Sleep disruptions are prevalent among ward patients and are associated with a number of negative health outcomes, including elevated blood pressures and delirium. Overnight vital signs are an especially bothersome disruptor and can deplete crucial health care resources. Although vital sign checks every 4 hours are often routine, there are limited data to support this level of monitoring for all ward patients. The Modified Early Warning Score (MEWS) has been used to identify high‐risk patients for rapid response team interventions. This study investigated whether evening MEWS could identify low‐risk patients who could forgo overnight vital signs.


We conducted a retrospective cohort study of consecutive adult inpatients at an academic institution between November 2008 and January 2011. All vital signs were extracted from the electronic medical record (EPIC, Verona, WI), and a MEWS was calculated for each set taken on the general floors, with median‐value imputation used for incomplete sets. The MEWS most closely preceding 11 pm each evening was used to stratify patients. The number of nighttime (11 pm–6 am) disruptions for vital signs and adverse events (AEs), defined as ICU transfers or cardiac arrests in the next 24 hours (11 pm–11 pm), were compared across all MEWS.


A total of 54,096 patients were included in the study, accounting for 182,828 patient‐days on the wards and 1699 AEs. The median evening MEWS score was 2 (IQR, 1–2). The AE rate increased with increasing evening MEWS, from a rate of 5.0 per 1000 patient‐days (when the MEWS was 0 or 1) to 157.3 (when the MEWS was greater than 6), P = 0.003 for trend. However, the frequency of vital sign disruptions was unchanged, with a median of 2 vital sign checks per patient per night and at least 1 disruption for vitals 99% of the nights, regardless of MEWS category. Almost half of all nighttime vital sign disruptions (48%) occurred in patients with a MEWS of 0 or 1.


Overnight vital signs are frequently collected in ward patients regardless of the patient's risk of clinical deterioration. The MEWS identified a subset of patients who had significantly fewer adverse events but had overnight vital signs taken at a rate similar to high‐risk patients. This suggests nighttime frequency of vital signs for low‐risk medical inpatients could be reduced, potentially improving patient sleep without forsaking safety. A tailored approach would also enable reallocation of resources to monitoring higher‐risk patients more frequently. Further prospective study of the safety and benefit of personalized vital sign collection is warranted.

Figure.Bars represent the adverse event rate (/1000 patient-days). Line represent nighttime vital signs (per patient median).