Many studies report higher prevalence of back pain and occupational back injuries for nurses compared with other occupational groups. 1–5 Swedish statistics show a sixfold excess risk of over-exertion back injuries among assistant nurses compared with other employed women in Sweden. 5 These injuries can lead to sick-leaves, 5 persistent medical problems, 6 or job changes. 3 Most injuries occur during patient transfer. 7–9 In a previous study, we showed that most accidents leading to a back injury occur not in emergency situations but during ordinary planned patient transfers performed by experienced nurses. 10
In this study our goal was to identify and quantify work-related and non-work-related risk indicators for reported over-exertion back injuries among nursing personnel.
The source population consisted of all nursing personnel (registered general nurses, state enrolled nurses and auxiliary nurses), who were employed in the Stockholm County hospitals from March 1, 1992 to December 31, 1994, approximately 24,500 persons.
Cases were nurses who reported on a work injury insurance form, a work-related over-exertion back injury (independently of severity) that was coded as an occupational accident. 11 We randomly selected three referents for each case from the source population, matching on sex and age (within 5 years).
In Sweden, all working persons are insured against occupational injuries. Employers report such injuries on an injury form, which is sent to the social insurance office with a copy to the occupational health care unit. When the copy of the injury form arrived at the occupational health care unit, the three referents were selected. All cases and referents had to have worked at least 1 week during the 3 months preceding the injury (cases) and preceding the enrollment in the study (referents). The three referents per case were drawn once per month to ensure that the numbers of exposed and unexposed referents would be in proportion to the length of exposed and unexposed person-time in the source population. 12 Psychiatric wards were excluded since patient violence constitutes a more severe problem at these wards. 13
During the study period, we identified 292 cases and 877 referents. Ninety-three per cent of the cases (240 women and 31 men) and 79% of the referents (614 women and 79 men) answered the postal questionnaire. Seventeen cases and 72 referents declined, three cases and 85 referents did not answer despite repeated reminders and for one case and 27 referents, addresses could not be traced. Given the low number of men in the study, we confined the data analyses to the 240 cases and 614 referents that were women.
We used postal questionnaires to assess work-related and non-work-related exposure factors, musculoskeletal symptoms, and prior accidents leading to back injuries. The exposure information referred to “the week before the over-exertion back injury” for the cases and to “the last working week” for the referents, except for prior injury, which referred to the previous 12 months.
The questions concerned work organization, physical exposure, psychosocial factors, background and life-style factors. Most questions had fixed answer alternatives, a few being followed by an open question to obtain additional information. All exposures were dichotomized, with cut-off points based on substantial results of previous studies, experience and knowledge of risk indicators and working conditions, and from the exposure distribution in the group studied.
We asked about occupation, type of clinic, working hours, overtime work, and whether the nurse had fixed working hours or worked on a rolling schedule.
We asked about patient transfers during a working shift, transfer training, practical training on transfer devices on their own wards, the use of transfer devices and physical exertion during work.
We assessed physical exertion at work using a modified rating of perceived exertion (RPE) scale. 14 The range was from “0, resting,” to “14, maximal exertion.”15 The nurses were asked, “How physically exerting did you in general perceive your work to be last week?” (for the cases: “… the week before the accident?”). We defined high physical exertion as an RPE rating greater than 8, corresponding to between “somewhat hard” and “hard.”
We used the Swedish version of Karasek’s and Theorell Psychological Demands and Decision Latitude Indexes. 16 The range of the psychological demand index score was 5–20 and a score ≥16, ie, the third quartile, was defined as high psychological demands. For decision latitude, scores ranged from 6–24, the definition of low decision latitude being a score ≤14, the first quartile. The combination of high psychological demands and low decision latitude at work was considered as a job strain situation and a potential risk indicator. 16
Background and Life-Styles Factors
We asked about age, height, weight, smoking habits, number of years in the nursing profession, back pain last week, accident leading to back injury during the previous 12 months, physical training during the previous 3 months, self-rated physical fitness compared with other persons of the same age, and whether the nurse had immigrated to Sweden. We calculated body mass index (BMI) as kg/m 2. Because we had a higher proportion of younger nurses, we classified the nurses into two age groups, <40 years, and ≥40 years.
Data Treatment and Statistical Analysis
We calculated the relative frequency of exposed cases and referents for the respective exposures. We estimated effects for reporting over-exertion back injury, with a 95% confidence interval (95% CI), using logistic regression and interpreted the odds ratios as incidence rate ratios. 17 We compared the effect associated with patient transfer for nurses who frequently used transfer devices with nurses who did not, and nurses who had received training in transfer technique and in using transfer devices with nurses who had received less, or no training.
The mean age of the nurses was 34 years (range 19–62). 46% had been working 11 years or longer in nursing. Work at orthopedic wards entailed the highest relative risk of accidents leading to over-exertion back injuries compared with work at all other clinics (RR = 5.2; 95% CI = 2.7–10.2) (Table 1). Elevated relative risk was also found for nurses who worked full time (RR = 2.4; 95% CI = 1.6–3.6) and who worked as assistant nurses (RR = 1.5; 95% CI = 1.0–2.3). The pattern of risk indicators was the same for registered general nurses and assistant nurses, but the effects were slightly higher among assistant nurses working on an orthopedic ward and working full time.
There was an increased relative risk for back injury among nurses who transferred patients once or more per shift (RR = 2.7; 95% CI = 1.6–4.5) compared with those who transferred patients at irregular intervals. The median value for number of patient transfers was the category of 3–10 transfers per shift with 21% performing ≥11 transfers per shift. The median value for using transfer devices comprised the category 10% of the patient transfers.
Forty-seven cases (20%) and 73 referents (12%) had had a back injury during the previous 12 months, and had a relative risk of 1.8 (CI = 1.2–2.9) for a new injury. In 95% of the cases and 94% of the referents, the previous injuries were not reported on an injury insurance form.
Twenty-three per cent of the cases and 16% of the referents had immigrated to Sweden. Nearly half of the cases, and one fourth of the referents that were immigrants were from a country outside Northern Europe. Immigrants had an increased relative risk (RR = 1.6; 95% CI = 1.0–2.4), with the highest risk among those younger than 40 years of age (RR = 2.1; 95% CI = 1.3–3.3).
We found little relation between the reported back injury and back pain during the previous week, neither with reported job strain nor with lack of regular physical training.
The effect of patient transfer was lower among nurses who used transfer devices more often and among those who had received practical training in how to use the transfer devices, compared with nurses who seldom used devices or were not trained in how to use them (Table 2). We detected no difference in effect between nurses who had been trained for more than 1 day and those who had received less than 1 day of training in patient transfer.
We observed a slightly higher relative risk of patient transfer among nurses older than 40 years (RR = 3.7; 95% CI = 1.8–7.6) compared with the younger (RR = 3.1; 95% CI = 1.8–5.3), while the relative risk increased greatly for nurses older than 50 years (RR = 6.3; 95% CI = 1.8–22.9) compared with younger nurses (RR = 2.9; 95% CI = 1.9–4.7).
Working on an orthopedic ward, performing more than one patient transfer per working shift, working full time, working as an assistant nurse, having had a previous back injury and being an immigrant increased the relative risk of an over-exertion back injury. Practical training in using transfer devices, and frequent use of these devices, decreased the relative risk associated with patient transfers. Earlier studies have shown, however, that transfer devices are seldom used because the nurses do not understand how to use them or lack experience in their use, 10,18–20 or because the devices are not suitable for the task or are out of order. 10
Often orthopedic patients have had recent surgery and/or have plaster or other contrivance that impedes transfer both in bed and to/from a bed, in which vicinity most injuries occur. 10 Orthopedic patients are also trained to walk early when they are still weak and insecure.
Working full-time in physically heavy work may cause fatigue and hence impaired neuromuscular control and awkward working movements and postures, which may increase the risk for back injury. 21 Fewer health problems have been observed among nurses working less than 20 hr/week than among those who work longer hours. 22
Assistant nurses perform more patient transfers and also do a greater share of other practical nursing tasks, eg, feeding and dressing compared with registered general nurses. Assistant nurses spend on average 71% of their working time in patient-handling tasks, compared with 41% for registered general nurses. 23
Immigrants might have difficulties in changing jobs. 24 Language difficulties might contribute to misunderstandings during, for example, patient transfer.
The frequency of earlier injuries during the previous 12 months was rather high both among cases (20%) and referents (12%), but very few of these injuries had been reported on an injury insurance form, however. This indicates that the magnitude of the problem is greater than statistics shows, owing to under reporting, which has been observed previously. 6,10,25
Age as a potential risk indicator could not be investigated as subjects were stratified by age when selecting referents. The relative risk associated with patient transfer was higher among nurses older than 50 years than among younger nurses, however. Nurses who report an injury due to an accident generally have long experience in their profession 11,26–28 and also of the specific task they were performing when the injury occurred. 10 It may be that many of the injuries reported in the present study are cumulative by nature, owing to repeated lifts, especially as earlier back injury was a risk indicator. Injuries among older assistant nurses lead to longer sick leave than injuries among younger ones. 5,29
Shift work showed no increased risk in our study. Others have commented that shift work can have adverse effects on the worker, such as disrupting social and family life and upsetting circadian rhythm. These effects may lead to sleep disturbances and fatigue, impaired work performance, and safety awareness. 30
Some studies showed a relation between overweight and occupational injury, especially low-back injury. Others, however, found no such association, and it has been suggested that the effects of overweight may only be substantial among the most obese individuals. 31
Back pain during the previous week was not associated with an increased relative risk for back injury; rather the opposite was observed. A possible explanation would be that a person with an aching back is more careful and may try to avoid the heaviest or more risky tasks if there are colleagues who can take over. In addition, it may be that a sudden injury has a different etiology than back pain, and is thereby not associated with it. Nearly half the cases and referents, however, reported back pain “last week,” demonstrating that nurses go to work despite back pain, which has also been reported earlier. 18
Job strain was not associated with increased relative risk for back injury, which conflicts with another study of workers performing lighter work than nurses, 32 which may indicate that in physically heavy work, physical factors are the most important risk indicators of back injury.
All who reported an injury, and had been working for at least 1 week during the previous 3 months, were included in our study regardless of whether they had been on sick-leave. This inclusion might lead to the observed relative risk appearing lower than if only cases with the most severe injuries had been included.
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