Int Arch Occup Environ Health DOI 10.1007/s00420-014-0957-2
Original Article
Does the association between musculoskeletal pain and sickness absence due to musculoskeletal diagnoses depend on biomechanical working conditions? Subas Neupane · Päivi Leino‑Arjas · Clas‑Håkan Nygård · Helena Miranda · Anna Siukola · Pekka Virtanen
Received: 4 December 2013 / Accepted: 23 June 2014 © Springer-Verlag Berlin Heidelberg 2014
Abstract Aim To investigate single-site and multi-site musculoskeletal pain as predictors of future sickness absence due to musculoskeletal disorders (MSD) among blue-collar employees in food industry, and to study to what extent this relationship depends on physical loading at work. Methods Survey responses of 901 employees on working conditions and musculoskeletal pain during the past week were linked to their future sickness absence records obtained from the personnel register of a food industry company. Negative binomial regression models were computed to determine associations of pain in one and in multisite with the number of sickness absence days due to MSD during a four-year follow-up. Analyses were made in the whole cohort and stratified by the occurrence of repetitive movements and awkward postures (low/high).
Results Multi-site pain occurred among 59 % in the total cohort and predicted sickness absence with a rate ratio of 1.48 [95 % confidence interval (CI) 1.21–1.80], adjusted for age, gender, biomechanical and psychosocial working conditions, body mass index and physical exercise. Similar associations were seen in the sub-cohorts with a low occurrence of repetitive movements (RR 2.18, CI 1.69–2.80) and awkward postures (RR 1.78, CI 1.39–2.28), but not in the sub-cohorts with a high occurrence of these exposure. Single-site pain was not predictive of sickness absence. Conclusions A very high level of sickness absence in biomechanically strenuous work was found. Multi-site pain predicted sickness absence due to MSD among the employees with low exposure, but not among those with high exposure. Keywords Multi-site pain · Food industry · Musculoskeletal diagnosis · Sickness absence · Physical working conditions
S. Neupane (*) · P. Leino‑Arjas · C.-H. Nygård · H. Miranda · A. Siukola · P. Virtanen School of Health Sciences, University of Tampere, 33014 Tampere, Finland e-mail: [email protected] S. Neupane · C.-H. Nygård · A. Siukola Gerontology Research Center, University of Tampere, 33014 Tampere, Finland P. Leino‑Arjas Finnish Institute of Occupational Health, Topeliuksenkatu 41 a A, 00250 Helsinki, Finland C.-H. Nygård · P. Virtanen Institute for Advanced Social Research, University of Tampere, Tampere, Finland H. Miranda Occupational Health Centre, Helsinki City, Helsinki, Finland
Introduction Musculoskeletal disorders are a major public health problem worldwide (Murray et al. 2012), causing significant suffering and healthcare needs for individuals as well as costs to the society. Among working populations, musculoskeletal disorders are the most common reason for workrelated consultations in general practice (Weevers et al. 2005; Taimela et al. 2007) and the spells due to musculoskeletal diagnoses account for a total of 35 % of long-term absence periods in Finland (Finnish Center for pensions [Eläketurvakeskus] 2013). Regarding the nature of musculoskeletal disorders, the leading symptom is pain, and often widespread pain. Either
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the musculoskeletal disease causes pain in more than one part of the body or an individual has more than one diseases causing pain at different sites. Central sensitization may also lead to multi-site musculoskeletal pain (MSP) (Woolf 2011). Several studies have shown that the consequences of MSP are more severe than those of single-site pain (Haukka et al. 2006; Miranda et al. 2010; Carnes et al. 2007; Kamaleri et al. 2008; Neupane et al. 2011). MSP has a substantial deteriorating impact on physical fitness, general health and well-being, activities of daily living (Carnes et al. 2007; Kamaleri et al. 2008) and perceived work ability (Miranda et al. 2010; Neupane et al. 2013a). MSP is a strong predictor of all-cause sickness absence (Nyman et al. 2007; Haukka et al. 2013). Both short- and long-term absences due to musculoskeletal disorders increase with the increase in the number of pain sites (Morken et al. 2003). However, Ijzelenberg and Burdorf (2004) found that concurrent neck/shoulder pain does not increase the risk of sickness absence due to low back pain. These above-mentioned studies, however, did not consider work-related factors as potential modifiers of the relationship between MSP and sickness absence. Moreover, in the study of Morken et al. (2003), the data on both pain and absence were based on self-report, which may be a source for a common method bias. As regards both the aetiological mechanisms of MSP and the need of sickness absence due to MSP, the biomechanical factors at work are of evident importance (Melchior et al. 2005). These factors also are a major explanation for the high rates of sickness absence and disability pensions due to musculoskeletal disorders among blue-collar workers (Morken et al. 2003; Brage et al. 1997). Once occurring, however, pain in multiple locations of the body seems to entail a risk of sickness absence in particular among the white-collar employees (Andersen et al. 2011). This finding in a Danish population study is somewhat unexpected; as one would anticipate that due to the less strenuous work tasks and environment in white-collar work, the need for pain-related absence is less urgent. The study unfortunately did not take into account the working conditions, and also the results with all-cause absence as the outcome leave unanswered the question about the impact of biomechanical working conditions to the sickness absence due to musculoskeletal complaints. This finding gives reason to ask whether a study with a corresponding design among bluecollar workers would give similar findings and to investigate the role of working conditions in this context. The aim of the present study was, first, to investigate the relationship of single site and MSP to future sickness absence due to musculoskeletal disorders among blue-collar employees in heavy industrial work and, second, to test the hypothesis that this relationship is stronger among employees with higher exposure to physical loading at work.
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Int Arch Occup Environ Health
Materials and methods The questionnaire survey The study draws on a questionnaire survey conducted in a Finnish food industry company which manufactured various products such as poultry and canned goods, snacks, preserves and convenience foods, meat products including sausages. The survey was conducted during the first half of 2005. The questionnaire forms were distributed to all workers at the workplaces, after which the closed reply envelopes were collected and sent to the researchers. As the forms were not addressed to individual employees, no reminders could be sent, and it was not possible to analyse the non-response exactly. The respondents either could reply anonymously or provide their name and a written consent for linking the survey data with the register data obtained from the personnel registers of the company. The study was approved by the ethical committee of the Pirkanmaa Hospital District. The present study concerns the blue-collar employees. There were 1,201 respondents of which 901 had a bluecollar occupation. With regard to the total number and occupations of the staff employed at the time of the survey, the response rate was 61 %, the blue-collar workers being somewhat less active. A modification of the validated Nordic Musculoskeletal Questionnaire (Kuorinka et al. 1987) was used to assess musculoskeletal pain. It included a question regarding whether the employee had felt pain, aching or numbness in four anatomical areas (hands or upper extremities; neck or shoulders; lower back; and feet or lower extremities) during the preceding week, with the reply scale being from 0 (not at all) to 10 (very much). The variables were dichotomised at the median (less than median: 0 = mild; more than median: 1 = severe). The cut-off values for upper extremities, neck and shoulder, lower back and lower extremities were 4, 5, 2 and 2, respectively. The dichotomised variables were summed up into a variable expressing the number of areas with severe pain (from zero to four) (Neupane et al. 2013a, b). The summed variable was further categorized into three, leaving zero as no pain, one as single-site pain and multisite pain by combining two-, three- and four-site pain. Biomechanical factors at work were addressed by asking questions about the occurrence of ‘repetitive movements’ and ‘awkward postures’ with the introduction ‘Do movements/postures cause inconvenience or strain in your work?’ reply options on a five-point Likert scale (1 = not at all, 5 = very much) were given. The variables were dichotomized into ‘Low’ and ‘High’ at the medians (cut-off value 3 for both). Psychosocial factors used in this study have been described in detail elsewhere (Neupane et al. 2013a, b).
Int Arch Occup Environ Health
Briefly, ‘incentive and participative leadership’, ‘team spirit’ and ‘possibilities to exert influence at work’ were measured by questionnaires with a Likert scale from 1 (totally disagree/very probably not) to 5 (totally agree/very probably) (Ruohotie 1993). Cronbach alphas of the measures were 0.71, 0.79 and 0.82, respectively. Body mass index (BMI) was calculated using workers’ self-reported weight and height. The level of physical exercise during the last month was elicited on a scale from 0 (not at all) to 7 (strenuous physical activity for more than 3 h a week).
repetitive movements and awkward postures, and after analysing the groups separately, significance of the betweengroup difference of the main effect was assessed with (multiplicative) interaction terms, adjusting for age, gender, BMI, physical exercise and psychosocial factors (team spirit, leadership and possibilities to influence). All the analyses were carried out with the statistical package SPSS version 20.0.
The register data
Descriptive analysis of the studied blue-collar employees (Table 1) shows that those with a high exposure to repetitive movements or awkward postures were more commonly younger and women, scored lower in the psychosocial variables, were less often pain-free and reported more commonly MSP than those with low exposures. With regard to repetitive movements, the high-exposure group had about 36 and the low-exposure group about 28 all-cause sickness absence days yearly, and the corresponding figures for MSD absence were 14 and 11. With regard to awkward postures, these figures were 37 and 28 for all absences, and 14 and 11 for MSD-related absences. Counting from these figures, the share of MSD absence was about 35 % irrespective of the exposure. Table 2 describes the associations between musculoskeletal pain and future sickness absence. The number of all-cause as well as of MSD absence days increased along with pain sites. Single-site pain, however, did not predict absence, whereas the employees with multi-site pain had a 1.5 times higher absence rate, which was statistically significant and robust to adjustments for the baseline covariates. Tables 3 and 4 present the analyses with respect to the interaction of pain and biomechanical exposure in predicting MSD sickness absence. The interaction terms were statistically significant (p
Original Article
Does the association between musculoskeletal pain and sickness absence due to musculoskeletal diagnoses depend on biomechanical working conditions? Subas Neupane · Päivi Leino‑Arjas · Clas‑Håkan Nygård · Helena Miranda · Anna Siukola · Pekka Virtanen
Received: 4 December 2013 / Accepted: 23 June 2014 © Springer-Verlag Berlin Heidelberg 2014
Abstract Aim To investigate single-site and multi-site musculoskeletal pain as predictors of future sickness absence due to musculoskeletal disorders (MSD) among blue-collar employees in food industry, and to study to what extent this relationship depends on physical loading at work. Methods Survey responses of 901 employees on working conditions and musculoskeletal pain during the past week were linked to their future sickness absence records obtained from the personnel register of a food industry company. Negative binomial regression models were computed to determine associations of pain in one and in multisite with the number of sickness absence days due to MSD during a four-year follow-up. Analyses were made in the whole cohort and stratified by the occurrence of repetitive movements and awkward postures (low/high).
Results Multi-site pain occurred among 59 % in the total cohort and predicted sickness absence with a rate ratio of 1.48 [95 % confidence interval (CI) 1.21–1.80], adjusted for age, gender, biomechanical and psychosocial working conditions, body mass index and physical exercise. Similar associations were seen in the sub-cohorts with a low occurrence of repetitive movements (RR 2.18, CI 1.69–2.80) and awkward postures (RR 1.78, CI 1.39–2.28), but not in the sub-cohorts with a high occurrence of these exposure. Single-site pain was not predictive of sickness absence. Conclusions A very high level of sickness absence in biomechanically strenuous work was found. Multi-site pain predicted sickness absence due to MSD among the employees with low exposure, but not among those with high exposure. Keywords Multi-site pain · Food industry · Musculoskeletal diagnosis · Sickness absence · Physical working conditions
S. Neupane (*) · P. Leino‑Arjas · C.-H. Nygård · H. Miranda · A. Siukola · P. Virtanen School of Health Sciences, University of Tampere, 33014 Tampere, Finland e-mail: [email protected] S. Neupane · C.-H. Nygård · A. Siukola Gerontology Research Center, University of Tampere, 33014 Tampere, Finland P. Leino‑Arjas Finnish Institute of Occupational Health, Topeliuksenkatu 41 a A, 00250 Helsinki, Finland C.-H. Nygård · P. Virtanen Institute for Advanced Social Research, University of Tampere, Tampere, Finland H. Miranda Occupational Health Centre, Helsinki City, Helsinki, Finland
Introduction Musculoskeletal disorders are a major public health problem worldwide (Murray et al. 2012), causing significant suffering and healthcare needs for individuals as well as costs to the society. Among working populations, musculoskeletal disorders are the most common reason for workrelated consultations in general practice (Weevers et al. 2005; Taimela et al. 2007) and the spells due to musculoskeletal diagnoses account for a total of 35 % of long-term absence periods in Finland (Finnish Center for pensions [Eläketurvakeskus] 2013). Regarding the nature of musculoskeletal disorders, the leading symptom is pain, and often widespread pain. Either
13
the musculoskeletal disease causes pain in more than one part of the body or an individual has more than one diseases causing pain at different sites. Central sensitization may also lead to multi-site musculoskeletal pain (MSP) (Woolf 2011). Several studies have shown that the consequences of MSP are more severe than those of single-site pain (Haukka et al. 2006; Miranda et al. 2010; Carnes et al. 2007; Kamaleri et al. 2008; Neupane et al. 2011). MSP has a substantial deteriorating impact on physical fitness, general health and well-being, activities of daily living (Carnes et al. 2007; Kamaleri et al. 2008) and perceived work ability (Miranda et al. 2010; Neupane et al. 2013a). MSP is a strong predictor of all-cause sickness absence (Nyman et al. 2007; Haukka et al. 2013). Both short- and long-term absences due to musculoskeletal disorders increase with the increase in the number of pain sites (Morken et al. 2003). However, Ijzelenberg and Burdorf (2004) found that concurrent neck/shoulder pain does not increase the risk of sickness absence due to low back pain. These above-mentioned studies, however, did not consider work-related factors as potential modifiers of the relationship between MSP and sickness absence. Moreover, in the study of Morken et al. (2003), the data on both pain and absence were based on self-report, which may be a source for a common method bias. As regards both the aetiological mechanisms of MSP and the need of sickness absence due to MSP, the biomechanical factors at work are of evident importance (Melchior et al. 2005). These factors also are a major explanation for the high rates of sickness absence and disability pensions due to musculoskeletal disorders among blue-collar workers (Morken et al. 2003; Brage et al. 1997). Once occurring, however, pain in multiple locations of the body seems to entail a risk of sickness absence in particular among the white-collar employees (Andersen et al. 2011). This finding in a Danish population study is somewhat unexpected; as one would anticipate that due to the less strenuous work tasks and environment in white-collar work, the need for pain-related absence is less urgent. The study unfortunately did not take into account the working conditions, and also the results with all-cause absence as the outcome leave unanswered the question about the impact of biomechanical working conditions to the sickness absence due to musculoskeletal complaints. This finding gives reason to ask whether a study with a corresponding design among bluecollar workers would give similar findings and to investigate the role of working conditions in this context. The aim of the present study was, first, to investigate the relationship of single site and MSP to future sickness absence due to musculoskeletal disorders among blue-collar employees in heavy industrial work and, second, to test the hypothesis that this relationship is stronger among employees with higher exposure to physical loading at work.
13
Int Arch Occup Environ Health
Materials and methods The questionnaire survey The study draws on a questionnaire survey conducted in a Finnish food industry company which manufactured various products such as poultry and canned goods, snacks, preserves and convenience foods, meat products including sausages. The survey was conducted during the first half of 2005. The questionnaire forms were distributed to all workers at the workplaces, after which the closed reply envelopes were collected and sent to the researchers. As the forms were not addressed to individual employees, no reminders could be sent, and it was not possible to analyse the non-response exactly. The respondents either could reply anonymously or provide their name and a written consent for linking the survey data with the register data obtained from the personnel registers of the company. The study was approved by the ethical committee of the Pirkanmaa Hospital District. The present study concerns the blue-collar employees. There were 1,201 respondents of which 901 had a bluecollar occupation. With regard to the total number and occupations of the staff employed at the time of the survey, the response rate was 61 %, the blue-collar workers being somewhat less active. A modification of the validated Nordic Musculoskeletal Questionnaire (Kuorinka et al. 1987) was used to assess musculoskeletal pain. It included a question regarding whether the employee had felt pain, aching or numbness in four anatomical areas (hands or upper extremities; neck or shoulders; lower back; and feet or lower extremities) during the preceding week, with the reply scale being from 0 (not at all) to 10 (very much). The variables were dichotomised at the median (less than median: 0 = mild; more than median: 1 = severe). The cut-off values for upper extremities, neck and shoulder, lower back and lower extremities were 4, 5, 2 and 2, respectively. The dichotomised variables were summed up into a variable expressing the number of areas with severe pain (from zero to four) (Neupane et al. 2013a, b). The summed variable was further categorized into three, leaving zero as no pain, one as single-site pain and multisite pain by combining two-, three- and four-site pain. Biomechanical factors at work were addressed by asking questions about the occurrence of ‘repetitive movements’ and ‘awkward postures’ with the introduction ‘Do movements/postures cause inconvenience or strain in your work?’ reply options on a five-point Likert scale (1 = not at all, 5 = very much) were given. The variables were dichotomized into ‘Low’ and ‘High’ at the medians (cut-off value 3 for both). Psychosocial factors used in this study have been described in detail elsewhere (Neupane et al. 2013a, b).
Int Arch Occup Environ Health
Briefly, ‘incentive and participative leadership’, ‘team spirit’ and ‘possibilities to exert influence at work’ were measured by questionnaires with a Likert scale from 1 (totally disagree/very probably not) to 5 (totally agree/very probably) (Ruohotie 1993). Cronbach alphas of the measures were 0.71, 0.79 and 0.82, respectively. Body mass index (BMI) was calculated using workers’ self-reported weight and height. The level of physical exercise during the last month was elicited on a scale from 0 (not at all) to 7 (strenuous physical activity for more than 3 h a week).
repetitive movements and awkward postures, and after analysing the groups separately, significance of the betweengroup difference of the main effect was assessed with (multiplicative) interaction terms, adjusting for age, gender, BMI, physical exercise and psychosocial factors (team spirit, leadership and possibilities to influence). All the analyses were carried out with the statistical package SPSS version 20.0.
The register data
Descriptive analysis of the studied blue-collar employees (Table 1) shows that those with a high exposure to repetitive movements or awkward postures were more commonly younger and women, scored lower in the psychosocial variables, were less often pain-free and reported more commonly MSP than those with low exposures. With regard to repetitive movements, the high-exposure group had about 36 and the low-exposure group about 28 all-cause sickness absence days yearly, and the corresponding figures for MSD absence were 14 and 11. With regard to awkward postures, these figures were 37 and 28 for all absences, and 14 and 11 for MSD-related absences. Counting from these figures, the share of MSD absence was about 35 % irrespective of the exposure. Table 2 describes the associations between musculoskeletal pain and future sickness absence. The number of all-cause as well as of MSD absence days increased along with pain sites. Single-site pain, however, did not predict absence, whereas the employees with multi-site pain had a 1.5 times higher absence rate, which was statistically significant and robust to adjustments for the baseline covariates. Tables 3 and 4 present the analyses with respect to the interaction of pain and biomechanical exposure in predicting MSD sickness absence. The interaction terms were statistically significant (p
