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Oral Session 19 – Musculoskeletal disorders and computers

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O19.1 A CROSS SECTIONAL STUDY OF THE RELATIONSHIP BETWEEN SYMPTOMS AND PHYSICAL FINDINGS IN COMPUTER OPERATORS

J. Riis Jepsen1, G. Thomsen1.1Department of Occupational Medicine, Sydvestjysk Sygehus, Esbjerg, Denmark

Introduction: The character of upper limb disorder in computer operators is yet to be defined. A peripheral nerve involvement is suggested from symptoms commonly including the triad of pain, paraesthesia, and weakness, as well as from clinical observations and recent research.

Objective: To examine the outcome of detailed neurological examination and to compare findings with the presence of symptoms.

Methods: In this study, 117 graphical computer operators answered a modified Nordic Questionnaire and underwent a blinded physical examination including manual assessment of individual muscle strength (11 upper limb muscles), algesia (five locations), vibratory threshold (three locations), and mechanical allodynia along nerves (seven locations). Localised neuropathy was defined according to the course and innervation patterns of nerves. Data were analysed by linear regression.

Results: Pain at any location was reported in 56 mouse operating limbs; however on a scale of 0 to 9, the summarised score exceeded 4 in only 16 limbs. Paraesthesia and subjective weakness were experienced in 24 and 12 limbs, respectively. Abnormal physical findings were prevalent. According to the pattern of findings, brachial neuropathy at cord level was defined in 12 limbs, median neuropathy at elbow level in 19 limbs, and osterior interosseous neuropathy in 19 limbs, with significant correlation to the reporting of pain for the latter. Neuropathy was defined in all these locations in 10 limbs and at least in one location in 35 limbs. The summarised scores for pain in isolation and in combination with paraesthesia and weakness correlated significantly with the summarised scores for muscle strength (deltoid, biceps, radial flexor of wrist, ulnar extensor of wrist), algesia, vibration threshold, and allodynia.

Conclusions: The outcome of this small scale study of a group of computer operators with fewer symptoms than frequently reported suggests that the peripheral nerves are involved in computer related upper limb disorder.

O19.2 DO AWKWARD ERGONOMICS OR ADVERSE PSYCHOSOCIAL WORK ENVIRONMENT PREDICT NECK AND UPPER LIMB PAIN AMONG COMPUTER WORKERS?

J. H. Andersen1, A. I. Kryger2,3, S. Mikkelsen2.1Department of Occupational Medicine, Herning Hospital, Denmark; 2Department of Occupational and Environmental Medicine, Bispebjerg Hospital, Denmark; 3Department of Occupational Medicine, Glostrup Hospital, Denmark

Introduction: Neck and upper limb pain is considered to be associated with computer work and awkward ergonomics, and psychosocial risk factors have been proposed to be related to higher occurrence of pain. The paper reports on baseline measures of ergonomic factors and psychosocial risk factors in relation to pain development for 1 year of follow up.

Methods: The Neck and Upper Extremity Disorders Among Technical Assistants Study was conducted as a survey of 6943 participants, with a 1 year follow response from 5658 (82%). The software program WorkPaceRecorder was installed by 2146 participants, which obtained activity based measurements of computer use for 52 weeks. The results were based on multivariate regression models, all adjusted for time using mouse and/or keyboard.

Results: There were no associations between posture variables related to screen position, mouse or keyboard position, and neck or upper limb pain. Arm/wrist support during work and the possibility of adjusting the chair and worktable did not contribute to elevated risk for regional pain. High job demands, low job control, and low social support did not predict future pain in the neck or upper limbs. Overall dissatisfaction with the physical layout of the workstation was consistently associated with pain in all regions, with odds ratios between 1.5 and 2.5.

Conclusion: Participants who reported overall dissatisfaction with their workstation had elevated risk of neck and upper limb pain, but this was independent of specified ergonomic and psychosocial risk factors. Perhaps the best advice would be to ensure that computer workers are satisfied with their workstation, probably by involving them in decisions on the arrangements of their own workstation, and not by fulfilling certain standards.

O19.3 UPPER LIMBS PAIN AMONG COMPUTER WORKERS: A 1 YEAR FOLLOW UP STUDY, WITH ACTIVITY BASED RECORDINGS OF COMPUTER WORK

A. I. Kryger1,2, C. F. Lassen1, S. Mikkelsen1, J. H. Andersen3.1Department of Occupational Medicine, Glostrup Hospital, Denmark; 2Department of Occupational and Environmental Medicine, Bispebjerg Hospital, Denmark; 3Department of Occupational Medicine, Herning Hospital, Denmark

Introduction: Upper limb disorders are considered to be associated with computer work and have been a matter of public concern since the introduction of computerised data processing. The object was to examine associations between computer work and pain in the elbow, forearm, and wrist/hand by objectively measured computer work.

Method: The Neck and Upper Extremity Disorders Among Technical Assistant Study was conducted as a postal survey in 2000 with 6943 participants and a 1 year follow up. Of the participant, 5658 responded to a questionnaire on ergonomic, psychosocial workplace, and personal factors, and 2146 participants installed the software program WorkPaceRecorder, which recorded mouse and keyboard time, speed, micropauses, and average duration of activity periods over 1 year.

Results: The risk for developing pain in the three regions was significantly associated with increase in mouse time (elbow: odds ratio 1.25; 95% confidence interval 1.15 to 1.36 per 5 hour increase). Mouse speed, micropauses, and duration of activity periods were not risk factors. Keyboard time was not a risk factor. A weak association were seen between ‘high job demands’ and forearm and hand pain (forearm: odds ratio 1.34 (1.07 to 1.67); hand: 1.35 (1.06–1.72)). Female sex was a risk factor for onset of pain in the three regions examined. Ergonomic characteristics at baseline were not risk factors.

Conclusion: Pain complaints in the upper limb would be reduced among computer workers if weekly mouse time were reduced.

O19.4 NECK AND SHOULDER DISORDERS WORKING WITH COMPUTER MOUSE

L. P. A. Brandt1, J. H. Andersen2, C. F. Lassen3, S. Mikkelsen3.1Department of Occupational and Environmental Medicine, Odense University Hospital, Odense, Denmark; 2Department of Occupational Medicine, Herning Hospital, Denmark;3 Department of Occupational Medicine, Glostrup Hospital, Glostrup, Denmark

Objective: To investigate associations between using a computer mouse and keyboard with neck and shoulder pain by objectively measured computer work.

Methods: Activity of computer work was recorded among 2146 technical assistants and machine technicians over 1 year by means of an installed computer software program, WorkPaceRecorder. Usage of computer mouse and keyboard, speed, micropauses, and average duration of activity periods were recorded up to 52 weeks. For every week, scores of pain level (0 = no pain to 7 = severe pain) in the neck and right shoulder were obtained by weekly questionnaire in the WorkPace Recorder; 105 848 weekly observations were recorded. Ordinal logistic regression analyses were performed, providing odds ratios (ORs) for neck and shoulder pain in relation to work with computer mouse per 5 hours/week increase and keyboard per 1 hour/week increase. The risk estimates were adjusted for other known risk factors.

Results: For every 5 hours’ increase in mouse work per week, the ORs for increasing one step in pain scores for pain in the neck and right shoulder were 1.03 (95% confidence interval 0.97 to 1.10) and 1.13 (1.05 to 1.21) respectively. When keyboard work increased by 1 hour, the ORs for increasing 1 step in pain score for pain in the neck and right shoulder were 1.03 (0.98 to 1.08) and 0.98 (0.93 to 1.04) respectively. Number of micropauses, mouse and keyboard speed, and duration of activity periods with mouse and keyboard were not found to be risk factors for pain in the neck or right shoulder.

Conclusion: Increasing work with computer mouse increases the risk for pain in the right shoulder. Numbers of micropauses, and mouse and keyboard speed were not found to be risk factors. No increased risks were found for increasing keyboard use.

O19.5 PHYSICAL RISK FACTORS FOR NECK AND UPPER LIMB DISORDERS IN INDUSTRIAL AND OFFICE WORKERS: RESULTS FROM THE SMASH STUDY

S. G. van den Heuvel1, B. M. Blatter1,2, A. J. van der Beek2,3, P. M. Bongers1,2,3.1TNO Work and Employment, Hoofddorp, the Netherlands; 2Body@Work, Research Center on Physical Activity, Work and Health TNO-Vumc, Amsterdam, the Netherlands; 3Institute for Research in Extramural Medicine, Vrije Universiteit Medical Center, Amsterdam, the Netherlands

Introduction: Although many cross sectional and self reported data have been analysed to study physical risk factors for upper limb disorders, epidemiological studies with longitudinal data based on objective exposure measurements are scarce. The SMASH study provides these data.

Methods: A prospective cohort study was conducted among 1742 employees from 34 companies in industrial, administrative, and service sectors. Physical exposure data were collected by video observation and by questionnaire at baseline. Potential confounders and outcome measures (neck/shoulder, elbow, wrist, and hand pain) were collected by questionnaire at baseline and at three, annually performed, follow up measurements. Separate analyses were performed for office workers and employees with other occupations (service and industrial occupations). The results were adjusted for age, sex, and psychosocial factors.

Results: In office workers (n = 189), prolonged computer work, long working hours, and working with a twisted neck (>45° more than 25% of the time) increased the risk of neck/shoulder pain, but none of the increased risks were statistically significant. Long working hours (relative risk 4.5; 95% confidence interval 1.2 to 17.1) and bending and twisting with the wrist (3.5; 1.2 to 9.9) were the most important risk factors for elbow, wrist, and hand symptoms. In industrial and service workers (n = 594), the strongest risk factor for neck/shoulder pain was lifting more than 25 kg 1–15 times a day, but the risk was only 1.4 (0.9 to 2.1). The risk of elbow, wrist, and hand symptoms was increased when workers used force in combination with repetitive tasks (2.0; 1.0 to 4.0) and worked with a twisted neck (1.9; 1.2 to 3.2).

Conclusions: This study demonstrated that some physical risk factors could be identified, but that repetition alone was not a risk factor for upper limb symptoms. This might be due to a low occurrence of repetitive tasks in this population and too broad a definition of repetitive tasks.

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