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Occupational Medicine Advance Access originally published online on July 12, 2006
Occupational Medicine 2006 56(7):455-460; doi:10.1093/occmed/kql062
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© The Author 2006. Published by Oxford University Press on behalf of the Society of Occupational Medicine. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org

Low back pain among Iranian industrial workers

Mostafa Ghaffari, Akbar Alipour, Irene Jensen, Ali Asghar Farshad and Eva Vingard

Karolinska Institute–Public Health, PO Box 12718, Stockholm 112 94, Stockholm, Sweden

Correspondence to: Mostafa Ghaffari, Karolinska Institute–Public Health, PO Box 12718, Stockholm 112 94, Stockholm, Sweden. Tel: +46-737751376; fax: +46-8-6539413; e-mail: mostafa.ghaffari{at}cns.ki.se


   Abstract
Top
 Abstract
Introduction
 Methods
 Results
 Discussion
 Conflicts of interest
 References
 
Background Most epidemiological data concerning low back pain (LBP) are from high-income countries and there is very little information about LBP in the working population in developing countries.

Objectives To determine the prevalence of LBP in Iranian industrial workers. To explore associations between LBP and physical and psychosocial factors at work, as well as lifestyle factors.

Methods Cross-sectional study of the largest car-manufacturing group in Iran. The prevalence of LBP, work exposures and lifestyle factors were recorded using the standardized Nordic questionnaire for analysis of musculoskeletal symptoms. Demographic data and lifestyle factors (age, sex, education, weight, work experience, smoking and fitness training) were also collected.

Results Of the 18 031 employees, 78% participated. The majority of subjects in this study population were young males (<30 years) and a small proportion was female (4%). The 1-year prevalence of self-reported LBP in this Iranian industrial population was 21% (20% males and 27% females). The prevalence rate of absence due to LBP was 5% per annum. The multiple logistic regression models indicated that the following remained risk indicators for LBP in the previous 12 months: increasing age, no regular exercise, heavy lifting, repetitive work and monotonous work.

Conclusion LPB is a common problem in the working population even in a developing country. Age and gender as well as certain work-related physical and psychosocial factors influenced the prevalence of LBP but the differences between different categories of workers were small.

Keywords      Industrial workers; low back pain; occupational


   Introduction
Top
 Abstract
 Introduction
Methods
 Results
 Discussion
 Conflicts of interest
 References
 
Most epidemiological data concerning low back pain (LBP) are related to developed and industrialized countries and there is little information about LBP in the general or working population in developing and low-income countries. This lack of research leaves a profound gap in what is known about LBP in a large part of the world, where the bulk of the world's working population resides [1].

International surveys of LBP report a point prevalence of 15–30%, and a 1-month prevalence of between 19 and 43% [2]. Worldwide estimates of lifetime prevalence of LBP vary from 50 to 84% [1–4]. In a general working population in Sweden, ~5% sought care because of a new LBP episode during a 3-year period [5].

The consequences of LBP are far-reaching, and associated with increased absence from work, lost productivity and corresponding increase in economic costs [2–8]. Individual factors such as age, sex, physical fitness, body mass index (BMI), strength, motor control and smoking habits have been discussed in association with LBP [2,9–12]. Work-related factors associated with LBP are physical and psychosocial in origin [2,13–15].

The labour market in Iran is characterized by workforce transition, a high unemployment rate, incomplete social insurance and a young population. During the last 20 years, the workforce in Iran has changed from an uneducated or poorly educated male-dominated working population to an educated or highly educated working population with an increasing proportion of educated females.

The aims of this study were

(i) to determine the prevalence of LBP in Iranian industrial workers and how it varies with demographic factors, job title and gender and
(ii) to explore associations between LBP and physical and psychosocial factors at work as well as lifestyle factors.


   Methods
Top
 Abstract
 Introduction
 Methods
Results
 Discussion
 Conflicts of interest
 References
 
The present study involved a cross-sectional, epidemiological analysis of LBP among Iranian industrial workers with data gathered by means of a self-reported questionnaire in 2003.

Ethical approval for this study was obtained from Karolinska Institute Ethics Committee (reference no. 03-082) and the Iranian Ministry of Health, respectively.

All employees in one of the biggest car-manufacturing industrial groups (IKCo) in Iran and also in the Middle East were chosen for this study. During 2003, IKCo had >18 000 full-time employees (17 300 men and 721 women) working in 14 main departments. The work titles were grouped into four main occupational categories: (i) unskilled workers, (ii) skilled workers and technicians, (iii) office workers and (iv) managers. Most employees at IKCo are young and only those who are absolutely fit are employed.

The prevalence of LBP, work exposures and lifestyle factors were recorded using the standardized Nordic questionnaire for analysis of musculoskeletal symptoms. The validity and reliability of this questionnaire have been investigated and approved in different studies and several languages, including the Persian language [16,17]. The questions about LBP during the last 12 months, during the last 7 days, and severe LBP that prevented subjects from working were phrased with dichotomized answer alternatives ‘yes’ and ‘no’.

Questions from the Nordic questionnaire about physical exposures (heavy lifting, repetitive work, sitting position and awkward working position) and psychosocial exposures (uninteresting work, monotonous work, organizational culture, support from superior, support from fellow workers, support if trouble at work, control at work, quantitative demand, qualitative demand and anxiety about change) were asked, with dichotomized answers ‘yes’ and ‘no’ both for the present work situation and in previous work. Demographic data and lifestyle factors (age, sex, education, weight, work experience, smoking and exercise) were also collected.

In this study, we used the following definitions for LBP and prevalence. LBP was defined as a person who had trouble (ache, pain and discomfort) in the low back. A 1-year prevalent case was defined as a subject who had at least one episode of LBP during the previous 12 months. A 7-day prevalent case was defined as a subject who had at least one episode of LBP during the past 7 days. A 1-year sickness absence prevalent case was defined as a subject who had been prevented from working because of LBP. All 18 031 employees were included and given a questionnaire. All employees at IKCo were literate.

Factors examined were frequency distributions of responses, and cross-tabulations of demographic, physical, psychosocial and lifestyle factors with reported history of LBP in the last 12 months, absence due to LBP in the last year and LBP in the past 7 days. Group differences were statistically tested by the chi-square test, and P values were derived from the chi-square test for trend, and the Pearson chi-square test. Odds ratio (OR) with 95% confidence interval (CI) was used to estimate the relationship between exposure and musculoskeletal symptoms, and multiple logistic regression analysis was used to study the influence of more than one variable on the outcome. Unadjusted OR calculations and multiple logistic regression analysis were made after excluding workers with <12 months of work experience. The occurrence of LBP in the previous year, and LBP-related absence, was chosen as an outcome variable for the risk analysis. The determinants consisted of variables representing the physical exposures, psychosocial exposures, lifestyle factors and individual data. All variables with significant OR with 95% CI in bivariate analysis were included in the multiple logistic regression analysis.


   Results
Top
 Abstract
 Introduction
 Methods
 Results
Discussion
 Conflicts of interest
 References
 
All 18 031 employees at Iran Khodro industrial group in Iran were provided with a self-reported questionnaire. A total of 14 384 employees completed the questionnaire (response rate of 78%). When calculating associations between work factors and LBP, only those who had been employed for at least 12 months were included. A final cohort of 10 941 workers remained.

Among the participants, 21% (2866 cases) had experienced LBP during the previous year. The 1-year prevalence in females was 7% higher than in males. One-week prevalence was 8.5% and 1-year prevalence rate of absence due to LBP was 5%. The majority of this study population was young males (<30 years) and a small proportion of the workforce was female (4%). The prevalence, demographic data and exposures are shown in Tables 1 and 2. Physical exposures, such as heavy lifting, repetitive work and awkward positions were frequently reported among unskilled workers and they also reported having an inferior psychosocial climate. Managers had the best working environment but reported high qualitative and quantitative demands.


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  		Table 1. Demographic characteristics and their association with LBP in employees of an Iranian car-manufacturing company, 2003 (n = 13 776)

 

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  		Table 2. Lifestyle, physical and psychosocial factors at work and their association with LBP in employees of an Iranian car-manufacturing company, 2003 (n = 13 776)

 
Most women were office workers, working in sitting positions, and the most common physical and psychosocial exposures in this group were high qualitative demands.

Results from bivariate analysis are reported in Table 3.


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  		Table 3. Unadjusted OR and multiple logistic regression with 95% CI for factors associated with LBP and absence due to LBP in previous 12 months in a working population in Iran

 
In the multiple logistic regression models with all significant variables in bivariate analysis, the following factors remained risk indicators: increasing age, no regular exercise, heavy lifting, repetitive work and monotonous work. The pattern was similar for the outcome ‘absence due to LBP’ (Table 3).


   Discussion
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
Conflicts of interest
 References
 
The results of this study showed that LBP was more prevalent among Iranian car-manufacturing workers compared to Western countries [18–21]. We found the prevalence of LBP to be higher in women but absence due to LBP was more frequent in male employees, which differs from findings in a recent review [7]. In our study, most women were office workers and exposures for males and females differed considerably [22,23].

In accordance with other studies [2,13,24], heavy lifting, sitting position and repetitive work were significant risk factors for LBP but heavy lifting was the only factor that significantly increased the risk of absence due to LBP in the previous year. Among the psychosocial exposures, monotonous work was a risk factor for LBP.

Our study achieved a high response in a large working population which included both white- and blue-collar workers. Very few studies have been able to provide a reliable estimate of the prevalence of LBP in the working population in a developing country. The study design was cross-sectional, which makes causation uncertain. The questionnaire was short and mostly used for screening purposes.

The physical and psychosocial exposures at work differed between occupational groups but LBP-prevalence was similar. This indicates that LBP is a common burden in the society regardless of work factors. However, this population, like most working populations in developing countries is young and initial employment is based on health status among other things. In a country with a high unemployment rate this may lead to healthy worker selection.

Gender differences in the prevalence of LBP are frequently observed, but might differ in degree from country to country [25–29]. In United States, a higher prevalence of back pain in male workers was reported [25], and a study on LBP in Japan showed that the incidence in male workers was four times greater than that in female workers [26]. In both the cases, the results are different from our observations.

Smoking as a risk factor for LBP has been extensively discussed [10,30,31]. In a review, Lebouef-Yde [11] suggested that smoking should be considered a weak risk factor but not a cause of LBP. In our study, smoking was not associated with LBP.

The role of psychosocial risk factors in the development of spinal disorders is still under debate and no conclusion could be reached about the causal role of psychosocial risk factors in the development of LBP [2,15].

The 1-year prevalence of LBP observed in our study (21%) was far from that reported by Elders [18] for scaffolders in the Netherlands (60%), by Schibye [19] for Danish sewing machine operators (45%), and by Jin [20], for different occupational groups in Shanghai (74%). However, caution must be exercised when comparing these studies, due to the differences in LBP definitions and study methods. In two different studies among automotive assembly workers in United Kingdom and Sweden, the 1-year prevalence of LBP has been reported by 65 and 46%, respectively [21,32]. Like our study both of them used the Nordic musculoskeletal questionnaire. Differences in social security systems, workers' compensation systems and benefits during sickness absence may explain the difference.

In Iran, sickness absence is only permitted after producing a medical certificate completed by a doctor. For long-term sickness absence (>60 days), sickness benefit is payable based on a confirmation of diagnosis by the expert medical board in the insurance organization. Sickness benefit is payable from the first day. According to insurance legislation in Iran, there is no time limit for sickness benefit payment. In severe cases, when employees lose their ability to work, either partially or completely, the committee will give them partial or complete disability pension. In both the cases, their income will be less than their usual income and pension.

There is no partial sick leave and benefit in Iran. In cases where a sickness certificate is approved, the benefit covers only 75% of the salary for married employees and 66% of salary for unmarried employees. In Iran, working extra hours is rather common and this accounts for a considerable part of the employee's income. In these cases, employees will lose this part of their income.

Iran, with ~70 million inhabitants, is a fast developing country with a very young working population. There are many important factors that affect the labour market in Iran and other similar developing countries such as high unemployment rate, low and incomplete social insurance coverage, high demands for finding employment, and cultural barriers for the female industrial workforce. In the last 20 years in Iran, there has been a transition in the workforce from old, uneducated or poorly educated males to young educated workers with an increasing female participation. This has changed the exposure at work and the employer, the employees and also policy makers must acquire new knowledge and awareness in developing countries to create and support a good working environment while the industry and economy develop.

It is important for the future to follow this cohort and its health status as well as introducing interventions to improve the work environment.


   Conflicts of interest
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 Conflicts of interest
References
 
None declared.


   Acknowledgements
 
This study was supported by IKCo Occupational Medicine Clinic, the Iranian Ministry of Health and Iran University of Medical Science. We are indebted to Hans Rosling at IHCAR division of Public Health Science department of Karolinska Institute, Alireza Alavi at IKCo PEDAR management, Abbas Motevallian at Tehran University of Medical Science and Shahram Tavajjohi.


   References
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 Conflicts of interest
 References
 

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This Article
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