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Revista da Escola de Enfermagem da USP

Print version ISSN 0080-6234On-line version ISSN 1980-220X

Rev. esc. enferm. USP vol.51  São Paulo  2017  Epub Apr 03, 2017 


Aging as a predictor of nursing workload in Intensive Care Unit: results from a Brazilian Sample

Envelhecimento como um preditor de carga de trabalho de enfermagem em Unidade de Terapia Intensiva: resultados de uma amostra brasileira

Renata Eloah de Lucena Ferretti-Rebustini1  * 

Lilia de Souza Nogueira2 

Rita de Cassia Gengo e Silva3 

Vanessa de Brito Poveda4 

Selma Pinheiro Machado5 

Elaine Machado de Oliveira6 

Rafaela Andolhe7 

Katia Grillo Padilha8 

1Universidade de São Paulo, Escola de Enfermagem, Departamento de Enfermagem Médico-Cirúrgica, São Paulo, SP, Brazil.

2Universidade de São Paulo, Escola de Enfermagem, Programa de Pós-Graduação em Enfermagem na Saúde do Adulto, São Paulo, SP, Brazil.

3Universidade Federal de Santa Maria, Departamento de Enfermagem, Santa Maria, RS, Brazil.



Verify if aging is an independent predictor of NW in ICU, according to age groups, and its predictive value as a determinant of NW in ICU.


Study was conducted from 2012 to 2016. A convenience sample composed by patients (age ≥ 18) admitted to nine ICU belonging to a Brazilian hospital, was analyzed. Age was assumed as an independent variable and NW (measured by the Nursing Activities Score - NAS) as dependent. Linear regression model and ROC curve were used for the analysis.


890 participants (361 older people), mostly males (58.1%). The mean NAS score was higher among older participants in comparison to adults (p=0.004) but not within categories of aging (p=0.697). Age was responsible for 0.6% of NAS score. Each year of age increases NAS score in 0.081 points (p=0.015). However, age was not a good predictor of NAS score (AUC = 0.394; p=0.320).


The care of older people in ICU is associated with an increase in NW, compared to adults. Aging can be considered an associated factor but not a good predictor of NW in ICU.

Descriptors Aging; Aged; Nursing; Workload; Intensive Care Units



Verificar se a idade é um preditor independente de Carga de trabalho de Enfermagem (CTE) em Unidade de Terapia Intensiva (UTI), de acordo com o grupo etário e qual sua capacidade preditiva como determinante de maior CTE em UTI.


O estudo foi realizado entre 2012 e 2016. Amostra de conveniência composta por pacientes (idade ≥ 18) admitidos em nove UTI de um hospital universitário brasileiro. A idade foi considerada como variável independente e a CTE (mensurada pelo Nursing Activities Score ‒ NAS) como dependente. Os dados foram analisados por meio de análise de regressão linear e curva ROC.


890 participantes (361 idosos), em sua maioria homens (58,1%). A média do NAS foi maior entre os idosos em comparação aos adultos (p=0,004), mas não entre os grupos etários (p=0,697). A idade foi responsável por 0,6% da pontuação do NAS. Para cada 1 ano de aumento da idade, a pontuação do NAS aumentou em 0,081 pontos (p=0,015). No entanto, a idade não foi um bom preditor de maior CTE (AUC = 0,394; p=0,320).


O cuidado de idosos em UTI está associado à maior CTE. A idade pode ser considerada um fator associado, mas não um bom preditor de CTE em UTI.

Descritores Envelhecimento; Idoso; Enfermagem; Carga de Trabalho; Unidades de Terapia Intensiva



Verificar si el envejecimiento es un predictor independiente de la Carga de Trabajo de Enfermería (CTE) en la Unidad de Cuidados Intensivos (UCI), según grupos etarios y su valor predictivo como determinante de la CTE en la UCI.


Se analizó una muestra de conveniencia compuesta por pacientes (edad ≥ 18) ingresados en nueve UCI pertenecientes a un hospital brasileño. La edad se asumió como variable independiente y como variable dependiente la carga de trabajo de enfermería -medida por el sistema Nursing Activities Score (NAS) de puntuación de actividades de enfermería. Para el análisis, se utilizaron el modelo de regresión lineal y la curva ROC.


890 participantes (361 adultos mayores), en su mayoría varones (58,1%). La puntuación NAS promedio fue mayor entre los participantes adultos mayores en comparación con los adultos (p=0,004), pero no en las categorías de envejecimiento (p=0,697). La edad fue responsable del 0,6% de la puntuación NAS. Cada año de edad aumenta la puntuación NAS en 0,081 puntos (p=0,015). Sin embargo, la edad no resultó un buen predictor de la puntuación NAS (AbC=0,394; p=0,320).


El cuidado de los adultos mayores en UCI se asocia con un aumento de la CTE en comparación con los adultos. El envejecimiento puede considerarse un factor asociado, pero no un buen predictor de la CTE en UCI.

Descriptores Envejecimiento; Anciano; Enfermería; Carga de Trabajo; Unidad de Cuidados Intensivos


The number of older people (> 60 years) in Intensive Care Units (ICU) is increasing substantially, as population ages. The mean age of patients in ICU is higher than it used to be. This is not an exclusive Brazilian phenomenon but a worldwide one: older people account for at least 50% of occupation in ICU and the number of oldest-old patients (≥ 80 years) is significant1-5. Nurses and all the health care team should be prepared to the care of these patients in acute and critical conditions.

Along time, the concept that age has to be considered during decision of whose patients should be admitted to ICU is changing. Nowadays, advanced age itself is not a contraindicative criterion for admission in ICU and several factors are considered6-7. Decisions have to be based on the condition of the person and the potential to benefit from ICU resources leading to recovery. Health professionals have to concentrate efforts in preventing older people to evolve into a critical condition indicative of ICU admission. Once it is not possible, they should be beneficiated from all available ICU resources, aiming to achieve expected outcomes of recovery and discharge, as soon as possible.

The specialized care of older people in the ICU requires skilled nurses, knowledgeable of specificities inherent to senescence and senility1,4,8-13. This is one of the most important determinants of quality of care and patient safety in ICU, when considering the intensive care of older people. Thus, one might think that the nursing process directed to the care of older people in critical condition is associated with an increase in nursing workload (NW), as they tend to have more morbidity, more risk of mortality and, in some situations, more dependency.

To date, some published researches explored the analysis of burden among caregivers of older people discharged from ICU. Therewithal, associated factors for NW in ICU have also been described14-17. The great majority of these previous studies focused on determining predictors of NW in adult patients admitted to ICU. Nonetheless, studies that aimed to determine predictors of NW in older people populations worldwide are lacking. In Brazil, one study18 analyzed predictors of NW among older patients admitted to ICU. Findings evidenced that severity, type of admission and old age (70-79 years) were determinants of NW. The predictive value of age to determine NW was not tested.

As far as it is known, no previous study analyzed the effect of age in NW in a representative sample, stablishing comparisons with other age groups. Thus, we aimed to verify whether age is an independent predictor of NW in ICU, according to age groups, and to verify its predictive value as a determinant of NW in ICU.


Study Design, Settings and Participants

This was a single center, retrospective cohort study. Study was conducted from 2012 to 2016. A convenience sample was used including patients (age ≥ 18) who were admitted to nine different specialties ICU (Surgery, Internal Medicine, Clinical Emergency, Infectious Diseases, Nephrology, Neurology, Pulmonology, Trauma and Burn) for clinical or surgical treatment, at a large Brazilian public general hospital. Data was collected from review of all available medical charts.

Study variables and data analysis

In this study we assumed age as an independent variable and the Nursing Activities Score (NAS), an instrument for measuring NW in ICU, as dependent. Other variables were analyzed to characterize the sample: sex, Charlson Comorbidity Index (CCI), condition of the patient according to death risk calculated by the Simplified Acute Physiology Score II (SAPS II) and Logistic Organ Dysfunction System (LODS), type of admission, length of stay (LOS) in ICU, type of ICU, and outcome (discharged or death) in critical care unit.

For the analysis, sample was stratified into age groups. To test if there was a difference in NW among adults vs older people, we stratified age in two subgroups: adults (<60 years old) an older people (≥ 60 years old). To test if there were differences in NW into older people age subgroup, we stratified age in three subgroups: young old (60├70), old (70 ├ 80) and oldest old (≥80). We also compared the four age groups: adults, young old, old, older old.

The descriptive analysis was conducted by using measures of central tendency and dispersion. T-Student test was used to compare NW between adults and older people. The Levene test was applied to identify the mean NAS distribution (normal or non-normal) among the three older people age groups. To compare the NW among the older people age group and among the four age groups, we applied One Way Anova with post-hoc analysis. The Fisher’s exact test was used to test associations among nominal variables. A Linear regression model (assuming age as a continuous independent variable) was built to identify if age is a predictor of NW. To determine whether age is a good predictor of NW, the area under the curve (AUC) with 95% confidence interval was estimated. For this, we used the NAS cut-off point obtained by a classification tree. Age was considered a good predictor of NW if the AUC was ≥ 0.70. All tests were two-tailed and the p-value was set at 0.05.

Ethical statement

The study protocol and waiver of consents were approved by the local Ethics Committee (process number 0196/2011) and the study was conducted in accordance with the Declaration of Helsinki.


Sample consisted of 890 participants (529 adults and 361 older people), mostly males (58.1%), with mean age of 54.1±17.4. Table 1 presents samples’ characteristics.

Table 1 Distribution of participants according to some selected characteristics, according to age group - São Paulo, SP, Brazil, 2012-2016. 

<60 60+ 70+ 80+ p-value
Sex (n;%)
Men 320; 36.0 114; 12.8 61; 6.9 22; 2.5 0.001*
Women 209; 23.5 68; 7.6 60; 6.7 36; 4.0
Age (mean±SD) 42.6±11.8 64.5±2.6 74.1±2.9 84.9±4.1 <0.001#
Charlson (mean±SD) 1.8±1.9 1.8±2.0 1.9±2.0 1.8±1.6 0.774#
SAPS2 - 1st day (mean±SD) 32.3±13.6 31.8±13.6 33.0±16.6 32.0±14.4 0.902#
LODS - 1st day (mean±SD) 5.2±3.7 5.1±4.0 5.3±4.3 4.7±3.7 0.722#
NAS (mean±SD) 69.9±13.9 73.2±18.2 71.9±13.1 73.8±7.7 0.027#
LOS-ICU (mean±SD) 7.0±10.9 6.3±8.9 7.2±7.7 7.3±8.3 0.808#
Type of ICU (n;%)
Clinical 171; 19.2 65; 7.3 55; 6.2 20; 2.2 0.799*
Surgical 221; 24.8 64; 7.2 41; 4.6 27; 3.0
Specialized 137; 15.4 53; 6.0 25; 2.8 11; 1.2
Type of admission (n;%)
Clinical 326; 36.6 114; 12.8 89; 10.0 38; 4.3 0.078*
Surgical (elective) 95; 10.7 38; 4.3 18; 2.0 7; 0.8
Surgical (emergency) 108; 12.1 30; 3.4 14; 1.6 13; 1.5
Outcome in ICU
Discharged 441; 49.6 132; 14.8 84; 9.4 41; 4.6 <0.001*
Death 88; 9.9 50; 5.6 37; 4.2 17; 1.9

# Anova

* Fischer exact test

The mean NAS score was higher among older people (p=0.004) in comparison to adults. This difference remains even when adults were compared to the stratified older people age group (p=0.027). It was observed that NAS has a normal distribution among the three older people age groups (Levene = 3.58; p<0.020), and no statistical difference was found among them (p=0.697). Post-hoc analysis certified that no difference in mean NAS score within older people age group exists, what indicates that there is no need to categorize older patients in age groups when analyzing nursing workload. The best NAS cut-off point was 52.0, as shown in Figure 1.

Figure 1 Classification tree for determining the cut-off point for NAS score according to age group (adults vs older people) - São Paulo, SP, Brazil, 2012-2016. 

Age accounts for only 0.6% of the NAS score. Each year of age increases NAS score in 0.081points (p=0.015), but it cannot be considered a good predictor of nursing workload, once its AUC is insignificant and below the theoretical limit (AUC= 0.394; CI 0.202 - 0.587; p=0.320), considering a cut-off point of 52.0 (Table 2; Figure 2).

Table 2 Linear regression model for age as predictor of Nursing Workload - São Paulo, SP, Brazil, 2012-2016. 

Model Adjusted R Square Durbin-Watson Unstandardized Coefficients Standardized Coefficients t Sig. 95.0% CI for B
B Std. Error Beta
1 (Constant) 67.476 1.587 42.517 0.000 64.361 - 70.591
Age 0.006 1.678 0.068 0.028 0.081 2.435 0.015 0.013 - 0.123

PredictorAge (measured continuously)

Dependent VariableNAS

Figure 2 Receiver Operating Characteristic Curve for predictive ability of age to best determine high nursing workload (NAS>52.0) in intensive care unit - São Paulo, SP, Brazil, 2012-2016. 


The results of the present study evidenced that the care of older people in ICU is associated with a higher NW, compared to adults. Despite the results pointed age as an independent predictor of NW in ICU, the strength of this causative relation was not of higher importance. The evidences found indicate that age accounts for a very modest part of NW; is responsible for very little difference in NAS score; and has no discrimination ability to predict high NW in ICU. On the other hand, when analyzing only older people group, age was not an independent predictor of NW in ICU. It means that despite the association, no causative relation can be stablished between older age groups (60+; 70+; 80+) and NW. In other words, NW among older people is higher when compared to adults, but advanced age is not an exclusive determinant of higher NW in ICU.

A previous study18 analyzed 71 patients admitted to ICU and found that there was no significant difference of NW in older age groups, what is consistent to our results. They did not investigate NW among older patients in comparison to adults. Nonetheless, they found an increased odds ratio (4.56) for having higher NW among septuagenarians. In another study19 no difference between the mean NAS scores for older (66.44%) and adult (66.33%) patients admitted to an ICU was found. A study that analyzed 600 patients20 and compared the NW required by adult (>18 and < 60 years), older (>60 and < 80 years) and oldest-old (>80 years) showed that the NW measured by NAS upon admission at the ICU (first 24 hours) was similar among age groups. At discharge, a statistically significant difference was found among groups and this difference occurred between adult (NAS=50.37) and older (NAS=55.85) patients.

No other study was found to enlarge comparisons with our findings, considering NW. However, it was possible to observe that our sample’s characteristics was similar to other previous studies in terms of: proportion of older people, gender distribution, type of treatment, comorbidity burden, length of stay in ICU, severity and mortality21-22.

In the present study, we specifically addressed age as a predictor of NW in ICU. The importance of NW in ICU in remarkable, mainly because of its association to adverse events23 that can affect patient’s safety and increase mortality23-25. In ICU, more than 50% of the occurrence of adverse events are in older people26, but whether it is determined by NW is yet to be investigated.

Another point to discuss is that by fixing age threshold, commonly used to categorize older people into groups, no association to NW was observed. While this categorization of age may be considered a ‘bad concept’ by some gerontologists, it helps to recognize heterogeneities within the old age. Old age comprehends a very long life period in a way that an old person with 65 years may be different from another with 85 years, in terms of physiologic aging. Physiologic organ reserve and tolerance to treatment decreases along aging and this have to be considered when caring for older people in ICU, otherwise adverse events may happen and patient safety may be compromised. Even so, nurses have to consider that chronologic age and physiologic age may not correspond because aging is a heterogeneous process, reinforcing the practice of individualized care.

Once it was a retrospective study, it was not possible to analyze baseline characteristics important to gerontological understanding of older patient’s health condition, such as cognitive and functional status. This information was not available in medical records, thus limiting interpretation about the impact of pre-admission dependence presented by the patient to NW, other than clinical condition. Dementia patients who are cognitively and functionally impaired, for example, tend to impose a higher burden to nursing staff, independent of being critically ill.

Surprisingly, the characteristics presented by older patients were very similar to the ones observed in adults, even considering comorbidity burden measured by Charlson Cumulative Index. Probably there was a selection bias related to ICU admission. Although nowadays age, itself, should not be used as a criterion for ICU admission, it is still associated with a decreased likelihood of admission. The oldest-old patients have 67% less chance of being admitted to ICU than adults27. As long as we did not assess patients who unfit admission criteria, we lost the possibility to understand whether these older patients with different clinical conditions would impose an even higher NW and change the findings of the present study.

If benefits from ICU directed to older people are not clearly defined and if misconceptions regarding aging and ageism still prevail, potential patients were missing and selection bias occurred. This is particular important to state because it suggests that the phenomenon should be further investigated by research methods directly designed to cover these aspects. Elsewhere, in clinical practice, criteria for determining whose older people shall benefit from ICU have to be established considering the intersection between institutional/ICU practices and gerontological principles.

Care for older people in ICU is epidemiologically proved to increase several times fold, worldwide. In Brazil, 11% of total population are above 60’s28. In 2013, life expectancy at birth was 74.9 years and after the age of 60 it was 21.8 years-old29. Health life expectancy at birth is 64 years28. Epidemiology of aging indicates a profile of patients with high morbidity with risk of being acute and critically ill21-22. Critical care nurses will have to cope with gerontological features of aging in their clinical practice

Last but not least, the present findings may contribute to evidence based nursing practice in a way that these results deconstruct the stereotype that older people is responsible for nursing workload in ICU. Although results are not conclusive, because complex interactions among aging, gerontological features and critical condition were not addressed, they can be used to guide actions in practice until further investigations can contribute by refuting or reinforcing the present findings.


The care of older people in ICU is associated with an increase in nursing workload, compared to adults. Aging can be considered an associated factor but not a predictor of nursing workload in ICU. Complex interaction of aging and other factors inherent to this special population and its impact in nursing workload requires further investigations.


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Financial support

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Fundação de Amparo à Pesquisa de Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) and Fundación Mapfre.

Received: September 19, 2016; Accepted: January 06, 2017

Corresponding author: Renata Eloah de Lucena Ferretti-Rebustini. Av. Dr. Enéas de Carvalho Aguiar, 419. 3º floor. Room 354 - Cerqueira César. CEP: 05403-000 São Paulo, SP, Brazil.

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