Inverse associations of outdoor activity and vitamin D intake with the risk of Parkinson's disease

Physical activity and risk of Parkinson's disease: an updated systematic review and meta-analysis

BACKGROUND AND OBJECTIVES

Although recent meta-analyses have shown that the association between physical activity (PA) and the risk of developing Parkinson's disease (PD) is influenced by gender differences, a growing number of studies are revealing the general applicability of this association across genders. This study aimed to reassess the association and dose-response relationship between PA and PD risk in populations.

METHODS

A systematic search of PubMed, Embase, Cochrane Library, and Web of Science databases was conducted in this study from inception to February 1, 2024, without language restrictions. Stratified analyses were conducted to explore the association between PA and PD risk, combining multivariate-adjusted effect estimates via random-effects models, and to validate the dose-response relationship between the two.

RESULTS

This study included 21 observational studies, comprising 13 cohort studies and 8 case-control studies. The pooled analysis revealed that PA significantly reduced the risk of developing PD [relative risk (RR) = 0.77, 95% CI 0.70-0.85]. In addition, the dose-response analysis revealed both linear and nonlinear associations, with linear results indicating a 9% reduction in PD risk for every 10 MET-h/wk increase in PA. The study also demonstrated that the protective effect of PA against PD was significant for both sexes. Moreover, no statistically significant effects of PA on preventing PD were observed in individuals with a BMI > 26 (RR = 0.35, 95% CI 0.12-1.02) or in Asian populations (RR = 0.78, 95% CI 0.60-1.01); however, the trends suggest potential protective effects, warranting further investigation. Sensitivity analyses confirmed the robustness of these findings.

CONCLUSION

This meta-analysis produced substantial evidence to reaffirm the protective effect of high PA on PD across various population groups and the inverse dose-response relationship with PD risk, and to validate the protective effect of PA among different demographic groups.

Multilayer factors associated with excess all-cause mortality during the omicron and non-omicron waves of the COVID-19 pandemic: time series analysis in 29 countries

BACKGROUND

The COVID-19 pandemic has resulted in significant excess mortality globally. However, the differences in excess mortality between the Omicron and non-Omicron waves, as well as the contribution of local epidemiological characteristics, population immunity, and social factors to excess mortality, remain poorly understood. This study aims to solve the above problems.

METHODS

Weekly all-cause death data and covariates from 29 countries for the period 2015-2022 were collected and used. The Bayesian Structured Time Series Model predicted expected weekly deaths, stratified by gender and age groups for the period 2020-2022. The quantile-based g-computation approach accounted for the effects of factors on the excess all-cause mortality rate. Sensitivity analyses were conducted using alternative Omicron proportion thresholds.

RESULTS

From the first week of 2021 to the 30th week of 2022, the estimated cumulative number of excess deaths due to COVID-19 globally was nearly 1.39 million. The estimated weekly excess all-cause mortality rate in the 29 countries was approximately 2.17 per 100,000 (95% CI: 1.47 to 2.86). Weekly all-cause excess mortality rates were significantly higher in both male and female groups and all age groups during the non-Omicron wave, except for those younger than 15 years (P < 0.001). Sensitivity analysis confirmed the stability of the results. Positive associations with all-cause excess mortality were found for the constituent ratio of non-Omicron in all variants, new cases per million, positive rate, cardiovascular death rate, people fully vaccinated per hundred, extreme poverty, hospital patients per million humans, people vaccinated per hundred, and stringency index. Conversely, other factors demonstrated negative associations with all-cause excess mortality from the first week of 2021 to the 30th week of 2022.

CONCLUSION

Our findings indicate that the COVID-19 Omicron wave was associated with lower excess mortality compared to the non-Omicron wave. This study's analysis of the factors influencing excess deaths suggests that effective strategies to mitigate all-cause mortality include improving economic conditions, promoting widespread vaccination, and enhancing overall population health. Implementing these measures could significantly reduce the burden of COVID-19, facilitate coexistence with the virus, and potentially contribute to its elimination.

Association of time spent outdoors with the risk of Parkinson's disease: a prospective cohort study of 329,359 participants

BACKGROUND

Studies on the association between time spent outdoors and the development of Parkinson's disease (PD) are lacking, and whether this relationship differs in different subgroups (age, sex) remains unclear.

OBJECTIVE

We here examined the association between time spent outdoors and the incidence of PD in different seasons.

METHODS

This study included 329,359 participants from the UK Biobank. Data regarding hours spent outdoors during a typical day were obtained through questionnaires. Cox proportional hazard regression models were used to estimate hazard ratios (HRs) for the association between exposure to outdoors duration and PD incidence. Restricted cubic spline was used to explore the potential nonlinear relationship between time spent outdoors and PD risk. To explore the potential mechanisms of time spent outdoors effecting the risk of PD incidence, their association with serum vitamin D was further analysed separately.

RESULTS

During a median follow-up of 13.57 years, 2,238 participants developed PD. In summer, time spent outdoors > 5.0 h/day was associated with a reduced PD risk compared with ≤ 2.0 h/day (HR = 0.84, 95% CI, 0.74-0.95). In winter too, time spent outdoors > 2.0 h/day was also associated with a reduced PD risk compared with ≤ 1.0 h/day (HR = 0.85, 95% CI, 0.76-0.94). For annual average time spent outdoors, participants who went outdoors for more than 3.5 h/day had a reduced PD risk than those who went outdoors for ≤ 1.5 h/day (HR = 0.85, 95% CI, 0.75-0.96). Additionally, sex and age differences were observed in the association between time spent outdoors and the PD risk. Moreover, Time spent outdoors was observed to be positively associated with serum vitamin D levels. Compared with serum vitamin D-deficient participants, the risk of PD was reduced by 15% in the sufficient participants.

CONCLUSION

In the total population, higher time spent outdoors was linked to a reduced PD risk. However, this association may vary among different age or sex groups.

No Vitamin D Deficiency in Patients with Parkinson’s Disease

Previous trials describe a decrease of vitamin D levels in patients with Parkinson’s disease and relationships to clinical disease severity. This case control study found higher but not significant 25-OH-vitamin D plasma levels in patients with Parkinson’s disease compared with age- and sex-matched controls and no associations to clinical parameters, such as rating scores of disease severity or assessments of cognitive function. A certain variability of vitamin D concentrations was observed in both cohorts, which were investigated during the same season. These outcomes put into perspective the emerging discussion on the importance of vitamin D in Parkinson’s disease. Our results warrant further confirmatory research with a strict matching design of patients and controls, which has not been done in previous investigations. We stress that this case control study does not allow any comment on the putative beneficial effects of vitamin D supplementation, ie, on bone mass or bone mineral density, in patients with Parkinson’s disease.

Genetic Variability of the Vitamin D Receptor Affects Susceptibility to Parkinson’s Disease and Dopaminergic Treatment Adverse Events

Vitamin D is a lipid-soluble molecule and an important transcriptional regulator in many tissues and organs, including the brain. Its role has been demonstrated also in Parkinson’s disease (PD) pathogenesis. Vitamin D receptor (VDR) is responsible for the initiation of vitamin D signaling cascade. The aim of this study was to assess the associations of VDR genetic variability with PD risk and different PD-related phenotypes. We genotyped 231 well characterized PD patients and 161 healthy blood donors for six VDR single nucleotide polymorphisms, namely rs739837, rs4516035, rs11568820, rs731236, rs2228570, and rs1544410. We observed that VDR rs2228570 is associated with PD risk (p < 0.001). Additionally, we observed associations of specific VDR genotypes with adverse events of dopaminergic treatment. VDR rs1544410 (GG vs. GA + AA: p = 0.005; GG vs. GA: p = 0.009) was associated with the occurrence of visual hallucinations and VDR rs739837 (TT vs. GG: p = 0.036), rs731236 (TT vs. TC + CC: p = 0.011; TT vs. TC: p = 0.028; TT vs. CC: p = 0.035), and rs1544410 (GG vs. GA: p = 0.014) with the occurrence of orthostatic hypotension. We believe that the reported study may support personalized approach to PD treatment, especially in terms of monitoring vitamin D level and vitamin D supplementation in patients with high risk VDR genotypes.

Vitamin D and Parkinson's Disease

Vitamin D is a fat-soluble secosteroid, traditionally considered a key regulator of bone metabolism, calcium and phosphorous homeostasis. Its action is made possible through the binding to the vitamin D receptor (VDR), after which it directly and indirectly modulates the expression of thousands of genes. Vitamin D is important for brain development, mature brain activity and associated with many neurological diseases, including Parkinson’s disease (PD). High frequency of vitamin D deficiency in patients with Parkinson’s disease compared to control population was noted nearly twenty years ago. This finding is of interest given vitamin D’s neuroprotective effect, exerted by the action of neurotrophic factors, regulation of nerve growth or through protection against cytotoxicity. Vitamin D deficiency seems to be related to disease severity and disease progression, evaluated by Unified Parkinson’s Disease Rating Scale (UPDRS) and Hoehn and Yahr (H&Y) scale, but not with age of PD onset and duration of disease. Additionally, fall risk has been associated with lower vitamin D levels in PD. However, while the association between vitamin D and motor-symptoms seems to be possible, results of studies investigating the association with non-motor symptoms are conflicting. In addition, very little evidence exists regarding the possibility to use vitamin D supplementation to reduce clinical manifestations and disability in patients with PD. However, considering the positive balance between potential benefits against its limited risks, vitamin D supplementation for PD patients will probably be considered in the near future, if further confirmed in clinical studies.

Assessing the Effects of Vitamin D on Neural Network Function in Patients With Parkinson's Disease by Measuring the Fraction Amplitude of Low-Frequency Fluctuation

Background: Recently, many studies have shown that low vitamin D (VD) levels may be related to an increased risk of Parkinson's disease (PD), but the underlying mechanisms remain unclear. Objective: To explore the relationship between PD and VD levels, as well as to analyze the effects of VD on spontaneous brain activity and explore the possible mechanism of its involvement in PD risk. Methods: In a cross-sectional study, we quantified the difference in VD levels between 330 PD patients and 209 healthy controls (HC) to explore the correlation between VD and PD risk. We also acquired resting-state Functional Magnetic Resonance Imaging (rs-fMRI) data from 46 PD patients and 21 HC. The PD patients were divided into three groups according to 25(OH)D levels: PD patients with VD deficiency (PD + VDD), PD patients with VD insufficiency (PD + VDI), and PD patients with normal VD (PD + NVD). The effect of VD status on spontaneous neuronal activity in the whole brain was analyzed by measuring the fraction amplitude of low-frequency fluctuation (fALFF). Results: Compared with HC, the PD patients had lower serum 25(OH)D levels (23.60 ± 7.27 vs. 25.60 ± 5.78, P < 0.001). The 25(OH)D level may have a potential dose-dependent effect on the risk of PD (P _trend = 0.007). A high risk of PD was associated with VD deficiency [25(OH)D < 20 ng/mL, OR = 2.319], and the lowest quartile of 25(OH)D concentration was associated with a high risk of PD (OR = 1.941). In the rs-fMRI study, PD + VDD patients had wider brain regions with altered fALFF than other PD groups when compared with the corresponding HC groups. Both PD + VDD and PD + VDI showed higher fALFF in the cuneus, left precuneus, calcarine cortex and right lingual, as well as lower fALFF in the left middle temporal gyrus. PD + VDD patients also showed higher fALFF in the left superior, middle and inferior frontal gyri, as well as the left precentral gyrus than HC. Among PD patients, there was only a statistically significant difference in fALFF between the PD + VDD and PD + NVD groups. Compared with the PD + NVD group, PD + VDD patients exhibited higher fALFF in the left precentral and left postcentral gyrus, as well as the left inferior parietal lobule. Conclusion: These results demonstrate that PD patients had lower serum VD levels than HC, and VD may have a potential dose-dependent effect on PD risk. Lower serum VD levels can affect the spontaneous neuronal activity of default-mode network (DMN) and visual pathway neurons in PD patients, providing a possible mechanism for its effect on PD risk.

Circulatory 25(OH)D and 1,25(OH)2D as differential biomarkers between multiple system atrophy and Parkinson's disease patients

Background and purpose

There is sufficient evidence to support vitamin D's noncalcemic effects and the role of vitamin D deficiency in the development of a wide range of neurological disorders. This study aimed to evaluate whether serum 25(OH)D and 1,25(OH) 2 D could be used as biomarkers to differentiate between healthy subjects (HS), multiple system atrophy (MSA) and Parkinson's disease (PD) patients of both genders.

Methods

A total of 107 subjects were included in this study, divided into three groups: 1- HS (n = 61), 2- MSA patients (n = 19), and 3- PD patients (n = 27). The patients were assessed using UMSARS II, UPDRS III, H&Y, MMSE and MoCA rating scales. The levels of 25(OH)D and 1,25(OH) 2 D in serum were determined using the radioimmunoassay technique.

Results

The levels of 25(OH)D and 1,25(OH) 2 D in HS were 26.85 +/- 7.62 ng/mL and 53.63 +/- 13.66 pg/mL respectively. 25(OH)D levels were lower in both MSA and PD by 61% and 50%, respectively (P = 0.0001 vs. HS). 1,25(OH) 2 D levels were lower in MSA by 29%(P = 0.001 vs HS). There was a correlation between 25(OH)D and 1,25(OH) 2 D in MSA and PD, but not in HS. 1,25(OH) 2 D regressed with MMSE (β = 0.476, P = 0.04, R 2 = 0.226) in MSA, and with UPDRS III (β = -0.432, P = 0.024, R 2 = 0.187) and MoCA (β = 0.582, P = 0.005,R 2 = 0.279) in PD. 25(OH)D displayed considerable differentiative strength between HS and MSA (Wald = 17.123, OR = 0.586, P = 0.0001; AUC = 0.982, sensitivity and Youden index = 0.882, P = 0.0001) and PD (Wald = 18.552, OR = 0.700, P = 0.0001; AUC = 0.943, sensitivity = 0.889, YI = 0.791, P = 0.0001). 1,25(OH) 2 D distinguished MSA from PD (Wald 16.178, OR = 1.117, P = 0.0001; AUC = 0.868, sensitivity = 0.926, Youden index =0.632, P = 0.0001). H&Y exhibited the highest sensitivity, AUC, and significant distinguishing power between MSA and PD.

Conclusions

Serum 25(OH)D and 1,25(OH) 2 D could be useful biomarkers for MSA and PD. 25(OH)D and H&Y provided the highest sensitivity and group classification characteristics.

The VDR FokI (rs2228570) polymorphism is involved in Parkinson's disease

The etiology of Parkinson's disease (PD) is presumably multifactorial and likely involves interactions between genetic and environmental factors, as well as mitochondrial dysfunction, oxidative stress and inflammation. Among environmental factors, Vitamin D was reported to associate with the risk of PD. Vitamin D activity is mediated by its binding to the vitamin D Receptor (VDR), a transcriptional factor for almost 3% of human genes. We genotyped for ApaI, BsmI, TaqI, FokI and rs1989969 VDR single nucleotide polymorphisms (SNPs) a cohort of 406 PD and 800 healthy controls (HC) and found a strong association between the FokI (rs2228570) VDR SNP and PD. Thus, the TT genotype and the T allele resulted associated with PD in the overall analyzed PD population. Gender-based stratification of data indicated that results were maintained for FokI TT genotype and T allele in male PD patients, whereas the FokI T allele alone was confirmed as a risk factor for PD in females. Co-segregation analyses indicated the TaqI ApaI FokI rs1989969 GCTG as a "risk" haplotype for PD. In a subgroup of patients and controls neural Vitamin D and VDR concentration was analyzed in extravesicles (NDEVs) isolated from peripheral blood: no differences emerged between PD and HC. NDEVs results will need to be validated in ampler cohort but we can speculate that, if at neuronal level the amounts of Vitamin D and of VDR are comparable, than the bioavailability of vitamin D and the efficacy of the vitamin D/VDR axis is differentially modulated in PD by VDR SNPs.

Implications of Vitamin D in Multiple Sclerosis and Other Neurodegenerative Processes: Bibliometric Analysis and Systematic Review

In recent years, numerous investigations focused on the pleiotropic actions of vitamin D have been carried out. These actions include the participation of this molecule in neurophysiological and neuropathological processes. As a consequence, abundant scientific literature on the role of this vitamin in neurodegenerative entities has emerged, even concerning clinical studies. To identify the level of scientific evidence concerning the relation between vitamin D and neurodegenerative diseases, from a quantitative and qualitative perspective. To describe, by means of a bibliometric analysis, the scientific production and its evolution through time in quantitative terms, regarding the implications of vitamin D in neurodegeneration. To analyse and present the degree of evidence in the aforementioned field of study, a systematic review of the literature focused on the most prevalent neurodegenerative diseases was carried out. We retrieved 848 articles in the bibliometric analysis, the majority of which were dated between the years 2010-2017. The most studied metabolite was the 25(OH)D3 and the most cited disease was multiple sclerosis. In the systematic review, we found studies about Alzheimer's and Parkinson's diseases and again, about multiple sclerosis prominently (in number and quality), with 12 randomised double-blind clinical trials. The research about vitamin D and its relations with neurodegenerative diseases shows a growing evolution over the last decade. More studies are needed to find correlations between the clinical severity of these diseases and the specific status of vitamin D and the genotypes related with them, which seems to be a future trend.

The relationships of vitamin D, vitamin D receptor gene polymorphisms, and vitamin D supplementation with Parkinson's disease

In recent years, many studies have investigated the correlations between Parkinson's disease (PD) and vitamin D status, but the conclusion remains elusive. The present review focuses on the associations between PD and serum vitamin D levels by reviewing studies on the associations of PD with serum vitamin D levels and vitamin D receptor (VDR) gene polymorphisms from PubMed, Web of Science, Cochrane Library, and Embase databases. We found that PD patients have lower vitamin D levels than healthy controls and that the vitamin D concentrations are negatively correlated with PD risk and severity. Furthermore, higher vitamin D concentrations are linked to better cognitive function and mood in PD patients. Findings on the relationship between VDR gene polymorphisms and the risk of PD are inconsistent, but the FokI (C/T) polymorphism is significantly linked with PD. The occurrence of FokI (C/T) gene polymorphism may influence the risk, severity, and cognitive ability of PD patients, while also possibly influencing the effect of Vitamin D3 supplementation in PD patients. In view of the neuroprotective effects of vitamin D and the close association between vitamin D and dopaminergic neurotransmission, interventional prospective studies on vitamin D supplementation in PD patients should be conducted in the future.

A Review of the Relationship Between Vitamin D and Parkinson Disease Symptoms

Vitamin D is a fat-soluble secosteroid that exerts its effects by binding to the vitamin D receptor (VDR), through which it directly and indirectly modulates the expression of hundreds to thousands of genes. While originally known for its role in regulating calcium homeostasis and metabolism, vitamin D is now associated with many other health conditions, including Parkinson's disease (PD). A high prevalence of vitamin D deficiency has been noted in PD for at least the past two decades. These findings, along with the discovery that the VDR and 1α-hydroxylase, the enzyme that converts vitamin D to its active form, are highly expressed in the substantia nigra, led to the hypothesis that inadequate levels of circulating vitamin D may lead to dysfunction or cell death within the substantia nigra. Studies investigating the relationship between vitamin D status and PD, however, have been inconsistent. Two prospective studies examined the association between mid-life vitamin D levels and risk of PD and produced conflicting results-one demonstrated an increased risk for PD with lower mid-life vitamin D levels, and the other showed no association between vitamin D and PD risk. One of the most consistent findings in the literature is the inverse association between serum vitamin D level and motor symptom severity in cross-sectional studies. While these data suggest that vitamin D may modify the disease, another likely explanation is confounding due to limited mobility. Fall risk has been associated with vitamin D in PD, but more study is needed to determine if supplementation decreases falls, which has been demonstrated in the general population. The association between vitamin D and non-motor symptoms is less clear. There is some evidence that vitamin D is associated with verbal fluency and verbal memory in PD. Studies in PD have also shown associations between vitamin D status and mood, orthostatic hypotension and olfactory impairment in PD. While more research is needed, given the numerous potential benefits and limited risks, vitamin D level assessment in PD patients and supplementation for those with deficiency and insufficiency seems justified.

Interhemispheric functional connectivity for Alzheimer's disease and amnestic mild cognitive impairment based on the triple network model

The purpose of this study was to explore the differences in interhemispheric functional connectivity in patients with Alzheimer's disease (AD) and amnestic mild cognitive impairment (aMCI) based on a triple network model consisting of the default mode network (DMN), salience network (SN), and executive control network (ECN). The technique of voxel-mirrored homotopic connectivity (VMHC) analysis was applied to explore the aberrant connectivity of all patients. The results showed that: (1) the statistically significant connections of interhemispheric brain regions included DMN-related brain regions (i.e. precuneus, calcarine, fusiform, cuneus, lingual gyrus, temporal inferior gyrus, and hippocampus), SN-related brain regions (i.e. frontoinsular cortex), and ECN-related brain regions (i.e. frontal middle gyrus and frontal inferior); (2) the precuneus and frontal middle gyrus in the AD group exhibited lower VMHC values than those in the aMCI and healthy control (HC) groups, but no significant difference was observed between the aMCI and HC groups; and (3) significant correlations were found between peak VMHC results from the precuneus and Mini Mental State Examination (MMSE) and Montreal Cognitive Scale (MOCA) scores and their factor scores in the AD, aMCI, and AD plus aMCI groups, and between the results from the frontal middle gyrus and MOCA factor scores in the aMCI group. These findings indicated that impaired interhemispheric functional connectivity was observed in AD and could be a sensitive neuroimaging biomarker for AD. More specifically, the DMN was inhibited, while the SN and ECN were excited. VMHC results were correlated with MMSE and MOCA scores, highlighting that VMHC could be a sensitive neuroimaging biomarker for AD and the progression from aMCI to AD.

Benefits of Vitamins in the Treatment of Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative disease in the elderly, which is clinically characterized by bradykinesia, resting tremor, abnormal posture balance, and hypermyotonia. Currently, the pathogenic mechanism of PD remains unclear. Numerous clinical studies as well as animal and cell experiments have found a certain relationship between the vitamin family and PD. The antioxidant properties of vitamins and their biological functions of regulating gene expression may be beneficial for the treatment of PD. Current clinical evidence indicates that proper supplementation of various vitamins can reduce the incidence of PD in the general population and improve the clinical symptoms of patients with PD; nevertheless, the safety of regular vitamin supplements still needs to be highlighted. Vitamin supplementation may be an effective adjuvant treatment for PD. In this review, we summarized the biological correlations between vitamins and PD as well as the underlying pathophysiological mechanisms. Additionally, we elaborated the therapeutic potentials of vitamins for PD.

Are the protective benefits of vitamin D in neurodegenerative disease dependent on route of administration? A systematic review

Background: The clinical and preclinical exploration of the therapeutic properties of vitamin D have significantly increased in the past decade, owing to the growing associative evidence suggesting vitamin D is neuroprotective. However, whether depletion of vitamin D contributes to the onset of neurological disorders or is a symptom of neurological disease has yet to be defined. Much remains unclear about the causal role of vitamin D and the method of use and forms of vitamin D.Objectives: We sought to quantitatively assess if neuroprotective benefits from vitamin D in neurodegenerative diseases are dependent on route of administration: comparing the effect of endogenously sourced vitamin D from UV exposure to exogenously derived vitamin D through synthetic supplementation.Design: We systematically searched PubMed, Embase and PsycInfo databases which included both pre-clinical and clinical studies investigating vitamin D in neurodegenerative diseases. Articles were subject to strict inclusion criteria and objectively assessed for quality. Additionally, Medline data was analysed to identify trends in topic publications and linguistic characteristics of papers.Results: From a total of 231 screened articles, we identified 73 appropriate for review based on inclusion criteria: original studies that investigated vitamin D levels or levels of vitamin D supplementation in neurodegenerative diseases or investigated past/present sun exposure in disease cohorts. Results indicate there is insufficient evidence to comprehensively reflect on a potential neuroprotective role for vitamin D and if this was dependent on route of administration. The majority of current data supporting neuroprotective benefits from vitamin D are based on pre-clinical and observational studies. Solid evidence is lacking to support the current hypothesis that the beneficial effect of UV exposure results from the synthesis of vitamin D. Sun exposure, independent of vitamin D production, may be protective against multiple Sclerosis, Parkinson's disease and Alzheimer's disease. Yet, further research is required to elucidate the beneficial mechanism of actions of UV exposure. The literature of vitamin D and amyotrophic lateral sclerosis was limited, and no conclusions were drawn. Therefore, in cases where UV-derived vitamin D was hypothesized to be the beneficial mediator in the neuroprotective effects of sun exposure, we propose results are based only on associative evidence.Conclusion: On the basis of this systematic review, strong recommendations regarding therapeutic benefits of vitamin D in neurodegenerative disease cannot be made. It is unclear if vitamin D mediates a protective benefit in neurodegenerative disease or whether it is an associative marker of UV exposure, which may contribute to as of yet unidentified neuroprotective factors.

Vitamin D and Sunlight Exposure in Newly-Diagnosed Parkinson's Disease

Circulating vitamin D has previously been found to be lower in patients with Parkinson’s disease (PD), while the effects of sunlight exposure have not yet been fully investigated. Therefore, we evaluated the associations between serum vitamin D, vitamin D intake, sunlight exposure, and newly-diagnosed PD patients in a Chinese population. This case-control study measured serum 25-hydroxyvitamin D (25(OH)D) levels and sunlight exposure in 201 patients with newly-diagnosed PD and 199 controls without neurodegenerative diseases. Data on vitamin D intake and sunlight exposure were obtained using a self-report questionnaire. Multivariable logistic regressions were employed to evaluate the associations between serum 25(OH)D levels, sunlight exposure, and PD. Adjustments were made for sex, age, smoking, alcohol use, education, BMI, and vitamin D intake. There were significantly lower levels of serum 25(OH)D (20.6 ± 6.5 ng/mL), daily vitamin D intake (8.3 ± 3.7 g/day), and sunlight exposure (9.7 ± 4.1 h/week) in patients with PD compared to healthy controls (p < 0.05). Crude odds ratios (ORs) for PD in the quartiles of serum 25(OH)D were 1 (reference), 0.710 (0.401, 1.257), 0.631 (0.348, 1.209), and 0.483 (0.267, 0.874), respectively. Crude ORs for PD in quartiles of sunlight exposure were 1 (reference), 0.809 (0.454, 1.443), 0.623 (0.345, 1.124) and 0.533 (0.294, 0.966), respectively. A significant positive correlation between serum 25(OH)D and sunlight exposure was found, but serum 25(OH)D was not correlated with daily vitamin D intake. This study indicates that lower levels of serum 25(OH)D and sunlight exposure are significantly associated with an increased risk for PD.

Associations between Vitamin D Status, Supplementation, Outdoor Work and Risk of Parkinson's Disease: A Meta-Analysis Assessment

The present study aimed to quantitatively assess the associations between vitamin D and Parkinson’s Disease (PD) risks, which include: (i) risk of PD in subjects with deficient and insufficient vitamin D levels; (ii) association between vitamin D supplementation and risk of PD; and (iii) association between outdoor work and PD risk, through meta-analyzing available data. An electronic literature search supplemented by hand searching up to March 2015 identified seven eligible studies comprising 5690 PD patients and 21251 matched controls. Odds ratio (OR) and 95% confidence interval (CI) of PD risk were assessed through pooling the collected data from eligible studies using Stata software. Pooled data showed that subjects with deficient and insufficient vitamin D levels had increased PD risks compared with matched-controls according to the corresponding OR: 2.08, 95% CI: 1.63 to 2.65, and 1.29, 95% CI: 1.10 to 1.51. Vitamin D supplementation was associated with significantly reduced risk of PD (OR: 0.62, 95% CI: 0.35 to 0.90). Outdoor work was also related to reduced risk of PD (OR: 0.72, 95% CI: 0.63 to 0.81). The findings may stimulate larger, well-designed studies to further verify the associations between vitamin D and PD risk.