Exposure to physical risk factors in Dutch agriculture: Effect on sick leave due to musculoskeletal disorders

Abstract

A case-control study examined the association between Dutch farmers’ exposure to single physical risk factors or combinations of them and sick leave due to back disorders and neck, shoulder or upper extremity disorders. The sick leave claims of an insurance company in the years 1998–2001 for back (SL-BP, $n=170$) and neck, shoulder or upper extremity complaints (SL-EXT, $n=76$) were analysed; the controls ($n=721$) were insured farmers who had not filed any claim for sick leave in this period. Exposure to physical risk factors was assessed by means of a questionnaire and experts. The questionnaire was used to collect information on the working methods (real or potential way to perform the various work elements within an operation or chain of operations) and the time per year spent on them. A total of 301 working methods were reported. Experts, familiar with the working methods, quantified the exposure to physical risk factors for each working method. Quantification included ‘intensity’, ‘frequency’ and ‘duration’ of exposure. The experts were unknown of the numbers of cases and controls applying each working method. The analysis indicated that sick leave was significantly associated with increased exposure to some single physical risk factors: twisting and whole body vibration with SL-BP and repetitive or static neck postures with SL-EXT. Exposure to medium or high combined physical load, consisting of eight risk factors in SL-BP and 26 risk factors in SL-EXT, showed strong associations with sick leave: Odds Ratios for high exposure varied from 3.3 in the SL-EXT model to 4.3 in the SL-BP model. It is concluded that when developing preventive strategies for the workplace, the effect of exposure to a combination of potential physical risk factors should be seriously considered.

Relevance to industry

This paper illustrates the importance of paying attention to exposure to single and combinations of physical risk factors in relation to sick leave due to musculoskeletal disorders in Dutch agriculture. It includes a thorough analysis and estimations of the proportion of sick leave cases that could have been prevented were made.

Introduction

Musculoskeletal disorders are an important cause of sick leave among the workers in many countries. In the Netherlands, they are the most important category of disease in terms of production losses and the costs to society due to absenteeism from work and disablement (Van Tulder et al., 1995). Sick leave due to musculoskeletal disorders is a huge problem among farmers. Earlier (Hartman et al., 2003), we reported that disorders of the neck, shoulder, upper extremity and back accounted for 30.2% of all sick leave claims of Dutch self-employed farmers from 1994 to 2001. The study focused on self-employed farmers because they themselves do most of the on-farm physical work: approximately 102,000 man-years in 2002, compared with 53,000 man-years for their employees (Statistics Netherlands/Agricultural Economics Research Institute, 2003).

In our study, we found that in Dutch farmers the main factors associated with sick leave due to musculoskeletal disorders were personal (age, smoking, obesity and former complaints). Furthermore, farm type was significantly associated with sick leave caused by neck, shoulder and upper extremity disorders, but not with sick leave caused by back disorders (Hartman et al., 2004b). One reason for the relatively small role of farm characteristics may be that within Dutch agriculture the work content varies greatly between branches in the sector. In the agricultural workplace, there is likely to be multiple exposure to physical risk factors, because of the variation in tasks within the branches of agriculture. It is therefore important to investigate the exposure to physical risk factors that results from the total ‘work package’. So far, no studies have been done on the association between the physical load that results from the work content and sick leave.

In other industrial sectors, a limited number of epidemiological studies have highlighted the work-related physical risk factors for sick leave due to musculoskeletal disorders. Wickstrom and Pennti (1998) revealed an association between sick leave from back disorders and exposure to awkward postures. Hoogendoorn et al. (2002) and Ariëns et al. (2002) showed that lifting, flexion or rotation of the trunk and neck flexion or neck rotation were associated with sick leave due to musculoskeletal disorders. In addition, Wickstrom and Pennti (1998) showed that sick leave due to back disorders appeared to be more strongly associated with ‘combined biomechanical load’ (a combination of lifting, carrying, pushing, pulling, awkward postures, standing and sitting) than with any individual physical risk factors. Herz-Picotto (1998) stressed the importance of a combination of factors rather than exposure to single factors in the causation of illness in general.

The objective of the study described here was to examine the association between exposure to single physical risk factors or combinations of these factors on sick leave taken by Dutch farmers because of musculoskeletal disorders. A case-control study was conducted, focusing on sick leave due to back disorders and to neck, shoulder or upper extremity disorders. By using questionnaires and consulting experts we were able to estimate the exposure to physical load of all cases and controls in different branches of the agricultural sector. We also estimated the percentage of sick leave cases that could have been prevented if there had been no exposure to ‘high combined physical load’. The results of the study provide insight into the avenues that must be explored to develop preventive strategies for the workplace.