Abstract
BackgroundTime trends and seasonal patterns have been observed in nurse staffing and nursing-sensitive patient outcomes in recent years. It is unknown whether these changes were associated.MethodsQuarterly unit-level nursing data in 2004–2012 were extracted from the National Database of Nursing Quality Indicators® (NDNQI®). Units were divided into groups based on patterns of missing data. All variables were aggregated across units within these groups and analyses were conducted at the group level. Patient outcomes included rates of inpatient falls and hospital-acquired pressure ulcers. Staffing variables included total nursing hours per patient days (HPPD) and percent of nursing hours provided by registered nurses (RN skill-mix). Weighted linear mixed models were used to examine the associations between nurse staffing and patient outcomes at trend and seasonal levels.ResultsAt trend level, both staffing variables were inversely associated with all outcomes (p < 0.001); at seasonal level, total HPPD was inversely associated (higher staffing related to lower event rate) with all outcomes (p < 0.001) while RN skill-mix was positively associated (higher staffing related to higher event rate) with fall rate (p < 0.001) and pressure ulcer rate (p = 0.03). It was found that total HPPD tended to be lower and RN skill-mix tended to be higher in Quarter 1 (January-March) when falls and pressure ulcers were more likely to happen.ConclusionsBy aggregating data across units we were able to detect associations between nurse staffing and patient outcomes at both trend and seasonal levels. More rigorous research is needed to study the underlying mechanism of these associations.Electronic supplementary materialThe online version of this article (doi:10.1186/s12912-016-0181-3) contains supplementary material, which is available to authorized users.
Highlights
Time trends and seasonal patterns have been observed in nurse staffing and nursing-sensitive patient outcomes in recent years
A meta-analysis based on findings from a systematic review of the literature identified a consistent relationship between higher nurse staffing and lower patient mortality; findings regarding the association between nurse staffing and other outcomes such as falls, pressure ulcers, and urinary tract infections varied across studies, and overall results were inconclusive in a pooled analysis [7]
Park et al showed that higher registered nurse (RN) hours per patient days (HPPD) was associated with lower unit-acquired pressure ulcer rates in adult care units [8], whereas other researchers reported that staffing and hospital-acquired pressure ulcers were not meaningfully associated [9] or they were associated in the opposite direction, that is, the higher staffing the higher pressure ulcer rate [10,11,12]
Summary
Data This longitudinal study was based on 2004–2012 data from the NDNQI. Participating NDNQI hospitals submit unit-level nurse staffing and inpatient falls data monthly and pressure ulcers data quarterly. There were 1240 units with complete fall data (36 quarters in 2004–2012) For each of these units, a linear model was used to test the trend (time) and seasonality (three dummy variables indicating four quarters) in the fall rate based on the 36 quarterly observations. For the analyses on falls, 42 final groups were built based on a total of 217,592 unitlevel quarterly observations; for the analyses on pressure ulcers, 41 groups were built based on a total of 187,368 unit-level quarter observations (see Additional file 1: Figure S1, flowcharts of data preparation). Variables All outcome and staffing variables used for analysis were change scores from the first quarter with data in this study for each group (baseline). The analyses were designed to examine temporal associations between nurse staffing and patient outcomes in aggregate, not at hospital or unit level.
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