Jensen, Jette Nygaard MSc; Karpatschof, Benny D Phil; Labriola, Merete PhD; Albertsen, Karen PhD
Today, almost all countries in the European Union, including Denmark, lack health care workers because of demographic changes.1,2 This constitutes a serious problem, as a significant decrease is expected in the working population (16 to 65 years old) along with an increase in the population (65 years old).1 This has led to increasing concern, both in the profession and within the government about whether the supply of educated health care workers is sufficient to meet future health care needs.
These problems are increased as many health care workers experience musculoskeletal pain, especially low back pain (LBP), where the annual prevalence ranges from 43% to 63%.3–7 Compared with the general population, the annual prevalence ranges from 15% to 50%.8–10 LBP is highly correlated with sickness absence11,12 also among health care workers.13,14 Although the research literature is not consistent on the effect sizes,6,15,16 the physical and psychosocial work demands have been associated with the high prevalence of LBP.17–19 In the Scandinavian countries, LBP is the most prevalent cause of sick leave and disability pension among health care workers.14,18,20 Burdorf and Jansen21 estimated (with the Markov model) that workers in the health care sector would have 140 weeks of sickness absence because of LBP if they worked 40 years in the job. Nevertheless, despite a clear association between LBP and sickness absence among health care workers, it is not necessarily causal. There is limited understanding of why some people with LBP are absent from work for longer or shorter periods, whereas others are not.
Research suggests that a person's coping style and beliefs about pain may be relevant for understanding sickness absence because of pain.22 Fear-avoidance beliefs (FAB) has been suggested as a central mechanism in the development of long-term LBP problems23 and the accompanying sickness absence.22,24
FAB is defined as the dysfunctional interpretation that some physical and social activities will worsen pain. When the level of FAB is high, a person's anticipation of how much pain in the low back a particular activity will produce tends to be greater than the pain levels actually experienced. It has been stated that “fear of pain and what we do about it may be more disabling than the pain itself.”24 Therefore, FAB may contribute to the explanation of why some people with musculoskeletal pain develop a chronic pain syndrome, whereas others are able to recover.23,24 In a study, 63 female health care workers with moderate to severe back pain were categorized in two groups: one group who had been off work due to back pain, and a second group who had not been off work. The two groups were matched on the pain level they experienced. It was found that the group who had been off had stronger beliefs that pain was directly related to activities, and that they had little control over their pain; further, they tended to focus more on their pain.22
Today's guidelines in LBP treatment emphasize staying active and continuing normal daily activities, including going to work when LBP is being treated (www.backpaineurope.org). Given these facts, it may be advisable to include beliefs about pain in the research on LBP and sickness absence.
The aims of this study were 1) to assess the predictive effect of FAB on sickness absence days and spells, 2) to assess the possible moderating effect of FAB on the relation between LBP and sickness absence days and spells. The analysis was based on data from a cohort of newly educated health care workers with LBP.
We hypothesized 1) that high FAB will have an independent effect on sickness absence days and spells, and 2) that the effect of LBP intensity on sickness absence will be stronger for health care workers with high FAB than for health care workers with low FAB.
MATERIALS AND METHODS
Data used in this study stemmed from a national survey—the Danish Health Care Worker Cohort-Class of 2004 (DHCWC-2004). The baseline data set comprised all students in Denmark in their last semester of education in health- and elderly-care. The students had graduated as health care helpers or health care assistants in 2004. Danish health care helpers have 14 to 19 months of education, depending on the length of their basic school education and are qualified to work with nursing and practical assistance in the eldercare sector. The education of health care assistants is a continuation of the health care helper education and takes an additional 20 months to fulfil. The health care assistants are qualified to work in the eldercare sector and, additionally, in hospitals. In this article, health care helpers and health care assistants are termed health care workers.
The cohort was followed for 2 years. In 2004 at baseline, 6365 students were invited to participate in the survey; 5696 (90%) returned the baseline questionnaire. In 2005 and 2006, data for the first and second follow-up were collected to follow the respondents 1 and 2 years after graduation, respectively, resulting in an overall response rate of 65% at first follow-up and 54% at second follow-up. For this study, we conducted analysis based on data from the first and second follow-up, except the confounding effect of previous sickness absence, which was measured at baseline.
The final sample in this study—1724 respondents—comprised female health care workers with LPB ≥1 day during the previous 12 months measured at first follow-up (Fig. 1).
We used self-reported sickness absence days and sickness absence spells measured at second follow-up. Sickness absence days and spells were measured by two open questions asking for number of days and spells of sickness absence during the previous 12 months: “How many days of sickness absence have you had in the previous 12 months?” and “How many sickness absence spells have you had in the previous 12 months?”
FAB was measured at first follow-up by the FAB about Work Questionnaire developed by Waddell et al.24 This questionnaire is designed to measure the beliefs about how work affects pain and to what extent work activities should be avoided. FAB about work was measured with a shortened version—item number 12, 13, and 14 in the original scale, because they were the most relevant to the overall aim of the study. The three items were “I should not do my normal work with my present pain,” “I cannot do my normal work with my present pain,” “I should not do my normal work until my pain is treated.” Each item was measured on a 1 to 5 point scale, with response categories “totally disagree”... to “agree.” The questions were translated by experienced researchers and tested in a qualitative study (N = 31). Cronbach α for the scale was 0.84. We also included the FAB physical activity scale although we did not find any effect of this scale on sickness absence (results not shown). This lack of positive results is in concordance with other studies have found greater utility of the work subscale for explaining outcomes.25
Low Back Pain Intensity
Low back pain intensity was measured as self-reported pain. The participants were asked to rate their pain intensity during the previous 3 months: “Please indicate the average level of low back trouble (pain or discomfort) during the previous 3 months.” The rating scale was 0 to 9, where 0 indicated no pain at all and 9 the worst possible pain.
The LBP intensity and FAB scales were categorized into three groups each by the number of respondents: low (LBP, 0 to 2; FAB, 0 to 12.50), moderate (LBP, 3 to 5; FAB, 12.51 to 66.67), and high (LBP, 6 to 9; FAB, 66.88 to 100). An analysis of variance of the nine possible combinations showed that the combinations with low and moderate FAB and LBP did not differ, differences related to only the group with high FAB and LBP. Therefore, the two three-point scales of FAB and LBP were simplified to two-point scales: low-moderate and high FAB and LBP intensity, respectively.
Previous Sickness Absence
To avoid over-control of confounding, sickness absence at first follow-up was not included. Instead, previous sickness absence at baseline was included as a confounder where participants were asked to report their sickness absence days during the previous 12 months.
As individual covariates, we included age and previous sickness absence because these variables have been found to be associated with future sickness absence.26 Furthermore, we included the following work environmental factors: emotional demands, hiding emotions, influence, role clarity, role conflicts, and physical work load.
Psychosocial Work Environmental Factors.
The research literature has demonstrated strong association between psychosocial work characteristics and both self-reported and registered sickness absence.27,28 Therefore, we included indicators of the psychosocial work environments as covariates in the analyses. Psychosocial work environmental factors were measured by the Copenhagen Psychosocial Questionnaire (COPSOQ).29 The following scales were used influence, two items, (Cronbach α, 0.73); meaning at work, three items, (Cronbach α, 0.74); role clarity, two items, (Cronbach α, 0.73); and role conflict, two items, (Cronbach α, 0.46). Two single items measured emotional demands, and demands for hiding emotions. There were five response categories to items: always or often or sometimes or rarely or never or almost never.
Physical Work Load.
Strong positive associations between physical work load and sickness absence have been found,14,30 so physical work load was included in the analyses as a covariate. Physical work load was measured with 14 items who described unfavourable postures of the body or the extremities, eg, bending, twisting, kneeling, or squatting as well as handling heavy loads during work. The answers were given on a 5-point rating scale ranging from “never” to “very often.”31 All questions were transformed into a physical work load index developed and validated by Hollmann et al,31 where each question has a weighted value. These values were aggregated to one value expressing the total work load of the lumbar spine in the job.
SPSS 17.0 (SPSS, Chicago, IL) was used for all statistical analyses. For the characteristics mean, minimum, and maximum were calculated. As absence days are counting data that do not follow the normal distribution, a generalized linear model with Poisson distribution was used in the prospective model. Poisson regression has been found to be suited to linear regression in predicting absence and is widely used in the absence literature.32,33 To account for the over-dispersion, we used a scale parameter in the Poisson regression model. To test the robustness of the results in the use of the Poisson model with a scale parameter, an additional analysis was made by using a negative binomial model instead. The use of a negative binomial reduced the deviance but did not change the effect of LBP and FAB on sickness absence days.
The association between FAB, LBP intensity, and sickness absence and the moderating effect of FAB was estimated in the following three steps: in model 1, the predictive effect of FAB and LBP (measured at first follow-up) on sickness absence days and spells (measured at second follow-up) was analyzed, controlling for age and previous sickness absence measured at baseline; in model 2, work environment factors (measured at first follow-up) were added as covariates; in model 3, interaction terms were computed between FAB and LBP to test for a moderating effect on sickness absence days and spells.
The average age at second follow-up was 35.01 years (SD, 10.57, range, 19 to 61). The reason for the large age range among respondents is that some students had come directly from high school and others have worked several years in the health care sector or other sectors but without having any education. The mean number of sickness absence days at second follow-up was 21.2 days (0 to 365) and 2.84 periods of sickness absence spells (0 to 41) (Table 1). At first follow-up, 1739 participants were categorized as having low-moderate FAB, and 429 as having high FAB. Among those with high FAB, there was a higher prevalence of previous sickness absence, sickness absence days and spells during the previous 12 months. The group with low-moderate FAB reported slightly better psychosocial and physical work environment than in the group with high FAB.
Main Effect of FABs and LBP on Sickness Absence
As it appears from Table 2—model 1, having a high level of FAB at first follow-up increased the risk of sickness absence days in the second follow-up by 45% compared with that in the group with a low-moderate level of FAB. There was no main effect of FAB on sickness absence spells.
Model 2 also investigated the main effect of FAB after adjustment for work environmental factors. FAB remained significantly associated with sickness absence days, although the estimate slightly decreased from 1.45 to 1.24. LBP intensity was significantly associated with sickness absence days but not with spells in both model 1 and model 2 where adjustments were made for work environmental factors, and the relative risk (RR) decreased from 1.81 to 1.61. Two of the psychosocial work-related factors were significantly related to sickness absence: emotional demands and role conflicts (results not shown).
Moderating Effect of FABs
In model 3, we found support for a moderating effect of FAB on the association between LBP intensity and sickness absence days, adjusted for age and previous sickness absence days (P = 0.01). The highest risk for sickness absence days was among those with high levels of FAB and a high degree of LBP intensity (Fig. 2). No moderating effect was found of FAB on the association between LBP intensity and sickness absence spells.
This study has three main findings. First, a high degree of FAB increased the risk for sickness absence days 1 year later, suggesting that female health care workers who report high FABs are likely to have more sickness absence than those with lower fear-avoidance, despite equal levels of LBP. We are unable to directly relate our results to results from other studies because study designs, aims, sickness absence outcomes, or the role of LBP differ in our study from those. In a prospective population-based cohort study among workers with back pain, Turner et al34 found that recovery expectations and FAB about work were significant predictors of chronic work disability 6 months later. A randomized control intervention study among sick-listed back pain patients found an effect of the belief that work would aggravate back pain problems on return to work, at 3- and 12-month' follow-up.35 In an intervention study, disability and work status were assessed after 4 weeks of physical therapy among workers with work-related LBP, and FAB about work was found to be the best predictor of return to work.25,36 Across different study designs and populations in previous research, FAB or related concepts seem to be consistent predictors of sickness absence-related outcomes. Most research on FAB has been conducted at chronic LBP patients. To our knowledge, only one previous study has investigated the effect of FAB in a healthy working population. This population consisted of young health care or distribution workers.37 So, there is actually no information on the effect of FAB in other job sectors than the health care sector. Nevertheless, as the theory of FAB is not developed for a specific occupational group, it seems likely that the results can be reproduced in other settings, particular in job groups that are similar to health care workers with regarding physical demands in work.
Second, adjustment for a range of potential work-related confounders showed that FAB continued to have an independent effect on sickness absence days, albeit smaller. Self-assessed health has been found to predict sickness absence38 and in an additional analysis, self-rated health at baseline was added to the potential confounders in model 2. The estimate for FAB decreased slightly from 1.24 to 1.23 and remained significant (results not shown).
Third, a moderating effect of FAB was found on the association between LBP intensity and sickness absence days, meaning that the effects of the intensity of LBP on sickness absence days are dependent on FAB. This suggests that health care workers who have a high degree of LBP intensity will have more sickness absence days if they also have a high degree of FAB. To our knowledge, no previous studies have examined a moderating effect of FAB.
This study found a predictive effect of FAB on sickness-absence days 1 year later. Nevertheless, for further clinical treatment and future prevention strategies, it is essential that beliefs about pain are not constant but changeable. We still lack knowledge about the development of FAB and LBP intensity, because we do not know to what extent FAB is a precursor of pain and disability or a consequence of it. It is known that FAB is present in pain-free people39 as well as in acute and chronic LBP patients25; one study found that FAB is lower in patients with acute LBP than among patients with chronic LBP.40 This indicates that FABs are not static personal traits but modifiable and might be a response to prolonged exposure.41 Although it has not been investigated in previous research, it could also be hypothesized that 1) FAB is activated by sickness absence and develops concurrently with the presence of sickness absence days in a reciprocal process, and 2) FAB is a consequence of sickness absence and not the other way around. Therefore, we made two tests: first, we tested whether FAB had a stronger association with sickness absence when they where measured at the same time (second follow-up). We found support for a stronger association between FAB and sickness absence at second follow-up (RR, 1.69, 95% confidence interval [CI] = 1.40 to 2.03) than between FAB at first follow-up and sickness absence at second follow-up (RR, 1.24, 95% CI = 1.01 to 1.51). Second, we used the cohort being measured at three different times and made a binary logistic regression to see whether a high number of sickness absence days at baseline predicted high FABs at first follow-up. When controlling for age and LBP intensity, the association between sickness absence days at baseline and FABs at first follow-up was insignificant (odds ratio, 1.11, 95% CI = 0.99 to 1.01). In summary, the results from the re-analyses yielded no support for the hypothesis that FAB should be a consequence of sickness absence rather than the other way around, however, it cannot be ruled out that FAB may be activated by sickness absence and develops concurrently with the presence of sickness absence days in a reciprocal process. It may be that the cognitions involved in the decision behind sickness absence are intimately linked to the development of FAB. Future research should take into consideration that FAB and sickness absence may develop in an interactive process.
In our study, FAB was not associated with sickness absence spells. The number of respondents answering the questions about sickness absence days and spells was almost equal (1536 vs 1522). It could be hypothesized that some respondents had only one or few sickness absence spells, but a high number of sickness absence days, ie, few longer periods of sickness absence. This would make it less likely to find an association between FAB and sickness absence spells.
One limitation of the study was the high dropout rate between baseline and the two follow-ups—from 90% to 65% to 55%. Analysis of drop-outs compared with responders at baseline found no significant differences in FAB (mean, 16.8 vs 17.9), sickness absence days (mean, 10.40 vs 10.34) and number of days with LBP at baseline (2.35 vs 2.40 days), mental health (mean, 75.05 vs 75.38), or vitality (65.49 vs 65.48).
A second potential limitation is that all data are based on self-report. According to the research literature on self-reported sickness absence, a recall period of 12 months is too long, and the possibility of a over- or underestimation is present, most probably underestimation of sickness absence.42 Most suitable are recall periods of <2 months. We could have eliminated the risk of recall bias if we had had access to employer records. If the number of sickness absence days was underestimated, it is likely that the effect of FAB on sickness absence is also underestimated. Third, in this study, we included only the female respondents, because they constituted 95% of the total sample. Because of gender differences in musculoskeletal symptoms and sickness absence,43 separate analyses should have been performed for men and women, and we considered that the male sample was to small for separate analyses.
Strengths of the study include a large, prospective cohort. Furthermore, previous studies on fear-avoidance, LBP, and sickness absence have mainly been conducted in groups of subjects already on sick leave.36,44,45 Of the 2308 respondents in our study, only 86 respondents were on sick leave and 1 respondent was on early retirement. The remaining 2221 respondents were eligible for the labor market.
In conclusion, the results of this study support those of other researchers, suggesting that FAB has a predictive effect on later sickness absence. This study also adds new information about the role of FAB on the association between LBP and sickness absence and finds that a high degree of LBP will cause more sickness absence days among persons who also have a high degree of FAB compared to those with low FAB. The findings may also suggest that many still holds the opinion that work is harmful in the presence of LBP and that this is translated into sickness absence day.
The results from this study point toward focusing preventive efforts on those with high FAB and high degree of LBP, because the results indicate that they have an increased risk for sickness absence. According to the results, a reduction in FAB already during education must be presumed beneficial.
The research literature emphasize that it is important to stay at work or return to work as fast as possible and that longer work absenteeism is associated with lower chances of ever returning to work,46 so, it may also be beneficial to reduce FAB among employees. To reduce sickness absence days and facilitate early return to work it may be important change the workplace culture to make it legitimate that employees go to work before he or she is pain free. In many cases, early return to work will require that tasks and working arrangements are temporarily modified, eg, with reduced working time and reduced work load. To facilitate a change in culture, education should be offered on pain management (FABs) among both employees with and without LBP. Nevertheless, the issue about FAB and sickness absence is still very complex and we need further research to clarify how to develop usable interventions among different working populations and at what stage of LBP interventions should be implemented.
This study was supported by a grant From the Danish Parliament (SATS 2004).
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