【Cochrane简语概要】补充维生素用于防治肺炎

研究背景

根据《2015年全球疾病负担研究》，下呼吸道感染是传染病死亡的主要原因，也是第五大最常见的死亡原因。维生素C可以调节对病原体的抵抗力，因此补充维生素C在预防和治疗肺炎中可能起着很重要的作用。

研究目的

评估补充维生素C对预防和治疗儿童和成人肺炎的影响。

检索策略

我们于2020年3月4日检索了CENTRAL、MEDLINE、Embase、CINAHL、LILACS、Web of science数据库，以及2项试验注册库（clinicaltrials.gov和WHO ICTRP）。我们还检索了参考文献列表以纳入其他研究。我们没有限制任何发表状态或语言。

纳入排除标准

纳入了随机对照试验（randomised controlled trials, RCTs）和类RCT（使用非随机分配方法的研究，例如出生日期，病历号），以对比评估补充维生素C与对照组或安慰机组在预防和治疗儿童和成人肺炎中的作用。

资料收集与分析

我们使用Cochrane推荐的标准方法学流程。

主要结果

纳入了7项研究，并纳入了2项正在进行的研究。纳入的7项研究总共涉及2774名受试者；五项RCT，两项半随机RCT。纳入的研究在高收入国家（英国、美国和智利）和中低收入国家（孟加拉国和巴基斯坦）中进行。4项研究在医院进行，2项研究在学校进行，1项研究在军事训练中心进行。3项研究纳入5岁以下儿童，2名学龄儿童，1名成年受试者，1名年龄在60至90岁之间的老年受试者。2项研究评估了补充维生素C预防肺炎的效果；四项研究评估了补充维生素C在肺炎治疗中的效果；一项研究评估了维生素C在预防和治疗肺炎方面的作用。在预防肺炎的研究中，纳入的研究包括每天使用500mg维生素C，持续14周，每天使用2g维生素C，持续8周，和每天使用2g维生素C，持续12周。在治疗肺炎的研究中，纳入的研究包括每天使用125mg维生素C（直至出院），每天使用200mg维生素C，持续4周，以及每天使用200mg维生素C直到出院，作为肺炎治疗的辅助治疗。我们将纳入研究的总体偏倚风险评为高或不明确，其中偏倚风险存在于随机序列产生、分配隐藏和盲法。我们将证据质量评定为极低。

三项研究评估了补充维生素C预防肺炎的效果；我们将该证据质量评价为极低。我们不确定补充维生素C对肺炎的影响（相对危险度（risk ratio, RR)=0.46, 95％置信区间（confidence interva, CI) [0.06, ‐3.61]; 2项研究，736名受试者；I²=75％；极低质量证据）和不良事件（荨麻疹）（RR=3.11, 95％CI [0.13, 76.03]; 1项研究，674名受试者；极低质量证据）。纳入研究均未报告本综述关注的的其他主要结局（肺炎患病率和死亡率）或本综述关注的次要结局。

5项研究评估了补充维生素C预防肺炎的效果；我们将该证据质量评价为极低。一项研究报告中，与对照组（4.5±2.35天）相比，补充维生素C组（3.4±2.54天）的病程缩短了，另一项研究报告了改善氧饱和度所需的天数与对照组相比有所减少（试验组1.03±0.16天，对照组1.14±1.0天），维生素C补充剂组的呼吸频率改善时间较对照组缩短（试验组3.61±1.50天，对照组4.04±1.62天）。我们尚不确定补充维生素C对肺炎死亡率的影响（RR=0.21, 95％CI [0.03, 1.66]; 1项研究，57名受试者；证据质量极低）。一项研究报告补充维生素C的儿童的平均住院时间为6.75天，而对照组的平均住院时间为7.75天。另一项研究报告与对照组相比，补充维生素C组的平均住院时间更少（试验组109.55±27.89小时，对照组130.64±41.76小时）。

（图片来源于pixabay.com）

结论: 

我们由于纳入研究的数量少，现有证据的质量很低，我们不确定补充维生素C对预防和治疗肺炎的效果。需要进一步的高质量研究来评估补充维生素C在预防和治疗肺炎中的作用。

译者：冯汝丽，北京中医药大学志愿者；审校：申晨，北京中医药大学循证医学中心；编辑排版：郑偌祥、张晓雯，北京中医药大学循证医学中心

相关文章链接

【Cochrane Plain Language Summary】

Vitamin C supplementation for prevention and treatment of pneumonia

Background

According to the Global Burden of Disease Study 2015, lower respiratory tract infection is the leading cause of infectious disease death, and the fifth most common cause of death overall. Vitamin C has a role in modulating resistance to infectious agents, therefore vitamin C supplementation may be important in preventing and treating pneumonia.

Objectives

To assess the impact of vitamin C supplementation to prevent and treat pneumonia in children and adults.

Search methods

We searched CENTRAL, MEDLINE, Embase, PubMed, CINAHL, LILACS, Web of Science, and two trials registers to 4 March 2020. We also checked references to identify additional studies. We did not apply any publication status or language filters.

Selection criteria

We included randomised controlled trials (RCTs) and quasi‐RCTs (studies using allocation methods that are not random, e.g. date of birth, medical record number) assessing the role of vitamin C supplementation in the prevention and treatment of pneumonia in children and adults compared to control or placebo.

Data collection and analysis

We used standard methodological procedures expected by Cochrane.

Main results

We included seven studies in the review and identified two ongoing studies. The seven included studies involved a total of 2774 participants; five studies were RCTs and two were quasi‐RCTs. The included studies were conducted in high‐income countries (UK, USA and Chile) and lower‐middle‐income countries (Bangladesh and Pakistan). Four studies were conducted in hospital inpatient settings, two in schools, and one in a military training centre. Three studies included children under five years of age, two school‐aged children, one adult participants, and one older participants aged 60 to 90 years. Two studies assessed the effect of vitamin C supplementation for pneumonia prevention; four studies assessed the effect of vitamin C supplementation as an adjunct to pneumonia treatment; and one study assessed the role of vitamin C for both prevention and treatment of pneumonia. For pneumonia prevention, the included studies provided supplementation in doses of 500 mg daily for 14 weeks, 2 g daily for 8 weeks, and 2 g daily for 12 weeks. For pneumonia treatment, the included studies provided vitamin C supplementation in doses of 125 mg daily (until discharge), 200 mg for 4 weeks, and 200 mg until discharge, as an adjunct to the pneumonia treatment. We assessed the included studies as at overall either high or unclear risk of bias for random sequence generation, allocation concealment, and blinding. We judged the quality of the evidence as very low.

Three studies assessed the effect of vitamin C supplementation for pneumonia prevention; we judged the quality of the evidence as very low. We are uncertain about the effect of vitamin C supplementation on pneumonia incidence (risk ratio (RR) 0.46, 95% confidence interval (CI) 0.06 to 3.61; 2 studies, 736 participants; I² = 75%; very low‐quality evidence) and adverse events (urticaria) (RR 3.11, 95% CI 0.13 to 76.03; 1 study, 674 participants; very low‐quality evidence). No included studies reported our other primary outcomes (pneumonia prevalence and mortality) or any of our secondary outcomes.

Five studies assessed the effect of vitamin C supplementation as an adjunct to pneumonia treatment; we judged the quality of the evidence as very low. One study reported a decrease in the duration of illness in the vitamin C supplementation group (3.4 days ± 2.54) compared to the control group (4.5 days ± 2.35), and one study reported a decrease in number of days required for improvement in oxygen saturation (1.03 days ± 0.16 versus 1.14 days ± 1.0) and respiratory rate (3.61 days ± 1.50 versus 4.04 days ± 1.62) in the vitamin C supplementation group compared to the control group. We are uncertain of the effect of vitamin C supplementation on mortality due to pneumonia (RR 0.21, 95% CI 0.03 to 1.66; 1 study, 57 participants; very low‐quality evidence). One study reported that the mean duration of hospital stay was 6.75 days amongst children in the vitamin C supplementation group and 7.75 days in the control group; another study reported a lower mean duration of hospital stay in the vitamin C supplementation group compared to the control group (109.55 hours ± 27.89 versus 130.64 hours ± 41.76).

Authors' conclusions: 

Due to the small number of included studies and very low quality of the existing evidence, we are uncertain of the effect of vitamin C supplementation for the prevention and treatment of pneumonia. Further good‐quality studies are required to assess the role of vitamin C supplementation in the prevention and treatment of pneumonia.

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