Serum levels of vitamin D are not associated with future risk of venous thromboembolism

Causality assessment of circulating Vitamin D level on venous thromboembolism: A Mendelian randomization study

BACKGROUND AND AIMS

The associations of vitamin D level with venous thromboembolism (VTE) reported in observational studies, whereas these causal associations were uncertain in European population. Therefore, we used Mendelian randomization (MR) method to explore the causal associations between 25-hydroxyvitamin D (25(OH)D) concentrations and the risk of VTE and its subtypes [including deep vein thrombosis (DVT) and pulmonary embolism (PE)].

METHODS AND RESULTS

We used three kinds of genetic instruments to proxy the exposure of 25(OH)D, including genetic variants significantly associated with 25(OH)D, expression quantitative trait loci of 25(OH)D target genes, and genetic variants within or nearby 25(OH)D target genes. MR analyses did not provide any evidence for the associations of 25(OH)D levels with VTE and its subtypes (p > 0.05). The summary-data-based MR (SMR) analyses indicated that elevated expression of VDR was associated with decreased risk of VTE (OR = 0.81; 95% CI, 0.65-0.998; p = 0.047) and PE (OR = 0.67; 95% CI, 0.50-0.91; p = 0.011), and expression of AMDHD1 was associated with PE (OR = 0.93; 95% CI, 0.88-0.99; p = 0.027). MR analysis provided a significant causal effect of 25(OH)D level mediated by gene AMDHD1 on PE risk (OR = 0.09; 95% CI, 0.01-0.60; p = 0.012).

CONCLUSION

Our MR analysis did not support causal association of 25(OH)D level with the risk of VTE and its subtypes. In addition, the expression of VDR and AMDHD1 involved in vitamin D metabolism showed a strong association with VTE or PE and might represent targets for these conditions.

Is Circulating Vitamin D Status Associated with the Risk of Venous Thromboembolism? A Meta-Analysis of Observational Studies

BACKGROUND

Although vitamin D is antithrombotic, associations between serum vitamin D status and the risk of venous thromboembolism (VTE) remain inconsistent.

METHODS

We searched the EMBASE, MEDLINE, Cochrane Library, and Google Scholar databases from inception to June 2022 to identify observational studies examining associations between vitamin D status and VTE risk in adults. The primary outcome presented as odds ratio (OR) or hazard ratio (HR) was the association of vitamin D levels with the risk of VTE. Secondary outcomes included the impacts of vitamin D status (i.e., deficiency or insufficiency), study design, and the presence of neurological diseases on the associations.

RESULTS

Pooled evidence from a meta-analysis of sixteen observational studies, including 47648 individuals published from 2013 to 2021, revealed a negative relationship between vitamin D levels and the risk of VTE either based on OR (1.74, 95% confidence interval (CI): 1.37 to 2.20, p < 0.00001; I² = 31%, 14 studies, 16074 individuals) or HR (1.25, 95% CI: 1.07 to 1.46, p = 0.006; I² = 0%, 3 studies, 37,564 individuals). This association remained significant in subgroup analyses of the study design and in the presence of neurological diseases. Compared to individuals with normal vitamin D status, an increased risk of VTE was noted in those with vitamin D deficiency (OR = 2.03, 95% CI: 1.33 to 3.11) but not with vitamin D insufficiency.

CONCLUSIONS

This meta-analysis demonstrated a negative association between serum vitamin D status and the risk of VTE. Further studies are required to investigate the potential beneficial effect of vitamin D supplementation on the long-term risk of VTE.

The Role of Vitamin D in the Relationship Between Gender and Deep Vein Thrombosis Among Stroke Patients

Introduction: Accumulating evidence had demonstrated that females had a higher risk of deep vein thrombosis (DVT) than males, but the mechanism was still unknown. Vitamin D was found to play an essential role in DVT, and gender may influence the serum vitamin D levels. This study aimed to explore whether vitamin D played a role in the gender difference in DVT.

Materials and Methods: A total of 444 patients with acute stroke were recruited, which were divided into the DVT group (n = 222) and the non-DVT group (n = 222). Serum vitamin D levels were measured after admission and were split into three categories, including deficiency (<50 nmol/L), insufficiency (52.5–72.5 nmol/L), and sufficiency (more than 75 nmol/L). Hierarchical regression analysis was adopted to analyze the relationship between gender and DVT, controlling the confounding factors.

Results: Females showed a higher proportion of DVT than males (60.7 vs. 42.5%, p < 0.001), and lower serum vitamin D levels than males (53.44 ± 16.45 vs. 69.43 ± 23.14, p < 0.001). Moreover, serum vitamin D levels were lower in the DVT group than in the non-DVT group (59.44 ± 19.61 vs. 66.24 ± 23.86, p < 0.001). Besides, the DVT group showed a lower proportion of vitamin D sufficiency than the non-DVT group (21.2 vs. 32.9%, p < 0.05). Hierarchical regression analysis showed that females had 2.083-fold (p < 0.001, unadjusted model) and 1.413-fold (p = 0.155, adjusted model) risk to develop DVT. In addition, the sufficiency status of vitamin D showed an independent protective effect on DVT (unadjusted model OR, 0.504, p = 0.004; adjusted model OR, 0.686, p = 0.011).

Conclusion: Females had a higher risk of DVT than males, and vitamin D may play an essential role in this relationship. Further studies are needed to explore whether vitamin D supplementation could reduce DVT risk in stroke patients, especially females.

Vitamin D status and complications, readmissions, and mortality after hip fracture

Low vitamin D in patients with hip fracture is common. In the present study, 407 of 872 (47%) patients had serum calcidiol less than 50 nmol/L. Patients with low vitamin D had more delirium, more new hip fractures, and more medical readmissions, but not more orthopedic complications after 1 year.

INTRODUCTION

We wanted to study the relation between vitamin D level and postoperative orthopedic and medical complications in patients with hip fracture. In addition, we investigated the effect of giving a single-dose cholecalciferol 100.000 IU.

METHODS

Data were taken from the local hip fracture register. Logistic regression analyses including vitamin D level and potentially confounding variables were performed for complications and readmissions.

RESULTS

A total of 407 (47%) of 872 included hip fractures had low vitamin D at baseline. A total of 155 (18%) developed delirium, and the risk was higher in vitamin D-deficient patients (odds ratio (OR) 1.48, 95% confidence interval (CI) 1.04 to 2.12; p = 0.03). A total of 261 (30%) were readmitted for non-hip-related conditions. Low vitamin D was associated with a higher risk of medical readmissions within 30 days (OR 1.64 (1.03 to 2.61); p = 0.036) and 12 weeks (OR 1.47 (95% CI 1.02 to 2.12); p = 0.039). There was a higher risk of a new hip fracture (OR 2.84 (95% CI 1.15 to 7.03) p = 0.024) in vitamin D-deficient patients. A total of 105 (12%) developed at least one orthopedic complication, with no correlation to baseline vitamin D. Among vitamin D-deficient patients, those receiving a single-dose of 100.000 IU cholecalciferol had fewer orthopedic complications (OR 0.32 (95% CI 0.11 to 0.97) p = 0.044) the first 30 days after surgery.

CONCLUSION

Low vitamin D at admission for hip fracture increased the risk of delirium, a new hip fracture, and medical readmissions, but not orthopedic complications. The role of vitamin D supplementation to prevent orthopedic complications requires further study.

Exploring the link between vitamin D and clinical outcomes in COVID-19

The immunomodulating role of vitamin D might play a role in COVID-19 disease. We studied the association between vitamin D and clinical outcomes in COVID-19 patients. This is a retrospective cohort study on COVID-19 patients with documented vitamin D levels within the last year. Vitamin D levels were grouped as ≥ 20 ng/mL or < 20 ng/mL. Main outcomes were mortality, need for mechanical ventilation, new DVT or pulmonary embolism, and ICU admission. A total of 270 patients (mean ± SD) age, 63.81 (14.69) years); 117 (43.3%) males; 216 (80%) Blacks; 139 (51.5%) in 65 and older age group were included. Vitamin D levels were less than 20 ng/mL in 95 (35.2%) patients. During admission, 72 patients (26.7%) died, 59 (21.9%) needed mechanical ventilation, and 87 (32.2%) required ICU. Vitamin D levels showed no significant association with mortality (OR = 0.69; 95% CI, 0.39-1.24; P = 0.21), need for mechanical ventilation (OR = 1.23; 95% CI, 0.68-2.24; P = 0.49), new DVT or PE(OR= 0.92; 95% CI, 0.16-5.11; P = 1.00) or ICU admission (OR = 1.38; 95% CI, 0.81-2.34; P = 0.23). We did not find any significant association of vitamin D levels with mortality, the need for mechanical ventilation, ICU admission and the development of thromboembolism in COVID-19 patients.NEW & NOTEWORTHY Low vitamin D has been associated with increased frequency and severity of respiratory tract infections in the past. Current literature linking clinical outcomes in COVID-19 with low vitamin D is debatable. This study evaluated the role of vitamin D in severe disease outcomes among COVID-19 patients and found no association of vitamin D levels with mortality, the need for mechanical ventilation, ICU admission, and thromboembolism in COVID-19.

Association between vitamin D levels and lower-extremity deep vein thrombosis: a case-control study

BACKGROUND

Vitamin D has relationships with pathogenesis and inflammation pathways in many diseases. Its deficiency may make clinicians think not only of supplementation but also of presence of other diseases.

OBJECTIVE

To investigate the relationship between vitamin D levels and deep vein thrombosis (DVT), given that reduced levels are related to increased risk of cardiovascular diseases.

DESIGN AND SETTING

Case-control study conducted in the cardiovascular surgery and family medicine departments of a hospital in Turkey.

METHODS

A total of 280 participants were included: 140 each in the DVT and control groups. Basic clinical characteristics, comorbidities and serum 25-hydroxyvitamin D (25(OH)D) levels were recorded and then compared between the groups. Serum 25(OH)D levels were also evaluated separately in three subgroups (sufficient, insufficient and deficient).

RESULTS

Serum 25(OH)D levels were significantly lower in the DVT group than in the controls (P < 0.001). Females in the DVT group had lower 25(OH)D levels than those in the control group (P = 0.002). Nonetheless, the median 25(OH)D level (16.41 ng/ml) of the control group was still below the reference value. Logistic regression analysis showed that 25(OH)D was a significant predictor of DVT. Weight, height and body mass index, which all presented interaction, were significant in the logistic regression analysis but not in individual analyses.

CONCLUSION

The serum vitamin D levels of DVT patients were lower than those of controls. If the results obtained from our study are supported by further large-scale randomized controlled trials, vitamin D replacement may be brought into the agenda for protection against DVT.

Association between serum vitamin D levels and venous thromboembolism (VTE): A systematic review and meta-analysis of observational studies

OBJECTIVE

Although many studies have attempted to unravel the relationship between vitamin D deficiency and the incidence of VTE, the results remained inconsistent. To address this discrepancy, we performed a systematic review and meta-analysis to precisely disentangle the relationship between serum vitamin D levels and VTE risk.

METHODS

The Web of Science, Scopus, PubMed/Medline, Embase, and Google Scholar databases were searched for all available observational studies that reported the risk of venous thromboembolism (VTE) based on serum vitamin D levels categories. The search was performed up to March 2020.

RESULTS

Seven studies were included. The overall analysis showed a significantly increased risk of VTE in subjects with low levels of serum vitamin D compared with those with normal vitamin D levels (RR = 1.34; 95% CI: 1.07-1.69; P = 0.011). In a sensitivity analysis, we did not observe a significant effect of any individual study on the combined effect sizes. Nevertheless, significant heterogeneity was present among the studies (Cochrane Q test, p = 0.018, I² = 61%). In the stratified analysis, low vitamin D levels were positively associated with an increased risk of VTE in prospective population-based studies (RR = 1.31; 95% CI: 1.06-1.61; P = 0.010) and in subjects below 60 years old (RR = 1.28; 95% CI: 1.07-1.54; P = 0.060).

CONCLUSION

our systematic review and meta-analysis showed that a low serum vitamin D level was indeed associated with an increased risk of VTE.

Venous Thromboembolism is Associated With Lack of Vitamin D Supplementation in Patients With Spinal Cord Injury and Low Vitamin D Levels

BACKGROUND

The role of vitamin D in the pathogenesis of venous thromboembolism (VTE) and prevalence of low vitamin D (LVitD) in spinal cord injury (SCI) has motivated vitamin D testing and supplementation. This is an exploratory study of data collected at a time before the routine clinical practice of vitamin D supplementation, allowing for evaluation of the natural history of vitamin D levels in patients with SCI.

OBJECTIVE

To determine if vitamin D supplementation in persons with SCI and LVitD levels is associated with decreased prevalence of VTE.

DESIGN

Retrospective cohort study.

SETTING

Rehabilitation Center at a Level I Trauma Center.

PARTICIPANTS

Patients with SCI admitted to acute inpatient rehabilitation (N = 282).

MAIN OUTCOME MEASURES

VTE prevalence in patients with LVitD levels, grouped by presence or absence of vitamin D supplementation.

RESULTS

Of the acute inpatient SCI population, 80% (227/282) of patients demonstrated vitamin D levels <30 ng/mL (LVitD). Although the incidence of VTE was almost double in the LVitD group, 19% (43/227) of the patients in the LVitD group had VTE versus 9% (5/55) of patients with vitamin D levels ≥30 ng/mL (normal VitD [NVitD]); this difference was not statistically significant (P = .108, Cramer's V = .104). When the role of vitamin D supplementation was analyzed, individuals in the LVitD group who received no vitamin D supplementation (LVitDSuppNegative) had a higher incidence of VTE (statistically significant) compared to the LVitD group with vitamin D supplementation (LVitDSuppPositive) (24% [42/178] vs. 2% [1/49]) (P < .001, Cramer's V = .226). In post hoc exploratory analyses, the VTE rate of patients in the LVitDSuppNegative group was noted to be significantly higher than that in all other patient groups combined (P < .001, Cramer's V = .229). A binary logistic regression model incorporating clinical covariates also showed this grouping to be significant.

CONCLUSION

A significant association appears to exist between lack of vitamin D supplementation and VTE occurrence in persons with acute SCI and LVitD levels.

LEVEL OF EVIDENCE

III.

Low Vitamin D Levels Are Associated With the Development of Deep Venous Thromboembolic Events in Patients With Ischemic Stroke

The objective is to determine whether a low serum 25-hydroxyvitamin D (25(OH)D) level is associated with an increased incidence of deep venous thromboembolic events in patients with ischemic stroke. One hundred eighty persons admitted consecutively for inpatient rehabilitation at the Department of Rehabilitation of the First Affiliated Hospital of Wenzhou Medical University with a diagnosis of ischemic stroke from January 2015 to December 2015 were enrolled. The following demographic data were collected: age, sex, body mass index, and history of risk factors. The levels of 25(OH)D and the presence of deep vein thrombosis (DVT) by routine duplex imaging were also recorded. The value of 25(OH)D needed to predict DVT was analyzed using logistic regression analysis, after adjusting for the possible confounders. We found that 80% of patients admitted to the acute inpatient rehabilitation unit had low levels of vitamin D. Forty-seven patients had DVT, and the incidence of DVT was 26.1% within 3 weeks after the stroke event. With all patients taken together, DVT occurrence as a dependent variable with the sufficient group as the reference used for vitamin D levels in the logistic analysis, deficiency of vitamin D was independently associated with the development of DVT (odds ratio = 4.683, 95% confidence interval: 1.396-15.703, P = .012). In conclusion, low serum 25(OH)D levels were independent predictors of DVT in patients with ischemic stroke during inpatient rehabilitation stay in China. This finding reveals the critical role played by 25(OH)D in the pathogenesis of DVT.

The anti-thrombotic effects of vitamin D and their possible relationship with antiphospholipid syndrome

The importance of the immunomodulatory effects of vitamin D has recently been associated with autoimmune and chronic inflammatory diseases. Vitamin D deficiency has been linked to the development of autoimmune conditions. Antiphospholipid syndrome is an autoimmune disease characterized by thrombotic events and obstetric complications in patients with antiphospholipid antibodies. Current data show that patients with antiphospholipid syndrome have a high prevalence of vitamin D deficiency even without classic risk factors. Several studies have suggested vitamin D may have anti-thrombotic functions. In antiphospholipid syndrome, low vitamin D serum levels have been associated with thrombotic manifestations, suggesting a possible protective role of vitamin D in antiphospholipid syndrome. This literature review presents current evidence on the haemostatic functions of vitamin D and their possible relationship with the clinical manifestations of antiphospholipid syndrome.

Vitamin-D concentrations, cardiovascular risk and events - a review of epidemiological evidence

Vitamin D has long been established as an elemental factor of bone physiology. Beyond mineral metabolism, the expression of the vitamin D receptor has been identified throughout the cardiovascular (CV) system. Experimental studies showed beneficial effects of vitamin D on heart and vessels, but vitamin D intoxication in animals also led to hypercalcemia and vascular calcification. Our knowledge has been extended by epidemiological studies that showed that 25-hydroxyvitamin D (25(OH)D) levels are inversely associated with an increased CV risk itself, but also with established CV risk factors, such as arterial hypertension, endothelial dysfunction and atherosclerosis. Conversely, randomized controlled trials could not document significant and consistent effects of vitamin D supplementation on CV risk or events. Potential explanations may lie in differences in reference ranges or the possibility that low vitamin D in CV disease is only an epiphenomenon. In the latter case, the key question is why low 25(OH)D levels are such a strong predictor of health. While we wait for new data, the current conclusion is that vitamin D is a strong risk marker for CV risk factors and for CV diseases itself.

Avoidance of sun exposure as a risk factor for major causes of death: a competing risk analysis of the Melanoma in Southern Sweden cohort

OBJECTIVE

Women with active sunlight exposure habits experience a lower mortality rate than women who avoid sun exposure; however, they are at an increased risk of skin cancer. We aimed to explore the differences in main causes of death according to sun exposure.

METHODS

We assessed the differences in sun exposure as a risk factor for all-cause mortality in a competing risk scenario for 29 518 Swedish women in a prospective 20-year follow-up of the Melanoma in Southern Sweden (MISS) cohort. Women were recruited from 1990 to 1992 (aged 25-64 years at the start of the study). We obtained detailed information at baseline on sun exposure habits and potential confounders. The data were analysed using modern survival statistics.

RESULTS

Women with active sun exposure habits were mainly at a lower risk of cardiovascular disease (CVD) and noncancer/non-CVD death as compared to those who avoided sun exposure. As a result of their increased survival, the relative contribution of cancer death increased in these women. Nonsmokers who avoided sun exposure had a life expectancy similar to smokers in the highest sun exposure group, indicating that avoidance of sun exposure is a risk factor for death of a similar magnitude as smoking. Compared to the highest sun exposure group, life expectancy of avoiders of sun exposure was reduced by 0.6-2.1 years.

CONCLUSION

The longer life expectancy amongst women with active sun exposure habits was related to a decrease in CVD and noncancer/non-CVD mortality, causing the relative contribution of death due to cancer to increase.

Vitamin D and cardiovascular disease prevention

Vitamin D is a precursor of the steroid hormone calcitriol that is crucial for bone and mineral metabolism. Both the high prevalence of vitamin D deficiency in the general population and the identification of the vitamin D receptor in the heart and blood vessels raised interest in the potential cardiovascular effects of vitamin D. Experimental studies have demonstrated various cardiovascular protective actions of vitamin D, but vitamin D intoxication in animals is known to induce vascular calcification. In meta-analyses of epidemiological studies, vitamin D deficiency is associated with an increased cardiovascular risk. Findings from Mendelian randomization studies and randomized, controlled trials (RCTs) do not indicate significant effects of a general vitamin D supplementation on cardiovascular outcomes. Previous RCTs, however, were not adequately designed to address extraskeletal events, and did not focus on vitamin D-deficient individuals. Therefore, currently available evidence does not support cardiovascular benefits or harms of vitamin D supplementation with the commonly used doses, and whether vitamin D has cardiovascular effects in individuals with overt vitamin D deficiency remains to be evaluated. Here, we provide an update on clinical studies on vitamin D and cardiovascular risk, discuss ongoing vitamin D research, and consider the management of vitamin D deficiency from a cardiovascular health perspective.

Identification of Regulatory Mutations in SERPINC1 Affecting Vitamin D Response Elements Associated with Antithrombin Deficiency

Antithrombin is a crucial anticoagulant serpin whose even moderate deficiency significantly increases the risk of thrombosis. Most cases with antithrombin deficiency carried genetic defects affecting exons or flanking regions of SERPINC1.We aimed to identify regulatory mutations inSERPINC1 through sequencing the promoter, intron 1 and 2 of this gene in 23 patients with antithrombin deficiency but without known genetic defects. Three cases with moderate antithrombin deficiency (63–78%) carried potential regulatory mutations. One located 200 bp before the initiation ATG and two in intron 1. These mutations disrupted two out of five potential vitamin D receptor elements (VDRE) identified in SERPINC1 with different software. One genetic defect, c.42-1060_-1057dupTTGA, was a new low prevalent polymorphism (MAF: 0.01) with functional consequences on plasma antithrombin levels. The relevance of the vitamin D pathway on the regulation of SERPINC1 was confirmed in a cell model. Incubation of HepG2 with paricalcitol, a vitamin D analog, increased dose-dependently the levels of SERPINC1transcripts and antithrombin released to the conditioned medium. This study shows further evidence of the transcriptional regulation of SERPINC1 by vitamin D and first describes the functional and pathological relevance of mutations affecting VDRE of this gene. Our study opens new perspectives in the search of new genetic defects involved in antithrombin deficiency and the risk of thrombosis as well as in the design of new antithrombotic treatments.

Serum levels of 25(OH)D are not associated with venous thromboembolism in the elderly population. A case-control study

The prevalence of both vitamin D deficiency and venous thromboembolism (VTE) is important in the elderly. Previous studies have provided evidence for a possible association between vitamin D status and the risk of VTE. Thus, we aimed to investigate the association between vitamin D levels and VTE in the population aged 75 and over included in the EDITH case-control study. The association between vitamin D status and VTE was analysed. We also analysed the monthly and seasonal variations of VTE and vitamin D. Between May 2000 and December 2009, 340 elderly patients (mean age 81.5 years, 32% men) with unprovoked VTE and their controls were included. The univariate and multivariate analysis found no significant association between serum levels of vitamin D and the risk of unprovoked VTE. In the unadjusted analysis, a higher BMI was statistically associated with an increased risk of VTE (OR 1.09; 95% CI 1.05-1.13) whereas a better walking capacity and living at home were associated with a decreased rate of VTE: OR 0.57; 95% CI 0.36-0.90 and 0.40; 95% CI 0.25-0.66, respectively. Although not significant, more VTE events occurred during winter (p=0.09). No seasonal variations of vitamin D levels were found (p=0.11). In conclusion, in contrast with previous reports our findings suggest that vitamin D is not associated with VTE in the elderly population.

Vitamin supplementation on the risk of venous thrombosis: results from the MEGA case-control study

BACKGROUND

Whether vitamin supplements decrease venous thrombosis risk is controversial. Previous reports did not all take confounding fully into account, either by randomization or by extensive adjustment.

OBJECTIVE

The aim of our study was to determine whether vitamin supplementation decreases the risk of venous thrombosis.

DESIGN

A large case-control study included 2506 patients with venous thrombosis, 2506 partner controls, and 2684 random-digit dialing (RDD) controls. When patients were compared with RDD controls, unconditional logistic regression was used to calculate ORs with 95% CIs. When patients were compared with partner controls, conditional logistic regression was used, providing further adjustment for unmeasured confounding.

RESULTS

Vitamin use yielded a 37% lower risk of venous thrombosis than no vitamin use (OR: 0.63; 95% CI: 0.57, 0.70) when comparing patients with RDD controls. Adjustment for several putative confounders did not change the estimate (OR: 0.68; 95% CI: 0.61, 0.77). The fully adjusted ORs for vitamin A, vitamin B-6, vitamin B-12, folic acid, vitamin C, vitamin D, vitamin E, and multivitamin use were in the same range. However, when patients were compared with partner controls, ORs attenuated to unity. Results were similar for provoked and unprovoked events, as well as for deep vein thrombosis and pulmonary embolism.

CONCLUSIONS

After extensive adjustments, vitamin supplementation was no longer associated with a decreased risk of venous thrombosis in this study. Previous positive results may have been spurious as a result of uncontrolled confounding.

The effect of calcium plus vitamin D supplementation on the risk of venous thromboembolism. From the Women's Health Initiative Randomized Controlled Trial

Experimental and epidemiological studies suggest that vitamin D may be implicated in haemostatic regulations and influence the risk of venous thromboembolism (VTE). The aim of this study was to investigate whether oral supplementation of vitamin D3 combined with calcium reduces the risk of VTE. In the randomised, double-blind, placebo-controlled Women's Health Initiative Calcium Plus Vitamin D trial, 36,282 postmenopausal women aged 50-79 years were randomised to receive 1,000 mg of calcium carbonate and 400 IU of vitamin D3 per day (n=18,176) or a matching placebo (n=18,106) during an average of seven years. This secondary analysis of the trial compared the incidence of VTE by treatment group using an intention-to-treat Cox regression analysis. The incidence of VTE did not differ between women randomised to calcium plus vitamin D and women randomised to placebo (320 vs 348 VTE events, respectively; hazard ratio (HR) 0.92, 95 % confidence interval (CI) 0.79-1.07). Results were not modified in an analysis using inverse-probability weights to take non-adherence into account (HR 0.94, 95 %CI 0.73-1.22) or in multiple subgroups. Whereas the risk of a non-idiopathic VTE was similar between groups, the risk of idiopathic VTE was lower in women randomised to calcium plus vitamin D (40 vs 65 events; HR 0.62, 95 %CI 0.42-0.92). In conclusion, daily supplementation with 1,000 mg of calcium and 400 IU of vitamin D did not reduce the overall incidence of VTE in generally healthy postmenopausal women. However, the observed reduced risk of idiopathic VTE in women randomised to calcium and vitamin D warrants further investigations.

The Effect of Vitamin D Supplementation on Thrombin Generation Assessed by the Calibrated Automated Thrombogram

Observational and in vitro studies suggest that vitamin D may have antithrombotic activity. This study aimed to examine the relationship between vitamin D supplementation and thrombin generation. Serum 25-hydroxyvitamin D (25(OH)D) and thrombin generation parameters were measured in 73 healthy volunteers. Participants with serum 25(OH)D <50 nmol/L (n = 53) were treated with vitamin D3and tested for 25(OH)D and thrombin generation at the end of treatment. Lag time and time to peak decreased after treatment by a mean of -0.49 ± 0.51 minute (P< .001) and -0.76 ± 0.70 minute (P< .001), respectively, whereas endogenous thrombin potential and peak height increased after treatment by a mean of 170.1 ± 339.8 nmol/L minute (P= .001) and 34.2 ± 47.8 nmol/L (P< .001), respectively. Treatment with vitamin D supplementation seems to have prothrombotic effect in patients with vitamin D insufficiency. These findings should be interpreted with caution and need to be replicated in future studies.

Serum 25-hydroxyvitamin D and risk of venous thromboembolism: the Atherosclerosis Risk in Communities (ARIC) Study

BACKGROUND

Some evidence suggests that an inadequate vitamin D level may increase the risk for atherosclerotic cardiovascular disease. Whether a low vitamin D level plays a role in venous thromboembolism (VTE), that is, venous thrombosis and pulmonary embolism, is largely unexplored.

OBJECTIVES

We tested prospectively, in the Atherosclerosis Risk in Communities (ARIC) cohort, whether the serum level of 25-hydroxyvitamin D (25[OH]D) is inversely associated with VTE incidence, and whether it partly explains the African American excess of VTE in the ARIC Study.

PATIENTS AND METHODS

We measured 25(OH)D by using mass spectroscopy in stored samples of 12 752 ARIC Study participants, and followed them over a median of 19.7 years (1990-1992 to 2011) for the incidence of VTE (n = 537).

RESULTS

The seasonally adjusted 25(OH)D level was not associated with VTE incidence. In a model adjusted for age, race, sex, hormone replacement therapy, and body mass index, the hazard ratios of VTE across 25(OH)D quintiles 5 (high) to 1 (low) were: 1 (ref.), 0.84 (95% confidence interval [CI] 0.65-1.08), 0.88 (95% CI 0.68-1.13), 1.04 (95% CI 0.78-1.38), and 0.90 (95% CI 0.64-1.27). The lowest 25(OH)D quintile contained 59% African Americans, whereas the highest quintile contained 7% African Americans. However, lower 25(OH)D levels explained little of the 63% greater VTE risk of African Americans over whites in this cohort.

CONCLUSIONS

A low 25(OH)D level was not a risk factor for VTE in this prospective study. However, the totality of the literature (three studies) suggests that a low 25(OH)D level might modestly increase VTE risk in whites, but this needs further confirmation.

The relationship between vitamin D status and idiopathic lower-extremity deep vein thrombosis

Background

Vitamin D has been shown to have an anticoagulant effect. A decrease in 25-hydroxyvitamin D [25(OH)D] concentration has also been associated with an increased risk of venous thromboembolism. Hence, we sought to determine the relationship between 25(OH) D levels and idiopathic lower-extremity deep vein thrombosis (DVT).

Methods

In a case control study, a total of 82 participants with idiopathic lower-extremity DVT were enrolled along with 85 sex- and age-matched healthy participants as controls. The plasma 25(OH)D levels were measured in all the studied samples.

Results

The participants’ mean age was 47.1±12.3 years. Baseline characteristics were not significantly different between the groups. The concentration of 25(OH)D was significantly lower in the DVT group compared to that of the control group (17.9±10.3 versus 23.1±12.5 ng/mL, P=0.004). The prevalence of participants with deficient 25(OH)D levels was significantly higher in the both DVT and control groups than those with sufficient 25(OH)D levels (68.3% versus 13.4%, and 49.4% versus 28.2%, respectively, P=0.027). In a multivariate analysis, 25(OH)D levels and sex were found to be the only independent predictors of DVT (odds ratio [OR] 1.05, 95% confidence interval [CI] 1.02–1.08, P=0.001 and OR 0.51, 95% CI 0.26–1.00, P=0.049, respectively).

Conclusion

Low levels of 25(OH)D are associated with idiopathic lower-extremity DVT. Further investigation is needed to establish determinants and probable causative role of 25(OH)D.