Susanne Wulff Svendsen

Work related shoulder disorders: quantitative exposure-response relations with reference to arm posture

Aims: To determine quantitative exposure-response relations between work with highly elevated arms and supraspinatus tendinitis, shoulder pain with disability, and shoulder pain without disability. Methods: A cross sectional study was conducted in a historical cohort of 1886 males from three occupational groups. Exposure measurements were performed for four consecutive working days in a random sample of 72 currently employed subjects. Individual work histories were obtained by questionnaire and register data. Health status was ascertained by physical examination blinded towards exposure and symptoms. Data were analysed by generalised estimating equation and multiple logistic regression with adjustment for potential confounders. Results: For current upper arm elevation above 90°, a duration increment of 1% of the daily working hours was associated with odds ratios of 1.23 (95% CI 1.10 to 1.39) for supraspinatus tendinitis, 1.16 (95% CI 1.08 to 1.24) for shoulder pain with disability, and 1.08 (95% CI 1.04 to 1.13) for shoulder pain without disability. The outcomes were not related to duration of employment in one of the three trades. Conclusions: Quantitative exposure-response relations were established between current work with highly elevated arms and clinically verified shoulder disorders. Substantial long term cumulative effects were not shown. A potential for primary prevention was revealed.

Task based exposure assessment in ergonomic epidemiology: a study of upper arm elevation in the jobs of machinists, car mechanics, and house painters

Aims: To explore the precision of task based estimates of upper arm elevation in three occupational groups, compared to direct measurements of job exposure. Methods: Male machinists (n = 26), car mechanics (n = 23), and house painters (n = 23) were studied. Whole day recordings of upper arm elevation were obtained for four consecutive working days, and associated task information was collected in diaries. For each individual, task based estimates of job exposure were calculated by weighting task exposures from a collective database by task proportions according to the diaries. These estimates were validated against directly measured job exposures using linear regression. The performance of the task based approach was expressed through the gain in precision of occupational group mean exposures that could be obtained by adding subjects with task based estimates to a group of subjects with measured job exposures in a “validation” design. Results: In all three occupations, tasks differed in mean exposure, and task proportions varied between individuals. Task based estimation proved inefficient, with squared correlation coefficients only occasionally exceeding 0.2 for the relation between task based and measured job exposures. Consequently, it was not possible to substantially improve the precision of an estimated group mean by including subjects whose job exposures were based on task information. Conclusions: Task based estimates of mechanical job exposure can be very imprecise, and only marginally better than estimates based on occupation. It is recommended that investigators in ergonomic epidemiology consider the prospects of task based exposure assessment carefully before placing resources at obtaining task information. Strategies disregarding tasks may be preferable in many cases.

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.

Understanding work related musculoskeletal pain: does repetitive work cause stress symptoms?

Background: Pain in the neck and upper extremity is reported with high frequency in repetitive work. Mechanical overload of soft tissues seems a plausible mechanism, but psychological factors have received considerable attention during the past decade. If psychological factors are important for development of regional pain in repetitive work, stress symptoms would likely be on the causal path. Aims: To examine whether objective measures of repetitive monotonous work are related to occurrence and development of stress symptoms. Methods: In 1994–95, 2033 unskilled workers with continuous repetitive work and 813 workers with varied work were enrolled. Measures of repetitiveness and force requirements were quantified using video observations to obtain individual exposure estimates. Stress symptoms were recorded at baseline and after approximately one, two, and three years by the Setterlind Stress Profile Inventory. Results: Repetitive work, task cycle time, and quantified measures of repetitive upper extremity movements including force requirements were not related to occurrence of stress symptoms at baseline or development of stress symptoms during three years of follow up. Conclusions: The findings do not indicate that repetitive work is associated with stress symptoms, but small effects cannot be ruled out. Thus the results question the importance of mental stress mechanisms in the causation of regional pain related to repetitive work. However, the findings should be interpreted with caution because the stress inventory has not been validated against a gold standard.

Ulnar neuropathy and ulnar neuropathy-like symptoms in relation to biomechanical exposures assessed by a job exposure matrix: a triple case–referent study

Objectives We aimed to evaluate relations between occupational biomechanical exposures and (1) ulnar neuropathy confirmed by electroneurography (ENG) and (2) ulnar neuropathy-like symptoms with normal ENG. Methods In this triple case–referent study, we identified all patients aged 18–65 years, examined with ENG at a neurophysiological department on suspicion of ulnar neuropathy, 2001–2007. We mailed a questionnaire to 546 patients with ulnar neuropathy, 633 patients with ulnar neuropathy-like symptoms and two separate groups of community referents, matched on sex, age and primary care centre (risk set sampling). The two patient groups were also compared to each other directly. We constructed a Job Exposure Matrix to provide estimates of exposure to non-neutral postures, repetitive movements, hand–arm vibrations and forceful work. Conditional and unconditional logistic regressions were used. Results The proportion who responded was 59%. Ulnar neuropathy was related to forceful work with an exposure–response pattern reaching an OR of 3.85 (95% CI 2.04 to 7.24); non-neutral postures strengthened effects of forceful work. No relation was observed with repetitive movements. Ulnar neuropathy-like symptoms were related to repetitive movements with an OR of 1.89 (95% CI 1.01 to 3.52) in the highest-exposure category (≥2.5 h/day); forceful work was unrelated to the outcome. Conclusions Ulnar neuropathy and ulnar neuropathy-like symptoms differed with respect to associations with occupational biomechanical exposures. Findings suggested specific effects of forceful work on the ulnar nerve. Thus, results corroborated the importance of an electrophysiological diagnosis when evaluating risk factors for ulnar neuropathy. Preventive effects may be achieved by reducing biomechanical exposures at work.

Lifestyle risk factors for ulnar neuropathy and ulnar neuropathy-like symptoms: Risk Factors for Ulnar Neuropathy

Introduction: We examined whether lifestyle factors differ between patients with ulnar neuropathy confirmed by electroneurography (ENG) and those with ulnar neuropathy‐like symptoms with normal ulnar nerve ENG. Methods: Among patients examined by ENG for suspected ulnar neuropathy, we identified 546 patients with ulnar neuropathy and 633 patients with ulnar neuropathy‐like symptoms. These groups were compared with 2 separate groups of matched community referents and to each other. Questionnaire information on lifestyle was obtained. The electrophysiological severity of neuropathy was also graded. We used conditional and unconditional logistic regression. Results: Responses were obtained from 59%. Ulnar neuropathy was related to smoking, adjusted odds ratio (OR) 4.31 (95% confidence interval [CI] 2.43–7.64) for >24 pack‐years. Ulnar neuropathy‐like symptoms were related to body mass index ≥30 kg/m2, OR 1.99 (95% CI 1.25–3.19). Smoking was associated with increased severity of ulnar neuropathy. Conclusions: Findings suggest that smoking specifically affects the ulnar nerve. Muscle Nerve 48: 507–515, 2013

Responsiveness and Minimal Clinically Important Change: A Comparison Between 2 Shoulder Outcome Measures

Study Design A prospective cohort study nested in a randomized controlled trial. Objectives To determine and compare responsiveness and minimal clinically important change of the modified Constant score (CS) and the Oxford Shoulder Score (OSS). Background The OSS and the CS are commonly used to assess shoulder outcomes. However, few studies have evaluated the measurement properties of the OSS and CS in terms of responsiveness and minimal clinically important change. Methods The study included 126 patients who reported having difficulty returning to usual activities 8 to 12 weeks after arthroscopic decompression surgery for subacromial impingement syndrome. The assessment at baseline and at 3 months included the OSS, the CS, and the European Quality of Life-5 Dimensions-3 Level (EQ-5D-3L) index. Responsiveness was assessed as follows: by correlation analysis between the change scores of the OSS, CS, and EQ-5D-3L index, and the Patient Global Impression of Change (PGIC) scale; by receiver-operating-characteristic (ROC) curve analysis using the PGIC scale as an external anchor; and by effect-size statistics. Results At 3 months, a follow-up assessment of 112 patients (89%) was conducted. The change scores of the CS and the OSS were more strongly correlated with the external anchor (PGIC scale) than the change score of the EQ-5D-3L index. The areas under the ROC curves exceeded 0.80 for both shoulder scores, with no significant differences between them, and comparable effect-size estimates were observed for the CS and the OSS. Minimal clinically important change ROC values were 6 points for the OSS and 11 points for the CS, with upper 95% cutoff limits of 12 and 22 points, respectively. Conclusion The CS and the OSS were both suitable for assessing improvement after decompression surgery.

Risk and prognosis of inguinal hernia in relation to occupational mechanical exposures - a systematic review of the epidemiologic evidence

OBJECTIVES The aim of this review was to evaluate the epidemiologic evidence for (i) a causal effect of occupational mechanical exposures on incidence of inguinal hernia, and (ii) a prognostic effect of such exposures on hernia recurrence and persistent pain after inguinal hernia repair. METHODS We performed a literature search in Medline, Embase, and Web of Science up to 3 November 2011. Central information was extracted from included studies, and strengths and limitations were discussed. RESULTS All 23 included studies focused on effects of (work) activities that hardly reflected specific occupational risk factors. Eight studies provided information on risk by occupation or occupational activities. Increased risk was reported in six studies, but inflationary bias was likely. The negative findings in two studies might well be explained by bias towards the null due to crude exposure and/or outcome assessment. Three studies on single strenuous events primarily reflected patients` beliefs regarding risk factors. Information on prognosis with respect to recurrence was found in seven studies. The studies used crude exposure assessment, and two were also underpowered. Four suggested an increased risk. Six studies on prognosis with respect to persistent pain (one of which also concerned recurrence) were practically non-informative for the purpose of this review. CONCLUSIONS There is insufficient epidemiologic evidence to draw meaningful conclusions about (i) the existence of causal associations between specific occupational mechanical exposures and the development of inguinal hernia, and (ii) the influence of these exposures on prognosis after inguinal hernia repair with respect to hernia recurrence and persistent pain.

Risk of surgery for subacromial impingement syndrome in relation to neck-shoulder complaints and occupational biomechanical exposures: a longitudinal study

OBJECTIVES The aim of this longitudinal study was to evaluate the risk of surgery for subacromial impingement syndrome (SIS) in relation to neck-shoulder complaints and occupational biomechanical shoulder exposures. METHODS The study was based on the Musculoskeletal Research Database at the Danish Ramazzini Centre. We linked baseline questionnaire information from 1993-2004 on neck-shoulder complaints, job titles, psychosocial work factors, body mass index, and smoking with register information on first-time surgery for SIS from 1996-2008. Biomechanical exposure measures were obtained from a job exposure matrix based on expert judgment. We applied multivariable Cox regression. RESULTS During 280 125 person-years of follow-up among 37 402 persons, 557 first-time operations for SIS occurred. Crude surgery rates increased from 1.1 to 2.5 per 1000 person-years with increasing shoulder load. Using no neck-shoulder complaints and low shoulder load at baseline as a reference, no neck-shoulder complaints and high shoulder load showed an adjusted hazard ratio (HR(adj)) of 2.55 [95% confidence interval (95% CI) 1.59-4.09], while neck-shoulder complaints in combination with high shoulder load showed an HR(adj) of 4.52 (95% CI 2.87-7.13). Subanalyses based on 18 856 persons showed an HR(adj) of 5.40 (95% CI 2.88-10.11) for complaints located specifically in the shoulder in combination with high shoulder load. CONCLUSIONS Based on these findings, persons with neck-shoulder and especially shoulder complaints in combination with high shoulder load seem an obvious target group for interventions aimed at reducing exposures to prevent surgery for SIS.

Impact of occupational mechanical exposures on risk of lateral and medial inguinal hernia requiring surgical repair

Objectives We undertook a register-based cohort study to evaluate exposure–response relations between cumulative occupational mechanical exposures, and risk of lateral and medial inguinal hernia repair. Methods Among all men born in Denmark between 1938 and 1988, we established a cohort comprising those aged 18–65 years of age, who had at least 1 year of full-time employment between 1993 and 2007. Using information from a Job Exposure Matrix based on expert judgement and year-by-year information on Danish International Standard Classification of Occupations codes for each individual since 1993, we established time-varying cumulative estimates of exposure to daily lifting activities and standing/walking. Cumulative exposures for lagged 5-year time windows were expressed in a way that corresponds to the pack-year concept of smoking (ton-years, frequent-heavy-lifting years, and standing-years). First-time inguinal hernia repairs in the period 1998–2008 were identified in the Danish Hernia Database. We used a logistic regression technique equivalent to survival analysis, adjusting for age, socioeconomic status, region of residence and calendar year. Results Within the cohort of 1 545 987 men, we identified 22 926 lateral, 15 877 medial and 1592 pantaloon or unspecified first-time inguinal hernia repairs. The risk of lateral hernia repair increased with ton-years, frequent-heavy-lifting-years, and standing-years, with ORs of up to around 1.4. The exposures correlated, but standing-years remained as the most robust risk factor after adjustment for lifting exposures. In general, the risk of medial hernia repair was unrelated to the exposures. Conclusions Our findings suggest an increased risk of lateral inguinal hernia repair in relation to occupational mechanical exposures and a preventive potential of around 15% of all cases.