Systematic review: Vitamin D and cardiometabolic outcomes

A Prospective Open-Label Dose-Response Study to Correct Vitamin D Deficiency in Cirrhosis

BACKGROUND

Patients with advanced liver disease often have vitamin D deficiency, but the daily dosages of vitamin D3 needed to raise their serum 25-hydrodroxyvitamin D [25(OH)D] concentrations are unknown.

OBJECTIVE

We aimed to establish the dose-response relationship between vitamin D3 and 25(OH)D in patients with liver cirrhosis.

DESIGN

An open-label study of orally-administered vitamin D3 (gelcaps) was conducted in patients with liver cirrhosis using a tiered-dosing regimen: 4,000 IU/d for baseline 25(OH)D ≤ 15 ng/mL and 2,000 IU/d for baseline 25(OH)D > 15 to ≤ 25 ng/mL (NCT01575717). Supplementation continued for 6 months, or until liver transplantation. Changes in 25(OH)D were measured after ≥ 3 months. Dose-response data on 48 patients (21 receiving 4000 IU/d and 27 receiving 2,000 IU/d) reporting ≥ 80% adherence were analyzed using generalized estimating equations (GEE).

RESULTS

Among the 48 patients, 39 (81%) had 25(OH)D > 20 ng/mL while on supplements, and none experienced hypercalcemia. The magnitude of the increase in 25(OH)D was approximately twofold greater in patients receiving the higher dose. The mean incremental increase was 5.1 ng/ml ± 3.9 of 25(OH)D per 1000 IU/d of vitamin D3. Multivariable models demonstrated a significant positive relationship between baseline 25(OH)D and serum albumin (p < 0.01) and hemoglobin (p = 0.01), and a negative relationship with the MELD score (p < 0.01) and total bilirubin (p < 0.01).

CONCLUSIONS

A two-tiered dosing regimen of daily oral vitamin D3 supplementation safely raised 25(OH)D concentrations in the majority of adults with liver cirrhosis who were adherent to supplement use.

Dietary supplements, nutraceuticals and functional foods use after myocardial infarction depend on the age, sex, BMI and professional activity - a pilot study

OBJECTIVES

To assess dietary supplements, functional foods and nutraceuticals use among the patients after myocardial infarction (MI).

MATERIAL AND METHODS

The authors prospectively enrolled 100 consecutive patients hospitalized due to MI and remaining under coordinated outpatient care after MI in the authors' cardiology department.

RESULTS

The authors showed that patients within median (interquartile range) 12.30 (10.18-14.57) months after MI use dietary supplements, nutraceuticals and functional foods in their everyday diet. Vitamins (53% patients), especially vitamin D (35%), were the most frequently used dietary supplements. In contrary to common usage of dietary supplements (59%), smaller proportion of patients use functional foods (21%) and nutraceuticals (5%), especially phytosterols. The authors found that the use of over-the-counter (OTC) drugs and dietary supplements is associated with age (participants <60 years old vs. participants ≥60 years old: OTC drugs: N = 8 [20.0%] vs. N = 32 [53.3%], p < 0.001; herbals: N = 3 [7.5%] vs. N = 16 [26.7%], p = 0.019), sex of the patients following MI (females vs. males: vitamins: N = 17 [70.8%] vs. N = 36 [47,4%], p = 0.045; vitamin D: N = 13 [54.2%] vs. N = 22 [28.9%], p = 0.024; omega-3 fatty acids: N = 3 [12.5%] vs. N = 1 [1.3%], p = 0.042; herbals: N = 8 [33.3%] vs. N = 11[14.5%], p = 0.040), as well as the BMI of the participants (BMI < 24.9 vs. BMI ≥ 25.0: multivitamin/ multimineral dietary supplements: N = 3 [15.0%] vs. N = 31 [42.5%], p = 0.035; vitamin B6: N = 1 [5.0%] vs. N = 21 [28.8%], p = 0.035). In the study group all participants with the age above retirement age have already withdrawn from professional activity and they more often used OTC drugs (N = 14 [25.9%] before retirement age vs. N = 26 [56.5%] above retirement age, p = 0.002).

CONCLUSIONS

The patients following MI use supplements, functional foods and nutraceuticals. Their use depends on sex, age, BMI and professional activity. The authors believe that their potential beneficial effects require further evaluation in clinical longitudinal studies. Int J Occup Med Environ Health. 2023;36(6):732-43.

Obesity-Associated Vitamin D Deficiency Correlates with Adipose Tissue DNA Hypomethylation, Inflammation, and Vascular Dysfunction

Vitamin D (VD) deficiency is a hallmark of obesity and vascular dysfunction. We sought to test the hypothesis that VD deficiency may contribute to obesity-related vascular dysfunction by inducing adipokine hypomethylation and augmented expression. To this end, we collected blood and adipose tissues (ATs) from a cohort of 77 obese participants who were classified as having mild, moderate, or severe VD deficiency. The body composition, vascular reactivity, cardiometabolic profiles, and DNA methylation of 94 inflammation-related adipokines were measured. Our results show that higher degrees of VD deficiency were associated with lower DNA methylation and induced the expression of inflammatory adipokines such as B-cell lymphoma 6 (BCL6), C-X-C Motif Chemokine Ligand 8 (CXCL8), histone deacetylase 5 (HDAC5), interleukin 12A (IL12A), and nuclear factor κB (NFκB) in the ATs. They were also associated with higher BMI and total and visceral fat mass, impaired insulin sensitivity and lipid profiles, AT hypoxia, and higher concentrations of circulating inflammatory markers. Moderate and severe VD deficiency correlated with impaired vasoreactivity of the brachial artery and AT-isolated arterioles, reduced nitric oxide generation, and increased arterial stiffness. In a multivariate regression analysis, the VD deficiency level strongly predicted the adipokine methylation score, systemic inflammation, and microvascular dysfunction. In conclusion, our findings suggest that VD deficiency is a possible contributor to obesity-related adipokine hypomethylation, inflammation, and vascular dysfunction.

An empirical evaluation of the impact scenario of pooling bodies of evidence from randomized controlled trials and cohort studies in medical research

BACKGROUND

Randomized controlled trials (RCTs) and cohort studies are the most common study design types used to assess treatment effects of medical interventions. We aimed to hypothetically pool bodies of evidence (BoE) from RCTs with matched BoE from cohort studies included in the same systematic review.

METHODS

BoE derived from systematic reviews of RCTs and cohort studies published in the 13 medical journals with the highest impact factor were considered. We re-analyzed effect estimates of the included systematic reviews by pooling BoE from RCTs with BoE from cohort studies using random and common effects models. We evaluated statistical heterogeneity, 95% prediction intervals, weight of BoE from RCTs to the pooled estimate, and whether integration of BoE from cohort studies modified the conclusion from BoE of RCTs.

RESULTS

Overall, 118 BoE-pairs based on 653 RCTs and 804 cohort studies were pooled. By pooling BoE from RCTs and cohort studies with a random effects model, for 61 (51.7%) out of 118 BoE-pairs, the 95% confidence interval (CI) excludes no effect. By pooling BoE from RCTs and cohort studies, the median I² was 48%, and the median contributed percentage weight of RCTs to the pooled estimates was 40%. The direction of effect between BoE from RCTs and pooled effect estimates was mainly concordant (79.7%). The integration of BoE from cohort studies modified the conclusion (by examining the 95% CI) from BoE of RCTs in 32 (27%) of the 118 BoE-pairs, but the direction of effect was mainly concordant (88%).

CONCLUSIONS

Our findings provide insights for the potential impact of pooling both BoE in systematic reviews. In medical research, it is often important to rely on both evidence of RCTs and cohort studies to get a whole picture of an investigated intervention-disease association. A decision for or against pooling different study designs should also always take into account, for example, PI/ECO similarity, risk of bias, coherence of effect estimates, and also the trustworthiness of the evidence. Overall, there is a need for more research on the influence of those issues on potential pooling.

Vitamin D Deficiency as an Independent Predictor of Myocardial Infarction in the Elderly

Cardiovascular diseases are among the most common causes of disability and death in the world, and the number of patients with this category of diseases is increasing every year. This study aimed to investigate the role of vitamin D and the problems caused by its deficiency on the cardiovascular system. Level of D-(25(OH]D) in blood was studied by enzyme immunoassay in 95 elderly patients with myocardial infarction (MI) (the main group) and 92 elderly patients with no history of MI. The level of lipid metabolism as an indicator was determined using a KoneLab 300 auto-analyzer. Based on the results of this study, it was found that the elderly group without MI had the highest amount of D-(25(OH]D)(24.5±1.2), compared to the elderly group with MI (14.8±1.3). The rates of expressed deficiency, deficiency, and insufficiency in the group of elderly with MI were 53.6±5.1, 23.2±4.4, and 12.6±3.4%, respectively. This experiment has shown that D-(25(OH]D) is involved in lipid metabolism and reduces the accumulation of cholesterol by macrophages. The content of vitamin D in blood plasma was a prognostic predictor of MI, which improved MI in the elderly. Regardless of pathological changes, the deficit level of D-(25(OH]D) should be considered a laboratory predictor of MI in the elderly.

Effect of 9 months of vitamin D supplementation on arterial stiffness and blood pressure in Graves' disease: a randomized clinical trial

PURPOSE

Risk of cardiovascular disease (CVD) is increased in Graves' disease (GD). CVD is predicted by increased pulse wave velocity (PWV) and blood pressure (BP). GD and these risk factors are all associated with lower levels of vitamin D. We aimed to assess the effect of supplemental vitamin D on PWV and BP in GD.

METHODS

In a double-blinded trial, newly diagnosed GD patients were randomized to vitamin D3 70 µg/day (n = 44) or placebo (n = 42) as add-on to anti-thyroid medication. At baseline, 3 and 9 months PWV, BP and wave analysis were performed in office and 24 h setting. Between-group differences in change at 9 months were analyzed using linear mixed modelling. In subanalysis, effect of intervention in regard to baseline vitamin D insufficiency (25(OH)D < 50 nmol/L) was investigated. (The DAGMAR study, clinicaltrials.gov ID NCT02384668).

RESULTS

PWV was unaffected by intervention in main analysis. However in the subanalysis, comparing the response to intervention in the vitamin D insufficient (n = 28) and the vitamin D replete patients, supplemental vitamin D induced a significant decrease in office PWV of 1.2 (95% CI: -2.3; -0.1) m/s compared to placebo. Of notice, baseline PWV was non-significantly higher among the vitamin D insufficient as compared to the replete participants. In response to vitamin D, office central systolic BP (-3.9 (95% CI: -7.5; -0.3) and brachial mean BP (-3.3 (95% CI: -6.5; -0.3) declined whereas 24 h measurements were unaffected.

CONCLUSIONS

High-dose vitamin D supplementation did not affect PWV. We observed significant reduction in office but not 24 h BP. Subanalysis showed a clinically relevant PWV reduction among vitamin D insufficient participants, although regression towards the mean might contribute to findings. Further studies on supplemental vitamin D in GD should focus on patients with vitamin D insufficiency.

Sun exposure and 25-hydroxyvitamin D3 levels in a community sample: Quantifying the association with electronic dosimeters

There is uncertainty about the amount of sun exposure required to increase low blood 25-hydroxyvitamin D (25(OH)D₃) levels, a possible disease risk factor. The study aimed to quantify the association between sun exposure and serum 25(OH)D₃ concentrations in a multiethnic community sample (n=502) living in Auckland (37°S) and Dunedin (46°S), New Zealand, aged 18-85 years. They wore electronic ultraviolet dosimeters between March and November (autumn, winter and spring) for 8 weeks to record their sun exposure. This was converted to standard erythemal doses (SEDs), corrected for clothing to generate equivalent full-body exposures, SED_EFB. Blood samples were collected at the end of weeks 4 and 8 to measure 25(OH)D₃. Median weekly SED_EFB was 0.33 during weeks 1-4 and 0.34 during weeks 5-8. Weekly exposures <0.5 SED_EFB during weeks 5-8 were associated with decreasing 25(OH)D₃ concentrations at the end of week 8. There was a non-linear association between sun exposure and 25(OH)D₃, with most of the increase in 25(OH)D₃ being at exposures <2 SED_EFB per week. This finding suggests that vitamin D status is increased by regular small sun exposures (<2 SED_EFB per week), and that greater exposures result in only small additional increases in 25(OH)D₃.

Vitamin D and extra-skeletal health: causality or consequence

Vitamin D deficiency /insufficiency is widely recognized as a global health problem that is likely to be involved in pathogenesis or progression of many acute and chronic health disorders. Its relation to skeletal health has been clearly demonstrated and thoroughly examined. This review aims to highlight the continuous debate about the relation between vitamin D and extra-skeletal health and whether it is a causality or just an association. Overall, the available evidence does not meet the criteria for establishing cause-and-effect relationships because of the limitations of observational studies to corroborate the causality due to many potential confounders. Moreover, the causal relationship couldn't be established in randomized studies or in many meta-analyses. This may reflect the fact that vitamin D level reduction is just a biomarker of ill health. The inflammatory processes involved in the disease occurrence and the functional limitations of the diseases would have a role in reducing serum 25-hydroxy vitamin D "25 (OH) D" level, which would explain why low vitamin D is reported in a wide range of disorders. This may underscore the possibility of harm instead of benefit of vitamin D supplementation when its exact role is not fully established, thus many guidelines and interest groups are still hesitant toward recommending replacement in extra-skeletal disease. Future directions entails the need for a large well-designed randomized control trials (RCTs) to resolve the active debate on the benefits of vitamin D replacement for extra-skeletal disease, and not only that, future studies should establish specific, clinically relevant effects of vitamin D repletion, provide cut-values for optimal serum levels of 25 (OH) D, and appropriate doses for non-skeletal health benefits.

Association of vitamin D status with arterial blood pressure and hypertension risk: a mendelian randomisation study

BACKGROUND

Low plasma 25-hydroxyvitamin D (25[OH]D) concentration is associated with high arterial blood pressure and hypertension risk, but whether this association is causal is unknown. We used a mendelian randomisation approach to test whether 25(OH)D concentration is causally associated with blood pressure and hypertension risk.

METHODS

In this mendelian randomisation study, we generated an allele score (25[OH]D synthesis score) based on variants of genes that affect 25(OH)D synthesis or substrate availability (CYP2R1 and DHCR7), which we used as a proxy for 25(OH)D concentration. We meta-analysed data for up to 108 173 individuals from 35 studies in the D-CarDia collaboration to investigate associations between the allele score and blood pressure measurements. We complemented these analyses with previously published summary statistics from the International Consortium on Blood Pressure (ICBP), the Cohorts for Heart and Aging Research in Genomic Epidemiology (CHARGE) consortium, and the Global Blood Pressure Genetics (Global BPGen) consortium.

FINDINGS

In phenotypic analyses (up to n=49 363), increased 25(OH)D concentration was associated with decreased systolic blood pressure (β per 10% increase, -0·12 mm Hg, 95% CI -0·20 to -0·04; p=0·003) and reduced odds of hypertension (odds ratio [OR] 0·98, 95% CI 0·97-0·99; p=0·0003), but not with decreased diastolic blood pressure (β per 10% increase, -0·02 mm Hg, -0·08 to 0·03; p=0·37). In meta-analyses in which we combined data from D-CarDia and the ICBP (n=146 581, after exclusion of overlapping studies), each 25(OH)D-increasing allele of the synthesis score was associated with a change of -0·10 mm Hg in systolic blood pressure (-0·21 to -0·0001; p=0·0498) and a change of -0·08 mm Hg in diastolic blood pressure (-0·15 to -0·02; p=0·01). When D-CarDia and consortia data for hypertension were meta-analysed together (n=142 255), the synthesis score was associated with a reduced odds of hypertension (OR per allele, 0·98, 0·96-0·99; p=0·001). In instrumental variable analysis, each 10% increase in genetically instrumented 25(OH)D concentration was associated with a change of -0·29 mm Hg in diastolic blood pressure (-0·52 to -0·07; p=0·01), a change of -0·37 mm Hg in systolic blood pressure (-0·73 to 0·003; p=0·052), and an 8·1% decreased odds of hypertension (OR 0·92, 0·87-0·97; p=0·002).

INTERPRETATION

Increased plasma concentrations of 25(OH)D might reduce the risk of hypertension. This finding warrants further investigation in an independent, similarly powered study.

FUNDING

British Heart Foundation, UK Medical Research Council, and Academy of Finland.

Hypertension and obesity after pediatric kidney transplantation: management based on pathophysiology: a mini review

Hypertension after pediatric renal transplant is a common and important risk factor for graft loss and patient survival. The mechanism of post kidney transplant hypertension is complex and multifactorial. Control of blood pressure in renal transplant patients is important but often times blood pressures remain uncontrolled. The management of hypertension and obesity in pediatric kidney transplant patients is based on the pathophysiology. Compared to the general pediatric hypertensive population, special attention needs to be focused on the additional impact of immunosuppressive medications side effects and interactions, recurrent disease, and donor and recipient comorbidities such as obesity on blood pressure control with thoughtful consideration of the risk of graft failure. In general, there is a need for prospective studies in pediatric kidney transplant patients to understand the pathophysiology of hypertension and obesity and the appropriate approach to achieve a balance between the primary need to avoid rejection and the need to lower blood pressure and prevent obesity.

Vitamin D, arterial hypertension & cerebrovascular disease

Vitamin D is mainly derived from endogenous ultraviolet-B induced vitamin D synthesis in the skin, and the current high prevalence of vitamin D deficiency can, therefore, largely be attributed to lifestyle related low sunlight exposure. Regulation of bone and mineral metabolism is a classic vitamin D effect, but the identification of the vitamin D receptor (VDR) in almost all human cells suggests a role for vitamin D also in extra-skeletal diseases. Experimental studies demonstrated several antihypertensive and vascular protective effects of vitamin D, such as suppression of the renin angiotensin aldosterone system, beneficial modulation of classic cardiovascular risk factors, and anti-atherosclerotic properties including improvements of endothelial function. Additional neuroprotective actions of vitamin D have also been reported. In line with this, epidemiological studies have largely shown that vitamin D deficiency is an independent risk factor for arterial hypertension and strokes. Data from randomized controlled trials (RCTs) are, however, limited and less promising, with currently no confirmation that vitamin D reduces stroke incidence. Whereas some RCTs suggest that vitamin D supplementation might modestly reduce blood pressure, this has not been consistently observed in all studies. It is, therefore, premature to recommend vitamin D supplementation for the prevention and treatment of arterial hypertension and stroke. Nevertheless, the fact that patients with arterial hypertension and cerebrovascular disease are at a relatively high risk of vitamin D deficiency, and therewith associated musculoskeletal diseases can serve as a rationale for the evaluation, prevention and treatment of vitamin D deficiency in these patients.

Association between vitamin D levels and blood pressure in a group of Puerto Ricans

OBJECTIVE

Hypertension is a global public health problem. The apparent association between vitamin D (VitD) and blood pressure (BP) has been studied in several populations but not in a Puerto Rican population. Therefore, we determined the association between serum 25(OH)D levels and BP in a convenience sample in Puerto Rico.

METHODS

A cross-sectional study of patients attending a local laboratory with an order for serum 25(OH)D levels was performed. Participants completed a questionnaire that solicited the following information: age, sex, weight, height, VitD intake, and history of both sun exposure and hypertension. BP was measured by a phlebotomist on-site and classified according to the Joint National Committee; serum 25(OH)D levels were taken from the record, and VitD status was classified as either optimal (25(OH)D > or = 30 ng/dl) or non-optimal (< 30 ng/dl). Mean, standard deviation, and percentiles were used for descriptive analysis. VitD status and BP were compared by gender, age, and body mass index (BMI) using ANOVA or chi-square. The association between VitD status and blood pressure was assessed by polytomous logistic regression adjusting for several variables.

RESULTS

Two hundred nineteen individuals were included in the analysis; most were females aged 21 to 50 years who were overweight/obese; 53% of the total population was pre-hypertensive or hypertensive; 60% had non-optimal VitD status; and the sun exposure index was 19.6. No significant associations were found between VitD status and blood pressure after adjusting for age, sex, BMI, total VitD intake, and solar exposure index.

CONCLUSION

VitD status was not found to be associated with blood pressure in this sample population; more studies with a larger sample population are needed to determine whether such an association does in fact exist.

The impact of medication on vitamin D status in older individuals

OBJECTIVE

Vitamin D deficiency and polypharmacy are common in the elderly. However, knowledge on the associations between the use of specific medicines and serum 25-hydroxyvitamin D (25(OH)D) is limited. The aim of this study was to (better) define the associations between the use of specific medicines and serum 25(OH)D.

METHODS

Two different cohorts (1995/1996 and 2002/2003) from the Longitudinal Aging Study Amsterdam (LASA) were used for cross-sectional analyses. LASA is based on an age and sex-stratified random sample of the Dutch older population. Study participants were aged 65-88 years in the first cohort (n = 1301) and 55-65 years in the second cohort (n = 736). Serum 25(OH)D of users of several groups of medicines were compared with levels of non-users using multiple linear regression analysis.

RESULTS

Of all participants, 75.4% (first cohort) and 61.1% (second cohort) were using at least one medicine. In both cohorts, the number of medicines was associated with lower serum 25(OH)D. In the first cohort, after adjustment for confounding, users of any kind of medicine, loop diuretics and inhaled corticosteroids (only men) had respectively 4.4 nmol/l (P<0.01), 4.7 nmol/l (P = 0.04) and 7.3 nmol/l (P = 0.02) lower serum 25(OH)D than non-users. In the second cohort, the use of oral antidiabetics, calcium-channel blockers and angiotensin-converting enzyme inhibitors was associated with respectively 7.4 nmol/l (P = 0.04), 7.7 nmol/l (P = 0.01) and 7.6 nmol/l (P<0.01) lower serum 25(OH)D.

CONCLUSIONS

These data show that users of several medicines have lower serum 25(OH)D than non-users. Vitamin D supplementation may be considered in patients with chronic use of medicines.

A prospective study of serum 25-hydroxyvitamin D levels, blood pressure, and incident hypertension in postmenopausal women

In randomized trials, the effect of vitamin D supplementation on blood pressure has been equivocal, while most prospective cohort studies have shown that the risk of incident hypertension is lower in people with higher levels of 25-hydroxyvitamin D (25(OH)D). The authors examined the association between levels of 25(OH)D and changes in blood pressure and incident hypertension in 4,863 postmenopausal women recruited into the Women's Health Initiative between 1993 and 1998. Over 7 years, there were no significant differences in the adjusted mean change in systolic or diastolic blood pressure by quartile of 25(OH)D. The covariate-adjusted risk of incident hypertension was slightly lower in the upper 3 quartiles of 25(OH)D compared with the lowest quartile, but this was statistically significant only in the third quartile (hazard ratio = 0.67, 95% confidence interval: 0.46, 0.96). There was no significant linear or nonlinear trend in the risk of incident hypertension by untransformed or log-transformed continuous values of 25(OH)D. In postmenopausal women in this study, serum levels of 25(OH)D were not related to changes in blood pressure, and evidence for an association with lower risk of incident hypertension was weak.

Narrow-band ultraviolet B exposure increases serum vitamin D levels in haemodialysis patients

BACKGROUND

Chronic kidney disease (CKD) patients are especially prone to vitamin D insufficiency. Narrow-band ultraviolet B (NB-UVB) treatment increases serum 25-hydroxyvitamin D [25(OH)D] in dermatological patients, and we studied whether it also improves vitamin D balance in CKD patients on haemodialysis.

METHODS

Fifteen dialysis patients (mean age 48.3 years) and 12 healthy subjects (mean age 43.6 years) received nine NB-UVB exposures on the upper body. Serum 25(OH)D and 1,25(OH)(2)D were measured before and after the exposures. From skin biopsy specimen messenger RNA (mRNA) expression levels of CYP24A1 and CYP27B1, two enzymes needed for hydroxylation of vitamin D into its active metabolites, and of antimicrobial peptide cathelicidin, were examined.

RESULTS

Before NB-UVB, mean serum 25(OH)D was 32.5 ± 10.2 nmol/L in the dialysis patients and 60.2 ± 18.0 nmol/L in the healthy subjects (P < 0.001). After eight NB-UVB exposures, serum 25(OH)D increased by 13.8 nmol/L (43%; P < 0.001) and serum 1,25(OH)(2)D by 3.3 pmol/L (27%; P = 0.002) in the dialysis patients. After NB-UVB exposures, CYP27B1 mRNA was increased (P = 0.04), whereas cathelicidin mRNA was decreased (P < 0.0001) compared to non-treated healthy subjects. One and 2 months after NB-UVB exposure, serum 25(OH)D was still 10% higher than initially in the dialysis patients.

CONCLUSIONS

The present study shows that a short course of NB-UVB exposure increases significantly serum 25(OH)D and 1,25(OH)(2)D in dialysis patients. The effect is, however, short lasting suggesting that the patients need cyclic NB-UVB exposure to maintain their improved vitamin D concentration.

Vitamin D status and mortality in chronic kidney disease

BACKGROUND

Vitamin D deficiency is found in the majority of patients with chronic kidney disease (CKD) and may contribute to various chronic diseases. Current guidelines suggest correcting reduced 25-hydroxyvitamin D [25(OH)D] concentrations in CKD patients with an estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m(2). Whether low 25(OH)D levels in these patients are associated with higher mortality is unclear. This issue was addressed in the present work.

METHODS

We examined 444 patients with eGFR <60 mL/min/1.73 m(2) from the Ludwigshafen Risk and Cardiovascular Health Study. This prospective cohort study includes Caucasian patients without primary kidney disease who were routinely referred to coronary angiography at baseline (1997-2000).

RESULTS

During a median follow-up time of 9.4 years, 227 patients died including 159 deaths from cardiovascular causes. Multivariate adjusted hazard ratios (HRs) (with 95% confidence intervals) in severely vitamin D-deficient [25(OH)D <10 ng/mL] compared to vitamin D-sufficient patients [25(OH)D ≥ 30 ng/mL] were 3.79 (1.71-8.43) for all-cause and 5.61 (1.89-16.6) for cardiovascular mortality. Adjusted HRs per 10 ng/mL increase in 25(OH)D levels were 0.63 (0.50-0.79) for all-cause and 0.59 (0.45-0.79) for cardiovascular mortality. There was no significant interaction with parathyroid hormone concentrations.

CONCLUSIONS

Low 25(OH)D levels are associated with increased all-cause and cardiovascular mortality in CKD patients. These findings support suggestions to correct vitamin D deficiency, but whether vitamin D supplementation improves survival remains to be proven in randomized controlled trials.

Vitamin D and all-cause mortality among adults in USA: findings from the National Health and Nutrition Examination Survey Linked Mortality Study

BACKGROUND

Whether concentrations of vitamin D are related to mortality remains unresolved. Our objective was to examine the relationship between serum concentrations of 25-hydroxyvitamin D and all-cause mortality in a national sample of US adults.

METHODS

We used data from the National Health and Nutrition Examination Survey Mortality Study from 2001 to 2004 with mortality compiled through 2006. Mortality status was established through a match to the National Death Index.

RESULTS

Of the 7531 participants, 347 died. Median follow-up was 3.8 years. The mean unadjusted concentrations of vitamin D were 54.1 nmol/l (21.7 ng/ml) among participants who died and 60.7 nmol/l (24.3 ng/ml) among participants who survived (P = 0.002). After adjustment for socio-demographic factors, the hazard ratios (HR) for all-cause mortality were 1.65 [95% confidence interval (CI): 95% CI: 1.13-2.40] for participants with a concentration <50 nmol/l (<20 ng/ml) and 1.02 (95% CI: 0.74-1.41) for participants with a concentration of 50 to <75 nmol/l (20 to <30 ng/ml) compared with participants who had a concentration of ≥ 75 nmol/l (≥ 30 ng/ml). After more extensive adjustment, the HRs were 1.28 (95% CI: 0.86-1.90) and 0.91 (95% CI: 0.63-1.33), respectively. The fully adjusted HR per 10 nmol/l of vitamin D was 0.93 (95% CI: 0.86-1.01). The HRs did not vary by gender (P = 0.80) or among the three major racial or ethnic groups (P = 0.46).

CONCLUSIONS

Concentrations of vitamin D were weakly and inversely related to all-cause mortality in this sample of US adults.