[Show abstract][Hide abstract] ABSTRACT: IntroductionIn Europe, vitamin D deficiency is highly prevalent varying between 40% to 60% in the healthy general adult population. The consequences of vitamin D deficiency for sepsis and outcome in critically ill patients remains controversial. We therefore systematically reviewed observational cohort studies on vitamin D deficiency on the intensive care unit.Methods
Fourteen observational reports published from January 2000 to March 2014, retrieved from Pubmed and Embase, involving 9,715 critically ill patients and serum 25-hydroxyvitamin D3 (25 (OH)-D) concentrations, were meta-analysed.ResultsLevels of 25 (OH)-D less than 50 nmol/L were associated with increased rates of infection (risk ratio (RR) 1.49, 95% (confidence interval (CI) 1.12 to 1.99), P =0.007), sepsis (RR 1.46, 95% (CI 1.27 to 1.68), P <0.001), 30-day mortality (RR 1.42, 95% (CI 1.00 to 2.02), P =0.05), and in-hospital mortality (RR 1.79, 95% (CI 1.49 to 2.16), P <0.001). In a subgroup analysis of adjusted data including vitamin D deficiency as a risk factor for 30 day-mortality the pooled RR was 1.76 (95% CI 1.37 to 2.26, P <0.001).Conclusions
This meta-analysis suggests that vitamin D deficiency increases susceptibility for severe infections and mortality of the critically ill.
Critical care (London, England) 12/2014; 18(6):660. · 5.04 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Overlapping meta-analyses on the same topic are now very common, and discordant results often occur. To explore why discordant results arise, we examined a common topic for overlapping meta-analyses- vitamin D supplements and fracture.
We identified 24 meta-analyses of vitamin D (with or without calcium) and fracture in a PubMed search in October 2013, and analysed a sample of 7 meta-analyses in the highest ranking general medicine journals. We used the AMSTAR tool to assess the quality of the meta-analyses, and compared their methodologies, analytic techniques and results. Applying the AMSTAR tool suggested the meta-analyses were generally of high quality. Despite this, there were important differences in trial selection, data extraction, and analytical methods that were only apparent after detailed assessment. 25 trials were included in at least one meta-analysis. Four meta-analyses included all eligible trials according to the stated inclusion and exclusion criteria, but the other 3 meta-analyses "missed" between 3 and 8 trials, and 2 meta-analyses included apparently ineligible trials. The relative risks used for individual trials differed between meta-analyses for total fracture in 10 of 15 trials, and for hip fracture in 6 of 12 trials, because of different outcome definitions and analytic approaches. The majority of differences (11/16) led to more favourable estimates of vitamin D efficacy compared to estimates derived from unadjusted intention-to-treat analyses using all randomised participants. The conclusions of the meta-analyses were discordant, ranging from strong statements that vitamin D prevents fractures to equally strong statements that vitamin D without calcium does not prevent fractures.
Substantial differences in trial selection, outcome definition and analytic methods between overlapping meta-analyses led to discordant estimates of the efficacy of vitamin D for fracture prevention. Strategies for conducting and reporting overlapping meta-analyses are required, to improve their accuracy and transparency.
PLoS ONE 12/2014; 9(12):e115934. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: No life can exist on the Earth without the Sun. Everything on the Earth, from favorable temperature conditions to creation of bioorganic mass and free oxygen in the atmosphere is created only due to the rays of the Sun. In the living world, a number of systems have been created that are capable of using solar radiation, such as photosynthesis in cyanobacteria and plants, regulation of diurnal rhythms by melatonin, etc. The photoisomerization of some biologically imporr tant compounds such as sterols, cholesterol and ergoo sterol, plays a special role. These molecules can be synn thesized only in living cells. However, their photoisomerr ization can occur not only in living cells, but also in organic remains and even simply in a test tube (in vitro) at temperatures above 25°C [1, 2]. The ability to synthesize sterols is thought to be a very ancient property of living organisms because these substances are indispensable components of biological membranes. Sterols and products of their photoisomerr ization are widely distributed in algae. Microalgae are an important part of the phytoplankton that is the first link in the food chain for the majority of aquatic animals . Therefore, sterols are likely to be found everywhere. There is an impression that vitamin D precursors, cholee sterol and ergosterol, also existed in Nature from very ancient times. For formation of vitamin D, only two addii tional factors are needed: UV radiation for photoisomerr ization of 77dehydroxycholesterol to previtamin D, and temperature above 25°C for thermoisomerization of pree vitamin D to vitamin D. In 1989, M. Holick wrote  that vitamin D seemed to be one of the first hormones, or even the very first horr mone existing on Earth. The phytoplankton species Emiliania huxleyi, which has existed without change in the Sargasso Sea for more than 750 million years, proo duces ergosterol (provitamin D 2) to ~0.1% of its dry matt ter. On irradiation of this organism with artificial solar light, ergosterol converts to previtamin D 2 , which rapidly turns to vitamin D 2 . Although it was unknown why these early life forms accumulated such a huge amount of provitamin D 2 , it was supposed that ergosterol could proo
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