

Hormones and neuroplasticity: A lifetime of adaptive responses

Major life transitions often co-occur with significant fluctuations in hormones that modulate the central nervous system. These hormones enact neuroplastic mechanisms that prepare an organism to respond to novel environmental conditions and/or previously unencountered cognitive, emotional, and/or behavioral demands. In this review, we will explore several examples of how hormones mediate neuroplastic changes in order to produce adaptive responses, particularly during transitions in life stages. First, we will explore hormonal influences on social recognition in both males and females as they transition to sexual maturity. Next, we will probe the role of hormones in mediating the transitions to motherhood and fatherhood, respectively. Finally, we will survey the long-term impact of reproductive experience on neuroplasticity in females, including potential protective effects and risk factors associated with reproductive experience in mid-life and beyond. Ultimately, a more complete understanding of how hormones influence neuroplasticity throughout the lifespan, beyond development, is necessary for understanding how individuals respond to life changes in adaptive ways.

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.

Female reproductive health and cognitive function

OBJECTIVE

The impact of sex hormones milieu on women's cognitive performance at different reproductive stages has caused increased caution. Our research aims to explore whether parity is negatively correlated with cognitive function.

METHODS

There were 1,093 postmenopausal participants recruited from the Health and Nutrition Examination Survey dataset. Cognitive functioning was evaluated by digit symbol substitution test (DSST). We performed log transformation to normalize the distributions of the DSST values.

RESULTS

Participants were categorized into tertile groups based on the number of pregnancies. Using the zero to one pregnancy group as the reference, there was a reduced DSST scores with β values of -0.13 (95% confidence interval [CI] -0.23 to -0.03; P = 0.008) in the ≥5 pregnancies group after adjusting for socioeconomic, medical disease, lifestyle, and reproductive components. Moreover, women who had their last pregnancy after 28 years old and education less than 12 years also was correlate with cognitive malfunction after adjusting relevant covariates (both P < 0.001).

CONCLUSIONS

Women with at least five pregnancies had poorer cognitive performance. Last pregnancy after 28 years old and education less than 12 years also was associated with poorer DSST scores. VIDEO SUMMARY:: http://links.lww.com/MENO/A634.

Apolipoprotein E4 and meningeal lymphatics in Alzheimer disease: a conceptual framework

The potential existence and roles of the meningeal lymphatic system in normal and pathological brain function have been a long-standing enigma. Recent evidence suggests that meningeal lymphatic vessels are present in both the mouse and human brain; in mice, they seem to play a role in clearing toxic amyloid-beta peptides, which have been connected with Alzheimer disease (AD). Here, we review the evidence linking the meningeal lymphatic system with human AD. Novel findings suggest that the recently described meningeal lymphatic vessels could be linked to, and possibly drain, the efferent paravascular glial lymphatic (glymphatic) system carrying cerebrospinal fluid, after solute and immune cell exchange with brain interstitial fluid. In so doing, the glymphatic system could contribute to the export of toxic solutes and immune cells from the brain (an exported fluid we wish to describe as glymph, similarly to lymph) to the meningeal lymphatic system; the latter, by being connected with downstream anatomic regions, carries the glymph to the conventional cervical lymphatic vessels and nodes. Thus, abnormal function in the meningeal lymphatic system could, in theory, lead to the accumulation, in the brain, of amyloid-beta, cellular debris, and inflammatory mediators, as well as immune cells, resulting in damage of the brain parenchyma and, in turn, cognitive and other neurologic dysfunctions. In addition, we provide novel insights into APOE4-the leading genetic risk factor for AD-and its relation to the meningeal lymphatic system. In this regard, we have reanalyzed previously published RNA-Seq data to show that induced pluripotent stem cells (iPSCs) carrying the APOE4 allele (either as APOE4 knock-in or stemming from APOE4 patients) express lower levels of (a) genes associated with lymphatic markers, and (b) genes for which well-characterized missense mutations have been linked to peripheral lymphedema. Taking into account this evidence, we propose a new conceptual framework, according to which APOE4 could play a novel role in the premature shrinkage of meningeal lymphatic vessels (meningeal lymphosclerosis), leading to abnormal meningeal lymphatic functions (meningeal lymphedema), and, in turn, reduction in the clearance of amyloid-beta and other macromolecules and inflammatory mediators, as well as immune cells, from the brain, exacerbation of AD manifestations, and progression of the disease. Altogether, these findings and their potential interpretations may herald novel diagnostic tools and therapeutic approaches in patients with AD.

Fertility History and Cognitive Function in Late Life: The Case of Mexico

OBJECTIVES

Mexico is aging rapidly, which makes identification of life-course factors influencing cognition a public health priority. We evaluate how the number of children one has relates to cognition in Mexico, a rapidly aging country that experienced fertility declines across recent cohorts of older people.

METHOD

We analyze older adults (age 50+, n = 11,380) from the 2015 Mexican Health and Aging Study. Respondents were categorized by number of children ever born (0-1, 2-3, 4-5, 6+). Using ordinary least squares regression, we estimate independent associations between fertility history and cognition accounting for demographic, socioeconomic, health, and psychosocial factors.

RESULTS

We observed an inverse U-shaped relationship between number of children (peaking at 2-3 children) and cognitive function, regardless of gender. In regression analyses adjusted for confounding variables, having 0-1 (vs 2-3 children) was associated with poorer cognitive function only for females. Regardless of gender, having 6+ (vs 2-3 children) was associated with poorer cognitive function. These associations remained significant even after accounting for socioeconomic, health, employment, and psychosocial factors.

DISCUSSION

Our results suggest fertility history may play a role in late-life cognitive health and provide evidence that both low and high fertility may relate to poorer cognitive function. We discuss differences by gender.

The maternal brain: Region-specific patterns of brain aging are traceable decades after childbirth

Pregnancy involves maternal brain adaptations, but little is known about how parity influences women's brain aging trajectories later in life. In this study, we replicated previous findings showing less apparent brain aging in women with a history of childbirths, and identified regional brain aging patterns linked to parity in 19,787 middle- and older-aged women. Using novel applications of brain-age prediction methods, we found that a higher number of previous childbirths were linked to less apparent brain aging in striatal and limbic regions. The strongest effect was found in the accumbens-a key region in the mesolimbic reward system, which plays an important role in maternal behavior. While only prospective longitudinal studies would be conclusive, our findings indicate that subcortical brain modulations during pregnancy and postpartum may be traceable decades after childbirth.

Parity and the risk of incident dementia: a COSMIC study

AIMS

To investigate the association between parity and the risk of incident dementia in women.

METHODS

We pooled baseline and follow-up data for community-dwelling women aged 60 or older from six population-based, prospective cohort studies from four European and two Asian countries. We investigated the association between parity and incident dementia using Cox proportional hazards regression models adjusted for age, educational level, hypertension, diabetes mellitus and cohort, with additional analysis by dementia subtype (Alzheimer dementia (AD) and non-Alzheimer dementia (NAD)).

RESULTS

Of 9756 women dementia-free at baseline, 7010 completed one or more follow-up assessments. The mean follow-up duration was 5.4 ± 3.1 years and dementia developed in 550 participants. The number of parities was associated with the risk of incident dementia (hazard ratio (HR) = 1.07, 95% confidence interval (CI) = 1.02-1.13). Grand multiparity (five or more parities) increased the risk of dementia by 30% compared to 1-4 parities (HR = 1.30, 95% CI = 1.02-1.67). The risk of NAD increased by 12% for every parity (HR = 1.12, 95% CI = 1.02-1.23) and by 60% for grand multiparity (HR = 1.60, 95% CI = 1.00-2.55), but the risk of AD was not significantly associated with parity.

CONCLUSIONS

Grand multiparity is a significant risk factor for dementia in women. This may have particularly important implications for women in low and middle-income countries where the fertility rate and prevalence of grand multiparity are high.

Does parity matter in women's risk of dementia? A COSMIC collaboration cohort study

BACKGROUND

Dementia shows sex difference in its epidemiology. Childbirth, a distinctive experience of women, is associated with the risk for various diseases. However, its association with the risk of dementia in women has rarely been studied.

METHODS

We harmonized and pooled baseline data from 11 population-based cohorts from 11 countries over 3 continents, including 14,792 women aged 60 years or older. We investigated the association between parity and the risk of dementia using logistic regression models that adjusted for age, educational level, hypertension, diabetes mellitus, and cohort, with additional analyses by region and dementia subtype.

RESULTS

Across all cohorts, grand multiparous (5 or more childbirths) women had a 47% greater risk of dementia than primiparous (1 childbirth) women (odds ratio [OR] = 1.47, 95% confidence interval [CI] = 1.10-1.94), while nulliparous (no childbirth) women and women with 2 to 4 childbirths showed a comparable dementia risk to primiparous women. However, there were differences associated with region and dementia subtype. Compared to women with 1 to 4 childbirths, grand multiparous women showed a higher risk of dementia in Europe (OR = 2.99, 95% CI = 1.38-6.47) and Latin America (OR = 1.49, 95% CI = 1.04-2.12), while nulliparous women showed a higher dementia risk in Asia (OR = 2.15, 95% CI = 1.33-3.47). Grand multiparity was associated with 6.9-fold higher risk of vascular dementia in Europe (OR = 6.86, 95% CI = 1.81-26.08), whereas nulliparity was associated with a higher risk of Alzheimer disease (OR = 1.91, 95% CI 1.07-3.39) and non-Alzheimer non-vascular dementia (OR = 3.47, 95% CI = 1.44-8.35) in Asia.

CONCLUSION

Parity is associated with women's risk of dementia, though this is not uniform across regions and dementia subtypes.

Towards an understanding of women's brain aging: the immunology of pregnancy and menopause

Women are at significantly greater risk of developing Alzheimer's disease and show higher prevalence of autoimmune conditions relative to men. Women's brain health is historically understudied, and little is therefore known about the mechanisms underlying epidemiological sex differences in neurodegenerative diseases, and how female-specific factors may influence women's brain health across the lifespan. In this review, we summarize recent studies on the immunology of pregnancy and menopause, emphasizing that these major immunoendocrine transition phases may play a critical part in women's brain aging trajectories.

Multiparity, Brain Atrophy, and Cognitive Decline

Background

Multiparity – grand multiparity (i.e., five or more childbirths) in particular – has been reported to have an association with increased risk of Alzheimer’s disease (AD) dementia or related cognitive decline in women. However, the pathological links underlying this relationship are still unknown. This study was conducted to examine the relationships of multiparity with cerebral amyloid-beta (Aβ) deposition, brain atrophy, and white matter hyperintensities (WMHs).

Methods

In this study, total of 237 older women with 148 cognitively normal and 89 mild cognitive impairment from the Korean Brain Aging Study for Early Diagnosis and Prediction of Alzheimer’s Disease (KBASE) were included. Participants underwent clinical and neuropsychological assessments in addition to ¹¹C-labeled Pittsburgh Compound B positron emission tomography, and magnetic resonance imaging. The associations of parity with Aβ deposition, hippocampal volume, cortical volume, WMH volume and mini-mental status examination (MMSE) score were examined.

Results

Participants with grand multiparity showed significantly reduced adjusted hippocampal volume, spatial pattern of atrophy for recognition of AD volume and spatial pattern of atrophy for recognition of brain aging volume even after controlling for potential confounders. Furthermore, MMSE score was also significantly lower in this group. In contrast, grand multiparity did not show any association with global Aβ retention, Aβ positivity rate, or WMH volume, regardless of covariates.

Conclusion

Our findings suggest that grand multiparity contributes to cognitive decline or increased dementia risk in older women by aggravating amyloid-independent hippocampal or cortical atrophy.

Aging Reduces Estradiol Protection Against Neural but Not Metabolic Effects of Obesity in Female 3xTg-AD Mice

Vulnerability to Alzheimer's disease (AD) is increased by several risk factors, including midlife obesity, female sex, and the depletion of estrogens in women as a consequence of menopause. Conversely, estrogen-based hormone therapies have been linked with protection from age-related increases in adiposity and dementia risk, although treatment efficacy appears to be affected by the age of initiation. Potential interactions between obesity, AD, aging, and estrogen treatment are likely to have significant impact on optimizing the use of hormone therapies in postmenopausal women. In the current study, we compared how treatment with the primary estrogen, 17β-estradiol (E2), affects levels of AD-like neuropathology, behavioral impairment, and other neural and systemic effects of preexisting diet-induced obesity in female 3xTg-AD mice. Importantly, experiments were conducted at chronological ages associated with both the early and late stages of reproductive senescence. We observed that E2 treatment was generally associated with significantly improved metabolic outcomes, including reductions in body weight, adiposity, and leptin, across both age groups. Conversely, neural benefits of E2 in obese mice, including decreased β-amyloid burden, improved behavioral performance, and reduced microglial activation, were observed only in the early aging group. These results are consistent with the perspective that neural benefits of estrogen-based therapies require initiation of treatment during early rather than later phases of reproductive aging. Further, the discordance between E2 protection against systemic versus neural effects of obesity across age groups suggests that pathways other than general metabolic function, perhaps including reduced microglial activation, contribute to the mechanism(s) of the observed E2 actions. These findings reinforce the potential systemic and neural benefits of estrogen therapies against obesity, while also highlighting the critical role of aging as a mediator of estrogens' protective actions.

Sex and gender differences in Alzheimer's disease: current challenges and implications for clinical practice: Position paper of the Dementia and Cognitive Disorders Panel of the European Academy of Neurology

Alzheimer's disease (AD) is characterized by high heterogeneity in disease manifestation, progression and risk factors. High phenotypic variability is currently regarded as one of the largest hurdles in early diagnosis and in the design of clinical trials; there is therefore great interest in identifying factors driving variability that can be used for patient stratification. In addition to genetic and lifestyle factors, the individual's sex and gender are emerging as crucial drivers of phenotypic variability. Evidence exists on sex and gender differences in the rate of cognitive deterioration and brain atrophy, and in the effect of risk factors as well as in the patterns of diagnostic biomarkers. Such evidence might be of high relevance and requires attention in clinical practice and clinical trials. However, sex and gender differences are currently seldom appreciated; importantly, consideration of sex and gender differences is not currently a focus in the design and analysis of clinical trials for AD. The objective of this position paper is (i) to provide an overview of known sex and gender differences that might have implications for clinical practice, (ii) to identify the most important knowledge gaps in the field (with a special regard to clinical trials) and (iii) to provide conclusions for future studies. This scientific statement is endorsed by the European Academy of Neurology.

Pregnancy, postpartum and parity: Resilience and vulnerability in brain health and disease

Risk and resilience in brain health and disease can be influenced by a variety of factors. While there is a growing appreciation to consider sex as one of these factors, far less attention has been paid to sex-specific variables that may differentially impact females such as pregnancy and reproductive history. In this review, we focus on nervous system disorders which show a female bias and for which there is data from basic research and clinical studies pointing to modification in disease risk and progression during pregnancy, postpartum and/or as a result of parity: multiple sclerosis (MS), depression, stroke, and Alzheimer's disease (AD). In doing so, we join others (Shors, 2016; Galea et al., 2018a) in aiming to illustrate the importance of looking beyond sex in neuroscience research.

Postmenopausal hormone therapy and Alzheimer's disease, dementia, and Parkinson's disease: A systematic review and time-response meta-analysis

Hormone therapy continues to be a favourable option in the management of menopausal symptomatology, but the associated risk-benefit ratios with respect to neurodegenerative diseases remain controversial. The study aim was to determine the relation between menopausal hormone therapy and Alzheimer's disease, dementia, and Parkinson's disease in human subjects. A literature search was performed in PubMed/Medline, Cochrane collaboration, and Scopus databases from onset of the database to September 2019. Random-effects model was used to estimate pooled odd ratio (OR) and 95 % confidence intervals (CI). Subgroup analysis was performed based on the type and formulation of hormone. In addition, the time-response effect of this relationship was also assessed based on duration of hormone therapy. Associations between hormone therapy and Alzheimer's disease, dementia, and Parkinson's disease in menopausal women were reported in 28 studies. Pooled results with random effect model showed a significant association between hormone therapy and Alzheimer's disease (OR 1.08, 95 % CI 1.03-1.14, I²: 69 %). This relationship was more pronounced in patients receiving the combined estrogen-progestogen formulation. Moreover, a significant non-linear time-response association between hormone therapy and Alzheimer's disease was also identified (Coef₁ = 0.0477, p₁<0.001; Coef₂ = -0.0932, p₂<0.001). Similarly, pooled analysis revealed a significant association between hormone therapy and all-cause dementia (OR 1.16, 95 % CI 1.02-1.31, I²: 19 %). Interestingly, no comparable relationship was uncovered between hormone therapy as a whole and Parkinson's disease (OR 1.14, 95 % CI 0.95-1.38, I²: 65 %); however, sub-group analysis revealed a significant relationship between the disease and progestogen (OR 3.41, 95 % CI 1.23-9.46) or combined estrogen-progestogen formulation use (OR 1.49, 95 % CI 1.34-1.65). Indeed, this association was also found to be driven by duration of exposure (Coef₁ = 0.0626, p₁ = 0.04). This study reveals a significant direct relationship between the use of certain hormonal therapies and Alzheimer's disease, all-cause dementia, and Parkinson's disease in menopausal women. However, the association appears to shift in direct after five years in the context of Alzheimer's disease, adding further weight to the critical window or timing hypothesis of neurodegeneration and neuroprotection.

The promises and pitfalls of sex difference research

Funding agencies in North America and Europe are recognizing the importance of the integration of sex differences into basic and clinical research. Although these mandates are in place to improve our knowledge of health for both men and women, there have been a number of implementation issues that require vigilance on the part of funders and the research community. Here we discuss issues on simple inclusion of both sexes in studies to specialisation of sex differences with attention paid to statistics and the need for sex-specific treatments. We suggest differing mandates need to be considered regarding simple integration versus the need for studies in the specialisation of sex differences and/or the need for research that recognises the importance of male-specific or female-specific factors that influence subsequent health such as menstruation, menopause or pregnancy.

Population-based neuroimaging reveals traces of childbirth in the maternal brain

Maternal brain adaptations have been found across pregnancy and postpartum, but little is known about the long-term effects of parity on the maternal brain. Using neuroimaging and machine learning, we investigated structural brain characteristics in 12,021 middle-aged women from the UK Biobank, demonstrating that parous women showed less evidence of brain aging compared to their nulliparous peers. The relationship between childbirths and a "younger-looking" brain could not be explained by common genetic variation or relevant confounders. Although prospective longitudinal studies are needed, the results suggest that parity may involve neural changes that could influence women's brain aging later in life.

Possibilities of Dementia Prevention - It is Never Too Early to Start

Dementia represents one of the greatest global challenges for health and social care in this century. More than 50 million people worldwide suffer from dementia, and this number is predicted to triple by 2050. Ageing is often associated with cognitive impairment. Therefore, prevention of cognitive impairment is an imperative. Dementia includes a heterogeneous group of disorders, the most common being Alzheimer's disease and vascular dementia. Most cardiovascular risk factors such as hypertension, diabetes mellitus, hypercholesterolemia, atrial fibrillation and smoking are not exclusive risk factors for vascular dementia but also for Alzheimer's disease. The ApoE4 allele is the single non-modifiable risk factor for Alzheimer's disease. Today we know that an important, modifiable risk factor is education. Better education means better protection against dementia. A large number of dementia cases are potentially preventable by early intervention. Early changes in the blood vessel wall can be detected by early ultrasound methods or early biomarkers. These methods allow us to detect changes before the disease becomes clinically evident. Early disease detection enables timely management, and studies have shown that careful control of vascular risk factors can postpone the onset or even reverse disease progression.

A Dynamic Memory Systems Framework for Sex Differences in Fear Memory

Emerging research demonstrates that a pattern of overlapping but distinct molecular and circuit mechanisms are engaged by males and females during memory tasks. Importantly, sex differences in neural mechanisms and behavioral strategies are evident even when performance on a memory task is similar between females and males. We propose that sex differences in memory may be best understood within a dynamic memory systems framework. Specifically, sex differences in hormonal influences and neural circuit development result in biases in the circuits engaged and the information preferentially stored or retrieved in males and females. By using animal models to understand the neural networks and molecular mechanisms required for memory in both sexes, we can gain crucial insights into sex and gender biases in disorders including post-traumatic stress disorder (PTSD) in humans.

Pregnancy loss and risk of later dementia: A nationwide cohort study, Denmark, 1977-2017

INTRODUCTION

Pregnancy losses may be associated with increased risks of dementia.

METHODS

We conducted a register-based cohort study in 1,243,957 women with ≥1 pregnancy in Denmark in the period 1977-2015. Using Cox regression, we estimated hazard ratios (HRs) comparing risks of dementia in women with and without pregnancy losses.

RESULTS

During 21,672,433 person-years of follow-up, 261,279 women experienced a pregnancy loss, and 2188 women were diagnosed with dementia. Stillbirth was associated with an 86% increased risk of dementia overall (HR 1.86, 95% confidence interval [CI] 1.28-2.71). By contrast, miscarriage was not associated with later risk of dementia overall (single miscarriage, HR 0.99, 95% CI 0.87-1.12; recurrent miscarriages, HR 1.06, 95% CI 0.84-1.35). Adjustment for cardiovascular disease, hypertension, and diabetes did not meaningfully alter the association magnitudes.

DISCUSSION

Stillbirth and dementia may share underlying mechanisms, suggesting that a history of stillbirth should be considered when assessing dementia risk in women.

The long and short term effects of motherhood on the brain

Becoming a mother is associated with dramatic changes in physiology, endocrinology, immune function, and behaviour that begins during pregnancy and persists into the postpartum. Evidence also suggests that motherhood is accompanied by long-term changes in brain function. In this review, we summarize the short (pregnancy and postpartum) and long-term (beyond the postpartum and into middle age) effects of pregnancy and motherhood on cognition, neuroplasticity, and neuroimmune signalling. We also discuss the effects of previous history of pregnancy and motherhood (parity) on brain health and disease (neurodegenerative diseases and stroke outcomes) and on efficacy of hormone and antidepressant treatments. Finally, we argue that pregnancy and motherhood are unique female experiences that need to be taken into account to better understand female brain function and aging.

Use of postmenopausal hormone therapy and risk of Alzheimer's disease in Finland: nationwide case-control study

OBJECTIVES

To compare the use of hormone therapy between Finnish postmenopausal women with and without a diagnosis for Alzheimer's disease.

DESIGN

Nationwide case-control study.

SETTING

Finnish national population and drug register, between 1999 and 2013.

PARTICIPANTS

All postmenopausal women (n=84 739) in Finland who, between 1999 and 2013, received a diagnosis of Alzheimer's disease from a neurologist or geriatrician, and who were identified from a national drug register. Control women without a diagnosis (n=84 739), matched by age and hospital district, were traced from the Finnish national population register.

INTERVENTIONS

Data on hormone therapy use were obtained from the Finnish national drug reimbursement register.

MAIN OUTCOME MEASURES

Odds ratios and 95% confidence intervals for Alzheimer's disease, calculated with conditional logistic regression analysis.

RESULTS

In 83 688 (98.8%) women, a diagnosis for Alzheimer's disease was made at the age of 60 years or older, and 47 239 (55.7%) women had been over 80 years of age at diagnosis. Use of systemic hormone therapy was associated with a 9-17% increased risk of Alzheimer's disease. The risk of the disease did not differ significantly between users of estradiol only (odds ratio 1.09, 95% confidence interval 1.05 to 1.14) and those of oestrogen-progestogen (1.17, 1.13 to 1.21). The risk increases in users of oestrogen-progestogen therapy were not related to different progestogens (norethisterone acetate, medroxyprogesterone acetate, or other progestogens); but in women younger than 60 at hormone therapy initiation, these risk increases were associated with hormone therapy exposure over 10 years. Furthermore, the age at initiation of systemic hormone therapy was not a decisive determinant for the increase in risk of Alzheimer's disease. The exclusive use of vaginal estradiol did not affect the risk of the disease (0.99, 0.96 to 1.01).

CONCLUSIONS

Long term use of systemic hormone therapy might be accompanied with an overall increased risk of Alzheimer's disease, which is not related to the type of progestogen or the age at initiation of systemic hormone therapy. By contrast, use of vaginal estradiol shows no such risk. Even though the absolute risk increase for Alzheimer's disease is small, our data should be implemented into information for present and future users of hormone therapy.

The insulin-like growth factor-1 system in the adult mammalian brain and its implications in central maternal adaptation

Our knowledge on the bioavailability and actions of insulin-like growth factor-1 (IGF-1) has markedly expanded in recent years as novel mechanisms were discovered on IGF binding proteins (IGFBPs) and their ability to release IGF-1. The new discoveries allowed a better understanding of the endogenous physiological actions of IGF-1 and also its applicability in therapeutics. The focus of the present review is to summarize novel findings on the neuronal, neuroendocrine and neuroplastic actions of IGF-1 in the adult brain. As most of the new regulatory mechanisms were described in the periphery, their implications on brain IGF system will also be covered. In addition, novel findings on the effects of IGF-1 on lactation and maternal behavior are described. Based on the enormous neuroplastic changes related to the peripartum period, IGF-1 has great but largely unexplored potential in maternal adaptation of the brain, which is highlighted in the present review.

Sex differences in risk factors for vascular contributions to cognitive impairment & dementia

Vascular contributions to cognitive impairment and dementia (VCID) is the second most common cause of dementia. While males overall appear to be at a slightly higher risk for VCID throughout most of the lifespan (up to age 85), some risk factors for VCID more adversely affect women. These include female-specific risk factors associated with pregnancy related disorders (e.g. preeclampsia), menopause, and poorly timed hormone replacement. Further, presence of certain co-morbid risk factors, such as diabetes, obesity and hypertension, also may more adversely affect women than men. In contrast, some risk factors more greatly affect men, such as hyperlipidemia, myocardial infarction, and heart disease. Further, stroke, one of the leading risk factors for VCID, has a higher incidence in men than in women throughout much of the lifespan, though this trend is reversed at advanced ages. This review will highlight the need to take biological sex and common co-morbidities for VCID into account in both preclinical and clinical research. Given that there are currently no treatments available for VCID, it is critical that we understand how to mitigate risk factors for this devastating disease in both sexes.