Vitamin D and Pain: Vitamin D and Its Role in the Aetiology and Maintenance of Chronic Pain States and Associated Comorbidities

Environmental factors and their impact on chronic pain development and maintenance

It is more than recognized and accepted that the environment affects the physiological responses of all living things, from bacteria to superior vertebrates, constituting an important factor in the evolution of all species. Environmental influences range from natural processes such as sunlight, seasons of the year, and rest to complex processes like stress and other mood disorders, infections, and air pollution, being all of them influenced by how each creature deals with them. In this chapter, it will be discussed how some of the environmental elements affect directly or indirectly neuropathic pain, a type of chronic pain caused by a lesion or disease of the somatosensory nervous system. For that, it was considered the edge of knowledge in translational research, thus including data from human and experimental animals as well as the applicability of such findings.

Prevalence of vitamin D deficiency and its association with cardiometabolic risk factors among healthcare workers in the Eastern Cape province, South Africa; cross-sectional study

This study assesses the prevalence of Vitamin D deficiency and its potential association with cardiometabolic risk factors among South African adults residing in the Eastern Cape province. In this cross-sectional study, 1244 healthcare workers (HCWs) completed a self-administered questionnaire and venous blood samples were drawn at two academic hospitals in the Eastern Cape. History of hypertension and diabetes mellitus were self-reported. Participants were categorised as obese if their body mass index (BMI) ≥ 30 kg/m2. Participants were classified as having metabolic syndrome if they had hypertension, diabetes mellitus and obesity. Vitamin D [25(OH)D] deficiency was defined as venous blood concentrations < 50 nmol/L. Associations between vitamin D deficiency and participants' characteristics were assessed using multivariate logistic regression model analysis. The prevalence of vitamin D deficiency was 28.5% (n = 355), of whom 292 were female. Among the participants who were deficient in vitamin D, the prevalence of obesity, diabetes mellitus, hypertension, chronic kidney disease, and metabolic syndrome was 64.9% (n = 230), 9% (n = 32), 16.6% (n = 59), 2.3% (n = 8) and 18% (n = 64), respectively. In the adjusted multivariate logistic regression model, black Africans (AOR = 2.87; 95% CI 1.52-5.43) and individuals ≥ 42 years (AOR = 1.37; 95% CI 1.07-1.77) were more likely to exhibit vitamin D deficiency. However, there was no significant association by age, sex, and cardiometabolic markers. More than one in four healthcare workers was deficient in vitamin D among the study sample, especially the black Africans and older individuals. Further studies are needed at the population level to elucidate on the vitamin D status in the region.

Evaluation of Candidemia in Solid-Organ Transplant Recipients

OBJECTIVES

Solid-organ transplant recipients have high rates of invasive fungal infections. Candida species are the most commonly isolated fungi. Our aim was to identify risk factors, clinical presentations, and outcomes of candidemia in solid-organ transplant recipients.

MATERIALS AND METHODS

We evaluated adult (≥18 years old) transplant recipients seen from May 2011 to December 2022 at Baskent University Ankara Hospital. From medical records, we retrospectively reviewed age, sex, transplant type, candidemia agent, risk factors, concomitant infections, and mortality of patients with Candida detected in blood culture. We used SPSS statistics software (version 25) to analyze data.

RESULTS

There were 1080 organ transplants performed during the study period (717 kidney, 279 liver, 84 heart). There were 855 who were ≥18 years (655 kidney, 127 liver, 73 heart), of whom candidemia was detected in 26 (16 male; 11 kidney, 11 liver, 4 heart) with a median age of 47.5 years. The most common agents were Candida albicans and Candida glabrata. The most common chronic diseases were hypertension, cirrhosis, and cardiomyopathy. Eighteen patients had a concomitant focus of infection. Ten patients had pneumonia accompanying candidemia. The 30-day mortality rate was as high as 53.8%. The mean duration of candidemia after transplant was 23 months. Catheter-related candidemia was observed in 65% of patients. The 30-day mortality was found to be significantly higher in patients followed in the intensive care unit (P = .014), receiving total parenteral nutrition (P = .001), using broad-spectrum antibiotics (P = .001), and having pneumonia (P = .042) accompanying candidemia.

CONCLUSIONS

For adult solid-organ transplant recipients with candidemia, careful monitoring is essential for successful management of total parenteral nutrition, central catheter, use of broadspectrum antibiotics, and invasive interventions.

Long-term effects of vitamin D supplementation and maintaining sufficient vitamin D on knee osteoarthritis over 5 years

OBJECTIVES

This study aimed to investigate the long-term effect of vitamin D supplementation compared to placebo over 5 years in participants with knee osteoarthritis (OA). We also aimed to describe the effect of maintaining sufficient serum vitamin D levels over five years in knee OA.

METHODS

Participants (n = 173) from the Hobart centre of the Vitamin D Effects on Osteoarthritis (VIDEO) trial were extensively followed up 3 years after the cessation of 2-year investigational treatment. Participants were classified as maintaining sufficient vitamin D (n = 79) and not maintaining sufficient vitamin D (n = 61) groups.

RESULTS

There was no significant difference in change in the knee symptoms, depression, and serum levels of IL6 and hs-CRP between both comparisons after 3 years of cessation of the clinical trial. However, among participants who reported no knee surgery (KS), there was a significant improvement in WOMAC function (β: - 83.7, 95% CI: - 167.3, 0) and depression scores (β: - 1.3, 95% CI: - 2.3, - 0.2) in vitamin D group compared to the placebo group. Similarly, those who maintained adequate vitamin D levels over 5 years had significantly less WOMAC knee pain (β: - 33.9, 95% CI: - 65.7, - 2) and physical dysfunction (β: - 105.5, 95% CI: - 198.2, - 12.8) than participants with vitamin D deficiency over 5 years.

CONCLUSION

Vitamin D supplementation over 2 years or maintaining vitamin D sufficiency for 5 years was not associated with statistically significant differences in change in knee symptom scores over 5 years. However, among participants who did not report KS, 2-year vitamin D supplementation and maintaining sufficient vitamin D was linked to modest improvements in knee symptoms and depression scores in knee OA.

Serum vitamin D le Serum vitamin D levels are associated with acute post e associated with acute postoperative pain and opioid analgesic consumption after laparoscopic cholecystect cholecystectomy: a str omy: a strobe compliant pr obe compliant prospectiv ospective obser e observational ational study

BACKGROUND

In this prospective observational study, we aimed to evaluate the relationship between serum levels of vitamin D and acute postoperative pain scores, as well as opioid analgesic consumption in patients undergoing laparoscopic cholecystectomy.

METHODS

: The study was performed in the Medical Faculty Hospital, from April 2020 to April 2021. Postoperative visual analog scale (VAS) pain scores, total tramadol consumption, number of requests on patient-controlled analgesia (PCA) were compared between the vitamin D deficient (≤20 ng/mL; n = 25) and vitamin D nondeficient (>20 ng/mL; n = 55) groups at five time points (T0: in the recovery room, T1: 1st hour in the ward, T2: 6th hour, T3: 12th hour, and T4: 24th hour).

RESULTS

Postoperative VAS pain scores were similar in the vitamin D deficient group at all time points (T0-4), but differed significantly only at the T-0 time point (p = 0.020). The mean cumulative tramadol consumption was significantly higher in the vitamin D deficiency group than in the nondeficiency group (p = 0.005). Vitamin D levels were lower in patients with VAS ≥ 4 at the postoperative T-0 time point (p = 0.009). In the multivariate linear regression analysis, 15.7% of cumulative tramadol consumption was due to vitamin D deficiency (β = -0.188).

DISCUSSION

: Our study shows that preoperative low vitamin D level was associated with an increase in acute postoperative pain scores and consumption of opioid analgesics in patients undergoing laparoscopic cholecystectomy. Our findings may be useful for postoperative pain management in patients with vitamin D deficiency.

The influence of vitamin D supplementation on the expression of mediators of inflammation in knee osteoarthritis

This trial aimed to determine the possible therapeutic and immunomodulatory effects of vitamin D3 in patients with knee OA. In this open-label clinical trial, symptoms were assessed over 3 months in patients with primary knee OA receiving oral vitamin D3 4000 IU/day. Clinical response was evaluated at baseline and 3 months using WOMAC subscores and VAS. Serum levels of cytokines IL-1β, TNF-α, IL-13, IL-17, IL-33, IL-4, and IL-10 were determined by ELISA method. Eighty patients with knee OA were included. All 80 completed the study; the median 25(OH)D3 level was 23.1 ng/ml at baseline and increased by 12.3 ng/ml after treatment. Vitamin D3 after 3 months of supplementation induced a significant reduction in VAS pain and WOMAC subscores. Using OMERACT-OARSI criteria, 86.7% of patients treated with vitamin D3 responded to treatment. At the end of 3 months, systemic values of IL-1β (p < 0.01), IL-23 (p < 0.01), and IL-33 (p < 0.01) were significantly increased, values of TNF-α (p < 0.01), IL-13 (p < 0.01), and IL-17 (p < 0.01) were significantly decreased, while value of IL-4 was not significantly changed. No adverse events were detected. Treatment with vitamin D is associated with improvement in pain, as well as stiffness and physical function. Vitamin D supplementation increased systemic values of IL-33. Our results indicate that vitamin D3 supplementation may be used as a novel therapeutic in knee OA. Future studies are needed to investigate a potential role of IL-33 in the pathogenesis of knee OA.

The Influence of Sleep Disturbance on Chronic Pain

PURPOSE OF REVIEW

The purpose of this review is to present an overview of common sleep disturbance pathologies and their impact on chronic pain, while examining various factors that are implicit in the relationship between sleep disturbance and chronic pain, including neurobiochemistry, anatomy, and systemic mediators, and reviewing recent and landmark literature.

RECENT FINDINGS

Earlier literature reviews and studies have introduced the bidirectional relationship between sleep disturbance and chronic pain; that is, impaired sleep may worsen chronic pain, and chronic pain causes sleep disturbance. However, more recent reviews and studies seem to show a more associative, rather than causative relationship. There have been recent studies that attempt to determine mechanisms that link sleep disturbance and chronic pain; the results of these studies were more varied, ultimately concluding that there may be a separate, yet-to-be discovered mechanism that shows the causative relationship between sleep disturbance and pain. There are several neurotransmitters that are involved in the mediation of chronic pain and sleep disturbance as separate entities, and some studies have shown that there may be mechanisms that govern both chronic pain and sleep disturbance as a single unit. Other neuroendocrine substances also serve to mediate chronic pain and sleep disturbance. All these substances are found to be associated with various sleep disorders and are also associated with chronic pain symptoms as well. Inflammation plays a role in chronic pain and sleep disturbance, with an increase in inflammatory substances and mediators associated with an increase or worsening in chronic pain symptoms and sleep disorders. The HPA axis plays a role in chronic pain and sleep disorders, influencing pain and sleep pathways through stress response, inflammation, and maintenance of homeostasis. There are several variables that influence both chronic pain and sleep disturbance, and more research into these variables may further our understanding into the complex pathways governing the influence of sleep disturbance on pain, and ultimately to improve treatment for this issue.

Vitamin D, oral health, and disease characteristics in juvenile idiopathic arthritis: a multicenter cross-sectional study

Background

Vitamin D deficiency has been associated with autoimmune diseases and oral health. Knowledge about the association between vitamin D status and oral conditions in JIA is limited. We aimed to investigate vitamin D status in a cohort of Norwegian children and adolescents with JIA and possible associations between serum vitamin D levels, clinical indicators of oral health, and JIA disease characteristics.

Methods

This multi-center, cross-sectional study, included individuals with JIA aged 4–16 years from three geographically spread regions in Norway. Demographic data, age at disease onset, disease duration, JIA category, disease status, medication, and vitamin D intake were registered. One blood sample per individual was analyzed for 25(OH) vitamin D, and the level of insufficiency was defined as < 50 nmol/L. A clinical oral examination was performed applying commonly used indices in epidemiological studies of dental caries, dental erosion, enamel defects, gingival bleeding, and oral hygiene. Serum vitamin D was used as exposure variable in multivariable regression analyses to estimate the associations between insufficient vitamin D level, JIA disease status, and oral conditions, with adjustments for age, sex, geographical region, BMI, seasonal blood sampling, and parental education.

Results

Among the 223 participants with JIA, 97.3% were Caucasians, 59.2% were girls, and median age was 12.6 years. Median disease duration was 4.6 years, and 44.4% had oligoarticular JIA. Mean serum vitamin D level was 61.4 nmol/L and 29.6% had insufficient levels. Vitamin D levels did not differ between sexes, but between regions, iso-BMI categories, age groups, and seasons for blood sampling. Insufficient vitamin D levels were associated with dentin caries (adjusted OR 2.89, 95% CI 1.43–5.86) and gingival bleeding (adjusted OR 2.36, 95% CI 1.10–5.01). No associations were found with active JIA disease or more severe disease characteristics.

Conclusion

In our study, nearly 30% had vitamin D insufficiency, with a particularly high prevalence among adolescents. Vitamin D insufficiency was associated with dentin caries and gingival bleeding, but not with JIA disease activity. These results point to the need for a multidisciplinary approach in the follow-up of children with JIA, including an increased focus on vitamin D status and oral health.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12903-022-02349-1.

The Efficacy of Vitamin D Supplementation in the Treatment of Fibromyalgia Syndrome and Chronic Musculoskeletal Pain

Fibromyalgia syndrome (FMS) and chronic widespread musculoskeletal pain (CMP) are diffuse suffering syndromes that interfere with normal activities. Controversy exists over the role of vitamin D in the treatment of these diseases. We carried out a systematic literature review of randomized controlled trials (RCT) to establish whether vitamin D (25OHD) deficiency is more prevalent in CMP patients and to assess the effects of vitamin D supplementation in pain management in these individuals. We searched PubMed, Physiotherapy Evidence Database (PEDro), and the Cochrane Central Register of Controlled Trials (CENTRAL) for RCTs published in English from 1 January 1990 to 10 July 2022. A total of 434 studies were accessed, of which 14 satisfied the eligibility criteria. In our review three studies, of which two had the best-quality evidence, a correlation between diffuse muscle pain and 25OHD deficiency was confirmed. Six studies, of which four had the best-quality evidence, demonstrated that appropriate supplementation may have beneficial effects in patients with established blood 25OHD deficiency. Eight studies, of which six had the best-quality evidence, demonstrated that 25OHD supplementation results in pain reduction. Our results suggest a possible role of vitamin D supplementation in alleviating the pain associated with FMS and CMP, especially in vitamin D-deficient individuals.

Lower Blood Vitamin D Levels Are Associated with Depressive Symptoms in a Population of Older Adults in Kuwait: A Cross-Sectional Study

Low serum vitamin D has been associated with an increased risk of neuropsychiatry disorders. This study aimed to examine the association between vitamin D deficiency and depression in adults aged 65 years and older. This cross-sectional study was conducted in seven primary healthcare centers across Kuwait (November 2020 to June 2021). The participants (n = 237) had their serum vitamin D 25-(OH)-D concentrations (analyzed by LC-MS) classified as sufficient, ≥75 nmol/L (30 ng/mL); insufficient, 50−75 nmol/L (20−30 ng/mL); or deficient, <50 nmol/L (20 ng/mL). Depressive symptoms were evaluated using the 15-Item Geriatric Depression Scale (15-item GDS). The mean serum 25-OH-D levels (nmol/L) in volunteers with normal, mild, moderate, and severe depression were 100.0 ± 31.7, 71.2 ± 38.6, 58.6 ± 30.1 and 49.0 ± 6.93, respectively (p < 0.001). The participants in the vitamin D sufficiency group were significantly less likely to exhibit depressive symptoms (88.2%) than patients with mild (36%) and moderate (21%) depression (p < 0.001). Ordinal logistic regression showed that vitamin D deficiency (OR = 19.7, 95% CI 5.60, 74.86, p < 0.001) and insufficiency (OR = 6.40, 95% CI 2.20, 19.91, p < 0.001) were associated with higher odds of having depressive symptoms. A low serum vitamin D level is a significant predictor of symptoms of depression among older individuals.

Prevalence of Vitamin D Deficiency and Its Relationship with Clinical Outcomes in Patients with Fibromyalgia: a Systematic Review of the Literature

Fibromyalgia is a debilitating chronic condition which poses a therapeutic challenge to the clinician. With a large backlog in patient flow subsequent to the COVID-19 pandemic and rising numbers of patients with post-acute sequelae of COVID-19 (PASC) presenting with fibromyalgia-like clinical features, there is an increasingly pressing need to identify broad cost-effective interventions. Low levels of vitamin D have previously been reported in patients with fibromyalgia, though any causative link has been difficult to establish. A systematic literature review on the association between vitamin D deficiency and fibromyalgia was performed examining retrospective evidence both for and against an association between vitamin D deficiency (VDD) and fibromyalgia and evaluating the therapeutic benefit from supplementation. A group of six studies were selected based on relevance, use of controls, quality of research and citations. Four primary studies assessing the prevalence of VDD in fibromyalgia patients versus controls were evaluated with a total 3,496 subjects. Three included females only and one larger study assessed males. Two (n = 313) concluded the presence of a statistically significant association, and two (n = 161) found none. Two randomised controlled trials assessing the effect of vitamin D supplementation in a total of 80 subjects found conflicting results, with pain reduction in one and none in the other. It is likely there exists an association between VDD deficiency and fibromyalgia in a large subset of patients, although establishing primary causation is difficult. There is a need for larger randomised controlled trial designs with more effective comparison with healthy subjects and control for confounding factors. Given VDD is a major problem in the general population, we recommend supplementation be recommended by healthcare professionals to fibromyalgia patients for the purpose of maintaining bone health given their potentially increased susceptibility to developing deficiency and its sequelae.

The Vitamin D Role in Preventing Primary Headache in Adult and Pediatric Population

Headache is among the main neurological disorders with a great impact on both adults and children. The diagnosis of primary headache and proper management is often delayed with a great impact on work productivity and overall quality of life. Chronic headache often requires prophylactic therapy to reduce the frequency and severity of the attacks and the use of abortive medications. Besides the use of several classes of drugs, another treatment modality is the use of Nutraceuticals. Some studies have suggested a possible role of vitamin D in headache prophylaxis. Indeed, vitamin D is involved in several pathways of brain development, neuroprotection and neurotransmission. Moreover, there is data suggesting a close relationship between primary headache and vitamin D deficiency, both in children and in adults. To date, a few studies have evaluated the effect of vitamin D on headaches. The aim of this review is to summarize the data collected on headache prophylaxis with vitamin D comparing the effects of vitamin D in pediatric and adult populations.

No improvement of sleep from vitamin D supplementation: insights from a randomized controlled trial

Background

Vitamin D has been linked to sleep health in observational studies. Data from randomized controlled trials (RCTs) with vitamin D is scarce.

Methods

This study presents the results of a secondary analysis of 189 vitamin D insufficient participants (47.1% women) in a previously performed RCT, of which 92 were randomized to vitamin D (100,000 IU (2500 μg) as a bolus dose followed by 20,000 IU (500 μg) per week), and 97 to placebo. At baseline and after 4 months at the end of the study serum 25-hydroxyvitamin D (s-25(OH)D) was measured, and the study questionnaire assessing sleep duration, daytime sleepiness, and symptoms of insomnia, was completed.

Results

At baseline, mean s-25(OH)D was 35.0 ± 11.8 and 35.5 ± 13.3 nmol/L in the vitamin D and placebo groups, respectively. After four months, we found no statistically significant differences between the intervention groups in any of the assessed sleep outcomes, neither when stratified by sex, nor when performed in subgroups based on baseline or end of study s-25(OH)D level or presence of sleep complaints at baseline.

Conclusions

We were not able to demonstrate a significant effect of vitamin D supplementation on sleep in this vitamin D insufficient population.

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RCT investigating vitamin D for 4 months in participants with low vitamin D status.

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Vitamin D did not improve sleep duration, excessive daytime sleepiness or insomnia.

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The role of vitamin D in sleep health remains controversial.

Effect of Crocus sativus (Saffron) Intake on Top of Standard Treatment, on Disease Outcomes and Comorbidities in Patients with Rheumatic Diseases: Synthesis without Meta-Analysis (SWiM) and Level of Adherence to the CONSORT Statement for Randomized Controlled Trials Delivering Herbal Medicine Interventions

Rheumatic diseases (RDs) are often complicated by chronic symptoms and frequent side-effects associated with their treatment. Saffron, a spice derived from the Crocus sativus L. flower, is a popular complementary and alternative medicine among patients with RDs. The present systematic review aimed to summarize the available evidence regarding the efficacy of supplementation with saffron on disease outcomes and comorbidities in patients with RD diagnoses. PubMed, CENTRAL, clinicaltrials.gov and the grey literature were searched until October 2021, and relevant randomized controlled trials (RCTs) were screened for eligibility using Rayyan. Risk of bias was assessed using the Cochrane’s Risk of Bias-2.0 (RoB) tool. A synthesis without meta-analysis (SWiM) was performed by vote counting and an effect direction plot was created. Out of 125 reports, seven fulfilled the eligibility criteria belonging to five RCTs and were included in the SWiM. The RCTs involved patients with rheumatoid arthritis, osteoarthritis and fibromyalgia, and evaluated outcomes related to pain, disease activity, depression, immune response, inflammation, oxidative stress, health, fatigue and functional ability. The majority of trials demonstrated some concerns regarding overall bias. Moreover, the majority of trialists failed to adhere to the formula elaborations suggested by the CONSORT statement for RCTs incorporating herbal medicine interventions. Standardization of herbal medicine confirms its identity, purity and quality; however, the majority of trials failed to adhere to these guidelines. Due to the great heterogeneity and the lack of important information regarding the standardization and content of herbal interventions, it appears that the evidence is not enough to secure a direction of effect for any of the examined outcomes.

Effect of intrapartum vitamin D levels on labor pain

AIM

Vitamin D has widespread receptor distribution in the body, and therefore it has vital roles in numerous pathophysiological conditions. It also affects pain manifestation through its functions at various stages of the pain pathways. This study aimed to investigate the effects of intrapartum vitamin D levels on pain experienced by women during the first stage of labor.

METHODS

A total of 127 term-nulliparous women at the early stage of labor were included in the study. Serum 25 (OH) vitamin D levels were measured at the beginning of labor to determine intrapartum vitamin D levels. Labor pain was assessed using the Visual Analog Scale at different stages of cervical dilation (VAS₀ , VAS₁ , VAS₂ ). Postpartum pain (VAS_pp ) and women's birth satisfaction score (BSS) were also evaluated during the early postpartum period.

RESULTS

There was a moderate negative correlation between vitamin D and VAS₀ and VAS₁ (r²  = 0.4, p = 0.000; r²  = -0.570, p = 0.000, respectively), and a weak negative correlation between vitamin D and VAS₂ (r²  = -0.373, p = 0.000). No significant correlation was found between vitamin D and BSS and length of labor (p = 0.127, p = 0.126, respectively).

CONCLUSION

In nulliparous women with low vitamin D levels, the first stage of labor and the early postpartum period may be more painful. To facilitate management of labor pain, during the antenatal period vitamin D levels should be monitored, and in cases where the levels are deficient, vitamin D supplementation should be started.

Double-Edged Sword of Vitamin D3 Effects on Primary Neuronal Cultures in Hypoxic States

The use of vitamin D3 along with traditional therapy opens up new prospects for increasing the adaptive capacity of nerve cells to the effects of a wide range of stress factors, including hypoxia-ischemic processes. However, questions about prophylactic and therapeutic doses of vitamin D3 remain controversial. The purpose of our study was to analyze the effects of vitamin D3 at different concentrations on morpho-functional characteristics of neuron-glial networks in hypoxia modeling in vitro. We showed that a single administration of vitamin D3 at a high concentration (1 µM) in a normal state has no significant effect on the cell viability of primary neuronal cultures; however, it has a pronounced modulatory effect on the functional calcium activity of neuron-glial networks and causes destruction of the network response. Under hypoxia, the use of vitamin D3 (1 µM) leads to total cell death of primary neuronal cultures and complete negation of functional neural network activity. In contrast, application of lower concentrations of vitamin D3 (0.01 µM and 0.1 µM) caused a pronounced dose-dependent neuroprotective effect during the studied post-hypoxic period. While the use of vitamin D3 at a concentration of 0.1 µM maintained cell viability, preventive administration of 0.01 µM not only partially preserved the morphological integrity of primary neuronal cells but also maintained the functional structure and activity of neuron-glial networks in cultures. Possible molecular mechanisms of neuroprotective action of vitamin D3 can be associated with the increased expression level of transcription factor HIF-1α and maintaining the relationship between the levels of BDNF and TrkB expression in cells of primary neuronal cultures.

Vitamin D and Sleep Regulation: Is there a Role for Vitamin D?

BACKGROUND

Vitamin D exerts multiple pleiotropic effects beyond its role in calcium-phosphate metabolism. Growing evidence suggests an association between hypovitaminosis D and sleep disorders, thus increasing the interest in the role of this vitamin in the regulatory mechanisms of the sleep-wake cycle.

OBJECTIVE

The study aimed to explore and summarize the current knowledge about the role of vitamin D in sleep regulation and the impact of vitamin D deficiency on sleep disorders.

METHODS

The main regulatory mechanisms of vitamin D on sleep are explained in this study. The literature was scanned to identify clinical trials and correlation studies showing an association between vitamin D deficiency and sleep disorders.

RESULTS

Vitamin D receptors and the enzymes that control their activation and degradation are expressed in several areas of the brain involved in sleep regulation. Vitamin D is also involved in the pathways of production of Melatonin, the hormone involved in the regulation of human circadian rhythms and sleep. Furthermore, vitamin D can affect sleep indirectly through non-specific pain disorders, correlated with alterations in sleep quality, such as restless legs syndrome and obstructive sleep apnea syndrome.

CONCLUSION

Vitamin D has both a direct and an indirect role in the regulation of sleep. Although vitamin D deficiency has been associated to sleep disorders, there is still scant evidence to concretely support the role of vitamin D supplementation in the prevention or treatment of sleep disturbances; indeed, more intervention studies are needed to better clarify these aspects.

Is hypovitaminosis D associated with fibromyalgia? A systematic review

CONTEXT

Recent findings have suggested a high prevalence of vitamin D deficiency or insufficiency in fibromyalgia (FM) patients despite the lack of clinical and pathophysiological evidence.

OBJECTIVE

A systematic review was conducted to examine the association between vitamin D status and FM, including the effect of vitamin D supplementation.

DATA SOURCE

PubMed, LILACS, Scopus, SciELO, Cochrane, and EMBASE were searched, from January 2000 to July 2018, using the descriptors "Fibromyalgia" and "Vitamin D."

STUDY SELECTION

Trials including FM patients in whom vitamin D levels were assessed were eligible for inclusion.

DATA EXTRACTION

Data comprised age, gender, country, aims, bias, diagnosis criteria, cutoff point, and status of vitamin D, together with FM symptoms and vitamin D supplementation protocol.

RESULTS

A total of 26 articles were selected. Most of the studies were found to present unreliable control groups and small samples. Experimental data on vitamin D supplementation indicated improvement in certain FM symptoms.

CONCLUSION

Prevalence of hypovitaminosis D in the FM population and the cause-effect relationship were inconclusive. Nevertheless, vitamin D supplementation may be considered as a co-adjuvant in FM therapy.

Randomized Trial on the Clinical Utility of a Novel Biomarker Panel to Identify Treatable Determinants of Chronic Pain

Millions suffer daily from chronic pain diagnosed anatomically and treated with opioids. Research shows that underlying nutritional, metabolic and oxidative stressors, which drive the development or worsening of chronic pain, are not diagnosed despite the fact that treatment of these primary pain pathways relieves pain and increases function. One of the main reasons for this gap in care is the lack of a simple diagnostic assay to help clinicians make these diagnoses. We examined the clinical utility of a urine-based pain biomarker panel. Primary care physicians were randomized into the test group and compared to controls. We measured their ability to make the diagnosis and treat a total of nine standardized patients, with common but challenging cases of chronic pain, over two rounds of data collection in a pre–post design using a fixed-effects model. Intervention doctors received educational materials on a novel pain biomarker panel after the baseline round and had access to biomarker test results. Provider responses were measured against evidence-based criteria. The two study arms at baseline provided similar, poor care for three different primary pain pathways: nutritional deficiencies (5.0% control versus 9.2% intervention treated, p = 0.208), metabolic abnormalities (1.0% control versus 0% for intervention treated, p = 0.314), and oxidative stress (1.2% control versus 0% intervention treated, p = 0.152). After the introduction of the Foundation Pain Index (FPI) biomarker test, physicians in the intervention group were 41.5% more likely to make the diagnosis of a micronutrient deficiency, 29.4% more likely to identify a treatable metabolic abnormality and 26.1% more likely to identify an oxidative stressor. These diagnostic and treatment improvements were seen across all three case types, ranging from a relative +54% (p = 0.004) for chronic neuropathic pain to +35% (p = 0.007) in chronic pain from other causes to +38% (p = 0.002) in chronic pain with associated mental health issues. Intervention doctors were also 75.1% more likely to provide a non-opioid treatment to patients on chronic opioids (O.R. 1.8, 95% C.I. 0.8–3.7), 62% less likely to order unnecessary imaging for their patients with low back pain (O.R. 0.38, 95% C.I. 0.15–0.97) and 66% less likely to order an unnecessary pain referral (O.R. 0.34, 95% C.I. 0.13–0.90). This experimental study showed significant clinical utility of a validated pain biomarker panel that determines nutritional deficiencies, metabolic abnormalities and oxidative stressors that drive underlying treatable causes of pain. When integrated into routine primary care practice, this testing approach could considerably improve diagnostic accuracy and provide more targeted, non-opioid treatments for patients suffering from chronic pain.

The effects of vitamin D supplementation on interictal serum levels of calcitonin gene-related peptide (CGRP) in episodic migraine patients: post hoc analysis of a randomized double-blind placebo-controlled trial

Background

Emerging evidence showed promising effects of vitamin D on headaches characteristics. Thus, it seems there is still a need for more researches to clarify the mechanisms by which this vitamin exerts anti-migraine effects.

Methods

The present study was conducted as a 16-week randomized double-blind placebo-controlled trial on 80 episodic migraine patients allocated in 2 parallel groups each consisted of 40 patients who received vitamin D 2000 IU/d or placebo. At baseline and after the intervention completion, headache diaries and migraine disability assessment questionnaire (MIDAS) were used to assess migraine related variables in patients. Also, interictal serum concentration of calcitonin gene-related peptide (CGRP) (as the dominant mediator of migraine pain pathogenesis) was evaluated using ELISA method.

Results

The mean (SD) of age in the vitamin D and placebo groups was 37 (8) and 38 (12) years, respectively. ANCOVA test adjusted for baseline values, and confounders showed vitamin D supplementation resulted in a significant improvement in MIDAS score after 12 weeks in the intervention group (21.49 (16.22–26.77)) compared to placebo (31.16 (25.51–36.82) P value: 0.016). Moreover, after controlling for baseline levels, and other variables using ANCOVA, CGRP level was appeared to be significantly lower following vitamin D supplementation (153.26 (133.03–173.49) ng/L) than the patients in the placebo arm (188.35 (167.15–209.54) ng/L) (P value = 0.022).

Conclusion

According to the current findings, vitamin D supplementation in episodic migraineurs, particularly in those with migraine with aura, may potentially improve migraine headache characteristics and disability probably through attenuating CGRP levels. Therefore, these results could provide a new insight into anti-nociceptive effects of vitamin D; however, more studies are required to confirm our findings.

Trial registration

The trial is registered in the Iranian registry of clinical trials (IRCT) at 11 July 2018, with IRCT code: IRCT20151128025267N6.

Serum Analysis in Patients with Temporomandibular Disorders: A Controlled Cross-Sectional Study in Norway

Temporomandibular disorder (TMD) is characterized by pain and dysfunction in the temporomandibular join (TMJ) and the masticatory apparatus. Associations with autoimmune diseases, inflammatory conditions, and nutrition deficiencies have been reported in previous studies of TMD patients. To evaluate essential proteins, hormones, electrolytes, and vitamins in serum from TMD patients, a standard blood sample analysis was performed in 60 TMD patients and 60 healthy controls matched for age and gender, retrieving 19 different analyses. We found that TMD patients had significantly higher values of hemoglobin (p=0.036), cobalamin (p=0.023), albumin (p=0.005), parathyroid hormone (PTH) (p=0.038), and vitamin D (p=0.005), and significantly lower values of creatinine (p=0.006) and potassium (p=0.011), compared to controls. In the TMD group, most of the determinants had a wider range, and several subjects, compared to the control group, had values outside the normal reference area. However, most of the TMD patients and controls had values within normal biological range. Our findings could not associate any severe systemic disease, malnutrition, or systemic inflammation with the TMD. Results from our study suggest that serum analyses should neither be used as a biomarker of TMD nor a diagnostic tool for an individual subject with TMD.

Oral loratadine in the management of G-CSF-induced bone pain: a pilot study

This pilot study aimed to ascertain if bone pain induced by granulocyte-colony stimulating factors (G-CSFs) can be alleviated or eliminated by oral antihistamine loratadine. Twelve patients with cancer receiving chemotherapy were included in the study. Daily pain increased between before treatment started and after cycle 1 in all patients. All 12 participants were started on loratadine on cycle 2; three patients were taking pain medications in addition to this as needed, which were ibruprofen (n=1) or tramadol (n=2). Pain decreased towards the later cycles after patients were started on loratadine in cycle 2, with the exception of one patient who also took tramadol as needed in cycle 3. Oral loratadine was found to be associated with pain reduction in patients with cancer receiving G-CSFs.

Vitamin D in migraine headache: a comprehensive review on literature

INTRODUCTION

As a primary headache, migraine has been established as the first leading disability cause worldwide in the subjects who aged less than 50 years. A variety of dietary supplements have been introduced for migraine complementary treatment. As an anti-inflammatory and antioxidant agent, vitamin D is one of these agents which has been of interest in recent years. Although higher prevalence of vitamin D deficiency/insufficiency has been highlighted among migraineurs compared to controls, there is not any consensus in prescribing vitamin D in clinical practice. Therefore, in the current review, in addition to observational and case-control studies, we also included clinical trials concerning the effects of vitamin D supplementation on migraine/headache.

METHODS

Based on a PubMed/MEDLINE and ScienceDirect database search, this review study includes published articles up to June 2019 concerning the association between migraine/headache and vitamin D status or supplementation.

RESULTS

The percentage of subjects with vitamin D deficiency and insufficiency among migraineurs and headache patients has been reported to vary between 45 and 100%. In a number of studies, vitamin D level was negatively correlated with frequency of headaches. The present findings show that supplementation with this vitamin in a dose of 1000-4000 IU/d could reduce the frequency of attacks in migraineurs.

CONCLUSION

It seems a high proportion of migraine patients might suffer from vitamin D deficiency/insufficiency. Further, the current evidence shows that in addition to routine drug therapy, vitamin D administration might reduce the frequency of attacks in migraineurs. However, these results have yet to be confirmed.

Chronic pain: a review of its epidemiology and associated factors in population-based studies

Chronic pain is a common, complex, and distressing problem that has a profound impact on individuals and society. It frequently presents as a result of a disease or an injury; however, it is not merely an accompanying symptom, but rather a separate condition in its own right, with its own medical definition and taxonomy. Studying the distribution and determinants of chronic pain allows us to understand and manage the problem at the individual and population levels. Targeted and appropriate prevention and management strategies need to take into account the biological, psychological, socio-demographic, and lifestyle determinants and outcomes of pain. We present a narrative review of the current understanding of these factors.

The Association Between Vitamin D and Premenstrual Syndrome: A Systematic Review and Meta-Analysis of Current Literature

A number of studies have assessed the association between vitamin D and premenstrual syndrome (PMS) in different populations, but the findings have been inconclusive. Herein, we systematically reviewed available observational and interventional evidence to elucidate the overall relationship between vitamin D and PMS. PubMed, Cochrane Library, ScienceDirect, Scopus, Google Scholar, and ISI Web of Science databases were searched for all available articles until September 2018. The Newcastle-Ottawa quality assessment scale and Jadad scale were used to assess the quality of the observational and interventional studies, respectively. A total of 16 studies out of 196 met our inclusion criteria and were included in the final analysis. Although no significant association between serum 25(OH)D and PMS (weighted mean difference (WMD) = 3.35; 95% confidence interval, -7.80 to 1.11; p = 0.14) was indicated in observational studies, vitamin D supplementation was effective in ameliorating PMS symptoms based upon findings from interventional studies. These results add to the existing literature supporting the fact that nutrition, especially vitamin D, plays an important role in women's health. Additional well-designed clinical trials should be considered in future research to develop firm conclusions on the efficacy of vitamin D on PMS. KEY TEACHING POINTS 5-8% of women experience severe PMS. Nutrition especially vitamin D plays an important role in the women's health. Vitamin D could exert significant clinical effects on PMS symptoms. This is a systematic review and meta-analysis in this regard.

Efficiency of vitamin D supplementation in patients with mechanical low back ache

BACKGROUND

Preliminary evidence suggests an association of hypovitaminosis D (hypo.D) with mechanical Low back ache (mLBA).

AIM

This study was designed to 1. Explore the relationship of hypovitaminosis D with mLBA in the absence of other confounding factors 2. Formulate and validate an appropriate treatment protocol and 3. Explore the differences in outcomes with various oral formulations of vitamin D available in Indian market.

MATERIALS & METHODS

Three randomised groups of patients with mLBA and hypo.D between 18 and 45 years of age without any co morbid conditions were studied for the effectiveness of adjunctive vit.D supplementation of 6,00,000 IUs (60,000 IUs/day for ten consecutive days) in the form of granule or nano syrup or soft gel capsule for the treatment of mLBA. Review evaluation of pain, functional disability and vit.D was done at three weeks and an additional evaluation of vit.D was done at nine months. Evaluation with 3,00,000 IUs of vit.D (60,000 IUs/day for five consecutive days) was done with nano syrup in a different cohort.

RESULTS

High prevalence of hypo.D (96%) was noted in patients with mLBA. Significant improvement was noted after supplementation of vit.D. The subjects of nano syrup group have shown significantly better improvement compared to others (P < 0.000). Non obese and chronic patients have shown significantly better results than their peers. Though there was significant difference in vit.D before treatment, the difference of improvement between the genders, deficiency and insufficiency, in-door and out-door, smokers and non smoker subgroups was not significant. Seasonal variation in vit.D before and after the treatment was significant.

CONCLUSION

Hypovitaminosis D can be a potential causative factor for mLBA in addition to the other known causes. Proper evaluation and adjunctive vit.D supplementation can effectively break the vicious cycle of low back ache with significant improvement in serum vit.D level, effective relief of pain and significant functional improvement without any adverse effects. Improvement in vit.D was not significantly related to its initial status and obese individuals have shown significantly lesser improvement. The results with nano syrup formulation were significantly better compared to others. Formulation based dosage adjustments assume significance in view of these results.

Association of the Vitamin D Level and Quality of School Life in Adolescents with Irritable Bowel Syndrome

There is no treatment of choice for irritable bowel syndrome, which affects up to 20% of school-aged children. This cross-sectional study evaluated the difference in the average vitamin D level between subtypes of irritable bowel syndrome, and the relationship between the vitamin D level as well as the severity of irritable bowel syndrome symptoms. We included 124 adolescents aged 10–17 years (68 boys, 56 girls; mean age 12.29 ± 1.92 years) from 2014 to 2016. Patients with irritable bowel syndrome were diagnosed by Rome III criteria and classified by clinical manifestation: irritable bowel syndrome with constipation (n = 29), irritable bowel syndrome with diarrhea (n = 63), and irritable bowel syndrome with constipation and diarrhea (n = 32). The severity of irritable bowel syndrome symptoms and school absence were evaluated. Vitamin D levels were measured by serum 25-hydroxyvitamin D. The chi-square test and analysis of variance were used. The patients’ average vitamin D level was 16.25 ± 6.58 ng/mL. There was a significant negative association of the 25-hydroxyvitamin D level with symptom severity and school absence (p = 0.022 and p < 0.001, respectively). Vitamin D supplementation could be considered as a choice of therapeutic method.

Vitamin D status and its influence on outcomes following major burn injury and critical illness

Vitamin D deficiency is common among the general population. It is also observed in up to 76% of critically ill patients. Despite the high prevalence of hypovitaminosis D in critical illness, vitamin D is often overlooked by medical staff as the clinical implications and consequences of vitamin D deficiency in acute contexts remain to be fully understood. Vitamin D has a broad range of pleotropic effects on various processes and systems including the immune-inflammatory response. 1α,25-dihydroxyvitamin D (1,25(OH)₂D), has been shown to promote a tolerogenic immune response limiting deleterious inflammatory effects, modulation of the innate immune system, and enhancement of anti-microbial peptides. Vitamin D deficiency is frequently observed in critically ill patients and has been related to extrinsic causes (i.e., limited sunlight exposure), magnitude of injury/illness, or the treatment started by medical doctors including fluid resuscitation. Low levels of vitamin D in critically ill patients have been associated with sepsis, organ failure, and mortality. Despite this, there are subpopulations of critical illness, such as burn patients, where the literature regarding vitamin D status and its influence on outcomes remain insufficient. Thermal injury results in damage to both burned and non-burned tissues, as well as induces an exaggerated and persistent immune-inflammatory and hypermetabolic response. In this review, we propose potential mechanisms in which burn injury affects the vitamin D status and summarizes current literature investigating the influence of vitamin D status on outcomes. In addition, we reviewed the literature and trials investigating vitamin D supplementation in critically ill patients and discuss the therapeutic potential of vitamin D supplementation in burn and critically ill patients. We also highlight current limitations of studies that have investigated vitamin D status and supplementation in critical illness. Thermal injury influences vitamin D status. More studies investigating vitamin D depletion in burn patients and its influence on prognosis, via standardized methodology, are required to reach definitive conclusions and influence clinical practice.

An in silico model of the effects of vitamin D3 on mycobacterium infected macrophage

Mycobacterium tuberculosis is a global health concern, causing over one million deaths a year. Alveolar macrophages, as the primary host cell of this intracellular bacterium, play an important role in the course of disease. Vitamin D3 is known to have a potent effect on macrophage behavior during infection, modulating the production of pro- and anti-inflammatory cytokines and immune effector molecules. In a vitamin D3 deficient host, the immune systems response to infection is greatly impaired. We used a quantitative systems biology approach to model the intracellular effects of vitamin D3 and compared our simulation output to our in vitro model of mycobacterium infection of macrophages in the presence and absence of Vitamin D3. Our in silico model results agreed with the in vitro assay results of interleukin-10, an anti-inflammatory protein whose production is known to be influenced by vitamin D3. This model will provide a platform for further investigation of the effects of vitamin D3 deficiency on host immune response to infection.

Is there role for vitamin D in the treatment of chronic pain?

Chronic pain is highly prevalent in the developed world, and levels of vitamin D are often lower among those with chronic pain conditions than those without. Supplementation of vitamin D has been investigated as a potential independent treatment for chronic pain. This paper presents an overview of the scientific evidence and provides recommendations for use of vitamin D in clinical practice with chronic pain patients.

Maternal 25-hydroxyvitamin D is inversely correlated with foetal serotonin

OBJECTIVE

Maternal vitamin D deficiency during pregnancy has been linked to impaired neurocognitive development in childhood. The mechanism by which vitamin D affects childhood neurocognition is unclear but may be via interactions with serotonin, a neurotransmitter involved in foetal brain development. In this study, we aimed to explore associations between maternal and foetal vitamin D concentrations, and foetal serotonin concentrations at term.

STUDY DESIGN AND MEASUREMENTS

Serum 25-hydroxyvitamin D (25(OH)D, nmol/l) and serotonin (5-HT, nmol/l) concentrations were measured in maternal and umbilical cord blood from mother-infant pairs (n = 64). Association between maternal 25(OH)D, cord 25(OH)D and cord serotonin was explored using linear regression, before and after adjusting for maternal serotonin levels. We also assessed the effects of siRNA knockdown of the vitamin D receptor (VDR) and administration of 10 nm 1,25-dihydroxyvitamin D₃ on serotonin secretion in human umbilical vein endothelial cells (HUVECs) in vitro.

RESULTS

We observed an inverse relationship between both maternal and cord 25(OH)D concentrations with cord serotonin concentrations. The treatment of HUVECs with 1,25-dihydroxyvitamin D₃ in vitro decreased the release of serotonin (193·9 ±14·8 nmol/l vs 458·9 ± 317·5 nmol/l, control, P < 0·05). Conversely, inactivation of VDR increased serotonin release in cultured HUVECs.

CONCLUSIONS

These observations provide the first evidence of an inverse relationship between maternal 25(OH)D and foetal serotonin concentrations. We propose that maternal vitamin D deficiency increases foetal serotonin concentrations and thereby contributes to longer-term neurocognitive impairment in infants and children.

Serum protein changes in a rat model of chronic pain show a correlation between animal and humans

In previous works we showed the overexpression of some proteins in biological fluids from patients suffering chronic pain. In this proteomic study we analysed serum from a rat model of neuropathic pain obtained by the chronic constriction injury (CCI) of sciatic nerve, at two time intervals, 2 and 5 weeks after the insult, to find proteins involved in the expression or mediation of pain. Sham-operated and CCI rats were treated with saline or indomethacin. Two weeks after ligation, we identified three serum proteins overexpressed in CCI rats, two of which, alpha-1-macroglobulin and vitamin D-binding protein (VDBP), remained increased 5 weeks post-surgery; at this time interval, we found increased levels of further proteins, namely apolipoprotein A-I (APOA1), apolipoprotein E (APOE), prostaglandin-H2 D-isomerase (PTGDS) and transthyretin (TTR), that overlap the overexpressed proteins found in humans. Indomethacin treatment reversed the effects of ligation. The qPCR analysis showed that transcript levels of APOA1, APOE, PTGDS and VDBP were overexpressed in the lumbar spinal cord (origin of sciatic nerve), but not in the striatum (an unrelated brain region), of CCI rats treated with saline 5 weeks after surgery, demonstrating that the lumbar spinal cord is a possible source of these proteins.

Vitamin D in Fibromyalgia: A Causative or Confounding Biological Interplay?

Fibromyalgia (FM) is a chronic syndrome with an increasing prevalence, characterized by widespread musculoskeletal pain in combination with a variety of cognitive symptoms and fatigue. A plethora of scientific evidence that has accumulated during the last decades, resulted in a significant improvement of the understanding of the pathophysiology of the disease. However, current therapeutic approaches in patients with FM remains a multidimensional approach including patient education, behavioral therapy, exercise, pain management, and relief of chronic symptoms, rather than the use drug therapies, based on the mechanisms of disease development. Vitamin D, a fat-soluble vitamin derived mainly from skin synthesis through ultraviolet radiation, has been recognized to manifest a plethora of extraskeletal actions, apart from its fundamental role in skeletal and calcium homeostasis, including modulation of cell growth, neuromuscular actions, and potential anti-inflammatory properties. Recent findings indicate that hypovitaminosis D to be highly prevalent in patients with FM. Supplementation studies are limited so far, indicating potential beneficial effects on pain and severity of the disease, however specific recommendations are lacking. This review aims to summarize and critically appraise data regarding the pathophysiological interplay between vitamin D and FM, available results from observational and supplementation studies so far, with a clinical discourse on current knowledge gaps and future research agenda.

Relationship between FokI polymorphism in the vitamin D receptor gene and fibromyalgia syndrome

AIM

The aim of this study was to evaluate the vitamin D receptor (VDR) gene FokI polymorphism frequencies distribution in subjects with fibromyalgia syndrome (FMS) compared to healthy controls.

METHOD

Using a case-control design, 100 female patients, who were diagnosed with FMS according to the American College of Rheumatology criteria and 100 healthy female subjects were enrolled in this study. FokI polymorphisms of the VDR gene were analyzed by restriction fragment length polymorphisms (RFLP) in both groups.

RESULTS

No significant differences in the frequencies distribution of both genotype and alleles of the FokI polymorphism in the VDR gene were observed between the two groups.

CONCLUSION

The relationship between VDR gene FokI polymorphism and FMS, particularly in Turkish women, could not be determined in this study. However, further studies with larger patient numbers may be needed to prove a relation between VDR gene polymorphism and FMS.

The evaluation of vitamin D levels in patients with carpal tunnel syndrome

The aim of this study was to evaluate the relationship between 25-hydroxyvitamin D (25(OH)D) levels and carpal tunnel syndrome (CTS). 25(OH)D levels were checked in 108 consecutive patients with CTS symptoms and 52 healthy controls. All patients underwent nerve conduction studies and completed Boston Carpal Tunnel Questionnaire (BQ) symptom severity and functional status scales to quantify symptom severity, pain status and functional status. There were 57 patients with electrophysiological confirmed CTS (EP+ group) and 51 electrophysiological negative symptomatic patients (EP- group). 25(OH) D deficiency (25(OH)D < 20 ng/ml) was found in 96.1 % of EP- group, in 94.7 % of EP+ group and in 73.8 % of control group. 25(0H) D level was found significantly lower both in EP+ and EP- groups compared to control group (p = 0.006, p < 0.001, respectively). Although mean vitamin D level in EP- group was lower than EP+ group, statistically difference was not significant between EP+ and EP- groups (p = 0.182). BQ symptom severity and functional status scores and BQ pain sum score were not significantly different between EP+ and EP- groups. We found no correlation with 25(OH) D level for BQ symptom severity, functional status and pain sum scores. 25(OH) D deficiency is a common problem in patients with CTS symptoms. As evidenced by the present study, assessment of serum 25(OH)D is recommended in CTS patients even with electrophysiological negative results.

Vitamin D for the treatment of chronic painful conditions in adults

BACKGROUND

This review is an update of a previously published review in the Cochrane Database of Systematic Reviews (Issue 1, 2010) on 'Vitamin D for the treatment of chronic painful conditions in adults'.Vitamin D is produced in the skin after exposure to sunlight and can be obtained through food. Vitamin D deficiency has been linked with a range of conditions, including chronic pain. Observational and circumstantial evidence suggests that there may be a role for vitamin D deficiency in the aetiology of chronic painful conditions.

OBJECTIVES

To assess the efficacy and safety of vitamin D supplementation in chronic painful conditions when tested against placebo or against active comparators.

SEARCH METHODS

For this update, we searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, and EMBASE to February 2015. This was supplemented by searching the reference lists of retrieved articles, reviews in the field, and online trial registries.

SELECTION CRITERIA

We included studies if they were randomised double-blind trials of vitamin D supplementation compared with placebo or with active comparators for the treatment of chronic painful conditions in adults.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected the studies for inclusion, assessed methodological quality, and extracted data. We did not undertake pooled analysis due to the heterogeneity of the data. Primary outcomes of interest were pain responder outcomes, and secondary outcomes were treatment group average pain outcomes and adverse events.

MAIN RESULTS

We included six new studies (517 participants) in this review update, bringing the total of included studies to 10 (811 participants). The studies were heterogeneous with regard to study quality, the chronic painful conditions that were investigated, the dose of vitamin D given, co-interventions, and the outcome measures reported. Only two studies reported responder pain outcomes; the other studies reported treatment group average outcomes only. Overall, there was no consistent pattern that vitamin D treatment was associated with greater efficacy than placebo in any chronic painful condition (low quality evidence). Adverse events and withdrawals were comparatively infrequent, with no consistent difference between vitamin D and placebo (good quality evidence).

AUTHORS' CONCLUSIONS

The evidence addressing the use of vitamin D for chronic pain now contains more than twice as many studies and participants than were included in the original version of this review. Based on this evidence, a large beneficial effect of vitamin D across different chronic painful conditions is unlikely. Whether vitamin D can have beneficial effects in specific chronic painful conditions needs further investigation.