Low Back Pain (LBP),work and absenteeism

Abstract

BACKGROUND:

Occupational physical demands are commonly assumed the cause of work-related Low Back Pain (LBP) and absenteeism.

OBJECTIVES:

To analyse relationships between LBP at work, physical demands and absenteeism.

METHODS:

Workers filled out a questionnaire on socio-demographic and work-related factors, general health, LBP (number of episodes in a 12-month period, pain severity and intensity), and occupational hazards related with physical demands.

RESULTS:

735 workers completed the questionnaire (male n = 359). A high proportion of workers n = 507 (69%), from different occupational backgrounds, reported at least one LBP episode in the previous 12-month period. The highest ratio of subjects with more than 6 episodes of LBP per year was found among public services employees (31.8%) and the lowest ratio among administrative workers (10.3%). The highest ratio of workers (39%) were classified as sedentary workers, 34% of workers having a low or moderate level of physical demands in their work, and 27% reported high levels of physical demands in their work. There was a 4 % absenteeism rate in a 12-month period, which was significantly higher in the group with physically demanding work. Those subjects with higher physical requirements at work have increased odds of having more than 3 episodes of LBP during the previous year (p < 0.05) in comparison with subjects with more sedentary jobs and those with low or moderate physical demands. High intensity work, compared to sedentary work, is associated with an increased probability of being absent of work because of LBP in a previous 12-month period (OR = 3.12; CI 1.23-7.89; p = 0.016).

CONCLUSIONS:

Our findings suggest there is an association between highly physically demanding jobs, LBP and absenteeism. These results may contribute to the improvement of LBP assessment and prevention programs in Occupational Health Services.

Keywords

Occupational health occupational disorders ergonomics

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.

Table 1
Workers’ socio-demographic characteristics

Variables Category n Frequency (%)

Sex Man 362 48.6

Woman 383 51.4

Age 16–24 22 3.1

25–34 153 21.4

35–44 224 31.4

45–54 201 28.2

55–65 114 16.0

Company A 113 15.3

B 98 13.3

C 370 50.1

D 158 21.4

Education No studies 10 1.4

9th year 141 19.6

Basic vocational training 28 3.9

12th year 275 38.1

Diploma 267 37.0

Variables	Category	n	Frequency (%)
Sex	Man	362	48.6
	Woman	383	51.4
Age	16–24	22	3.1
	25–34	153	21.4
	35–44	224	31.4
	45–54	201	28.2
	55–65	114	16.0
Company	A	113	15.3
	B	98	13.3
	C	370	50.1
	D	158	21.4
Education	No studies	10	1.4
	9th year	141	19.6
	Basic vocational training	28	3.9
	12th year	275	38.1
	Diploma	267	37.0

Table 2

LBP description

Variables	Categories	n	Frequency (%)
LBP episodes in the last year	0	218	29.7
	1–2	222	30.3
	3–6	131	17.9
	>6	162	22.1
Pain duration	≤1 day	166	32.9
	2–14 days	284	56.2
	15–30 days	27	5.4
	>30 days	28	5.5
Duration of the longest episode	≤1 day	117	23.5
	2–14 days	286	57.6
	15–30 days	54	10.9
	>30 days	40	8.0
Low back pain radiated down the leg (sciatica)	Yes	216	43.6
	No	279	56.4
Low back pain when lying down	Yes	264	37.2
	No	445	62.8
Low back pain when getting out of bed	Yes	271	38.1
	No	440	61.9
LBP when in a sitting position	Yes	337	47.7
	No	370	52.3

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).

Table 3

Work-related LBP in the last 12 mounts and physical demands

		Company
		A		B		C		D
		n	(%)	n	(%)	n	(%)	n	(%)
LBP episodes in the last 12 months	None	24	(21.60%)	39	(40.20%)	118	(32.70%)	35	(22.70%)
	1–2	33	(29.70%)	34	(35.10%)	112	(31.00%)	40	(26.00%)
	3–6	21	(19.40%)	90	(91.80%)	125	(35.70%)	39	(26.20%)
	>6	42	(38.90%)	5	(5.10%)	145	(41.40%)	47	(31.50%)
Work physical demands	Sedentary work	45	(41.70%)	3	(3.10%)	80	(22.90%)	63	(42.30%)
	Light/moderate work	28	(25.20%)	14	(14.40%)	58	(16.10%)	30	(19.50%)
	Intense work	26	(23.40%)	10	(10.30%)	73	(20.20%)	49	(31.80%)

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.

Table 4

Self-reported LBP psychosocial variables

Variables	Category	n	Frequency (%)
Absenteeism due to low back pain	Yes	30	6.3
	No	465	93.9
Ability to go to work with low back pain	Totally incapable	13	2.5
	Moderately incapable	199	38.0
	Able	307	59.0
Opportunity to take time off work due to low back pain	None	198	28.2
	Few	347	49.4
	Moderate	121	17.2
	Enough	26	3.7
	Lots of	10	1.4
Being off duty would affect my economic situation	Nothing	20	2.8
	A little	72	10
	Moderately	196	27.3
	Significantly	247	34.4
	Highly	182	25.4
Company’s reaction to low back pain	Empathetic	09	1.4
	Reasonable	90	14
	Neither good nor bad	400	62.4
	Bad	103	16.1
	Very bad	39	6.1
Reaction of colleagues to low back pain	Empathetic	16	2.5
	Reasonable	107	16.8
	Neither good nor bad	381	59.8
	Bad	101	15.9
	Very bad	32	5
Variable	Average	Minimum	Maximum
Absenteeism (days) due to low back pain	1.88	0	210.0

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).

Table 5

Work- related physical demands that influences the appearance of LBP episodes

	Categories	LBP episodes in the last year	OR *	CI 95%		p value
				Min.	Max.
Physical demands	Sedentary work	1–2	0.8	0.5	1.3	0.325
		3–6	0.4	0.2	0.8	0.008
		>6	0.5	0.3	0.9	0.026
		None	Reference category
	Low/moderate work physical demands	1–2	0.7	0.4	1.2	0.248
		3–6	0.5	0.3	0.9	0.023
		>6	0.6	0.3	1	0.043
		None	Reference category
	High intensity work		Reference category

*Adjusted for sex, age, and company.

Table 6

Variables associated with LBP absenteeism

Dependent variable	Independent variables	Category	OR*	CI 95%		p value
				Min	Max
LBP Absenteeism	Sex	Male	0.71	0.33	1.52	0.377
		Female		Reference category
	Age Classes	25-34	0.41	0.11	1.51	0.180
		35–44	0.91	0.32	2.59	0.866
		45–54	0.82	0.28	2.42	0.725
		>55		Reference category
	DMQ	High intensity work	3.12	1.23	7.89	0.016
		Light/moderate work	1.44	0.51	4.06	0.488
		Sedentary work		Reference category

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).

4 Discussion

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.

Footnotes

Acknowledgments

Gratitude to the Authority for Working Conditions (ACT – Autoridade para as Condições de Trabalho), for their support in funding the project 027ESC / 13: “Chronic low back pain and Work”. The collaboration of the participating companies and their Occupational Health Services is greatly appreciated, especially the dedication showed by all the workers and occupational doctors who participated in this study.

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