Association between vitamin D deficiency and vasovagal syncope: A systematic review and meta-analysis.

Vasovagal syncope (VVS) is the most prevalent type of syncope and its management includes pharmacologic and non-pharmacologic interventions. Recently, studies have investigated vitamin D levels in VVS patients. In this systematic review and meta-analysis, we aim to review these studies to find possible associations between vitamin D deficiency and vitamin D levels with VVS. International databases including Scopus, Web of Science, PubMed, and Embase were searched with keywords related to "vasovagal syncope" and "vitamin D." Studies were screened and the data were extracted from them. Random-effect meta-analysis was conducted to calculate the standardized mean difference (SMD) and 95% confidence interval (CI) for vitamin D levels in comparison to VVS patients and controls. Also, VVS occurrence was measured and the odds ratio (OR) and 95% CI were calculated for comparison of vitamin D deficient cases and nondeficient individuals. Six studies were included with 954 cases investigated. Meta-analysis showed that patients with VVS had significantly lower vitamin D serum levels in comparison to non-VVS cases (SMD -1.05, 95% CI -1.54 to -0.57, p-value < .01). Moreover, VVS occurrence was higher in vitamin D-deficient individuals (OR 5.43, 95% CI 2.40 to 12.27, p-value < .01). Our findings which show lower vitamin D levels in VVS patients can have clinical implications in order for clinicians to pay attention to this when approaching VVS. Further randomized controlled trials are certainly warranted to assess the role of vitamin D supplementation in individuals with VVS.

Adjunctive therapy with lipid-lowering agents in COVID-19: a systematic review and meta-analysis of randomized controlled trials.

BACKGROUND: Many commonly used drugs were evaluated as repurposed treatment options since the emergence of the COVID-19 pandemic. The benefit of lipid-lowering agents has been controversial in this regard. In this systematic review, we assessed the effect of these medications as adjunctive therapy in COVID-19 by the inclusion of randomized controlled trials (RCTs). METHODS: We searched four international databases including PubMed, the Web of Science, Scopus, and Embase for RCTs in April 2023. The primary outcome was mortality, while other efficacy indices were considered secondary outcomes. In order to estimate the pooled effect size of the outcomes, considering the odds ratio (OR) or standardized mean difference (SMD) and 95% confidence interval (CI), random-effect meta-analyses was conducted. RESULTS: Ten studies involving 2,167 COVID-19 patients using statins, omega-3 fatty acids, fenofibrate, PCSK9 inhibitors, and nicotinamide as intervention compared to control or placebo, were included. No significant difference was found in terms of mortality (OR 0.96, 95% CI 0.58 to 1.59, p-value = 0.86, I2 = 20.4%) or length of hospital stay (SMD -0.10, 95% CI -0.78 to 0.59, p-value = 0.78, I2 = 92.4%) by adding a statin to the standard of care. The trend was similar for fenofibrate and nicotinamide. PCSK9 inhibition, however, led to decreased mortality and an overall better prognosis. Omega-3 supplementation showed contradicting results in two trials, suggesting the need for further evaluation. CONCLUSION: Although some observational studies found improved outcomes in patients using lipid-lowering agents, our study found no benefit in adding statins, fenofibrate, or nicotinamide to COVID-19 treatment. On the other hand, PCSK9 inhibitors can be a good candidate for further assessment. Finally, there are major limitations in the use of omega-3 supplements in treating COVID-19 and more trials are warranted to evaluate this efficacy.