Sigurd Mikkelsen

Risk factors in the onset of neck/shoulder pain in a prospective study of workers in industrial and service companies

Aims: To quantify the relative contribution of work related physical factors, psychosocial workplace factors, and individual factors and aspects of somatisation to the onset of neck/shoulder pain. Methods: Four year prospective cohort study of workers from industrial and service companies in Denmark. Participants were 3123 workers, previously enrolled in a cross sectional study, where objective measurement of physical workplace factors was used. Eligible participants were followed on three subsequent occasions with approximately one year intervals. Outcomes of interest were: new onset of neck/shoulder pain (symptom cases); and neck/shoulder pain with pressure tenderness in the muscles of the neck/shoulder region (clinical cases). Results: During follow up, 636 (14.1%) participants reported neck/shoulder pain of new onset; among these, 82 (1.7%) also had clinical signs of substantial muscle tenderness. High shoulder repetition was related to being a future symptom case, and a future clinical case. Repetition was strongly intercorrelated with other physical measures. High job demands were associated with future status as a symptom case, and as a clinical case. A high level of distress predicted subsequent neck/shoulder pain, and neck/shoulder pain with pressure tenderness. Conclusions: High levels of distress, and physical and psychosocial workplace factors are predictors of onset of pain in the neck and/or shoulders, particularly pain with pressure tenderness in the muscles.

Physical, psychosocial, and individual risk factors for neck/shoulder pain with pressure tenderness in the muscles among workers performing monotonous, repetitive work.

STUDY DESIGN Cross-sectional study. OBJECTIVES To evaluate the effect of individual characteristics and physical and psychosocial workplace factors on neck/shoulder pain with pressure tenderness in the muscles. SUMMARY OF BACKGROUND DATA Controversy prevails about the importance of workplace factors versus individual factors in the etiology of pain in the neck and/or shoulders. METHODS Study participants were 3123 workers from 19 plants. Physical risk factors were evaluated via video observations, and psychosocial risk factors were assessed with the job content questionnaire. Other procedures included symptom survey, clinical examination, and assessment of health-related quality of life (SF-36). The main outcome variable, neck/shoulder pain with pressure tenderness, was defined on the basis of subjective pain score and pressure tenderness in muscles of the neck/shoulder region. RESULTS The prevalence of neck/shoulder pain with pressure tenderness was 7.0% among participants performing repetitive work and 3.8% among the referents. We found an association with high repetitiveness (prevalence ratio 1.8, 95% confidence interval 1.1-2.9), high force (2.0, 1.2-3.3), and high repetitiveness and high force (2.3, 1.4-4.0). The strongest work-related psychosocial risk was high job demands (1.8, 1.2-2.7). Increased risk was also associated with neck/shoulder injury (2.6, 1.6-4.1), female gender (1.8, 1.2-2.8), and low pressure pain threshold (1.6, 1.1-2.3). Neck/shoulder pain was strongly associated with reduced health-related quality of life. CONCLUSIONS Work-related physical and psychosocial factors, as well as several individual risk factors, are important in the understanding of neck/shoulder pain. The findings suggest that neck/shoulder pain has a multifactorial nature. Reduced health-related quality of life is associated with subjective pain and clinical signs from the neck and shoulders. The physical workplace factors were highly intercorrelated, and so the effect of individual physical exposures could only be disentangled to a minor degree.

Does computer use pose an occupational hazard for forearm pain; from the NUDATA study

Aims: To determine the occurrence of pain conditions and disorders in the forearm and to evaluate risk factors for forearm pain in a cohort of computer workers. Methods: A total of 6943 participants with a wide range of computer use and work tasks were studied. At baseline and at one year follow up participants completed a questionnaire. Participants with relevant forearm symptoms were offered a clinical examination. Symptom cases and clinical cases were defined on the basis of self reported pain score and palpation tenderness in the muscles of the forearm. Results: The seven days prevalence of moderate to severe forearm pain was 4.3%. Sixteen of 296 symptom cases met criteria for being a clinical forearm case, and 12 had signs of potential nerve entrapment. One year incidence of reported symptom cases was 1.3%; no subjects developed new signs of nerve entrapment. Increased risk of new forearm pain was associated with use of a mouse device for more than 30 hours per week, and with keyboard use more than 15 hours per week. High job demands and time pressure at baseline were risk factors for onset of forearm pain; women had a twofold increased risk of developing forearm pain. Self reported ergonomic workplace factors at baseline did not predict future forearm pain. Conclusion: Intensive use of a mouse device, and to a lesser extent keyboard usage, were the main risk factors for forearm pain. The occurrence of clinical disorders was low, suggesting that computer use is not commonly associated with any severe occupational hazard to the forearm.

Job Strain and the Risk of Depression: Is Reporting Biased?

It is unknown whether the relation between job strain and depression reflects causal characteristics of the working environment or reporting bias. The authors investigated reporting bias by analyzing individual versus work-unit measures of job strain and the risk of depressive symptoms (n = 287) and a diagnosis of depression (n = 97) among 4,291 employees within 378 work units in Aarhus, Denmark, 2007. All participants reported psychological demands and decision latitude, and the authors estimated mean values for each work unit. The odds ratios predicting depressive symptoms or a diagnosis of depression for the highest versus the lowest levels of individual, self-reported high psychological demands and low decision latitude were significantly increased above 2.5. When participants were classified by the work-unit mean levels, these associations were substantially smaller. For depressive symptoms, the odds ratios were 1.49 (95% confidence interval (CI): 0.88, 2.53) and 1.08 (95% CI: 0.84, 1.39), respectively, for psychological demands and decision latitude. For a diagnosis of depression, the odds ratios were 1.33 (95% CI: 0.57, 3.09) and 1.02 (95% CI: 0.68, 1.56), respectively, for psychological demands and decision latitude. These findings indicate that reporting bias inflates associations between job strain and the occurrence of depression, if studies rely on individual self-reports.

Computer mouse use predicts acute pain but not prolonged or chronic pain in the neck and shoulder

Background: Computer use may have an adverse effect on musculoskeletal outcomes. This study assessed the risk of neck and shoulder pain associated with objectively recorded professional computer use. Methods: A computer programme was used to collect data on mouse and keyboard usage and weekly reports of neck and shoulder pain among 2146 technical assistants. Questionnaires were also completed at baseline and at 12 months. The three outcome measures were: (1) acute pain (measured as weekly pain); (2) prolonged pain (no or minor pain in the neck and shoulder region over four consecutive weeks followed by three consecutive weeks with a high pain score); and (3) chronic pain (reported pain or discomfort lasting more than 30 days and “quite a lot of trouble” during the past 12 months). Results: Risk for acute neck pain and shoulder pain increased linearly by 4% and 10%, respectively, for each quartile increase in weekly mouse usage time. Mouse and keyboard usage time did not predict the onset of prolonged or chronic pain in the neck or shoulder. Women had higher risks for neck and shoulder pain. Number of keystrokes and mouse clicks, length of the average activity period, and micro-pauses did not influence reports of acute or prolonged pain. A few psychosocial factors predicted the risk of prolonged pain. Conclusions: Most computer workers have no or minor neck and shoulder pain, few experience prolonged pain, and even fewer, chronic neck and shoulder pain. Moreover, there seems to be no relationship between computer use and prolonged and chronic neck and shoulder pain.

Identification of neck-shoulder disorders in a 1 year follow-up study. Validation Of a questionnaire-based method.

&NA; A cohort of 243 female sewing machine operators were studied by questionnaire and clinical examinations with the purpose to study the efficiency of a screening questionnaire‐based method to identify prevalent and incident cases of neck‐shoulder disorders. The cross‐sectional correlation between self‐reported neck‐shoulder complaints scores and clinical signs of a neck‐shoulder disorder was high. An assessed cut‐of point of complaints could identify 90% of all cases fulfilling the criteria of rotator cuff tendinitis, while the complaint score with regard to clinical signs of myofascial pain syndrome was about 67%. In the follow‐up analyses, incident clinical signs of disorders at 1 year follow‐up were used as ‘golden standard’ in the validation of screening criteria, which included a defined increase of symptoms. Apparently increase of symptoms did not seem to be the optimal criteria for identification of incident cases. Alternatively a cut‐of point of regional complaints in close relation to clinical examinations is recommended.

Risk Factors for Neck and Upper Extremity Disorders among Computers Users and the Effect of Interventions: An Overview of Systematic Reviews

Background To summarize systematic reviews that 1) assessed the evidence for causal relationships between computer work and the occurrence of carpal tunnel syndrome (CTS) or upper extremity musculoskeletal disorders (UEMSDs), or 2) reported on intervention studies among computer users/or office workers. Methodology/Principal Findings PubMed, Embase, CINAHL and Web of Science were searched for reviews published between 1999 and 2010. Additional publications were provided by content area experts. The primary author extracted all data using a purpose-built form, while two of the authors evaluated the quality of the reviews using recommended standard criteria from AMSTAR; disagreements were resolved by discussion. The quality of evidence syntheses in the included reviews was assessed qualitatively for each outcome and for the interventions. Altogether, 1,349 review titles were identified, 47 reviews were retrieved for full text relevance assessment, and 17 reviews were finally included as being relevant and of sufficient quality. The degrees of focus and rigorousness of these 17 reviews were highly variable. Three reviews on risk factors for carpal tunnel syndrome were rated moderate to high quality, 8 reviews on risk factors for UEMSDs ranged from low to moderate/high quality, and 6 reviews on intervention studies were of moderate to high quality. The quality of the evidence for computer use as a risk factor for CTS was insufficient, while the evidence for computer use and UEMSDs was moderate regarding pain complaints and limited for specific musculoskeletal disorders. From the reviews on intervention studies no strong evidence based recommendations could be given. Conclusions/Significance Computer use is associated with pain complaints, but it is still not very clear if this association is causal. The evidence for specific disorders or diseases is limited. No effective interventions have yet been documented.

Work-related knee disorders in floor layers and carpenters.

Previous studies indicate an increased prevalence of knee disorders in some occupations possibly related to kneeling working positions. The purpose of the present study was to examine the relationship among knee-straining work, self-reported knee-complaints, and physical signs of knee disorders. The duration of knee-straining work was estimated from videotapes of representative work tasks. Floor layers (n = 133), carpenters (n = 506), and compositors (n = 327) aged 26 to 72 years without previous acute knee traumas were examined in a cross-sectional study by questionnaire. A stratified random sample of the questionnaire responders; 67 floor layers, 127 carpenters, and 101 compositors had independent double examinations for physical signs of knee disorders. The videotapes showed that knee-straining work constituted 56% of working time for floor layers, 26% for carpenters, and none for compositors. The prevalences of self-reported knee-complaints were positively associated with the amount of knee-straining work and were significantly different for the three trades. Floor layers and carpenters who were presently working in their trade had a higher prevalence of knee complaints than floor layers and carpenters who had left their trade. Age, seniority, weight, body mass index, smoking, and knee-straining sports activity had no significant effects. The clinical study showed a positive association for knee-straining work, hyperkeratosis, and bursitis. A similar pattern was found for signs of intraarticular knee disorders by one physician but not by another. The reproducibility of these signs was low. More studies are needed to define clinically important knee disorders for epidemiological studies.

Prognosis of shoulder tendonitis in repetitive work: a follow up study in a cohort of Danish industrial and service workers.

Background: The physical and psychosocial work environment is expected to modify recovery from shoulder disorders, but knowledge is limited. Methods: In a follow up study of musculoskeletal disorders in industrial and service workers, 113 employees were identified with a history of shoulder pain combined with clinical signs of shoulder tendonitis. The workers had yearly reexaminations up to three times. Quantitative estimates of duration, repetitiveness, and forcefulness of current tasks were obtained from video recordings. Perception of job demands, decision latitude, and social support was recorded by a job content questionnaire. Recovery of shoulder tendonitis was analysed by Kaplan-Meier survival technique and by logistic regression on exposure variables and individual characteristics in models, allowing for time varying exposures. Results: Some 50% of workers recovered within 10 months (95% CI 6 to 14 months). Higher age was strongly related to slow recovery, while physical job exposures were not. Perception of demands, control, and social support at the time when the shoulder disorder was diagnosed, were associated with delayed recovery, but these psychosocial factors did not predict slow recovery in incident cases identified during follow up. Conclusion: The median duration of shoulder tendonitis in a cross sectional sample of industrial and service workers was in the order of 10 months. This estimate is most likely biased towards too high a value. Recovery was strongly reduced in higher age. Physical workplace exposures and perceived psychosocial job characteristics during the period preceding diagnosis seem not to be important prognostic factors.

Validity of questionnaire self-reports on computer, mouse and keyboard usage during a four-week period

Objective: To examine the validity and potential biases in self-reports of computer, mouse and keyboard usage times, compared with objective recordings. Methods: A study population of 1211 people was asked in a questionnaire to estimate the average time they had worked with computer, mouse and keyboard during the past four working weeks. During the same period, a software program recorded these activities objectively. The study was part of a one-year follow-up study from 2000–1 of musculoskeletal outcomes among Danish computer workers. Results: Self-reports on computer, mouse and keyboard usage times were positively associated with objectively measured activity, but the validity was low. Self-reports explained only between a quarter and a third of the variance of objectively measured activity, and were even lower for one measure (keyboard time). Self-reports overestimated usage times. Overestimation was large at low levels and declined with increasing levels of objectively measured activity. Mouse usage time proportion was an exception with a near 1:1 relation. Variability in objectively measured activity, arm pain, gender and age influenced self-reports in a systematic way, but the effects were modest and sometimes in different directions. Conclusion: Self-reported durations of computer activities are positively associated with objective measures but they are quite inaccurate. Studies using self-reports to establish relations between computer work times and musculoskeletal pain could be biased and lead to falsely increased or decreased risk estimates.