Background

The contribution of registered nurses towards safe patient care has been demonstrated in many studies. However, most of the evidence linking staffing levels to outcomes is cross-sectional with intrinsic limitations including an inability to establish that presumed cause (staffing) precedes the effect. No reviews have summarised longitudinal studies considering nurse staffing and patient outcomes.

Objectives

To identify and assess the evidence for an association between nurse staffing levels, including the composition of the nursing team, and patient outcomes in acute care settings from longitudinal studies.

Methods

We undertook a systematic review of studies where the association between nurse staffing with patient outcomes was assessed in a longitudinal design. Studies with repeated cross-sectional analyses were excluded unless a difference-in-difference design was used. We searched Medline, CINAHL, Embase and the Cochrane Library up to February 2022. We used the ROBINS-I tool to assess risk of bias. We synthesised results in a tabular form and a narrative grouped by outcome.

Results

27 papers were included. Studies were conducted in a variety of settings and populations, including adult general medical/surgical wards and adult and neonatal intensive care units. Staffing measures were operationalised in a variety of different ways, making direct comparisons between studies difficult and pooled estimates impossible. Most studies were either at serious (n = 12) or critical (n = 5) risk of bias, with only 3 studies at low risk of bias. Studies with the most risk of bias were judged as likely to underestimate the effect of higher registered nurse staffing. Findings are consistent with an overall picture of a beneficial effect from higher registered nurse staffing on preventing patient death. The evidence is less clear for other patient outcomes with a higher risk of bias, but in general the proposition that higher registered nurse staffing is likely to lead to better patient outcomes is supported. Evidence about the contribution of other nursing staff groups is unclear.

Conclusion

The causal relationship between low registered nurse staffing and mortality is plausible and these estimates of relationships from longitudinal studies provide further support. To address residual uncertainties, future studies should be conducted in more than one hospital and using standardised measures when reporting staffing levels.

Tweetable abstract

Having more registered nurses on hospital wards is causally linked to reduced mortality – new review shows there is little room for doubt @ora_dall @workforcesoton @turnel.

中文翻译：

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护士人员配备水平和患者结果：纵向研究的系统评价

背景

许多研究都证明了注册护士对患者安全护理的贡献。然而，大多数将人员配备水平与结果联系起来的证据都是横断面的，具有内在局限性，包括无法确定假定的原因（人员配备）先于结果。没有评论总结了考虑护士人员配备和患者结果的纵向研究。

目标

从纵向研究中识别和评估护士人员配备水平（包括护理团队的组成）与急性护理环境中的患者结果之间关联的证据。

方法

我们对在纵向设计中评估护士配备与患者结局之间的关联的研究进行了系统评价。除非使用差异设计，否则重复横断面分析的研究被排除在外。我们检索了 Medline、CINAHL、Embase 和 Cochrane 图书馆，截至 2022 年 2 月。我们使用 ROBINS-I 工具来评估偏倚风险。我们以表格形式和按结果分组的叙述综合了结果。

结果

收录了 27 篇论文。研究在各种环境和人群中进行，包括成人普通内科/外科病房以及成人和新生儿重症监护病房。人员配备措施以各种不同的方式实施，使得研究之间的直接比较变得困难，并且不可能进行汇总估计。大多数研究存在严重（n = 12）或严重（n = 5）偏倚风险，只有 3 项研究存在低偏倚风险。具有最大偏倚风险的研究被认为可能低估了较高注册护士人员配置的影响。调查结果与更高的注册护士人员配置对预防患者死亡的有益影响的总体情况一致。对于具有较高偏倚风险的其他患者结果，证据不太清楚，但总的来说，支持更高的注册护士人员配置可能会导致更好的患者结果的主张得到支持。关于其他护理人员团体的贡献的证据尚不清楚。

结论

低注册护士人员配置和死亡率之间的因果关系是合理的，这些来自纵向研究的关系估计提供了进一步的支持。为了解决剩余的不确定性，未来的研究应该在不止一家医院进行，并在报告人员配备水平时使用标准化措施。

可推文摘要

在医院病房拥有更多的注册护士与降低死亡率有因果关系——新的评论表明，几乎没有怀疑的余地@ora_dall @workforcesoton @turnel。