Reproductive factors, exogenous estrogen use, and risk of Parkinson's disease

Exploring the Nicotine-Parkinson's disease link - Insights from the UK Biobank

INTRODUCTION

Evidence suggests an inverse correlation between smoking and Parkinson's disease (PD), yet the mechanisms remain unclear. This study examines the changing risk relationship between smoking and PD diagnosis using alcohol consumption, another reward-driven behavior, as a comparative measure.

METHODS

A nested case-control study was conducted using the UK Biobank (UKBB) database. Participants in the prediagnostic phase of PD were identified, and self-reported data on tobacco and alcohol use were analyzed employing conditional binary logistic regression. Polynomial and piece-wise regression models were employed to discern shifting associations with PD over time.

RESULTS

Of 502,304 participants (63 ± 5.3 years, 63 % male), 3049 prediagnostic PD cases were identified. Non-smokers had a heightened PD risk, and this association strengthened closer to diagnosis. The odds ratio (OR [95 % CI]) associated with PD in non-smokers was 2.02 [1.07-3.81] 1-4 years before diagnosis, compared to 1.36 [1.02-1.83] at >10-year intervals (linear trend, p = 0.012). The time trajectory of ORs was best depicted by a quadratic function, identifying a shift in risk 7.5 years before diagnosis documentation. Similar patterns emerged among alcohol non-consumers, with an 8.5-year interval inflection point.

CONCLUSION

This study identified two disparate risk trajectories among non-smokers: an initial low-amplitude increased risk at prolonged prediagnostic intervals possibly related to genetic/personality factors, followed by a sharp escalation in risk association commencing 7-8 years before diagnosis, possibly propelled by reverse causality. Similar trends in alcohol consumption reinforce these conclusions. These findings could suggest that smoking cessation may serve as an early indicator of PD.

Reproductive life factors and estro-progestin exposure in women with early-onset Parkinson's disease compared to late-onset disease and controls: A retrospective cohort study

BACKGROUND

Parkinson's disease (PD) is more common in men than women. Although hormonal factors may partially explain this difference, there are no studies evaluating reproductive life factors and exogenous estroprogestin exposure in women with Early Onset Parkinson Disease (EOPD).

OBJECTIVE

To compare reproductive life factors and exogenous estroprogestin exposure among female patients with EOPD, late-onset Parkinson's disease (LOPD), and EOPD-matched unaffected controls.

METHODS

We identified female patients with EOPD from 1989 to 2021, defining EOPD as PD with motor-symptoms onset before age 50 and LOPD as PD with motor onset after 50. We paired EOPD patients to age-matched, unaffected controls. We reviewed medical records to determine demographic characteristics, clinical history, and reported reproductive menopausal history (reviewing medical records).

RESULTS

We included 87 EOPD patients, 84 LOPD patients, and 91 unaffected controls with information about reproductive life factors and exogenous estroprogestin exposure in their medical records. There were no significant differences in race, ethnicity, or BMI between the three groups. EOPD patients were more likely to have used hormonal contraception than LOPD patients (23/49 (47 %) vs 0/84 (0 %), p < 0.001). LOPD patients had higher numbers of pelvic surgeries (48/84 [57 %] in LOPD, 23/87 [26 %] in EOPD, p < 0.001) and higher usage of perimenopausal hormonal therapy (52/84 [62 %] in LOPD, 10/87 [11 %] in EOPD, p < 0.001) in LOPD than EOPD.

CONCLUSIONS

Our study reports no significant difference in reproductive life factors and exogenous estroprogestin exposure between controls and EOPD patients, except for higher exposure to hormonal contraception in EOPD. There was no apparent difference in reproductive life factors and exogenous estroprogestin exposure between EOPD and LOPD patients. Our findings therefore do not observe that hormonal exposure is different between earlier onset of female EOPD compared to female LOPD patients, or between female EOPD patients and unaffected female controls.

17-β-estradiol potentiates the neurotrophic and neuroprotective effects mediated by the dopamine D3/acetylcholine nicotinic receptor heteromer in dopaminergic neurons

Dopaminergic neurons express a heteromer composed of the dopamine D3 receptor and the α4β2 nicotinic acetylcholine receptor, the D3R-nAChR heteromer, activated by both nicotine and dopamine D2 and D3 receptors agonists, such as quinpirole, and crucial for dopaminergic neuron homeostasis. We now report that D3R-nAChR heteromer activity is potentiated by 17-β-estradiol which acts as a positive allosteric modulator by binding a specific domain on the α4 subunit of the nicotinic receptor protomer. In mouse dopaminergic neurons, in fact, 17-β-estradiol significantly increased the ability of nicotine and quinpirole in promoting neuron dendritic remodeling and in protecting neurons against the accumulation of α-synuclein induced by deprivation of glucose, with a mechanism that does not involve the classical estrogen receptors. The potentiation induced by 17-β-estradiol required the D3R-nAChR heteromer since either nicotinic receptor or dopamine D3 receptor antagonists and interfering TAT-peptides, but not the estrogen receptor antagonist fulvestrant, specifically prevented 17-β-estradiol effects. Evidence of estrogens neuroprotection, mainly mediated by genomic mechanisms, have been provided, which is in line with epidemiological data reporting that females are less likely to develop Parkinson's Disease than males. Therefore, potentiation of D3R-nAChR heteromer activity may represent a further mechanism by which 17-β-estradiol reduces dopaminergic neuron vulnerability.

Interaction between caffeine consumption & genetic susceptibility in Parkinson's disease: A systematic review

BACKGROUND

Caffeine is one of the most consumed psychoactive substances globally. Caffeine-gene interactions in Parkinson's disease (PD) has not been systematically examined.

OBJECTIVES

To conduct a systematic review on the interaction between caffeine consumption and genetic susceptibility to PD.

METHODOLOGY

We conducted PubMed and Embase search using terms "Genetic association studies", "Caffeine", "polymorphism" and "Parkinson's disease", from inception till 2023. Of the initial 2391 studies, 21 case-control studies were included. The demographic, genetic and clinical data were extracted and analyzed.

RESULTS

We identified 21 studies which involved a total of 607,074 study subjects and 17 gene loci (SNCA, MAPT, HLA-DRA, NOS1, NOS3, GBA, ApoE, BST1, ESR2, NAT2, SLC2A13, LRRK2, NOS2A, GRIN2A, CYP1A2, ESR1, ADORA2A) have been investigated for the effect of gene-caffeine interaction and PD risk. The genes were identified through PD GWAS or involved in caffeine or related metabolism pathways. Based on the genetic association and interaction studies, only MAPT, SLC2A13, LRRK2, ApoE, NOS2A, GRIN2A, CYP1A2, and ADORA2A have been shown by at least one study to have a positive caffeine-gene interaction influencing the risk of PD.

CONCLUSION

Studies have shown an interaction between caffeine with genetic variants of MAPT, SLC2A13, LRRK2, ApoE, NOS2A, GRIN2A, CYP1A2, and ADORA2A in modulating the risk of PD. Due to the potential limitations of these discovery/pilot studies, further independent replication studies are needed. Better designed genetic association studies in multi-ancestry and admixed cohorts to identify potential shared or unique multivariate gene-environmental interactions, as well as functional studies of gene-caffeine interactions will be useful.

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.

X-Chromosome Association Study in Latin American Cohorts Identifies New Loci in Parkinson's Disease

BACKGROUND

Sex differences in Parkinson's disease (PD) risk are well-known. However, the role of sex chromosomes in the development and progression of PD is still unclear.

OBJECTIVE

The objective of this study was to perform the first X-chromosome-wide association study for PD risk in a Latin American cohort.

METHODS

We used data from three admixed cohorts: (1) Latin American Research consortium on the Genetics of Parkinson's Disease (n = 1504) as discover cohort, and (2) Latino cohort from International Parkinson Disease Genomics Consortium (n = 155) and (3) Bambui Aging cohort (n = 1442) as replication cohorts. We also developed an X-chromosome framework specifically designed for admixed populations.

RESULTS

We identified eight linkage disequilibrium regions associated with PD. We replicated one of these regions (top variant rs525496; discovery odds ratio [95% confidence interval]: 0.60 [0.478-0.77], P = 3.13 × 10-5 replication odds ratio: 0.60 [0.37-0.98], P = 0.04). rs5525496 is associated with multiple expression quantitative trait loci in brain and non-brain tissues, including RAB9B, H2BFM, TSMB15B, and GLRA4, but colocalization analysis suggests that rs5525496 may not mediate risk by expression of these genes. We also replicated a previous X-chromosome-wide association study finding (rs28602900), showing that this variant is associated with PD in non-European populations.

CONCLUSIONS

Our results reinforce the importance of including X-chromosome and diverse populations in genetic studies. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Association of women-specific health factors in the severity of Parkinson's disease

Parkinson's disease (PD) is an age-related neurological disorder known for the observational differences in its risk, progression, and severity between men and women. While estrogen has been considered to be a protective factor in the development of PD, there is little known about the role that fluctuations in hormones and immune responses from sex-specific health experiences have in the disease's development and severity. We sought to identify women-specific health experiences associated with PD severity, after adjusting for known PD factors, by developing and distributing a women-specific questionnaire across the United States and creating multivariable models for PD severity. We created a questionnaire that addresses women's specific experiences and their PD clinical history and deployed it through The Parkinson's Foundation: PD Generation. To determine the association between women-specific health factors and PD severity, we constructed multivariable logistic regression models based on the MDS-UPDRS scale and the participants' questionnaire responses, genetics, and clinical data. For our initial launch in November 2021, we had 304 complete responses from PD GENEration. Univariate and multivariate logistic modeling found significant associations between major depressive disorder, perinatal depression, natural childbirth, LRRK2 genotype, B12 deficiency, total hysterectomy, and increased PD severity. This study is a nationally available questionnaire for women's health and PD. It shifts the paradigm in understanding PD etiology and acknowledging how sex-specific experiences may contribute to PD severity. In addition, the work in this study sets the foundation for future research to investigate the factors behind sex differences in 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.

Sex and Brain: The Role of Sex Chromosomes and Hormones in Brain Development and Parkinson's Disease

Sex hormones and genes on the sex chromosomes are not only key factors in the regulation of sexual differentiation and reproduction but they are also deeply involved in brain homeostasis. Their action is crucial for the development of the brain, which presents different characteristics depending on the sex of individuals. The role of these players in the brain is fundamental in the maintenance of brain function during adulthood as well, thus being important also with respect to age-related neurodegenerative diseases. In this review, we explore the role of biological sex in the development of the brain and analyze its impact on the predisposition toward and the progression of neurodegenerative diseases. In particular, we focus on Parkinson's disease, a neurodegenerative disorder that has a higher incidence in the male population. We report how sex hormones and genes encoded by the sex chromosomes could protect from the disease or alternatively predispose toward its development. We finally underline the importance of considering sex when studying brain physiology and pathology in cellular and animal models in order to better understand disease etiology and develop novel tailored therapeutic strategies.

Improving work life balance among female educationists during the COVID-19 lockdown

BACKGROUND

The entire education industry switched from offline to online modes as a result of the coronavirus outbreak. Numerous teachers who were diagnosed with musculoskeletal, psychological, and other neurodegenerative diseases have reported increased exhaustion, lack of sleep, a decline in quality of life (QoL), a decrease in physical activity, and excessive stress from online classes during the COVID-19 lockdown, especially women.

OBJECTIVE

The aim of this study is to evaluate the effectiveness of three-modal exercise on fatigue, sleep, QoL as well as to determine the relationship between age, disease severity, disease stage and working years with women diagnosed with Parkinson's disease (PD).

METHODS

In this randomized controlled trial, 44 female educators in stages I-II with PD who were between the ages of 40 and 60 volunteered. For a total of 36 sessions over the course of six weeks, Group A received a three-modal fitness program through online video sessions, whereas Group B received Nordic walking. The outcome measures included the Fatigue Severity Scale, Parkinson's Disease Sleep Scale, and Parkinson's Disease Quality of Life Questionnaire-39.

RESULTS

Age, Hoehn and Yahr scale, working years, and PD in years did not correlate with each other (p > 0.50). The three-modal exercise experimental Group A showed statistically significant improvement in QoL (p 0.001), sleep (p 0.001), and fatigue (p 0.001).

CONCLUSION

Women in the field of education who participated in a three-modal exercise programme for PD reported a significant improvement in their level of exhaustion, sleep patterns, and quality of life.

X-Chromosome Association Study in Latin American Cohorts Identifies New Loci in Parkinson Disease

Sex differences in Parkinson Disease (PD) risk are well-known. However, it is still unclear the role of sex chromosomes in the development and progression of PD. We performed the first X-chromosome Wide Association Study (XWAS) for PD risk in Latin American individuals. We used data from three admixed cohorts: (i) Latin American Research consortium on the GEnetics of Parkinson's Disease (n=1,504) as discover cohort and (ii) Latino cohort from International Parkinson Disease Genomics Consortium (n = 155) and (iii) Bambui Aging cohort (n= 1,442) as replication cohorts. After developing a X-chromosome framework specifically designed for admixed populations, we identified eight linkage disequilibrium regions associated with PD. We fully replicated one of these regions (top variant rs525496; discovery OR [95%CI]: 0.60 [0.478 - 0.77], p = 3.13 × 10 ^-5 ; replication OR: 0.60 [0.37-0.98], p = 0.04). rs525496 is an expression quantitative trait loci for several genes expressed in brain tissues, including RAB9B, H2BFM, TSMB15B and GLRA4 . We also replicated a previous XWAS finding (rs28602900), showing that this variant is associated with PD in non-European populations. Our results reinforce the importance of including X-chromosome and diverse populations in genetic studies.

Association Between Menopausal Hormone Therapy and Risk for Parkinson's Disease

BACKGROUND

The relationship between menopausal hormone therapy (MHT) and risk of Parkinson's disease (PD) remains controversial.

OBJECTIVE

This nationwide population-based cohort study investigated the association between MHT and PD development.

METHODS

Data from the National Health Insurance System of South Korea from 2007 to 2020 were used. The MHT group included women who underwent MHT for the first time between 2011-2014, while the non-MHT group included women who visited a healthcare provider for menopause during the same period but never received hormonal therapy. We used propensity score matching (1 : 1) to adjust for potential confounders, and Cox regression models to assess the association between MHT and PD.

RESULTS

We selected 303,260 female participants (n = 151,630 per MHT and non-MHT groups). The median age of the participants was 50 (48-54) years, and the follow-up period lasted 7.9 (6.9-8.9) years. Cox regression analysis revealed an increased risk of PD with MHT (hazard ratio [HR] 1.377, 95% confidence interval [CI] 1.184-1.602), particularly with tibolone (HR 1.554, 95% CI 1.297-1.861) and estrogen alone (HR 1.465, 95% CI 1.054-2.036). Tibolone and estrogen alone were linked to PD within three years; however, no association was observed after three years. In contrast, the use of combined estrogen-progesterone was linked to a higher risk of PD, which increased with the duration of MHT (HR 1.885, 95% CI 1.218-2.918 for over five years).

CONCLUSIONS

This study demonstrated that the MHT is closely associated with the risk of PD in a regimen- and duration-specific manner.

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.

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.

Sex Differences in Neurodegeneration: The Role of the Immune System in Humans

Growing evidence supports significant involvement of immune dysfunction in the etiology of neurodegenerative diseases, several of which also display prominent sex differences across prevalence, pathology, and symptomology. In this review, we summarize evidence from human studies of established and recent findings of sex differences in multiple sclerosis, Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis and discuss how sex-specific central nervous system innate immune activity could contribute to downstream sex differences in these diseases. We examine human genomic and transcriptomics studies in each neurodegenerative disease through the lens of sex differences in the neuroimmune system and highlight the importance of stratifying sex in clinical and translational research studies. Finally, we discuss the limitations of the existing studies and outline recommendations for further advancing sex-based analyses to uncover novel disease mechanisms that could ultimately help treat both sexes.

Lifestyle Factors and Parkinson Disease Risk: Korean Nationwide Cohort Study With Repeated Health Screening Data

OBJECTIVE

Many previous studies, mostly performed in Western countries, on the effects of lifestyle factors on Parkinson's disease, used baseline lifestyle characteristics without directly accounting for changes in covariate values over time. The objective of this study was to evaluate the association of repeatedly measured lifestyle factors with Parkinson's disease risk in Korean population.

METHODS

We conducted a nationwide population-based cohort study. Among 512,836 Koreans in the national health checkup database, we selected individuals who underwent health screening ≥ 3 times between 2002 and 2015 and followed up until December 31, 2015. Parkinson's disease was defined using the International Classification of Diseases, Tenth Revision code G20 (with ≥ 3 times clinic visits for PD, to increase the diagnostic validity). Data on lifestyle factors such as smoking, alcohol consumption, and physical activity were collected using self-reported questionnaires. Logistic regression analysis with time-dependent covariates using generalized estimation equation models was performed to determine Parkinson's disease development.

RESULTS

During the 14-year follow-up, 2,655 patients developed Parkinson's disease. Smoking showed a dose-response inverse association with Parkinson's disease only in males (ex-smoker, Odds ratio [OR] =0.782, 95% confidence interval [CI] 0.713-0.858; current smoker, OR = 0.556, 95% CI 0.488-0.632). Alcohol consumption and regular physical activity were related to reduced Parkinson's disease development in both sexes; however, alcohol consumption in males (≤ 3 per week, OR=0.717, 95% CI 0.658-0.780; ≥ 4 per week, OR = 0.745, 95% CI 0.644-0.861) and physical activity in females (moderate, OR=0.792, 95% CI 0.748-0.840; vigorous, OR = 0.830, 95% CI 0.756-0.911) had more consistent associations with Parkinson's disease development compared to those of either sex. Participants with regular health screening showed a consistent relationship between lifestyle factors and Parkinson's disease development, whereas lifestyle factors in those without regular health screening had a decreased relationship with PD, even smoking habit.

CONCLUSIONS

Analysis using repeatedly measured lifestyle factors showed an association between lifestyle factors and Parkinson's disease development. Characteristics of lifestyle data including repeated measurements, timing, or regularity might influence results, and future studies with appropriate lifestyle factors could increase Parkinson's disease risk prediction.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that smoking, alcohol use, and physical activity are associated with reduced risk of Parkinson's disease in a Korean population.

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.

Childbirth and Delayed Parkinson's Onset: A Reproducible Nonbiological Artifact of Societal Change

BACKGROUND

Uncontrolled studies have reported associations between later Parkinson's disease onset in women and a history of giving birth, with age at onset delayed by nearly 3 years per child. We tested this association in two independent data sets, but, as a control to test for nonbiological explanations, also included men with PD.

METHODS

We analyzed valid cases from the Parkinson's Progressive Markers Initiative incident sample (145 women, 276 men) and a prevalent sample surveyed by the New Zealand Brain Research Institute (210 women, 394 men).

RESULTS

The association was present in both women and men in the Parkinson's Progressive Markers Initiative study, and absent in both in the New Zealand Brain Research Institute study. This is consistent with generational differences common to men and women, which confound with age at onset in incident-dominant samples.

CONCLUSIONS

Despite being replicable in certain circumstances, associations between childbirth and later PD onset are an artifact of generational cohort differences. © 2020 International Parkinson and Movement Disorder Society.

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.

Gender Differences in Neurodegeneration, Neuroinflammation and Na+-Ca2+ Exchangers in the Female A53T Transgenic Mouse Model of Parkinson's Disease

Twelve-month-old male mice expressing the human A53T variant of α-synuclein (A53T) develop dopamine neuron degeneration, neuroinflammation, and motor deficits, along with dysfunctions of the mitochondrial Na⁺-Ca²⁺ exchanger (NCX) isoforms 1 (NCX1) and 3 (NCX3) in the nigrostriatal system. Since gender is thought to play a role in the etiology of Parkinson's disease (PD), we characterized neurochemical and behavioral alterations in 12-month-old female A53T transgenic mice. We investigated the presence of dopaminergic degeneration, astrogliosis and microgliosis using immunohistochemistry for tyrosine hydroxylase (TH), glial fibrillary acidic protein (GFAP) and ionized calcium-binding adaptor molecule-1 (IBA-1) in both the substantia nigra pars compacta (SNc) and striatum. In the same regions, we also evaluated the co-localization of NCX1 in cells positive for IBA-1 and the co-localization of NCX3 in TH-positive neurons and fibers. Furthermore, in both male and female mice, we performed motor (beam walking and pole tests) and memory [novel object recognition (NOR) and spontaneous alternation] tasks, together with tests to evaluate peripheral deficits (olfactory and stool collection tests). Female A53T transgenic mice displayed degeneration of nigral dopaminergic neurons, but neither microgliosis nor astrogliosis in the SNc and striatum. Moreover, female A53T transgenic mice displayed co-localization between NCX1 and IBA-1 positive cells in the striatum but not SNc, whereas NCX3 did not co-localize with either TH-positive terminals or neuronal bodies in the nigrostriatal system. Furthermore, female A53T transgenic mice showed increased crossing time in the beam walking test, but no impairments in the pole or memory tests, and in tests that evaluated peripheral deficits, whereas male A53T transgenic mice displayed motor, memory and peripheral deficits. Immunohistochemical and behavioral results obtained here in the female mice differ from those previously observed in males, and suggest a dissimilar influence of NCX1 and NCX3 on dopaminergic function in female and male A53T transgenic mice, strengthening the validity of these mice as a model for studying the etiological factors of 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.

Modifiable risk and protective factors in disease development, progression and clinical subtypes of Parkinson's disease: What do prospective studies suggest?

Parkinson's disease (PD) is a neurodegenerative disorder whose pathogenesis depends on a combination of genetic and environmental factors. The aim of the present review was to provide an updated description of the findings emerging from prospective longitudinal cohort studies on the possible risk/protective factors underlying the development, progression and clinical subtypes of PD. We reviewed all the environmental, lifestyle, dietary, comorbid and pharmacological factors that have been investigated as possible modifiable protective/risk factors for PD by longitudinal studies. Only a few factors have the epidemiological evidence and the biological plausibility to be considered risk (pesticides, dairy products, β2-adrenoreceptor antagonists) or protective (smoking, caffeine and tea intake, physical activity, gout, vitamin E intake, non-steroidal anti-inflammatory drugs and β2-adrenoreceptor agonists) factors for PD. Caffeine intake and physical activity also seem to slow down the progression of the disease, thus representing good candidates for primary prevention and disease modifying strategies in PD. Possible modifiable risk factors of PD subtypes is almost unknown and this might depend on the uncertain biological and neuropathological reliability of clinical subtypes. The results of the present review suggest that only eleven risk/protective factors may be associated with the risk of PD. It may be possible to target some of these factors for preventive interventions aimed at reducing the risk of developing and the rate of progression of PD.

Cognitive characteristics in Chinese non-demented PD patients based on gender difference

Background

Cognitive impairment is one of the non-motor symptoms in Parkinson’s disease (PD). In the present study, we aim to examine the cognitive function of non-demented Parkinson’s disease patients and compare the results between male and female patients as well as control groups in search of any gender effect.

Methods

Sixty PD Patients (30 males and 30 females) from the Movement Disorders Clinic at Huashan Hospital Affiliated to Fudan University were recruited to participate in the study. One hundred age and gender matched control subjects without neurological or psychiatric disorders were voluntarily recruited. The participants were administered measures of cognition in five domains including memory, language, spatial processing abilities, attention and executive function.

Results

PD patients attained significantly lower scores in the visual spatial function, language and attention/executive function compared with the control group. Anti-parkinsonian treated patients performed worse in Rey-copy score, Clock Drawing Test (CDT) and Verbal Fluency-City than untreated ones. In regard to gender differences, though no general cognitive differences were found in Mini-mental State Examination (MMSE), men surpassed women on Boston naming test (BNT) while women were superior on Auditory Verbal Learning Test-long (AVLT) delayed cued recall test.

Conclusions

Cognitive impairments were common in PD patients even in the absence of dementia. PD patients with anti-parkinsonian medication had worse cognitive impairment than untreated patients. Genders may have different manifestations of cognitive impairment in PD patients.

Differences in Parkinson's Disease Risk with Caffeine Intake and Postmenopausal Hormone Use

BACKGROUND

Caffeine intake has been associated with a lower risk of Parkinson's disease (PD). This association is robust in men, but inconsistent in women due to a possible interaction with post-menopausal hormone (PMH) use.

OBJECTIVE

To (1) evaluate the association between caffeine intake and PD risk and (2) assess potential effect modification of the association by PMH use among women.

METHODS

We examined associations between caffeine intake and incident PD risk in the Nurses' Health Study (NHS) (N = 121,701 women) and the Health Professionals Follow-up Study (HPFS) (N = 51,529 men). Dietary data on coffee and caffeine from other sources were collected every four years using a validated semi-quantitative food frequency questionnaire for both cohorts. Information on lifestyle and incident PD diagnosis was updated biennially and PD diagnoses were confirmed by medical record review. We estimated hazard ratios (HR) and 95% confidence intervals (CI) using Cox proportional hazards models.

RESULTS

We documented a total of 1,219 PD cases over the follow-up period. The multivariable-adjusted HR comparing the highest to lowest quintile of caffeine intake was 0.50 (95% CI: 0.37, 0.68; Ptrend<0.0001) in the HPFS. Among women, there was a suggestion of an interaction between coffee intake and PMH use (P = 0.08). In the pooled analyses combining men and women who have never used PMH, the risk of PD was lower as coffee intake increased (Ptrend<0.001).

CONCLUSIONS

Our results support previous findings that increased caffeine intake may be associated with a decreased PD risk in men and women who have never used PMH.

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.

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.

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.

The epidemiology of Parkinson's disease: risk factors and prevention

Since 2006, several longitudinal studies have assessed environmental or behavioural factors that seem to modify the risk of developing Parkinson's disease. Increased risk of Parkinson's disease has been associated with exposure to pesticides, consumption of dairy products, history of melanoma, and traumatic brain injury, whereas a reduced risk has been reported in association with smoking, caffeine consumption, higher serum urate concentrations, physical activity, and use of ibuprofen and other common medications. Randomised trials are investigating the possibility that some of the negative risk factors might be neuroprotective and thus beneficial in individuals with early Parkinson's disease, particularly with respect to smoking (nicotine), caffeine, and urate. In the future, it might be possible to identify Parkinson's disease in its prodromal phase and to promote neuroprotective interventions before the onset of motor symptoms. At this time, however, the only intervention that seems justifiable for the primary prevention of Parkinson's disease is the promotion of physical activity, which is likely to be beneficial for the prevention of several chronic diseases.

Associations between cancer and Parkinson's disease in U.S. elderly adults

BACKGROUND

Several studies suggest that cancer is reduced before and after a Parkinson's disease (PD) diagnosis. However, determining relationships among diseases of ageing is challenging due to possible biases in ascertaining disease. This study evaluates the PD and cancer relationship, addressing potential biases.

METHODS

Using Surveillance, Epidemiology, and End Results-Medicare linked data (1992-2005) of adults ≥ 65 years, we assessed PD risk after cancer comparing PD in 743 779 cancer patients with PD in a non-cancer group (n = 419 432) in prospective cohort analyses. We also conducted a case-control study of 836 947 cancer cases and 142 869 controls to assess cancer following PD. We applied Cox proportional hazards models to estimate hazards ratios (HRs) for PD after cancer and unconditional logistic regression to estimate odds ratios (ORs) for PD preceding cancer, controlling for physician visits and other factors. To explore biases in ascertaining cancer, we examined relationships between cancer and automobile accident injuries, which we expected to be null.

RESULTS

No association was observed between cancer and subsequent PD [HR = 0.97; 95% confidence interval (CI) = 0.92-1.01] nor between cancer and subsequent automobile injuries (HR = 1.03; 95% CI = 0.98-1.07). One site, lung cancer, was associated with subsequent reduced PD, which may reflect confounding by smoking. In the case-control analysis, PD was associated with reduced subsequent cancer, overall (OR = 0.77; 95% CI = 0.71-0.82) and for several cancer sites. However, the automobile injury/ subsequent cancer association was similar (OR = 0.83; 95% CI = 0.78-0.88), suggesting a cancer detection bias after serious health outcomes.

CONCLUSIONS

In totality, our data do not support a biological relationship between PD and cancer.

The Impact of Gonadal Hormones on the Expression of Human Neurological Disorders

The effects of gonadal steroids on neurological well-being and disease constitute a rich and rapidly expanding area of basic and clinical neuroscience. Gonadal hormones exert potent effects on monoaminergic, cholinergic and peptidergic pathways as well as neurosteroidogenesis which, in turn, impact normal brain organization and function. A spectrum of human neurological conditions are influenced by hormonal fluctuations associated with the menstrual cycle, pregnancy, the menopause and use of oral contraceptives. An appreciation of these relationships may facilitate the development of specific hormonal and anti-hormonal therapies for neurological disorders as disparate as catamenial epilepsy and acute intermittent porphyria.

Neuroactive gonadal drugs for neuroprotection in male and female models of Parkinson's disease

The existence of sex differences in Parkinson's disease (PD) incidence is well documented with greater prevalence and earlier age at onset in men than in women. These reported sex differences could be related to estrogen exposure. In PD animal models, estrogen is well documented to be neuroprotective against dopaminergic neuron loss induced by neurotoxins. Using the 1-methyl 4-phenyl-1,2,3,6 tetrahydropyridine (MPTP) mouse model, we showed that several compounds are neuroprotective on dopaminergic neurons including estrogen, the selective estrogen receptor modulator raloxifene, progesterone, dehydroepiandrosterone, the estrogen receptor alpha (ERα) agonist PPT as well as the G protein-coupled membrane estrogen receptor (GPER1) specific agonist G1. Accumulating evidence suggests that GPER1 could be implicated in the neuroprotective effects of estrogen, raloxifene and G1 in collaboration with ERα. We recently reported that the 5α-reductase inhibitor Dutasteride is also neuroprotective and could bring an alternative to estrogens for therapy in male. Additional studies are needed to optimize therapies with these gonadal drugs into safe personalized treatments according to sex for treatment of PD.

Hormone replacement therapy and Parkinson's disease risk in women: a meta-analysis of 14 observational studies

BACKGROUND AND PURPOSE

Published data on the relationship of hormone replacement therapy (HRT) with Parkinson's disease (PD) were inconclusive. Thus, a systematic meta-analysis of observational studies was performed to clarify this topic.

METHODS

The databases of PubMed and EMBASE were searched for case-control or cohort studies published up till June 2, 2014. Meta-analysis of the relative risks (RRs) with 95% confidence intervals (CIs) was estimated using random-effects models.

RESULTS

A final total of ten case-control and four cohort studies were included in our meta-analysis. The overall combined RR of PD for ever users versus never users of HRT was 1.00 (95% CI: 0.84-1.20). Limited to those subjects who only use estrogen, a similar trend was detected (RR: 0.95, 95% CI: 0.69-1.30). In the subgroup analysis by study design, no significant association was observed in case-control studies (RR: 0.79, 95% CI: 0.62-1.02), whereas a positive association was found in cohort studies (RR: 1.24, 95% CI: 1.10-1.40). In further analysis according to study quality, an inverse association was found in the low-quality group (RR: 0.58, 95% CI: 0.40-0.82), whereas a positive association was found in the high-quality group (RR: 1.16, 95% CI: 1.02-1.31).

CONCLUSION

In summary, our results of meta-analysis do not support a protective role of HRT in female PD development.

Formulations of hormone therapy and risk of Parkinson's disease

Hormone therapy (HT) is a class of medications widely prescribed to women in the Western world. Evidence from animal models and in vitro studies suggests that estrogen may protect against nigrostriatal system injury and increase dopamine synthesis, metabolism, and transport. Existing epidemiologic research indicates a possible reduced risk of Parkinson's disease (PD) associated with HT use. The objective of this study was to evaluate PD risk associated with specific HT formulations. Neurologist-confirmed cases and age-matched controls were identified from Group Health Cooperative (GHC) of Washington State. Final analysis included 137 female cases and 227 controls. Hormone therapy use was ascertained from the GHC pharmacy database, further classified as conjugated estrogens, esterified estrogens, and progestin. Ever use of HT formulation demonstrated a suggested elevated risk with esterified estrogen use (odds ratio [OR], 3.1; 95% confidence interval [CI], 1.0-9.8), and no risk associated with conjugated estrogen use (OR, 0.6; 95% CI, 0.6-1.3). Restricting this analysis to prescriptions that included progestin further elevated the risk associated with esterified estrogen use (OR, 6.9; 95% CI, 2.1-22.9); again, no risk was associated with conjugated estrogen use (OR, 1.7; 95% CI, 0.6-5.0). The findings from this study suggest an increase in PD risk associated with esterified estrogen use combined with progestin, and no risk associated with conjugated estrogen with progestin. These findings could have important implications for choice of HT in clinical practice.

Reproductive life characteristics in females affected with Parkinson's disease and in healthy control subjects - a comparative study on Polish population

BACKGROUND

Sex and blood level of sex hormones play a key role not only in the susceptibility to develop Parkinson's disease (PD) but also influence the natural course of the disease. The aim of this study was to compare reproductive lifespan events in females affected with PD and in "non-parkinsonian" age matched subjects and to evaluate whether the whole life endogenous oestrogen level is associated with variables describing the course of the disease.

MATERIALS AND METHODS

Reproductive lifespan, age at menarche, age at menopause, gynaecological interventions and parity were compared in 76 women with idiopathic PD and in the age-adjusted control group of 74 subjects. Affected women underwent neurological and psychological assessment. Data were analysed using Mann-Whitney U Test and Spearman Rank Correlation Test.

RESULTS

Women affected with PD had a shorter reproductive lifespan and experienced final menstruation earlier than the control group. Early menopause was reported by 24% of the patients and only by 16% of the control subjects. Parkinsonian women reported more commonly the history of surgical menopause. Duration of reproductive lifespan, age at menopause and the type of menopause influenced both motor and cognitive functioning of patients.

CONCLUSIONS

There may be a relationship between the lifetime average endogenous oestrogen level and the susceptibility to develop PD. Longer reproductive lifespan resulting in higher "whole life" female sex steroids concentrations may exert a protective effect on central nervous system, resulting in milder course of the disease.

Lifetime exposure to estrogens and Parkinson's disease in California teachers

INTRODUCTION

Parkinson's disease (PD) is consistently observed to occur less frequently in women than men, prompting investigation into whether estrogen protects against neurodegeneration of dopaminergic neurons.

METHODS

We used baseline data in the California Teachers Study, a prospective cohort of women, to investigate whether reproductive factors indicating higher long-term estrogen levels are associated with PD using a nested case-control approach. We identified 228 PD cases and 3349 unaffected controls frequency matched by age and race.

RESULTS

Women who reported using combined estrogen/progesterone therapy or progesterone only formulations had a 57% increase in PD risk (OR = 1.57, 95% CI = 1.06, 2.34) compared to never having used HT. Compared to women with menopause at 50-52 years, menopause at younger (<35-46 years: OR = 0.59, 95% CI = 0.37, 0.94) and older ages (≥53 years: OR = 0.54, 95% CI = 0.36, 0.83) had lower PD risk. A derived composite estrogen summary score for women's exposure to both endogenous and exogenous estrogens throughout life indicated that women with presumed higher cumulative lifetime levels of estrogen (a score of 3-5) had a significantly reduced PD risk [(OR = 0.57, 95% CI = 0.35, 0.91) relative to those with lower lifetime estrogen exposure or a composite estrogen summary score of 0-1].

CONCLUSIONS

These results provide some support for the hypothesis that lifelong high estrogen is protective in PD, suggesting that the level and persistence of exposure over the long term may be important in PD risk reduction.

Reproductive factors and Parkinson's disease risk in Danish women

BACKGROUND AND PURPOSE

Parkinson's disease is more common in men than women by a ratio of about 1.5:1 and yet there is no consensus to date as to whether female reproductive factors including hormone use affect Parkinson's disease risk. Our objective was to examine the relationship between Parkinson's disease and female reproductive factors in the largest population-based Parkinson's disease case-control study to date.

METHODS

Seven hundred and forty-three female Parkinson's disease cases diagnosed between 1996 and 2009 were selected from the Danish National Hospital Register, diagnoses confirmed by medical record review, and the cases were matched by birth year to 765 female controls randomly selected from the Danish Civil Registration System. Covariate information was collected in computer-assisted telephone interviews covering an extensive array of topics including reproductive and lifestyle factors.

RESULTS

After adjusting for smoking, caffeine and alcohol use, education, age, and family Parkinson's disease history, inverse associations between Parkinson's disease and early menarche (first period at ≤11 years), oral contraceptives, high parity (≥4 children) and bilateral oophorectomy were found; adjusted odds ratios and 95% confidence limits were respectively 0.68 (0.45-1.03) for early menarche, 0.87 (0.69-1.10) for oral contraceptives, 0.79 (0.59-1.06) for high parity and 0.65 (0.45-0.94) for bilateral oophorectomy. Little support for associations between Parkinson's disease and fertile life length, age at menopause or post-menopausal hormone treatment was found.

CONCLUSIONS

Reproductive factors related to women's early- to mid-reproductive lives appear to be predictive of subsequent Parkinson's disease risk whereas factors occurring later in life seem less important.

Sex differences in Parkinson's disease and other movement disorders

Movement disorders including Parkinson's disease (PD), Huntington's disease (HD), chorea, tics, and Tourette's syndrome (TS) display sex differences in disease susceptibility, disease pathogenesis, and clinical presentation. PD is more common in males than in females. Epidemiologic studies suggest that exposure to endogenous and exogenous estrogen contributes to these sex differences. There is extensive evidence that estrogen prevents dopaminergic neuron depletion induced by neurotoxins in PD animal models and therefore is neuroprotective. Estrogen may also decrease the efficacy of other neuroprotective substances such as caffeine in females but not males. Sex chromosomes can exert effects independent of sex steroid hormones on the development and maintenance of the dopamine system. As a result of hormone, chromosome and other unknown effects, there are sexual dimorphisms in the basal ganglia, and at the molecular levels in dopaminergic neurons that may lead to distinct mechanisms of pathogenesis in males and females. In this review, we summarize the evidence that estrogen and selective estrogen receptor modulators are neuroprotective in PD and discuss potential mechanisms of action. We also briefly review how sex differences in basal ganglia function and dopaminergic pathways may impact HD, chorea, and tics/Tourette's syndrome. Further understanding of these sex differences may lead to novel therapeutic strategies for prevention and treatment of these diseases.