Low Back Pain (LBP),work and absenteeism

1 Introduction

Low back pain (LBP) is a main cause of disability-adjusted life years (DALYs) worldwide [1, 2]. Despite some occupational factors, such as physical demands at work, are frequently not seen as a major cause of LBP [3, 4], there is not much research suggesting an association between these factors and their contribution to workers disability and related absenteeism [5] with a mixed evidence on the role of heavy physical work load as a risk factor of LBP [3].

There is some evidence in the association between employee’s individual characteristics (age, sex, and personality) and LBP [6] and also a significant effect for those of working age and have a demanding physical job to report increase in LBP prevalence [7].

Even though LBP absenteeism is often associated to individual than work organizational factors, there are different individual attitudes at work (psychosocial factors) associated [8]. Frequently organizational factors that increase job demands (physical and psychosocial), such as time schedules, time pressure, worker’s autonomy, and monotony [9] are also presents.

Also few studies evidence that biomechanical work tasks, mainly those with higher physical demands and psychosocial risk factors (individual psychosocial factors, and work organizational factors) at the workplace, may have an influence on both LBP and absenteeism [10–14].

Nevertheless, the evidence of LBP and work-related musculoskeletal disorders as a main cause of work disability and absenteeism is not enough visible [15, 16]. However, workers with tasks involving handling loads and frequent lifting are at a higher level of occupational LBP risk [4].

The association between higher physically demanding work and LBP is not enough expressive and recent studies evidencing that only 11% to 18% of all LBP episodes are associated to physically demanding tasks at work [17]. Also the association between LBP and absenteeism is slightly present [18, 19].

Studies did not show an evident relationship between heavy work, frequent loads lifting and absenteeism. Occupational physical demands are strongly suspected of causing LBP but evidence is not enough to support it [3].

Our research hypotheses were: (i) different occupational backgrounds result in different worker self-reported LBP outcomes during the preceding 12 months; (ii) there is an association between LBP and work physical demands, (iii) and with psychosocial variables; and (iv) LBP absenteeism is related with work physical demands.

This study aims to analyze the relations between work demands, workers LBP episodes, and LBP related absenteeism among workers with different professional backgrounds.

2 Material and methods

An observational study was conducted at different Occupational Health and Safety Services, from Lisbon, Portugal. Four companies participated in the study, including one large teaching hospital, two large privately owned companies (the first was an industrial company and the second one an IT company), and a state-owned truck service, repair and maintenance company. These companies were referred to as A, B, C and D.

Employees visiting the Occupational Health Service during a six months period were invited to participate in the study. All signed their informed consent and completing a questionnaire detailing data on socio-demographic profile, professional background, general health, previous LBP events, intensity of work physical demands at work, using for these purposes the ‘Dutch Musculoskeletal Questionnaire’, DMQ-[20], and their related absenteeism over a preceding 12 month period.

Descriptive statistical methods were used to present main results. Multinomial models were applied to assess the association between the “number of LBP episodes”, “work and work-related physical demands intensity”, and “absenteeism”. Logistic regression was used to quantify the association between absenteeism from LBP and individual and work demands. Results were analyzed using SPSS statistical software through univariate and bivariate statistical tests. Absenteeism associations with individual and work were adjusted for age, sex, and company using multinomial regression. For all statistical tests a significance level of 0.05 was set.

3 Results

745 workers completed the questionnaire. Most were female (51.4%), manual workers (52.3%), worked at night (21%), and 11.6% worked in shifts. Their mean age was 43 years, and they had been working for an average of 16 years.

Almost two-thirds (60.5%) of the self-reported participants worked in private companies, and one-third (34.3%) in public companies. Most workers (53.2%) were at large companies with more than 250 employees.

Regarding the intensity of work-related physical demands, 38.7% performed a sedentary work, 34.2% worked in a low to moderate physical demands environment, and 27.1% had a physically demanding work.

The most frequent work-related physical demands were (i) “remaining in a seated position for more than 50% of the working day” (57.1%); (ii) “ remaining in a standing position for more than 50% of the working day” (42.9%), (iii) “frequent rotation of the body” (40.3%), (iv) “or trunk” (35.5%), and (v) “manual handling of heavy loads” (32.6%). The less frequent demands were (vi) “exposure to vibrations transmitted to the whole body (2.1%).

About 60% of participants (Table 2) had experienced one or two episodes of LBP in the previous year, from 1 to 14 days in 89.1% of the cases.

Low back pain was associated to sciatica (pain referred down to the leg) in 43.6% of participants. Among those who reported having suffered “one or more episodes of LBP in the previous year”, 37.2% reported feeling pain when lying down, 47.7% when standing up, 64.6% when sitting down, and 86.2% needed to move their torso frequently to feel more comfortable.

The outcome “suffering more than 6 episodes of LBP in the previous year” was more common in company D, where the majority of workers reported work demands to be more physically intense (χ2 = 29.7, p = 0.001) (Table 3).

Only a small proportion of workers (6.3%) had been on sick leave for LBP at some point during the previous12 months, and the mean duration of the sick leave was 31 days (Table 4). A big proportion of those subjects (77.6%) believed that it would be unlikely to take sick leave for the same reason again during the following year.

The multivariate analysis showed workers with a sedentary profession had a decreased odd (protecting factor) of having 3 to 6 or more than 6 episodes of LBP during the previous year (Table 5). LBP related absenteeism was also associated with subjects with a profession that implied intense work-related physical demands (Table 6).

High intensity work, compared to sedentary work, is associated with an increased probability of being absent of work because of LBP in the previous year (OR = 3.12; CI 1.23-7.89; p = 0.016). Other variables such as sex, age, education and shift work were not associated (Table 6).

Several studies carried out on the etiology of LBP, essentially over the last two decades, emphasize individual factors, mainly psychosocial variables, and assign a predominant role to them, ascribing a lower relevance to occupational hazards such as the intensity of physical demands at work [21, 22]. The referred model, which attributes a psychosocial explanation to low back pain, has focused almost exclusively on individual variables, underestimating professional risk factors and health effects [24–27].

Some recent reviews for non-specific low back pain interventions, as clinical guidelines [23], are mainly focused on individuals’ prevention (education and self-care, non-pharmacological therapy, pharmacological therapy, intervention therapies and surgery) not referring the need of interventions at work. Physical and work psychosocial demands that may influence a LBP onset (as the aggravation, the likely absenteeism, and the impact that may results in the workers’ ability to perform their physically demanding jobs) were omitted.

Seidler et al. [28] found a relationship between the cumulative lumbar load, for instance at work, and the risk acceleration of lumbar disc narrowing, referring that without this exposure, the occurrence of a disc narrowing (with LBP) probably would have never been occurred. In the same context, Oliv et al. [29], reported that elderly workers not exposed to physically demanding jobs during their lifetime suffer from less LBP prevalence, than those who have been exposed to highly demanding physical work.

We did not find differences between LBP symptoms and workers age, but there was LBP associations with physical demanding jobs, and with absenteeism. Our results also show sedentary work as a protective factor for having more than 3 LBP episodes during the preceding 12 months.

Nowadays, occupational LBP research is frequently focused in biomechanical factors and psychosocial variables that had an increased importance in time, namely at individual factors, as genetic and biochemical [30].

As recognized by the WHO International Classification of Functioning Disability and Health (ICF), LBP is influenced by personal characteristics, such as gender, age and anthropometric variables, and also workplace factors [31, 32].

At workplaces that have high physically demanding jobs, we are frequently dealing with an imbalance between workers capacity and work demands. Often, that starts the disorder process, as a physiological cascade with a tissue load-tolerance discrepancy, and promote tissue symptoms, LBP, impairment, disability and absenteeism [33]. In our study, workers that self-reported high physical demands had also higher reported LBP episodes.

Psychosocial (individual and organizational) results have a different expression in our study. One of the most expressive outcomes show just about 2.5% of workers referring to be unfit to work (“totally incapable”) because of LBP. Perhaps, Portuguese workers consider physically demanding jobs and LBP not so dramatic, or a lower issue in order to maintain their jobs.

Disagreement about occupational, psychosocial and individual factors that increase the risk of LBP and absenteeism is generalized and for some authors up to 37% of LBP is attributed to an occupational background, with a two-fold variation across regions [34].

Hoy et al. shows that the complexity of different levels of physical efforts demands is a consequence of a much wider variability of job tasks and despite of a whole host of factors involved, work physical demands are indeed related with LBP and disability results in absenteeism [35].

Results from other studies [16, 36], as ours, suggest workers who face more intense physical demands at work are at a higher risk of LBP and absenteeism, in comparison to workers with lower effort job tasks.

We also found an association between LBP and work physical demands being the variable “high intensity work” associated to absenteeism in a logistic regression analysis.

Petersen et al. [5] asserts occupational interventions to reduce sick leave due to LBP may have to focus more on those with high self-reported physical demands and high fear avoidance.

In our study, we find some evidence that having a physically demanding job is likely to be playing a main role for LBP and absenteeism. Psychosocial demands did not have a significant role in our results but they need to be considered in future studies.

There is a greater need for more long-term incidence studies before we can concrete on how much of an effect from physical workload will play on the onset and obviously, we could find a whole host of limitations in our study. The companies we studied had diverse work demands and blue collars were in a higher proportion. We also had no control about the study participants. Respondents were randomly selected at companies Occupational Health Services, and work-related physical demands and worker self-reported LBP, in the last 12 months, were different in the four companies studied.

In terms of prognosis, the picture is much wider and the real goal of research now is to attempt to these key factors and how they work together, rather than to attempt to pinpoint a single factor.

5 Conclusions

This study found a significant association between the intensity of work-related physical demands, a higher number of LBP episodes from the preceding 12 months period and related absenteeism.

Although LBP absenteeism can be influenced by other factors such as job satisfaction, financial situation, individual and other psychosocial risk factors playing multiple roles, we observed repetitive LBP episodes in the preceding 12-month period also seems to be associated with the role of heavy physical workload as a risk factor.

Developing a better knowledge of the relationship between work-related physical demands, LBP and absenteeism are required to improve work-related prevention and suggests a greater need for more studies.

Conflict of interest

None to report.