Using findings from observational studies to guide vitamin D randomized controlled trials

A randomized double-blinded placebo controlled trial of ergocalciferol 40,000 versus 100,000 IU per week for vitamin D inadequacy in institutionalized postmenopausal women

BACKGROUND

Vitamin D inadequacy is common in institutionalized post-menopausal women who are at the highest risk for osteoporotic fracture.

AIM

To evaluate efficacy and safety of ergocalciferol 40,000 versus 100,000 IU per week for 12 weeks for vitamin D inadequacy in institutionalized postmenopausal women.

METHOD

A randomized double-blinded placebo-controlled trial was conducted in 94 institutionalized subjects with baseline 25(OH)D levels < 30 ng/mL. Subjects were randomized to receive ergocalciferol 40,000 (standard dose) or ergocalciferol 100,000 IU (high dose) per week. Serum 25(OH)D levels, calcium, phosphate, handgrip strength, time up and go (TUG) test and quality of life by EQ-5D-5L were measured at baseline and 12 weeks after randomization.

RESULTS

Of the 94 subjects enrolled, 85 subjects completed the study. Subjects in the high dose group had higher mean 25(OH)D levels than subjects in the standard group (51.73 ± 19.35 and 34.5 ± 9.12, p < 0.001). More subjects in the high dose group (90.9%) achieved optimal 25(OH)D levels (> 30 ng/mL) than those in the standard group (65.9%), p = 0.007. In a subgroup analysis of subjects with vitamin D deficiency (< 20 ng/mL, n = 44) and severe vitamin D deficiency (< 10 ng/mL, n = 9), more subjects in the high dose group achieved optimal 25(OH)D levels than those in the standard group (88% and 100% versus 47.4% and 16.7% with p of 0.007 and 0.018, respectively). There were no differences in handgrip strength, TUG, EQ-5D-5L and adverse events between groups.

DISCUSSION/CONCLUSIONS

Subjects who received high dose ergocalciferol achieved more optimal 25(OH)D levels than those who received standard dose. High dose ergocalciferol is preferred to optimize 25(OH)D levels in subjects with severe vitamin D deficiency.

Vitamin D and cardiovascular diseases: Causality

Vitamin D regulates blood pressure, cardiac functions, and endothelial and smooth muscle cell functions, thus, playing an important role in cardiovascular health. Observational studies report associations between vitamin D deficiency with hypertension and cardiovascular-related deaths. Peer-reviewed papers were examined in several research databases as per the guidelines of the Preferred Reporting Items for Systematic Reviews, using key words that address the relationship between vitamin D and cardiovascular disease. Correlations and interpretations were made considering the risks-benefits, broader evidence, and implications. This review analyzed current knowledge regarding the effects of vitamin D on the cardiovascular system. 1,25(OH)₂D and related epigenetic modifications subdue cellular inflammation, improve overall endothelial functions, reduce age-related systolic hypertension and vascular rigidity, and attenuate the actions of the renin-angiotensin-aldosterone system. Most observational and ecological studies support 25(OH)vitamin D having protective effects on the cardiovascular system. However, the association of vitamin D deficiency with cardiovascular diseases is based primarily on observational and ecological studies and thus, is a matter of controversy. Adequately powered, randomized controlled clinical trial data are not available to confirm these associations. Thus, to test the hypothesis that correction of vitamin D deficiency protects the cardiovascular system, well-designed, statistically powered, longer-term clinical trials are needed in persons with vitamin D deficiency. Nevertheless, the available data support that adequate vitamin D supplementation and/or sensible sunlight exposure to achieve optimal vitamin D status are important in the prevention of cardiovascular disease and other chronic diseases.

Associations of lower vitamin D concentrations with cognitive decline and long-term risk of dementia and Alzheimer's disease in older adults

INTRODUCTION

Hypovitaminosis D has been associated with several chronic conditions; yet, its association with cognitive decline and the risk of dementia and Alzheimer's disease (AD) has been inconsistent.

METHODS

The study population consisted of 916 participants from the Three-City Bordeaux cohort aged 65+, nondemented at baseline, with assessment of vitamin D status and who were followed for up to 12 years.

RESULTS

In multivariate analysis, compared with individuals with 25(OH)D sufficiency (n = 151), participants with 25(OH)D deficiency (n = 218) exhibited a faster cognitive decline. A total of 177 dementia cases (124 AD) occurred: 25(OH)D deficiency was associated with a nearly three-fold increased risk of AD (hazard ratio = 2.85, 95% confidence interval 1.37-5.97).

DISCUSSION

This large prospective study of French older adults suggests that maintaining adequate vitamin D status in older age could contribute to slow down cognitive decline and to delay or prevent the onset of dementia, especially of AD etiology.

Does sufficient evidence exist to support a causal association between vitamin D status and cardiovascular disease risk? An assessment using Hill's criteria for causality

Serum 25-hydroxyvitamin D (25(OH)D) levels have been found to be inversely associated with both prevalent and incident cardiovascular disease (CVD) risk factors; dyslipidemia, hypertension and diabetes mellitus. This review looks for evidence of a causal association between low 25(OH)D levels and increased CVD risk. We evaluated journal articles in light of Hill's criteria for causality in a biological system. The results of our assessment are as follows. Strength of association: many randomized controlled trials (RCTs), prospective and cross-sectional studies found statistically significant inverse associations between 25(OH)D levels and CVD risk factors. Consistency of observed association: most studies found statistically significant inverse associations between 25(OH)D levels and CVD risk factors in various populations, locations and circumstances. Temporality of association: many RCTs and prospective studies found statistically significant inverse associations between 25(OH)D levels and CVD risk factors. Biological gradient (dose-response curve): most studies assessing 25(OH)D levels and CVD risk found an inverse association exhibiting a linear biological gradient. Plausibility of biology: several plausible cellular-level causative mechanisms and biological pathways may lead from a low 25(OH)D level to increased risk for CVD with mediators, such as dyslipidemia, hypertension and diabetes mellitus. Experimental evidence: some well-designed RCTs found increased CVD risk factors with decreasing 25(OH)D levels. Analogy: the association between serum 25(OH)D levels and CVD risk is analogous to that between 25(OH)D levels and the risk of overall cancer, periodontal disease, multiple sclerosis and breast cancer.

CONCLUSION

all relevant Hill criteria for a causal association in a biological system are satisfied to indicate a low 25(OH)D level as a CVD risk factor.