Serum 25-Hydroxyvitamin D level estimation among patients with parkinson's disease in West Bengal, India, and its relationship with motor impairment

Uma Sinharoy; Shankar Prasad Saha

doi:10.4103/cjhr.cjhr_63_20

ORIGINAL ARTICLE

Year : 2021 | Volume : 8 | Issue : 4 | Page : 239-244

Serum 25-Hydroxyvitamin D level estimation among patients with parkinson's disease in West Bengal, India, and its relationship with motor impairment

Uma Sinharoy¹, Shankar Prasad Saha²
¹ Department of Neuromedicine, Bangur Institute of Neurosciences, IPGMER and SSKM Hospital, Kolkata, West Bengal, India
² Professor and Consultant Neurologist, Institute of Neurosciences Kolkata, West Bengal, India

Date of Submission	28-May-2020
Date of Decision	04-Sep-2020
Date of Acceptance	12-Mar-2021
Date of Web Publication	27-May-2022

Correspondence Address:
Uma Sinharoy
IA-298/3, Sector-3, Salt Lake City, Kolkata - 700 097, West Bengal
India

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/cjhr.cjhr_63_20

Abstract

Context: Worldwide, the association of Vitamin D deficiency in Parkinson's disease (PD) has recently been proposed. However, to the best of our knowledge, such studies are lacking from eastern India. Aims: This study compares the prevalence of Vitamin D deficiency in a cohort of patients with PD with the prevalence in age-matched healthy controls. It also aimed at determining a significant correlation of the severity of the various motor manifestations in PD with low serum vitamin levels. Settings and Design: It was a prospective observational case–control study to estimate the level of serum 25-hydroxyvitamin D (25[OH] D) concentrations of the sample population. Subjects and Methods: One hundred consecutive PD patients were selected for this study between 2015 and 2018 from the patients attending neurology outpatient department. Control (n = 100) participants were randomly selected after matching for age sex, and geographic location. Statistical Analysis Used: Statistical Package for the Social Sciences version 15 with multivariate logistic regression (the Pearson correlation coefficient (r) and P value) was applied. Results: Among 100 PD patients 48, patients (48%) had Vitamin D deficiency, 34 patients (34%) had Vitamin D insufficiency, and 18 patients (18%) had normal Vitamin D level; whereas age- and sex-matched control population shows Vitamin D deficiency in 46% people, normal vitamin level in 42%, and insufficient Vitamin D level in 12% control population. The mean (standard deviation) 25(OH) D concentration in the PD cohort was significantly lower than in the control cohorts (20.72 [8.21] ng/mL vs. 25.56 [11.99] ng/mL, respectively; P = 0.001). There was major association between 25(OH) D levels and severity of motor scores (P = 0.028), tremor (P = 0.0001), bradykinesia (P = 0.001), and severity of freezing (P = 0.002), whereas no significant association was found between Vitamin D levels and rigidity (P = 0.05) and postural instability (P = 0.395). Conclusions: This study demonstrates a significantly higher prevalence of hypovitaminosis in PD versus healthy controls. The severity of motor scores, tremor, and bradykinesia and severity of freezing were found to have a direct inverse correlation with low serum Vitamin D levels which further emphasizes the provision of preventive and therapeutic supplementation of Vitamin D in PD.

Keywords: 25-hydroxy Vitamin D, Movement Disorder Society-sponsored revision of the Unified PD Rating scale, Parkinson's disease

How to cite this article:
Sinharoy U, Saha SP. Serum 25-Hydroxyvitamin D level estimation among patients with parkinson's disease in West Bengal, India, and its relationship with motor impairment. CHRISMED J Health Res 2021;8:239-44

How to cite this URL:
Sinharoy U, Saha SP. Serum 25-Hydroxyvitamin D level estimation among patients with parkinson's disease in West Bengal, India, and its relationship with motor impairment. CHRISMED J Health Res [serial online] 2021 [cited 2023 Mar 25];8:239-44. Available from: https://www.cjhr.org/text.asp?2021/8/4/239/346102

Introduction

Parkinson's disease (PD), the most common movement disorder among the elderly, is characterized by six cardinal motor features: bradykinesia, rigidity, rest tremor, postural instability, flexed posture, and freezing.^[1] Interest in the field of Vitamin D and PD was grown up with the molecular biomarker studies revealing the increased expansion of the Vitamin D receptor (VDR) gene in the blood of PD patients.^[2] VDRs are present in the prostate, breast, colon, kidney, immune cells, and brain.^[3] In the human brain, the final converting enzyme for Vitamin D was demonstrated in all the regions (prefrontal cortex, cingulated gyrus, hippocampus, amygdale, caudate/putamen, basal forebrain, thalamus, substantia nigra, and cerebellum) examined and its receptor (VDR) in all but one region (the basal forebrain).^[4] The degree of immunoreactivity varied: hippocampal regions were mostly stained moderately or intensely for the enzyme and receptor, whereas the amygdala had less intense staining; weak for the receptor, and moderate for the enzyme.^[5] VDR is the primary mediator through which Vitamin D acts. Various studies have demonstrated that Vitamin D acts on cells of the nervous system and might have multiple neuroprotective effects. The active form of Vitamin D, 1,25-dihydroxyvitamin D3 regulates the synthesis of nerve growth factor and inhibits the synthesis of inducible nitric oxide synthase (iNOS), which affects the outcome of neuronal damage resulting from various insults or diseases, such as ischemia, Alzheimer's disease (AD), and PD.^[6]

Vitamin D has been recently reported as an environmentally modifiable factor playing an important role in the pathogenesis of PD.^[7] Reduced serum levels of the primary circulating Vitamin D metabolite 25-hydroxyvitamin D (25[OH] D) have been observed in various cross-sectional studies in PD patients.^[8] Vitamin D has been investigated in association with cognitive dysfunction among elderly population. Increasing evidence suggests that hypovitaminosis D is more pronounced in PD than in AD or among healthy controls.^[9],[10] The Harvard Biomarker Study in 2013 reconfirms this association and supports the monitoring of Vitamin D levels in patients with PD.^[11] In addition, an inverse relationship of serum 25(OH) D levels with disease severity in PD has been evident from cross sectional studies, particularly from China.^[12] Peterson et al. in their landmark study of neuropsychiatric assessment of PD patients found that higher Vitamin D level was associated with better mood and cognition among nondemented PD patients.^[13] Hypovitaminosis D is highly prevalent among Indians. Vitamin D deficiency is particularly common in North India (27 ° N) where 96% of neonates, 91% of healthy schoolgirls, 78% of healthy hospital staff, and 84% of pregnant women have hypovitaminosis D.^[14],[15] However, its prevalence among PD patients along with its relation to clinical severity in Indian patients remains to be investigated. We designed this study to estimate the level of serum 25(OH) D in Bengali patients with PD from eastern India and analyze its relationship with motor function among the study population.

Subjects and Methods

This study is a prospective, observational; case–control hospital-based single center study. This was conducted in the department of neurology in a tertiary care medical college and hospital in Kolkata on 100 PD patients for a period of 3 years from 2015 to 2018 after getting approval from the Institutional Ethics Committee. Patients both male and female aged more than 40 years, with parkinsonian features (bradykinesia, rest tremor, rigidity, postural instability, and short shuffling/freezing gait) attending the outpatient department of neurology, were enrolled and those fulfilling the inclusion criteria (PD diagnosis using UKPDS Brain Bank criteria) were included in the study. A similar number of healthy adults without neurological illness from the same source population matched for age and gender acted as the control. Each PD patient got a pro forma and a consent form on the first visit. Each item of this pro forma (though written in English) was explained and verbally translated into the local language. After getting written informed consent, patients were methodically examined and additional data were collected through face-to-face interview for eligible patients. Good drug compliance was ensured and drug dose (of levodopa and or anticholinergics) was optimized for every PD patient on the very first visit. The study parameters included detailed history focusing on the patient profile (demographic and socioeconomic) and duration of disease, detailed treatment history and drug history, and thorough neurological examination. Disease severity was assessed by Modified Hoehn and Yahr (H and A) staging.^[16] Patients having H and Y staging >3 were considered to have severe disease. Motor function assessment was done by the part III motor subscore of Movement Disorder Society-sponsored revision of the Unified PD Rating Scale (MDS-UPDRSm).^[17] MDS-UPDRSm has altogether 132 maximum points including maximum 20 points for rigidity, maximum 48 points for bradykinesia, maximum 4 points for freezing, again 4 points for postural instability, and maximum 40 points for tremor. Apart from routine blood and biochemical testing, serum 25(OH) D estimation was done by 25(OH) Vitamin D enzyme-linked immunoassay (ELISA) kit, a solid phase ELISA based on the principal of competitive binding. At least 2 ml whole blood was collected by venipuncture in an on-dose state and allowed clotting. Samples were centrifuged as soon as possible after collection to separate serum. Hemolyzed samples were discarded. The specimens might be refrigerated at 2°C–8°C for 2 weeks. Prior to assay, the refrigerated were allowed to equilibrate to room temperature for 30 min and mixed well. The resulting values were expressed as ng/ml. In this study, Vitamin D deficiency is defined as serum 25(OH) D concentration < 20 ng/mL, between 20 ng/ml and 30 ng/ml was considered as Vitamin D insufficiency, and above 30 ng/ml was considered as the normal level.^[18] Inclusion criteria were according to the UKPDS Brain Bank Criteria for the diagnosis of PD (bradykinesia [slowness of initiation of voluntary movement with a progressive reduction in speed and amplitude of repetitive actions] and at least one of the following – muscular rigidity, 4–6 Hz rest tremor, postural instability not caused by primary visual, vestibular, cerebellar, or proprioceptive dysfunction). Exclusion criteria were any history of repeated strokes with the stepwise progression of parkinsonian features or history of repeated head injury, history of definite encephalitis, oculogyric crises, neuroleptic treatment at the onset of symptoms, features suggestive of supranuclear gaze palsy, cerebellar signs, early severe autonomic involvement, early severe dementia, presence of a cerebral tumor or communicating hydrocephalus on CT scan, and recent supplementation of Vitamin D.

Summation of the data was done using a grand chart in MicrosoftEexcel software and suitable statistical analysis was performed using computerized statistical software Statistical Package for the Social Sciences (SPSS IBM, Kolkata, India) version 15. The clinical, demographic data and serum Vitamin D level for PD patients and controls were described as mean ± standard deviation (SD) and percentage numbers (%). The serum levels of 25(OH) D between PD patients and controls were compared through the Student's t-test. For cross-sectional analysis, multivariate logistic regression was applied. The Pearson correlation coefficient (r) was used to assess the association between serum Vitamin D level and severity (Modified Hoehn and Yahr staging) and motor parametric scores of (MDS-UPDRSm) UPDRS. P ≤ 0.05 was considered statistically significant.

Results

In this study, 100 PD patients were studied. Forty-four of them (44%) were males and 56 were females (56%). The mean age of the patients was 57.32 ± 9.18 years (age range: 45–81 years). The mean duration of symptoms onset was 2.9 ± 2.12 years (range: 1–14 years). The basic demographic profile of PD patients with motor performance in UPDRS scoring is illustrated in [Table 1].

Table 1: Descriptive statatistical values

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The mean 25(OH) D level was 20.72 ± 8.26 ng/ml (range: 8.2–34 ng/ml) (normal value: >30 ng/ml). There was a statistically significant difference between 25(OH) D levels of PD patients (P = 0.001) compared to the levels of 25(OH) D in the control population. Among 100 PD patients, 48 patients (48%) had Vitamin D deficiency, 34 patients (34%) had Vitamin D insufficiency, and 18 patients (18%) had normal Vitamin D level, whereas age- and sex-matched control population shows Vitamin D deficiency in 46% of people, normal vitamin level in 42%, and insufficient Vitamin D level in 12% of control population.

Paired t-test and confidence interval: Serum Vitamin D levels of patient versus control

N Mean StDev SE Mean

Patient's Vitamin D 100 20.72 8.21 0.82

Control Vitamin D 100 25.56 11.99 1.20

Difference 100 -4.84 13.55 1.36

95% confidence interval for mean difference: (−7.53, −0.2.15)

t-test of mean difference: T-Value = −3.57; P = 0.001

The correlation of Vitamin D levels in PD versus control population is shown in [Figure 1].

Figure 1: Correlation of Vitamin D levels in Parkinson's disease versus control population

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There was no statistically significant difference in 25(OH) D levels between males and females (P = 0.018). Our analysis showed no significant association between 25(OH) D levels and age of the patient (P = 0.56), disease duration (P = 0.697), and severity of the disease (P = 0.33).There was major association between 25(OH) D levels and severity of motor scores (P = 0.028), tremor (P = 0.0001), bradykinesia (P = 0.001), and severity of freezing (P = 0.002), whereas no significant association was found between Vitamin D levels and rigidity (P = 0.05) and postural instability (P = 0.395). Correlations of serum Vitamin D levels and severity of tremor, bradykinesia, and freezing of gait have been expressed as scatter plots in [Figure 2].

Figure 2: (a) Scatter plot shows correlation of tremor and Vitamin D levels in Parkinson's disease patients (Pearson correlation of tremor and Vitamin D = −0.485; P = 0.0001). (b) Scatter plot shows correlations between bradykinesia and Vitamin D levels in Parkinson's disease patients (Pearson correlation of bradykinesia and Vitamin D = −0.567; P = 0.001). (c) Scatter plot of freezing and Vitamin D levels in Parkinson's disease patients (Pearson correlation of freezing and Vitamin D = −0.423; P = 0.002)

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Discussion

25-hydroxyvitamin D (Vitamin D) is suggested to have a neuroprotective and neurotrophic role in the brain, especially in neurodegenerative diseases as PD and dementia; however, the relationship is not well understood. Therefore, a good number of research articles as well as meta-analysis have been performed to establish association of serum vitamin levels with PD. After a thorough literature search, we have come across at least four large systematic reviews cum meta-analysis on this issue which have encountered more than twenty studies with a total of 2866 PD patients and 2734 controls and all of them have proved that serum Vitamin D levels are inversely associated with the risk and severity of PD.^{[19],[20],[21],[22]} However, to the best of our knowledge, such studies are lacking from eastern India. In our study, we have also directly correlated the severity of different cardinal motor manifestations of PD patients to the low serum Vitamin D levels.

This case–control study has shown a statistically significant difference between 25(OH) D levels of PD patients (P = 0.001) compared to the levels in age-matched control population. About 48% of PD patients had Vitamin D deficiency, 34% patients had Vitamin D insufficiency, and only18% of PD patients had normal serum Vitamin D levels. The mean (SD) 25(OH) D concentration in the PD cohort was significantly lower than in the control cohorts (20.72 [8.21] ng/mL vs 25.56 [11.99] ng/mL, respectively; P = 0.001). In this study, the mean 25(OH) D level (20.72 ± 8.21 ng/ml) was lower in comparison with previous studies. In the study of Evatt et al. in Atlanta, the mean 25(OH) D level was significantly higher than our patients.^[23] It is probably due to differences between geographical latitude, sun radiation, coating conditions, and amount of skin pigmentation. Vitamin D deficiency prevails in epidemic proportions all over the Indian subcontinent and subclinical Vitamin D deficiency is highly prevalent in both urban and rural settings and across all socioeconomic groups.^[24] Bengali-speaking community in West Bengal is heterogeneous in terms of mixed race and culture. Garg et al. in their rural community-based study from Kolkata, West Bengal (Dr. P. C. Sen Best Award winning paper on Rural Health Practice, 2018), have reported mean (SD) Vitamin D level of 27.01 (6.8) ng/ml with a median of 26.30 ng/ml (min – max: 7.1–45.70 ng/ml) with overall Vitamin D insufficiency in 67.5% of the study participants.^[25] In our study also, the mean (SD) value of serum 25(OH) D of the control population was 25.56 (11.99) ng/ml. The recent most retrospective multicentric study by Dr. Sanjiv Goel from Punjab on Vitamin D status in the Indian population has reported the prevalence rate of 83.4% (for Vitamin D level <30 ng/ml) and 53.1% (for Vitamin D level <20 ng/ml) from eastern India.^[26] Another study by Srimani et al. from West Bengal have reported 51% prevalence of Vitamin D <20 ng/ml.^[27]

This study showed statistically significant correlation between 25(OH) D levels and tremor (P = 0.0001), bradykinesia (P = 0.001), and severity of freezing (P = 0.002). Our study did not show any association of Vitamin D levels with age, gender, duration of PD, rigidity, and postural instability. Although there was major association between 25(OH) D levels and severity of motor scores (P = 0.028), our study failed to show any significant correlation of Vitamin D concentration with PD disease severity with Modified Hoehn and Yahr (H and Y) staging, which may be due to the fact that we have not included severely disabled patients having H and Y staging >3 (cases belonged to m [H and Y] stage 1.5–3). Sato et al. made a separate analysis of Vitamin D status in patients with Hoehn and Yahr (H and Y) stage 1–2 and with stage 3–5; serum 25(OH) D was lower in the group with HandY stage 3–5 compared with patients with stage 1–2.^[7] Just like our observation, Liu and Zhang and Serdarolu Beyazal et al. have shown that serum Vitamin D concentrations were not associated with duration of PD (P = 0.37) and age of patients (P = 0.49).^[12],[28] Moghaddasi et al. from Iran in their study have shown similar results with a significant association between the presence of freezing, postural instability, and abnormal postures with lower levels of 25(OH) D.^[29] In the study of Sato et al., the higher incidence of nonvertebral fractures was seen in female patients with PD that might be due to frequent falls and osteoporosis caused by deficiency of Vitamins D.^[30] Persons with more severe PD are less ambulatory, get less sun exposure, and subsequently have lower Vitamin D. It is also possible that Vitamin D has an effect on PD symptoms considering high density of the final converting enzyme and receptors for Vitamin D in the substantia nigra, raising the issue whether low Vitamin D is cause or consequence of PD. There are several limitations to the study. Causation cannot be inferred from these cross-sectional data alone. Our study has not considered the effect of antiparkinsonian drugs while scoring motor function. Data are lacking about controlling dietary intake and exposure to sunlight in the study and also the portions of plasma samples drawn in different seasons were not matched. Currently, measurement of Vitamin D compounds by liquid chromatography–tandem mass spectrometry (HPLC-MS) detection has been established as the gold standard testing.^[31] In this study, serum 25(OH) D was measured by enzymatic immunoassay in our microbiology laboratory with an acceptable intra-assay and inter-assay variability (<7%) and we did not have the scope to compare with HPLC-MS methods.

Finally, the study population is small and heterogeneous in terms of demographic background.

This study demonstrates a significantly higher prevalence of hypovitaminosis in PD versus healthy controls. The severity of motor scores, tremor, and bradykinesia, and severity of freezing were found to have a direct inverse correlation with low serum Vitamin D levels which further emphasizes the provision of preventive and therapeutic supplementation Vitamin D in PD.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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