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Overcrowding in psychiatric wards and physical assaults on staff: data-linked longitudinal study

  • Marianna Virtanen (a1), Jussi Vahtera (a2), G. David Batty (a3), Katinka Tuisku (a4), Jaana Pentti (a5), Tuula Oksanen (a5), Paula Salo (a1), Kirsi Ahola (a1) and Mika Kivimäki (a6)...

Abstract

Background

Patient overcrowding and violent assaults by patients are two major problems in psychiatric healthcare. However, evidence of an association between overcrowding and aggressive behaviour among patients is mixed and limited to small-scale studies.

Aims

This study examined the association between ward overcrowding and violent physical assaults in acute-care psychiatric in-patient hospital wards.

Method

Longitudinal study using ward-level monthly records of bed occupancy and staff reports of the timing of violent acts during a 5-month period in 90 in-patient wards in 13 acute psychiatric hospitals in Finland. In total 1098 employees (physicians, ward head nurses, registered nurses, licensed practical nurses) participated in the study. The outcome measure was staff reports of the timing of physical assaults on both themselves and ward property.

Results

We found that 46% of hospital staff were working in overcrowded wards, as indicated by >10 percentage units of excess bed occupancy, whereas only 30% of hospital personnel were working in a ward with no excess occupancy. An excess bed occupancy rate of >10 percentage units at the time of an event was associated with violent assaults towards employees (odds ratio (OR) = 1.72, 95% CI 1.05–2.80; OR = 3.04, 95% CI 1.51–6.13 in adult wards) after adjustment for confounding factors. No association was found with assaults on ward property (OR = 1.06, 95% CI 0.75–1.50).

Conclusions

These findings suggest that patient overcrowding is highly prevalent in psychiatric hospitals and, importantly, may increase the risk of violence directed at staff.

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Copyright

Corresponding author

Marianna Virtanen, Finnish Institute of Occupational Health, Unit of Expertise in Work and Organizations, Topeliuksenkatu 41 a A, FIN-00250 Helsinki, Finland. Email: marianna.virtanen@ttl.fi

Footnotes

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The study was supported by the Academy of Finland (grant numbers: 124322, 124271 and 129262) and the BUPA Foundation, UK. The Medical Research Council (MRC) Social and Public Health Sciences Unit receives funding from the UK MRC and the Chief Scientist Office at the Scottish Government Health Directorates. The Centre for Cognitive Ageing and Cognitive Epidemiology is supported by the Biotechnology and Biological Sciences Research Council, the Engineering and Physical Sciences Research Council, the Economic and Social Research Council, the Medical Research Council and the University of Edinburgh as part of the cross-council Lifelong Health and Wellbeing initiative.

Declaration of interest

None.

Footnotes

References

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Overcrowding in psychiatric wards and physical assaults on staff: data-linked longitudinal study

  • Marianna Virtanen (a1), Jussi Vahtera (a2), G. David Batty (a3), Katinka Tuisku (a4), Jaana Pentti (a5), Tuula Oksanen (a5), Paula Salo (a1), Kirsi Ahola (a1) and Mika Kivimäki (a6)...
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eLetters

Re: Overcrowding in psychiatric wards and physical assaults on staff

Marianna Virtanen, Senior researcher
08 March 2011

Overcrowding in psychiatric wards and physical assaults on staff: Response to Dr Mohinder Kapoor

We are of course pleased by Dr Kapoor’s interest in our paper on overcrowding in hospital wards and physical assaults on staff (1). The impact of overcrowding is a potentially serious, albeit understudied, problem in healthcare research. In addition to the potentially increasing risk of violence perpetrated by patients, overcrowding has been shown to be associated with work overload in hospital staff and an increase their risk of mental health problems (2-4).

Dr Kapoor suggests that we were in error in reporting in the text that men were more likely than women to be working in high-occupancy wards. This is a misunderstanding. In table 1 the proportion of men was indeed higher in overcrowded wards. More specifically, 264 of all 343 men in the study (77%) worked in wards with excess bed occupancy; 193 men (56%) worked in wards with the highest overcrowding. The number of women in overcrowded wards was 506, that is, 67% of all 755 women; 317 women (42%) worked in wards with the highest overcrowding. Conversely, 79 men (23%) and 249 (33%) women worked in wards with no overcrowding.

We agree with Dr Kapoor’s view that simply by satisfying one of the Bradford Hill’s criteria of causation (in this case, temporality) does not provide sufficient evidence of a causal link between exposure and outcome. There is currently no consensus on the number of criteria required for determining whether an observed association is causal (5). DrKapoor also referred to another of Bradford Hill's criteria - consideration of alternate explanations for a given association. Interpretation of findings from observational studies are inevitably constrained by concerns over confounding; that is, the role of unmeasured or poorly measured covariates. As we were careful to do in the paper, Dr Kapoor also describes some examples of such confounding factors.

We agree that the Overt Aggression Scale could provide interesting comparison to our findings. However, this scale (or its newer revised version) does not specifically measure physical assaults on staff, which was our study question, but instead a large spectrum of aggressive behaviours ranging from unspecified verbal aggression (loud noises, shouting) to physical attacks, which are not defined specifically as attacks on staff (6). However, owing to the extra resources needed and their time-consuming nature, such detailed instruments are most suitable for smaller scale studies. In a large study based staff (N=1098) drawn from 90 bed-wards, use of those instruments would not have been feasible.

Finally, just as any discussion section based on analyses of observational data inevitably touches on the problem of confounding, though similarly trite, it is also true to state, as Dr Kapoor indicates, that additional studies are now required to replicate and extend our findings before we can conclude with certainty that overcrowding increasesphysical assaults on staff.

Conflict of interest: None declared.

References:

1. Virtanen M, Vahtera J, Batty GD, Tuisku K, Pentti J, Oksanen T, Salo P, Ahola K, Kivimäki M. Patient overcrowding in psychiatric wards andphysical assaults on staff: a data-linked, longitudinal study. Brit J Psychiatry 2011;198:149-55.

2. Kivimäki M, Vahtera J, Kawachi I, Ferrie JE, Oksanen T, Joensuu M,Pentti J, Salo P, Elovainio M, Virtanen M. Psychosocial work environment as a risk factor for absence with a psychiatric diagnosis: an instrumental-variables analysis. Am J Epidemiol 2010;172:167-72.

3. Virtanen M, Pentti J, Vahtera J, Ferrie JE, Stansfeld SA, HeleniusH, et al. Overcrowding in hospital wards as a predictor of antidepressant treatment among hospital staff. Am J Psychiatry 2008;165:1482-6.

4. Virtanen M, Batty GD, Pentti J, Vahtera J, Oksanen T, Tuisku K, etal. Patient Overcrowding in hospital wards as a predictor of diagnosis-specific mental disorders among staff: Prospective cohort study. J Clin Psychiatry 2010;71:1308-12.

5. Bradford Hill, A. The environment and disease: association or causation? Proc Royal Soc Med 1965;58:295-300.

6. Mattes JA. Suggested Improvements to the Overt Aggression Scale-Modified. J Neuropsychiatry Clin Neurosci 2010; 22:E1.
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Conflict of interest: None Declared

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Overcrowding in psychiatric wards and physical assaults on staff

MOHINDER KAPOOR, Specialty Registrar (ST5) Old Age Psychiatry
16 February 2011

Virtanen et al 1 draw our attention to an important issue of overcrowding in psychiatric wards associated with increased risk of violence directed at staff. They reported 46% of hospital staff were working in overcrowded wards, as indicated by > 10 percentage units of excess bed occupancy. This was associated with violent assaults towards employees. Authors used observational study design to find the evidence and present the data. I agree with them that although randomised controlled trials are the best possible ways to demonstrate causality, this type of design would have not been either feasible or ethical in thisstudy.

It appears that authors have reported in error, in results section, that men are more likely than women to be working in high-occupancy wards.This is contrary to what is presented in table 1 where women are more likely than men to be working in high-occupancy wards. Authors have listedimportant limitations relating to this study. Some of these could have been related to the retrospective design of the study. In this study, datawere drawn solely from the self-reporting of staff where the recall periodwas 5 months. This could have potentially led to errors arising from recall problems and under or over reporting. It has been suggested that using structured instruments such as the Overt Aggression Scale 2 or the Staff Observation Aggression Scale 3 can minimize this underreporting. Because of the retrospective nature of this study, authors could have not used such instruments.

Authors suggest a dose-response pattern after they found a strong linear trend between higher occupancy and a high probability of assault. ‘Dose-response relationship’ is one of the Hills criteria of causation. Hills Criteria of Causation 4 outlines the minimal conditions needed to establish a causal relationship between two items. While credit should begiven to authors to describe this dose-response relationship; other criteria's need to be fulfilled before one can establish a causal relationship between higher occupancy and violence. This study was unable to collect data relating to staffing variables and acuity levels of the ward, which may be associated with the incidence of aggression. Complex relationships have been reported between staffing, patient mix, and violence. Risk of violence has been reported to increase with more nursing staff (of either sex), more non nursing staff on planned leave, more patients known to instigate violence, a greater number of disorientedpatients, more patients detained compulsorily, and more use of seclusion. On the other hand risk of violence has been reported to decrease with moreyoung staff (under 30 years old), more nursing staff with unplanned absenteeism, more admissions, and more patients with substance abuse or physical illness. 5 It will be necessary for future studies to take intoaccount other possible explanations (as mentioned above) and effectively rule out such alternate explanations in order to fulfil other Hills criteria of causation one of which is 'Consideration of Alternate Explanations’.

Declaration of interest: None

References:

1.Virtanen et al. Overcrowding in psychiatric wards and physical assaults on staff: data – linked longitudinal study. Br J Psychiatry 2011;198: 149-155.

2.Yudofsky SC, Silver JM, Jackson W, et al. The Overt Aggression Scale for the objective rating of verbal and physical aggression. AmericanJournal of Psychiatry 1986; 143: 35–39.

3.Palmstierna T, Wistedt B. Staff Observation Aggression Scale: presentation and evaluation. Acta Psychiatrica Scandinavica 1987; 76: 657–663.

4.http://www.drabruzzi.com/hills_criteria_of_causation.htm

5.Owen et al. Violence and aggression in Psychiatric Units. Psychiatr Serv November 1998; 49:1452-1457.
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Conflict of interest: None Declared

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