P011 Effect size of vitamin-C on indices of sleep-quality, fatigue, endothelial-function, circulating HIF-1alpha and patient mortality: a systematic review
Authors: Black D 
Published: October 2021

Background-Patients-with-untreated-or-undiagnosed-disordered-breathing have increased-risk-of-perioperative-complications. Increased-vitamin-C was-associated with-improved-quality-of-sleep. Furthermore, supplemental-vitamin-C has been associated with-reduced-fatigue, improved-endothelial-function, and regulation-of-HIF-1α-expression-and-reactive-oxygen-species(ROS). Administration of supplemental-vitamin-C-to-patients-treated-for-life-threatening-disease-states-with-excessive-ROS was associated-with-lowered-mortality. Since patients scheduled for elective-surgery have-a-risk of untreated-or-undiagnosed-sleep-disorder such as OSA; the hypothesis emerged that administering-supplemental-vitamin-C during the pre-operative period to people with high-STOP-BANG-scores maybe associated with lower-levels of perioperative-adverse-events. The objective of this study was to quantify the effect-sizes of vitamin-C for promoting sleep-quality, reducing-fatigue, regulating endothelial-function and circulating HIF-1α-expression, lowering mortality amongst people treated for life-threatening conditions associated with high-levels of ROS; and the impact of untreated-or-undiagnosed-OSA on peri-operative adverse-events.

Methods-A Prospero-registered(ID 262766) systematic-review in accordance with the PRISMA-2020-statement was undertaken using Comprehensive-Meta-Analysis-software to quantify effect-sizes of vitamin-C and OSA on-patient-outcomes.

Progress to date-Four-studies were identified examining-the-impact-of-higher-levels-of-vitamin-C on sleep-quality, Hedges’ g=0.384(95%CI-0.180-to-0.588),p&lt;0.001. Eleven-studies were identified examining the impact-of-supplemental-vitamin-C on fatigue. Hedges’ g=0.484(95%CI-0.314-to-0.653), p&lt;0.001. Five-studies explored the impact of supplemental-vitamin-C on improved-endothelial-function. Hedges’ g = 0.988(95%CI-0.516-to-1.461), p&lt;0.001. Five-studies examined the-impact-of-supplemental-vitamin-C on reducing-HIF-1α-expresion. Hedges’g=4.282(95%CI-2.482-to-6.066), p&lt;0.001. Sixty-seven studies comparing-the-impact of supplemental-vitamin-C on mortality, OR=0.706(95%CI-0.615-to-0.810), p&lt;0.001. Fourteen-studies-compared the odds of perioperative-adverse-events amongst patients at high-risk-of-OSA with controls; OR = 2.687(95%CI-1.705-to-4.233), p&lt;0.001).

Intended Outcome and Impact-Statistically-and-clinically-significant-evidence was-observed-supporting the hypothesis that-the-biology-of-abnormal-sleep-states could be regulate-by supplemental-vitamin-C; and untreated-or-undiagnosed-OSA was associated with increased-perioperative-adverse events. Due to the-lack-of-clinical-equipoise regarding supplemental-vitamin-C promoting-healthy-sleep, regulate-the-pathological-impacts of intermittent-hypoxaemia and oxidative-stress, future-ethical-research will require all-eligible-subjects to-be-offered vitamin-C. Prospective-supplemental-vitamin-C-treated-groups could be compared with historic-controls; or standard pre-operative-care and standard pre-operative-care-plus supplemental-vitamin-C could be randomised according to surgical-centre to promote ethical-clinical-investigation. These experimental-design-considerations also have implications for improving-clinical-governance in the current-era-of-fiscal-restraint.