Risk of Parkinson disease in women: Effect of reproductive characteristics

A biological characterization of patients with postmenopausal Parkinson's disease

Menopause increases the risk for Parkinson's disease (PD), although the underlying biological mechanisms have not been established in patients. Here, we aimed to understand the basis of menopause-related vulnerability to PD. Main motor and non-motor scores, blood levels of estradiol, testosterone, follicle-stimulating hormone, and luteinizing hormone, CSF levels of total α-synuclein, amyloid-β-42, amyloid-β-40, total tau, and phosphorylated-181-tau were examined in 45 women with postmenopausal-onset PD and 40 age-matched controls. PD patients had higher testosterone and lower estradiol levels than controls, and the residual estradiol production was associated with milder motor disturbances and lower dopaminergic requirements. In PD but not in controls, follicle-stimulating hormone levels correlated with worse cognitive scores and CSF markers of amyloidopathy and neuronal loss. In conclusion, menopause-related hormonal changes might differentially contribute to clinical-pathological trajectories of PD, accounting for the peculiar vulnerability to the disease.

Association of bilateral oophorectomy with incidence of Parkinson's disease: A systematic review and meta-analysis

INTRODUCTION

Current evidence in the literature is inconclusive due to conflicting results with regards to an association between B/L (B/L) oophorectomy and Parkinson's disease (PD). We included large, powered studies to assess the association of PD in women who have undergone B/L oophorectomy.

METHODS

We conducted a comprehensive search across three databases from inception to October 2022 for observational studies including pre-menopausal or post-menopausal women undergoing B/L oophorectomy. Primary outcome of interest was incidence of PD or parkinsonism. The results for these associations were presented as Risk Ratios (RR) with 95% confidence intervals (CI), which were pooled using a generic invariance weighted random effects model using Review Manager (RevMan).

RESULTS

Data was included from a total of 4 studies. No significant association was found between B/L oophorectomy and PD (RR: 1.38; 95% CI: 0.76 to 2.49; I2:89 %) in contrast significant association was found with parkinsonism (RR: 1.80; 95% CI: 1.29 to 2.52). Age at surgery didn't significantly affect Parkinsonism incidence (RR: 0.88; 95% CI: 0.59 to 1.3). No significant association was found between ovarian indication and Parkinsonism (RR: 1.08; 95% CI: 0.69 to 1.68). B/L oophorectomy with hysterectomy was associated with higher Parkinson's risk compared to without hysterectomy (RR: 1.4; 95% CI: 1.13 to 1.74). Lastly, there was no significant association between Post Menopausal Hormonal (PMH) use and Parkinson's disease (RR: 1.07; 95% CI: 0.92 to 1.26).

CONCLUSION

Our findings suggest that B/L oophorectomy is significantly associated with the incidence of Parkinsonism. Further research is needed to understand the potential relationship between oophorectomy and Parkinson's disease.

Pleiotropy with sex-specific traits reveals genetic aspects of sex differences in Parkinson's disease

Parkinson's disease is an age-related neurodegenerative disorder with a higher incidence in males than females. The causes for this sex difference are unknown. Genome-wide association studies (GWAS) have identified 90 Parkinson's disease risk loci, but the genetic studies have not found sex-specific differences in allele frequency on autosomal chromosomes or sex chromosomes. Genetic variants, however, could exert sex-specific effects on gene function and regulation of gene expression. To identify genetic loci that might have sex-specific effects, we studied pleiotropy between Parkinson's disease and sex-specific traits. Summary statistics from GWASs were acquired from large-scale consortia for Parkinson's disease (n cases = 13 708; n controls = 95 282), age at menarche (n = 368 888 females) and age at menopause (n = 69 360 females). We applied the conditional/conjunctional false discovery rate (FDR) method to identify shared loci between Parkinson's disease and these sex-specific traits. Next, we investigated sex-specific gene expression differences in the superior frontal cortex of both neuropathologically healthy individuals and Parkinson's disease patients (n cases = 61; n controls = 23). To provide biological insights to the genetic pleiotropy, we performed sex-specific expression quantitative trait locus (eQTL) analysis and sex-specific age-related differential expression analysis for genes mapped to Parkinson's disease risk loci. Through conditional/conjunctional FDR analysis we found 11 loci shared between Parkinson's disease and the sex-specific traits age at menarche and age at menopause. Gene-set and pathway analysis of the genes mapped to these loci highlighted the importance of the immune response in determining an increased disease incidence in the male population. Moreover, we highlighted a total of nine genes whose expression or age-related expression in the human brain is influenced by genetic variants in a sex-specific manner. With these analyses we demonstrated that the lack of clear sex-specific differences in allele frequencies for Parkinson's disease loci does not exclude a genetic contribution to differences in disease incidence. Moreover, further studies are needed to elucidate the role that the candidate genes identified here could have in determining a higher incidence of Parkinson's disease in the male population.

Neuroactive steroids and Parkinson's disease: Review of human and animal studies

The greater prevalence and incidence of Parkinson's disease (PD) in men suggest a beneficial effect of sex hormones. Neuroactive steroids have neuroprotective activities thus offering interesting option for disease-modifying therapy for PD. Neuroactive steroids are also neuromodulators of neurotransmitter systems and may thus help to control PD symptoms and side effect of dopamine medication. Here, we review the effect on sex hormones (estrogen, androgen, progesterone and its metabolites) as well as androstenediol, pregnenolone and dehydroepiandrosterone) in human studies and in animal models of PD. The effect of neuroactive steroids is reviewed by considering sex and hormonal status to help identify specifically for women and men with PD what might be a preventive approach or a symptomatic treatment. PD is a complex disease and the pathogenesis likely involves multiple cellular processes. Thus it might be useful to target different cellular mechanisms that contribute to neuronal loss and neuroactive steroids provide therapeutics options as they have multiple mechanisms of action.

Increased palmitoylation improves estrogen receptor alpha-dependent hippocampal synaptic deficits in a mouse model of synucleinopathy

Parkinson's disease (PD) is characterized by conversion of soluble α-synuclein (αS) into intraneuronal aggregates and degeneration of neurons and neuronal processes. Indications that women with early-stage PD display milder neurodegenerative features suggest that female sex partially protects against αS pathology. We previously reported that female sex and estradiol improved αS homeostasis and PD-like phenotypes in E46K-amplified (3K) αS mice. Here, we aimed to further dissect mechanisms that drive this sex dimorphism early in disease. We observed that synaptic abnormalities were delayed in females and improved by estradiol, mediated by local estrogen receptor alpha (ERα). Aberrant ERα distribution in 3K compared to wild-type mice was paired with its decreased palmitoylation. Treatment with ML348, a de-palmitoylation inhibitor, increased ERα availability and soluble αS homeostasis, ameliorating synaptic plasticity and cognitive and motor phenotypes. Our finding that sex differences in early-disease αS-induced synaptic impairment in 3KL mice are in part mediated by palmitoylated ERα may have functional and pathogenic implications for clinical PD.

Reproductive characteristics, use of exogenous hormones and Parkinson disease in women from the E3N study

Despite experimental studies suggesting a disease-modifying role of oestrogens, results from epidemiological studies on the relation of reproductive characteristics and hormonal exposures with Parkinson disease in women are conflicting. We used the data from the E3N cohort study including 98 068 women aged 40-65 years in 1990 followed until 2018. Parkinson disease was ascertained using a validation process based on drug claim databases and medical records. Reproductive characteristics and hormonal exposures were self-reported (11 questionnaires). Associations of exposures with Parkinson disease incidence were investigated using time-varying Cox proportional hazards regression with a 5-year exposure lag and age as the timescale adjusted for confounders. We identified 1165 incident Parkinson disease cases during a mean follow-up of 22.0 years (incidence rate = 54.7 per 100 000 person-years). Parkinson disease incidence was higher in women with early (<12 years, HR = 1.21, 95% CI = 1.04-1.40) or late age at menarche (≥14 years, HR = 1.18, 95% CI = 1.03-1.35) than in women with menarche at 12-13 years. Nulliparity was not associated with Parkinson disease, but Parkinson disease incidence increased with the number of children in parous women (P-trend = 0.009). Women with artificial (surgical, iatrogenic) menopause were at greater risk than women with natural menopause (HR = 1.28, 95% CI = 1.09-1.47), especially when artificial menopause occurred at an early age (≤45.0 years). Postmenopausal hormone therapy tended to mitigate greater risk associated with artificial or early menopause (≤45.0 years). While fertility treatments were not associated with Parkinson disease overall, ever users of clomiphene were at greater Parkinson disease risk than never users (HR = 1.81, 95% CI = 1.14-2.88). Other exposures (breastfeeding, oral contraceptives) were not associated with Parkinson disease. Our findings suggest that early and late age at menarche, higher parity, and artificial menopause, in particular at an early age, are associated with increased Parkinson disease incidence in women. In addition, there was some evidence that use of exogenous hormones may increase (fertility treatments) or decrease (postmenopausal hormone therapy) Parkinson disease incidence. These findings support the hypothesis that hormonal exposures play a role in the susceptibility to neurodegenerative diseases. If confirmed, they could help to identify subgroups at high risk for Parkinson disease.

The impact of biological clock and sex hormones on the risk of disease

Molecular clocks are responsible for defining 24-h cycles of behaviour and physiology that are called circadian rhythms. Several structures and tissues are responsible for generating these circadian rhythms and are named circadian clocks. The suprachiasmatic nucleus of the hypothalamus is believed to be the master circadian clock receiving light input via the optic nerve and aligning internal rhythms with environmental cues. Studies using both in vivo and in vitro methodologies have reported the relationship between the molecular clock and sex hormones. The circadian system is directly responsible for controlling the synthesis of sex hormones and this synthesis varies according to the time of day and phase of the estrous cycle. Sex hormones also directly interact with the circadian system to regulate circadian gene expression, adjust biological processes, and even adjust their own synthesis. Several diseases have been linked with alterations in either the sex hormone background or the molecular clock. So, in this chapter we aim to summarize the current understanding of the relationship between the circadian system and sex hormones and their combined role in the onset of several related diseases.

Three-Dimensional Analysis of Sex- and Gonadal Status- Dependent Microglial Activation in a Mouse Model of Parkinson’s Disease

Parkinson’s disease (PD) is characterized by neurodegeneration and neuroinflammation. PD prevalence and incidence are higher in men than in women and modulation of gonadal hormones could have an impact on the disease course. This was investigated in male and female gonadectomized (GDX) and SHAM operated (SHAM) mice. Dutasteride (DUT), a 5α-reductase inhibitor, was administered to these mice for 10 days to modulate their gonadal sex hormones. On the fifth day of DUT treatment, mice received 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to model PD. We have previously shown in these mice the toxic effect of MPTP in SHAM and GDX males and in GDX females on dopamine markers and astrogliosis whereas SHAM females were protected by their female sex hormones. In SHAM males, DUT protected against MPTP toxicity. In the present study, microglial density and the number of doublets, representative of a microglial proliferation, were increased by the MPTP lesion only in male mice and prevented by DUT in SHAM males. A three-dimensional morphological microglial analysis showed that MPTP changed microglial morphology from quiescent to activated only in male mice and was not prevented by DUT. In conclusion, microgliosis can be modulated by sex hormone-dependent and independent factors in a mice model of PD.

Progesterone exerts a neuroprotective action in a Parkinson's disease human cell model through membrane progesterone receptor α (mPRα/PAQR7)

Parkinson's disease (PD) is the second most common neurodegenerative disease worldwide, and current treatment options are unsatisfactory on the long term. Several studies suggest a potential neuroprotective action by female hormones, especially estrogens. The potential role of progestogens, however, is less defined, and no studies have investigated the potential involvement of membrane progesterone receptors (mPRs). In the present study, the putative neuroprotective role for mPRs was investigated in SH-SY5Y cells, using two established pharmacological treatments for cellular PD models, 6-hydroxydopamine (6-OHDA) and 1-methyl-4-phenylpyridinium (MPP+). Our results show that both the physiologic agonist progesterone and the specific mPR agonist Org OD 02-0 were effective in reducing SH-SY5Y cell death induced by 6-OHDA and MPP⁺, whereas the nuclear PR agonist promegestone (R5020) and the GABA_A receptor agonist muscimol were ineffective. Experiments performed with gene silencing technology and selective pharmacological agonists showed that mPRα is the isoform responsible for the neuroprotective effects we observed. Further experiments showed that the PI3K-AKT and MAP kinase signaling pathways are involved in the mPRα-mediated progestogen neuroprotective action in SH-SY5Y cells. These findings suggest that mPRα could play a neuroprotective role in PD pathology and may be a promising target for the development of therapeutic strategies for PD prevention or management.

State-of-the-art review of the clinical research on menopause and hormone replacement therapy association with Parkinson's disease: What meta-analysis studies cannot tell us

The menopause is a midlife endocrinological process that greatly affects women's central nervous system functions. Over the last 2 decades numerous clinical studies have addressed the influence of ovarian hormone decline on neurological disorders like Parkinson's disease and Alzheimer's disease. However, the findings in support of a role for age at menopause, type of menopause and hormone replacement therapy on Parkinson's disease onset and its core features show inconsistencies due to the heterogeneity in the study design. Here, we provide a unified overview of the clinical literature on the influence of menopause and ovarian hormones on Parkinson's disease. We highlight the possible sources of conflicting evidence and gather considerations for future observational clinical studies that aim to explore the neurological impact of menopause-related features in Parkinson's disease.

Reproductive Lifespan and Motor Progression of Parkinson’s Disease

Objectives: Estrogen not only plays a key role in the decreased risk of Parkinson’s disease (PD) but also influences its severity. We aimed to explore the effect of the reproductive lifespan on the motor progression of PD female patients in a large prospective cohort study. Methods: A competing risk analysis with a Fine and Gray model on 491 female and 609 male patients with PD was conducted. We regarded the chance of faster motor progression (as measured by the Unified Parkinson’s Disease Rating Scale (UPDRS) III increasing by ≥16 points during follow-up) and the chance of death as competing risks. The reproductive lifespan was regarded as the variable of interest, while faster motor progression was set as the primary outcome. Results: In the multivariable competing risk analysis, the male sex was not significantly associated with faster motor progression (subdistribution hazard ratio (SHR) 0.888, 95% CI 0.652–1.209, p = 0.450), while a shorter reproductive lifespan was associated with faster motor progression in women (SHR 0.964, 95% CI 0.936–0.994, p = 0.019). Sensitivity analysis indicated that a shorter reproductive lifespan was also significantly associated with faster motor progression in the 48 female patients who reported menopause after the onset of PD (SHR 0.156, 95% CI 0.045–0.542, p = 0.003). A linear mixed model also revealed the significant main effects of a short reproductive lifespan on the higher UPDRS III score in PD female patients at the last visit (p = 0.026). Conclusions: Our study indicates that a short reproductive lifespan contributes to faster motor progression in PD female patients, which has important implications for understanding the role of endogenous estrogen exposure in female PD and is beneficial to select appropriate patients in clinical trials.

Association of Premenopausal Bilateral Oophorectomy With Parkinsonism and Parkinson Disease

IMPORTANCE

The association of premenopausal bilateral oophorectomy with parkinsonism and Parkinson disease (PD) remains controversial.

OBJECTIVE

To assess whether women who underwent premenopausal bilateral oophorectomy were at increased risk of parkinsonism and PD and whether the associations varied by age at oophorectomy and by receipt of estrogen replacement therapy.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study used data from a combination of 2 independent cohort studies, the Mayo Clinic Cohort Study of Oophorectomy and Aging 1 and 2, which were based on the Rochester Epidemiology Project medical records-linkage system. A population-based sample of 5499 women from Olmsted County, Minnesota, were included; of those, 2750 women underwent bilateral oophorectomy for a benign indication before spontaneous menopause between January 1, 1950, and December 31, 2007 (oophorectomy cohort), and 2749 age-matched women who did not undergo bilateral oophorectomy were randomly sampled from the general population (reference cohort). Data were analyzed from March 1 to April 30, 2022. The date of oophorectomy was considered the index date for both groups.

EXPOSURES

Medical record documentation of bilateral oophorectomy abstracted from a medical records-linkage system (Rochester Epidemiology Project).

MAIN OUTCOMES AND MEASURES

Incidence and risk of parkinsonism or PD, with diagnoses confirmed by in-person examination or medical record review.

RESULTS

Among 5499 participants (median [IQR] age, 45.0 [40.0-48.0] years; 5312 [96.6%] White), 2750 women (2679 White [97.4%]) underwent bilateral oophorectomy at a median age of 45.0 years (IQR, 40.0-48.0 years), and 2749 women (2633 White [95.8%]) with a median age of 45.0 years (IQR, 40.0-48.0 years) at the index date were included in the reference cohort. Bilateral oophorectomy was associated with an increased risk of parkinsonism overall (hazard ratio [HR], 1.59; 95% CI, 1.02-2.46) and in women younger than 43 years at oophorectomy (HR, 7.67; 95% CI, 1.77-33.27). There was a pattern of increasing risk with younger age at the time of oophorectomy using 4 age strata (≥50 years: HR, 1.43 [95% CI, 0.50-4.15]; 46-49 years: HR, 1.55 [95% CI, 0.79-3.07]; 40-45 years: HR, 1.36 [95% CI, 0.64-2.89]; <40 years: HR, 8.82 [95% CI, 1.08-72.00]; P = .02 for trend). The number needed to harm was 53 women overall and 27 women younger than 43 years at the time of oophorectomy. Bilateral oophorectomy was also associated with an increased risk of PD in women younger than 43 years at oophorectomy (HR, 5.00; 95% CI, 1.10-22.70), with a number needed to harm of 48 women. Among women who underwent oophorectomy at 45 years and younger, the risk was lower in women who received estrogen after the procedure and through age 50 years compared with women who did not. For parkinsonism, the HRs were 1.72 (95% CI, 0.54-5.53) vs 2.05 (95% CI, 0.80-5.23); for PD, the HRs were 1.53 (95% CI, 0.29-8.23) vs 2.75 (95% CI, 0.84-9.04). However, the differences were not significant.

CONCLUSIONS AND RELEVANCE

In this study, premenopausal women who underwent bilateral oophorectomy before age 43 years had an increased risk of parkinsonism and PD compared with women who did not undergo bilateral oophorectomy. These findings suggest that a reduction in the practice of prophylactic bilateral oophorectomy in premenopausal women at average risk of ovarian cancer may have substantial benefit for reducing the risk of parkinsonism and PD.

Age Cutoff for Early-Onset Parkinson's Disease: Recommendations from the International Parkinson and Movement Disorder Society Task Force on Early Onset Parkinson's Disease

Background

Early-onset Parkinson's disease (EOPD)/young-onset Parkinson's disease (YOPD) is defined as Parkinson's disease (PD) with an age at onset (AAO) after age 21 years but before the usual AAO for PD. Consensus is lacking, and the reported maximal age for EOPD/YOPD has varied from 40 to 60 years, leading to a lack of uniformity in published studies and difficulty in harmonization of data. EOPD and YOPD have both been used in the literature, somewhat interchangeably.

Objective

To define the nomenclature and AAO cutoff for EOPD/YOPD.

Methods

An extensive review of the literature and task force meetings were conducted. Conclusions were reached by consensus.

Results

First, the literature has seen a shift from the use of YOPD toward EOPD. This seems motivated by an attempt to avoid age-related stigmatization of patients. Second, in defining EOPD, 56% of the countries use 50 or 51 years as the cutoff age. Third, the majority of international genetic studies in PD use an age cutoff of younger than 50 years to define EOPD. Fourth, many studies suggest that changes in the estrogen level can affect the predisposition to develop PD, making the average age at menopause of 50 years an important factor to consider when defining EOPD. Fifth, considering the differential impact of the AAO of PD on professional and social life, using 50 years as the upper cutoff for the definition of EOPD seems reasonable.

Conclusions

This task force recommends the use of EOPD rather than YOPD. It defines EOPD as PD with AAO after 21 years but before 50 years.

Estrogen receptors observed at extranuclear neuronal sites and in glia in the nucleus accumbens core and shell of the female rat: Evidence for localization to catecholaminergic and GABAergic neurons

Estrogens affect dopamine-dependent diseases/behavior and have rapid effects on dopamine release and receptor availability in the nucleus accumbens (NAc). Low levels of nuclear estrogen receptor (ER) α and ERβ are seen in the NAc, which cannot account for the rapid effects of estrogens in this region. G-protein coupled ER 1 (GPER1) is observed at low levels in the NAc shell, which also likely does not account for the array of estrogens' effects in this region. Prior studies demonstrated membrane-associated ERs in the dorsal striatum; these experiments extend those findings to the NAc core and shell. Single- and dual-immunolabeling electron microscopy determined whether ERα, ERβ, and GPER1 are at extranuclear sites in the NAc core and shell and whether ERα and GPER1 were localized to catecholaminergic or γ-aminobutyric acid-ergic (GABAergic) neurons. All three ERs are observed, almost exclusively, at extranuclear sites in the NAc, and similarly distributed in the core and shell. ERα, ERβ, and GPER1 are primarily in axons and axon terminals suggesting that estrogens affect transmission in the NAc via presynaptic mechanisms. About 10% of these receptors are found on glia. A small proportion of ERα and GPER1 are localized to catecholaminergic terminals, suggesting that binding at these ERs alters release of catecholamines, including dopamine. A larger proportion of ERα and GPER1 are localized to GABAergic dendrites and terminals, suggesting that estrogens alter GABAergic transmission to indirectly affect dopamine transmission in the NAc. Thus, the localization of ERs could account for the rapid effects of estrogen in the NAc.

Management strategies of sexual dysfunctions in Parkinson's disease

Sexual dysfunctions (SD) are frequent and highly disabling nonmotor manifestations of Parkinson's disease (PD) but are also potentially treatable. Neurologists should actively discuss, recognize and treat sexual health issues as an integral part of the management of the disease. In this chapter, we provide recommendations for managing and treating both primary and secondary SD in PD. Many sexual problems can be, at least partially, improved by adjusting the treatment of motor, nonmotor symptoms and comorbidities. Although some treatments of primary SD are evidence-based, many therapeutic options have not been yet systematically studied in patients with PD. The development of new treatments and repurposing of existing remedies in patients with PD remain an unmet need.

Reproductive factors and cognitive impairment in natural menopausal women: A cross-sectional study

INTRODUCTION

Little information on rural older women in northern China has been reported, apart from three studies in southern and eastern China in the past decade. This study aims to evaluate the relationships between reproductive factors and the risk of cognitive impairment, including mild cognitive impairment (MCI) and dementia, in Chinese women with natural menopause.

METHODS

The cross-sectional study was conducted in 112 community primary healthcare centers in rural northern China between April 2019 and January 2020. A total of 4,275 women aged ≥65 years who had natural menopause were included. Reproductive factors as well as the reproductive period (= age at menopause - age at menarche) were recorded. The relationships between reproductive factors and cognitive impairment were evaluated by correlation and logistic regression analysis.

RESULTS

Overall, 28.6% and 11.4% of women were diagnosed with MCI or dementia, respectively. In natural menopause women, the age at menopause (adjusted r = 0.070, p < 0.001), reproductive period (adjusted r = 0.053, p = 0.001), and number of pregnancies (adjusted r = -0.042, p = 0.007) and parities (adjusted r = -0.068, p < 0.001) were correlated with Mini-Mental State Examination (Chinese version) scores, and with similar findings concerning MCI and dementia with Lewy bodies (DLB). Greater age at menopause and a long reproductive period significantly decreased the risk of MCI and Alzheimer's disease (AD), and more parities significantly increased the risks of MCI (odds ratio (OR) = 1.111, 95% confidence interval (CI): 1.039-1.187, p = 0.002), dementia (OR = 1.162, 95% CI: 1.061-1.271, p = 0.001), particular AD (OR = 1.131, 95% CI: 1.010-1.266, p = 0.032), DLB (OR = 1.238, 95% CI: 1.003-1.528, p = 0.047), and vascular dementia (VaD) (OR = 1.288, 95% CI: 1.080-1.536, p = 0.005).

CONCLUSIONS

The prevalence rates of MCI and dementia were 28.6% and 11.4% in older women. Greater age at menarche, young age at menopause, shorter reproductive period, and larger numbers of pregnancies/parities were correlated with poor cognition and significantly increased the risks of MCI and dementia, particularly AD, DLB, and VaD.

Respiratory disorders of Parkinson's disease

Parkinson's disease (PD) is characterized by the progressive loss of dopaminergic neurons in the substantia nigra, mainly affecting people over 60 yr of age. Patients develop both classic symptoms (tremors, muscle rigidity, bradykinesia, and postural instability) and nonclassical symptoms (orthostatic hypotension, neuropsychiatric deficiency, sleep disturbances, and respiratory disorders). Thus, patients with PD can have a significantly impaired quality of life, especially when they do not have multimodality therapeutic follow-up. The respiratory alterations associated with this syndrome are the main cause of mortality in PD. They can be classified as peripheral when caused by disorders of the upper airways or muscles involved in breathing and as central when triggered by functional deficits of important neurons located in the brainstem involved in respiratory control. Currently, there is little research describing these disorders, and therefore, there is no well-established knowledge about the subject, making the treatment of patients with respiratory symptoms difficult. In this review, the history of the pathology and data about the respiratory changes in PD obtained thus far will be addressed.

Role of estrogen receptors in health and disease

Estrogen receptors (ERs) regulate multiple complex physiological processes in humans. Abnormal ER signaling may result in various disorders, including reproductive system-related disorders (endometriosis, and breast, ovarian, and prostate cancer), bone-related abnormalities, lung cancer, cardiovascular disease, gastrointestinal disease, urogenital tract disease, neurodegenerative disorders, and cutaneous melanoma. ER alpha (ERα), ER beta (ERβ), and novel G-protein-coupled estrogen receptor 1 (GPER1) have been identified as the most prominent ERs. This review provides an overview of ERα, ERβ, and GPER1, as well as their functions in health and disease. Furthermore, the potential clinical applications and challenges are discussed.

Increased Menopausal Age Reduces the Risk of Parkinson's Disease: A Mendelian Randomization Approach

BACKGROUND

Studies of Parkinson's disease (PD) and the association with age at menarche or menopause have reported inconsistent findings. Mendelian randomization (MR) may address measurement errors because of difficulties accurately reporting the age these life events occur.

OBJECTIVE

We used MR to assess the association between age at menopause and age at menarche with PD risk.

METHODS

We performed inverse variant-weighted (IVW) MR analysis using external genome-wide association study (GWAS) summary data from the United Kingdom biobank, and the effect estimates between genetic variants and PD among two population-based studies (Parkinson's disease in Denmark (PASIDA) study, Denmark, and Parkinson's Environment and Gene study [PEG], United States) that enrolled 1737 female and 2430 male subjects of European ancestry. We, then, replicated our findings for age at menopause using summary statistics from the PD consortium (19 773 women), followed by a meta-analysis combining all summary statistics.

RESULTS

For each year increase in age at menopause, the risk for PD decreased (odds ration [OR], 0.84; 95% confidence interval [CI], 0.73-0.98; P = 0.03) among women in our study, whereas there was no association among men (OR, 0.98; 95% CI, 0.85-1.11; P = 0.71). A replication using summary statistics from the PD consortium estimated an OR of 0.94 (95% CI, 0.90-0.99; P = 0.01), and we calculated a meta-analytic OR of 0.93 (95% CI, 0.89-0.98; P = 0.003). There was no indication for an association between age at menarche and PD (OR, 0.75; 95% CI, 0.44-1.29; P = 0.29).

CONCLUSIONS

A later age at menopause was associated with a decreased risk of PD in women, supporting the hypothesis that sex hormones or other factors related to late menopause may be neuroprotective in PD. © 2021 International Parkinson and Movement Disorder Society.

From Menopause to Neurodegeneration-Molecular Basis and Potential Therapy

The impacts of menopause on neurodegenerative diseases, especially the changes in steroid hormones, have been well described in cell models, animal models, and humans. However, the therapeutic effects of hormone replacement therapy on postmenopausal women with neurodegenerative diseases remain controversial. The steroid hormones, steroid hormone receptors, and downstream signal pathways in the brain change with aging and contribute to disease progression. Estrogen and progesterone are two steroid hormones which decline in circulation and the brain during menopause. Insulin-like growth factor 1 (IGF-1), which plays an import role in neuroprotection, is rapidly decreased in serum after menopause. Here, we summarize the actions of estrogen, progesterone, and IGF-1 and their signaling pathways in the brain. Since the incidence of Alzheimer’s disease (AD) is higher in women than in men, the associations of steroid hormone changes and AD are emphasized. The signaling pathways and cellular mechanisms for how steroid hormones and IGF-1 provide neuroprotection are also addressed. Finally, the molecular mechanisms of potential estrogen modulation on N-methyl-d-aspartic acid receptors (NMDARs) are also addressed. We provide the viewpoint of why hormone therapy has inconclusive results based on signaling pathways considering their complex response to aging and hormone treatments. Nonetheless, while diagnosable AD may not be treatable by hormone therapy, its preceding stage of mild cognitive impairment may very well be treatable by hormone therapy.

Increased Risk of Parkinson's Disease in Women after Bilateral Oophorectomy

BACKGROUND

Results regarding the association between hormonal exposure and risk of Parkinson's disease (PD) are heterogeneous.

OBJECTIVES

To investigate the association of reproductive life characteristics with PD among postmenopausal women.

METHODS

The PARTAGE case-control included 130 female cases and 255 age-matched female controls. Information on gynecological history was obtained from a standardized questionnaire and PD was validated by neurological examination. Odds ratios (ORs) and 95% confidence intervals (CIs) were computed using conditional logistic regression.

RESULTS

After adjustment for education level, smoking status, professional exposure to pesticides, and coffee and alcohol drinking, bilateral oophorectomy (OR = 3.55, 95%CI = 1.75-7.20), but neither menopause before age 50 years (OR = 1.24, 95%CI = 0.74-2.09) nor hormone therapy (HT; OR = 1.07, 95%CI = 0.62-1.86), was associated with PD.

CONCLUSION

Our findings suggest that bilateral oophorectomy is associated with increased risk of PD. © 2021 International Parkinson and Movement Disorder Society.

The Impact of Estrogen and Estrogen-Like Molecules in Neurogenesis and Neurodegeneration: Beneficial or Harmful?

Estrogens and estrogen-like molecules can modify the biology of several cell types. Estrogen receptors alpha (ERα) and beta (ERβ) belong to the so-called classical family of estrogen receptors, while the G protein-coupled estrogen receptor 1 (GPER-1) represents a non-classical estrogen receptor mainly located in the plasma membrane. As estrogen receptors are ubiquitously distributed, they can modulate cell proliferation, differentiation, and survival in several tissues and organs, including the central nervous system (CNS). Estrogens can exert neuroprotective roles by acting as anti-oxidants, promoting DNA repair, inducing the expression of growth factors, and modulating cerebral blood flow. Additionally, estrogen-dependent signaling pathways are involved in regulating the balance between proliferation and differentiation of neural stem/progenitor cells (NSPCs), thus influencing neurogenic processes. Since several estrogen-based therapies are used nowadays and estrogen-like molecules, including phytoestrogens and xenoestrogens, are omnipresent in our environment, estrogen-dependent changes in cell biology and tissue homeostasis have gained attention in human health and disease. This article provides a comprehensive literature review on the current knowledge of estrogen and estrogen-like molecules and their impact on cell survival and neurodegeneration, as well as their role in NSPCs proliferation/differentiation balance and neurogenesis.

A Report of Tamoxifen and Parkinson's Disease in a US Population and a Review of the Literature

BACKGROUND

Tamoxifen, a selective estrogen receptor modulator, has been shown to variably affect Parkinson's disease (PD) risk.

OBJECTIVE

The aim of this study was to review epidemiological literature and evaluate the rate of PD in women with breast cancer with tamoxifen exposure in a US population.

METHODS

A literature search was conducted to identify relevant studies. We performed a retrospective cohort analysis using the Nurses' Health Study Version One to report descriptive statistics.

RESULTS

Most studies suggest there may be a time-dependent effect of tamoxifen on PD risk, with the risk increasing with time from exposure. However, rates of PD in persons exposed to tamoxifen overall appear to be low. In our cohort, PD was evident in 6.2 per 1,000 of those with tamoxifen use and 3.6 per 1,000 of those without tamoxifen use. Time from breast cancer to PD diagnosis was 9.7 years among women with tamoxifen exposure and 11.7 among women without.

CONCLUSIONS

Tamoxifen may be associated with an increased risk for PD. Further research is needed to elucidate the role of estrogen and selective estrogen antagonism in PD. © 2021 International Parkinson and Movement Disorder Society.

The Effect of Estrogen Replacement Therapy on Alzheimer's Disease and Parkinson's Disease in Postmenopausal Women: A Meta-Analysis

Background: Estrogen replacement therapy (ERT) is a common treatment method for menopausal syndrome; however, its therapeutic value for the treatment of neurological diseases is still unclear. Epidemiological studies were performed, and the effect of postmenopausal ERT on treating neurodegenerative diseases, including Alzheimer's disease (AD) and Parkinson's disease (PD), was summarized through a meta-analysis.

Methods: Twenty-one articles were selected using a systematic searching of the contents listed on PubMed and Web of Science before June 1, 2019. Epidemiological studies were extracted, and relevant research data were obtained from the original articles based on the predefined inclusion criteria and data screening principles. The Comprehensive Meta-Analysis Version 2 software was used to pool effective size, test heterogeneity, conduct meta-regression and subgroup analysis, and to calculate publication bias.

Results: Our results showed that ERT significantly decreased the risk of onset and/or development of AD [odds ratio (OR): 0.672; 95% CI: 0.581–0.779; P < 0.001] and PD (OR: 0.470; 95% CI: 0.368–0.600; P < 0.001) compared with the control group. A subgroup and meta-regression analysis showed that study design and measure of effect were the source of heterogeneity. Age, sample size, hormone therapy ascertainment, duration of the treatment, or route of administration did not play a significant role in affecting the outcome of the meta-analysis.

Conclusion: We presented evidence here to support the use of estrogen therapy for the treatment of AD and PD.

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.

Sex differences in movement disorders

In a range of neurological conditions, including movement disorders, sex-related differences are emerging not only in brain anatomy and function, but also in pathogenesis, clinical features and response to treatment. In Parkinson disease (PD), for example, oestrogens can influence the severity of motor symptoms, whereas elevation of androgens can exacerbate tic disorders. Nevertheless, the real impact of sex differences in movement disorders remains under-recognized. In this article, we provide an up-to-date review of sex-related differences in PD and the most common hyperkinetic movement disorders, namely, essential tremor, dystonia, Huntington disease and other chorea syndromes, and Tourette syndrome and other chronic tic disorders. We highlight the most relevant clinical aspects of movement disorders that differ between men and women. Increased recognition of these differences and their impact on patient care could aid the development of tailored approaches to the management of movement disorders and enable the optimization of preclinical research and clinical studies.

Pregnancy in Parkinson's disease with PARK2 mutations

We report a pregnancy in a patient with Parkinson's disease with PARK2 mutations. Although pregnancy is uncommon in patients with Parkinson's disease, an early-onset Parkinson's patient with three silent and two missense mutations in the PARK2 gene is presented here.

Female Sex and Brain-Selective Estrogen Benefit α-Synuclein Tetramerization and the PD-like Motor Syndrome in 3K Transgenic Mice

Many studies report a higher risk for Parkinson's disease (PD) and younger age of onset in men. This, and the fact that the neuropathological process underlying PD symptoms may begin before menopause, suggests that estrogen-based hormone therapy could modify this higher risk in males. However, the effects of female sex or estrogen on α-synuclein (αS) homeostasis and related PD neuropathology remain unknown. Here, we used an αS tetramer-abrogating mouse model of PD (3K) that amplifies the familial E46K PD mutation to investigate the effects of female sex and brain-selective estrogen treatment on αS tetramerization and solubility, formation of vesicle-rich αS⁺ aggregates, dopaminergic and cortical fiber integrity, and associated motor deficits. In male 3K mice, the motor phenotype became apparent at ∼10 weeks and increased to age 6 months, paralleled by PD-like neuropathology, whereas 3K females showed a significant delay in onset. At 6 months, this beneficial phenotypic effect in 3K females was associated with a higher αS tetramer-to-monomer ratio and less decrease in dopaminergic and cortical fiber length and quantity. Brain-selective estrogen treatment in symptomatic 3K mice significantly increased the tetramer-to-monomer ratio, turnover by autophagy of aggregate-prone monomers, and neurite complexity of surviving DAergic and cortical neurons, in parallel with benefits in motor performance. Our findings support an upstream role for αS tetramer loss in PD phenotypes and a role for estrogen in mitigating PD-like neuropathology in vivo Brain-selective estrogen therapy may be useful in delaying or reducing PD symptoms in men and postmenopausal women.SIGNIFICANCE STATEMENT The mechanisms responsible for the male-to-female preponderance in Parkinson's disease (PD) are not well understood yet important for treatment efficacy. We previously showed that abrogating native α-synuclein (αS) tetramers produces a close PD model, including dopaminergic and cortical fiber loss and a progressive motor disorder responsive to l-DOPA. Here, we analyzed sex and use 10b-17β-dihydroxyestra-1,4-dien-3-one treatment of symptomatic 3K males, and demonstrate that the beneficial effects of female sex on PD-like neuropathology can be reinstated by elevating estrogen in the male brain. The study provides evidence that 17β-estradiol restores the tetramer-to-monomer ratio by autophagy turnover of excess αS monomers, vesicle and fiber integrity in brain regions critically involved in motor behavior. These data provide the basis for understanding sex differences in αS homeostasis and the development of therapeutic approaches to treating men and postmenopausal women with PD.

Sex-related differences in homebound advanced Parkinson's disease patients

Background

Women with Parkinson’s disease (PD) are more likely to be older, have greater disease severity and comorbidities, and yet are less likely to receive care from a neurologist, as compared with men with PD. Within the PD population, homebound individuals are a particularly vulnerable group facing significant barriers to care, yet within this understudied population, sex-related differences have not been reported.

Purpose

To identify and describe differences in homebound men and women with advanced PD and related disorders, participating in an interdisciplinary home visit program.

Patients and methods

This was an exploratory analysis of homebound patients seen between February 2014 and July 2016 using data collected via in-person interviews and chart review.

Results

We enrolled 85 patients, of whom 52% were women. PD was the most common diagnosis (79%), followed by dementia with Lewy bodies (5%), and other atypical parkinsonism (16%). Men were more likely to have a PD dementia diagnosis than women (17.1% vs 2.3%, p=0.03). Women were more likely to live alone (18.1% of women had no caregiver vs 2.4% of men, p=0.05).

Conclusion

The role of the caregiver in facilitating safe aging-in-place is crucial. Among homebound individuals with advanced PD, women were far more likely to live alone. The absence of a spouse or care partner may be due in part to variable sex-based life expectancies. Our findings suggest that homebound women with advanced PD may face greater barriers to accessing support.

Exposure to Pesticides and Welding Hastens the Age-at-Onset of Parkinson's Disease

BACKGROUND

The age-at-onset (AAO) of Parkinson's disease (PD) is thought to be influenced by environmental factors and polygenic predispositions. Professional exposures to pesticides and toxic metals were shown to be associated with an earlier onset in small sample studies.

AIM OF STUDY

The aim of this study was to confirm the association between professional exposures to pesticides and toxic metals and the AAO of PD, on a larger cohort of patients, defined with a clinic-based ascertainment scheme.

METHODS

We used an incident cohort of 290 patients recruited through three designated movement disorder clinics in the province of Quebec, Canada. Patients completed a detailed questionnaire regarding professional exposures to pesticides and toxic metals. We compared the AAO in patients without prior professional exposure (N = 170) and those with exposure to pesticides (N = 53) or toxic metals through welding (N = 30). We further subdivided patients exposed to pesticides according to the frequency and proximity of their contacts.

RESULTS

Patients with prior exposure to pesticides (AAO = 54.74 years) or toxic metals (54.27 years) had a significantly earlier AAO compared to the control group (59.26 years) (p = 0.003). In those exposed to pesticides, closer (p = 0.03) and more frequent (p = 0.02) contacts were negatively correlated with AAO.

CONCLUSION

Exposure to pesticides and toxic metals were both associated with an earlier onset of PD, an effect that was greater with higher levels of exposure, both in terms of frequency and proximity.

Beneficial effect of estrogen on nigrostriatal dopaminergic neurons in drug-naïve postmenopausal Parkinson's disease

This study aimed to investigate the potential beneficial effects of estrogen on nigrostriatal dopaminergic neuron degeneration in postmenopausal drug-naïve Parkinson's disease (PD). Based on the ratio of lifetime estrogen exposure length to the total length of the estrogen exposure and deprivation period, postmenopausal women with drug-naïve PD were divided into low (n = 31) and high (n = 31) estrogen exposure ratio groups. We performed a comparative analysis of the striatal dopamine transporter (DAT) availability between the two groups. Additionally, we evaluated the longitudinal change in the levodopa equivalent dose per month using a linear mixed model. The motor symptoms were more severe in the low estrogen exposure ratio group than in the high estrogen exposure ratio group (P = 0.016). PD patients in the two groups had significantly lower DAT availability on all striatal sub-regions except for ventral striatum than did age- and sex-matched normal controls. When comparing the two groups, PD patients in the low estrogen exposure ratio group exhibited significantly lower DAT availability in the posterior putamen (P = 0.024) and in the ventral putamen (P = 0.036) than those in the high estrogen exposure ratio group. The estimated monthly levodopa equivalent dose changes were 10.9 in the low estrogen exposure ratio group and 7.1 in the high estrogen exposure ratio group with a significant interaction between the two groups (P = 0.001). These in vivo data provide indirect evidence showing that estrogen may elicit a beneficial effect on nigrostriatal dopamine neurons in PD.

Neurological health and premature ovarian insufficiency - pathogenesis and clinical management

Premature ovarian insufficiency (POI) is related to neurological problems through neurological symptoms of oestrogen deficiency, diseases caused by oestrogen deficiency, and neurological genetic diseases. Neurological symptoms of oestrogen deficiency are usually reported as climacteric symptoms. Diseases caused by oestrogen deficiency are dementia, cognitive decline, and Parkinsonism. Among genetic neurological disorders, ovarioleukodystrophy and fragile X-associated tremor/ataxia syndrome (FXTAS) are reported.

Repurposing sex steroids and related drugs as potential treatment for Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder for which a greater prevalence and incidence is described in men. This suggests a protective effect of sex hormones in the brain. Therefore, steroids and drugs to treat endocrine conditions could have additional application for PD. Here, we review the protective effect of sex hormones, particularly estrogens, progesterone, androgens and dehydroepiandrosterone, in animal models of PD and also in human studies. Data also support that drugs affecting estrogen neurotransmission such as selective estrogen receptor modulators or affecting steroid metabolism with 5α-reductase inhibitors could be repositioned for treatment of PD. Sex steroids are also modulator of neurotransmission, thus they could repurposed to treat PD motor symptoms and to modulate the response to PD medication. No drug is yet available to limit PD progression. PD is a complex disease implicating multiple pathological processes and a therapeutic strategy using drugs with several mechanisms of action, such as sex steroids and endocrine drugs are interesting repositioning options for symptomatic treatment and disease-modifying activity for PD. This article is part of the Special Issue entitled 'Drug Repurposing: old molecules, new ways to fast track drug discovery and development for CNS disorders'.

Lifetime exposure to estrogen and progressive supranuclear palsy: Environmental and Genetic PSP study

BACKGROUND

Studies suggesting a protective effect of estrogen in neurodegenerative diseases prompted us to investigate this relationship in progressive supranuclear palsy (PSP).

METHODS

This case-control study evaluated the self-reported reproductive characteristics and estrogen of 150 women with PSP and 150 age-matched female controls who participated in the Environmental Genetic-PSP study. Conditional logistic regression models were generated to examine associations of PSP with estrogen.

RESULTS

There was no association between years of estrogen exposure duration and PSP. There was a suggestion of an inverse association between composite estrogen score and PSP that did not reach statistical significance (P = .06). Any exposure to estrogen replacement therapy halved the risk of PSP (odds ratio = 0.52; 95% confidence interval = 0.30-0.92; P = .03). Among PSP cases, earlier age at menarche was associated with better performance on Hoehn and Yahr stage (β = -0.60; SE = 0.26; P = .02) and Unified Parkinson's Disease Rating Scale II score (β = -5.19; SE = 2.48; P = .04) at clinical examination.

CONCLUSIONS

This case-control study suggests a protective role of lifetime estrogen exposure in PSP. Future studies will be needed to confirm this association. © 2018 International Parkinson and Movement Disorder Society.

Effect of the 5α-reductase enzyme inhibitor dutasteride in the brain of intact and parkinsonian mice

Dutasteride is a 5alpha-reductase inhibitor in clinical use to treat endocrine conditions. The present study investigated the neuroprotective mechanisms of action of dutasteride in intact and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned mice using a low dose of MPTP not affecting motor activity modeling early stages of Parkinson's disease (PD). We hypothesized that dutasteride neuroprotection is due to altered steroids levels. Dutasteride pre-treatment prevented loss of striatal dopamine (DA) and its metabolite DOPAC. Dutasteride decreased effects of MPTP on striatal dopamine transporter (DAT), vesicular monoamine transporter 2 (VMAT2) and D2 DA receptor specific binding while D1 receptor specific binding remained unchanged. Dutasteride enhanced DAT specific binding and the glycosylated form of DAT in intact mice. MPTP-lesioned mice had plasma and brain testosterone and dihydrotestosterone levels lower than control mice whereas progesterone and its metabolites (dihydroprogesterone, isopregnanolone and tetrahydroprogesterone) pathway showed increases. Dutasteride treatment by inhibiting transformation of progesterone and testosterone to its metabolites elevated plasma and brain concentrations of testosterone compared to MPTP mice and decreased DHT levels in intact mice. Plasma and brain estradiol levels were low and remained unchanged by MPTP and/or dutasteride treatment. Dutasteride treatment did not affect striatal phosphorylation of Akt and its downstream substrate GSK3β as well as phosphorylation of ERK1/2 in intact and MPTP lesioned MPTP mice. Striatal glial fibrillary acidic protein (GFAP) levels were markedly elevated in MPTP compared to control mice and dutasteride reduced GFAP levels in MPTP mice. Treatment with dutasteride post-lesion left unchanged striatal DA levels. These results suggest dutasteride as promising drug for PD neuroprotection.

Tamoxifen usage correlates with increased risk of Parkinson's disease in older women with breast cancer: a case-control study in Taiwan

BACKGROUND AND OBJECTIVES

Little is known about the association between tamoxifen usage and risk of Parkinson's disease in women with breast cancer. The present study aimed to evaluate the association between tamoxifen usage and Parkinson's disease in older women with breast cancer in Taiwan.

METHODS

We conducted a retrospective nationwide case-control study using the database of the Taiwan National Health Insurance Program. In total, 293 female subjects with breast cancer, aged 65 years and above, who were newly diagnosed with Parkinson's disease between 2000 and 2011 were included. Additionally, 1053 female subjects with breast cancer aged 65 years and above without Parkinson's disease were randomly selected as controls. Both cases and controls were matched for age and comorbidities. Ever use of tamoxifen was defined as subjects who had at least a prescription for tamoxifen before the index date, whereas never use of tamoxifen was defined as those who never had a prescription for tamoxifen before the index date. We used the unconditional logistic regression model to calculate the odds ratio (OR) and 95% confidence interval (CI) for the association between tamoxifen usage and risk of Parkinson's disease.

RESULTS

After adjusting for confounding variables, the adjusted OR of Parkinson's disease was 3.32 for subjects with ever use of tamoxifen (95% CI, 2.50-4.43), compared with nonusers. Further analysis showed that the adjusted ORs of Parkinson's disease were 3.21 (95% CI, 2.29-4.49), 3.95 (95% CI, 2.77-5.64), and 11.4 (95% CI, 2.63-49.7) for subjects with < 2, 2-6, and ≥ 6 years of cumulative tamoxifen usage, respectively, when compared with nonusers.

CONCLUSIONS

Tamoxifen usage was associated with a 3.32-fold increase in the likelihood of having Parkinson's disease among older women with breast cancer in Taiwan.

Increase of Reproductive Life Span Delays Age of Onset of Parkinson's Disease

One striking observation in Parkinson’s disease (PD) is the remarkable gender difference in incidence and prevalence of the disease. Data on gender differences with regard to disease onset, motor and non-motor symptoms, and dopaminergic medication are limited. Furthermore, whether estrogen status affects disease onset and progression of PD is controversially discussed. In this retrospective single center study, we extracted clinical data of 226 ambulatory PD patients and compared age of disease onset, disease stage, motor impairment, non-motor symptoms, and dopaminergic medication between genders. We applied a matched-pairs design to adjust for age and disease duration. To determine the effect of estrogen-related reproductive factors including number of children, age at menarche, and menopause on the age of onset, we applied a standardized questionnaire and performed a regression analysis. The male to female ratio in the present PD cohort was 1.9:1 (147 men vs. 79 women). Male patients showed increased motor impairment than female patients. The levodopa equivalent daily dose was increased by 18.9% in male patients compared to female patients. Matched-pairs analysis confirmed the increased dose of dopaminergic medication in male patients. No differences were observed in age of onset, type of medication, and non-motor symptoms between both groups. Female reproductive factors including number of children, age at menarche, and age at menopause were positively associated with a delay of disease onset up to 30 months. The disease-modifying role of estrogen-related outcome measures warrants further clinical and experimental studies targeting gender differences, specifically hormone-dependent pathways in PD.

Peripheral Lymphocyte Subsets as a Marker of Parkinson's Disease in a Chinese Population

In this study, we conducted a clinical analysis of lymphocyte subtypes in 268 patients with Parkinson's disease (PD) to assess their clinical impact as a potential marker of advanced PD in Chinese patients. The participants comprised 268 sporadic PD patients and 268 healthy controls. The numbers of natural killer (NK) cells and CD3+, CD3+CD4+, CD3+CD8+, and CD19+ lymphocytes from peripheral blood were determined by immunostaining and flow cytometric analysis and the percentages of these CD+ T cells were calculated. The ratio of regulatory T (Treg)/helper T 17 (Th17) lymphocytes from 64 PD patients and 46 controls was determined by flow cytometric analysis. The results showed that the percentage of NK cells was higher in advanced PD patients than in controls (22.92% ± 10.08% versus 19.76% ± 10.09%, P = 0.006), while CD3+ T cells are decreased (62.93% ± 9.27% versus 65.75% ± 9.13%, P = 0.005). The percentage of CD19+ B cells in male patients was lower (P = 0.021) than in female patients, whereas NK cells were increased (P < 0.0001). The scores on the Unified Parkinson's Disease Rating Scale (UPDRS) and the Non-Motor Symptoms Scale in late-onset PD patients were significantly higher than those in early-onset patients (P = 0.024 and P = 0.007, respectively). The percentage of CD19+ B cells in patients with UPDRS scores >24 was lower than in those with scores <24 (10.17% ± 4.19% versus 12.22% ± 5.39%, P = 0.009). In addition, the Treg/Th17 ratio in female patients was higher than that in female controls (13.88 ± 6.32 versus 9.94 ± 4.06, P = 0.042). These results suggest that the percentages of NK cells, CD3+ T cells, and CD19+ B cells along with the Treg/Th17 ratio in peripheral blood may be used to predict the risk of PD in Chinese individuals and provide fresh avenues for novel diagnostic biomarkers and therapeutic designs.

Reproductive factors and risk of Parkinson's disease in women: A meta-analysis of observational studies

Evidence on the relationship between reproductive factors, use of oral contraceptives (OCs) and the incidence of Parkinson's disease (PD) remain inconclusive. The aim of this meta-analysis is to evaluate whether relevant reproductive factors including age at menarche, age at menopause, fertile lifespan, parity, type of menopause (surgical versus natural), and use of OCs are associated with risk of PD in women via random-effects model. PubMed and EMBASE database were used to search for case-control or cohort studies published before February17, 2017. 6 case-control and 5 cohort studies were included in the meta-analysis. The pooled relative risks (RRs) of PD risk were 1.00 (95% CI: 0.79-1.28) for use of OCs (ever versus never), 1.03 (95% CI: 0.84-1.26) for age at menarche, 0.98 (95% CI: 0.75-1.29) for age at menopause, 0.98(95% CI: 0.77-1.25) for fertile lifespan, 0.99(95% CI:0.0.79-1.25) for parity, 0.93 (95% CI:0.68-1.29) for type of menopause (surgical versus natural). In the subgroup analysis stratified by study design, age, caffeine intake and smoking, an inverse association was found between surgical menopause and risk of PD for those adjusting for caffeine intake (RR: 0.67, 95% CI: 0.45-0.99) and smoking (RR: 0.77, 95% CI: 0.63-0.94); while a positive association was found between surgical menopause and PD risk for those not adjusting for smoking (RR: 1.91, 95% CI: 1.29-2.83). In conclusion, our meta-analysis provided little epidemiological support for the role of reproductive factors in the incidence of PD. Whether surgical menopause is inversely associated with the risk of PD requires further explorations.

Gender, aging and longevity in humans: an update of an intriguing/neglected scenario paving the way to a gender-specific medicine

Data showing a remarkable gender difference in life expectancy and mortality, including survival to extreme age, are reviewed starting from clinical and demographic data and stressing the importance of a comprehensive historical perspective and a gene–environment/lifestyle interaction. Gender difference regarding prevalence and incidence of the most important age-related diseases, such as cardiovascular and neurodegenerative diseases, cancer, Type 2 diabetes, disability, autoimmunity and infections, are reviewed and updated with particular attention to the role of the immune system and immunosenescence. On the whole, gender differences appear to be pervasive and still poorly considered and investigated despite their biomedical relevance. The basic biological mechanisms responsible for gender differences in aging and longevity are quite complex and still poorly understood. The present review focuses on centenarians and their offspring as a model of healthy aging and summarizes available knowledge on three basic biological phenomena, i.e. age-related X chromosome inactivation skewing, gut microbiome changes and maternally inherited mitochondrial DNA genetic variants. In conclusion, an appropriate gender-specific medicine approach is urgently needed and should be systematically pursued in studies on healthy aging, longevity and age-related diseases, in a globalized world characterized by great gender differences which have a high impact on health and diseases.

Influence of Estrogen Modulation on Glia Activation in a Murine Model of Parkinson's Disease

Epidemiological data suggest a sexual dimorphism in Parkinson disease (PD), with women showing lower risk of developing PD. Vulnerability of the nigrostriatal pathway may be influenced by exposure to estrogenic stimulation throughout fertile life. To further address this issue, we analyzed the progression of nigrostriatal damage, microglia and astrocyte activation and microglia polarization triggered by intrastriatal injection of dopaminergic neurotoxin 6-hydroxydopamine (6-OHDA) in male, female and ovariectomized (OVX) mice, as well as in OVX mice supplemented with 17βestradiol (OVX+E). Animals were sacrificed at different time points following 6-OHDA injection and brain sections containing striatum and substantia nigra pars compacta (SNc) underwent immunohistochemistry for tyrosine hydroxylase (TH) (dopaminergic marker), immunofluorescence for IBA1 and GFAP (markers of microglia and astrocyte activation, respectively) and triple immunoflorescent to identify polarization of microglia toward the cytotoxic M1 (DAPI/IBA1/TNFα) or cytoprotective M2 (DAPI/IBA1/CD206) phenotype. SNc damage induced by 6-OHDA was significantly higher in OVX mice, as compared to all other experimental groups, at 7 and 14 days after surgery. Astrocyte activation was higher in OVX mice with respect the other experimental groups, at all time points. Microglial activation in the SNc was detected at earlier time points in male, female and OVX+E, while in OVX mice was detected at all time-points. Microglia polarization toward the M2, but not the M1, phenotype was detected in female and OVX+E mice, while the M1 phenotype was observed only in male and OVX mice. Our results support the protective effects of estrogens against nigrostriatal degeneration, suggesting that such effects may be mediated by an interaction with microglia, which tend to polarize preferentially toward an M2, cytoprotective phenotype in the presence of intense estrogenic stimulation.

Parkinson's disease and pregnancy: An updated review

Pregnancy does not often occur in the setting of Parkinson's disease (PD) as the most common age of onset is beyond the childbearing years, yet management of these two conditions is crucial for the health of both mother and child. Here we review treatment data of PD during pregnancy, primarily from case reports and drug registries, and focus on available evidence regarding the pregnancy risks for patient and fetus. Historically, it was reported that many women had worsening of symptoms during pregnancy but this may be because anti-parkinsonian medications were not recommended or were under dosed. Levodopa has the best safety data for use in pregnancy and amantadine should be avoided in women who are pregnant or trying to become pregnant. The data for other pharmacological and surgical treatments is less clear. There is no evidence that women with PD have higher rates of birth or fetal complications.

Effects of progesterone administered after MPTP on dopaminergic neurons of male mice

Progesterone neuroprotection of striatal dopamine (DA) in male mice lesioned with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) was previously reported when administered before MPTP or an hour after. A dose of MPTP to induce a partial lesion was used to model early stages or prodromal Parkinson. We hypothesized that brain DA can be restored by progesterone administered early (24 h) or later (5 days) after MPTP. Male mice received 4 injections of MPTP (8 mg/kg) and progesterone (8 mg/kg) once daily for 5 days started 24 h or 5 days after MPTP. The lesion decreased striatal DA and its metabolites but not serotonin contents. MPTP mice treated with progesterone starting 24 h but not 5 days after MPTP had higher striatal DA and its metabolites content than vehicle-treated MPTP mice. Striatal DA transporter (DAT) and vesicular monoamine transporter 2 (VMAT2) specific binding decreased in lesioned mice and were corrected with progesterone treatment starting 24 h but not 5 days after MPTP. Striatal glial fibrillary acidic protein (GFAP) levels, a marker of activated astrocytes, were elevated by the MPTP lesion and were corrected with progesterone treatment starting 24 h after MPTP. Striatal brain derived neurotrophic factor (BDNF) levels were decreased by the MPTP lesion and were prevented by progesterone treatments whereas no change of Akt, GSK3β, ERK1 and 2 and their phosphorylated forms were observed. Thus, progesterone administered after MPTP in mice protected dopaminergic neurons through modulation of neuroinflammation and BDNF. In humans, progesterone could possibly be used as a disease-modifying drug in prodromal Parkinson.

Motor Nerve Conduction Velocity In Postmenopausal Women with Peripheral Neuropathy

INTRODUCTION

The post-menopausal phase is characterized by a decline in the serum oestrogen and progesterone levels. This phase is also associated with higher incidence of peripheral neuropathy.

AIM

To explore the relationship between the peripheral motor nerve status and serum oestrogen and progesterone levels through assessment of Motor Nerve Conduction Velocity (MNCV) in post-menopausal women with peripheral neuropathy.

MATERIALS AND METHODS

This cross-sectional study was conducted at Jawaharlal Nehru Medical College during 2011-2013. The study included 30 post-menopausal women with peripheral neuropathy (age: 51.4±7.9) and 30 post-menopausal women without peripheral neuropathy (control) (age: 52.5±4.9). They were compared for MNCV in median, ulnar and common peroneal nerves and serum levels of oestrogen and progesterone estimated through enzyme immunoassays. To study the relationship between hormone levels and MNCV, a stepwise linear regression analysis was done.

RESULTS

The post-menopausal women with peripheral neuropathy had significantly lower MNCV and serum oestrogen and progesterone levels as compared to control subjects. Stepwise linear regression analysis showed oestrogen with main effect on MNCV.

CONCLUSION

The findings of the present study suggest that while the post-menopausal age group is at a greater risk of peripheral neuropathy, it is the decline in the serum estrogen levels which is critical in the development of peripheral neuropathy.