Niklas Krause

Occupational disability due to low back pain: a new interdisciplinary classification based on a phase model of disability.

Study Design This study critically reviewed current conceptualizations of occupational disability resulting from low back pain (LBP). It proposes a new classification system for back pain built on a phase-model of disability. Objectives The goal was to develop a classification system that overcomes the shortcomings of existing classification schemes and is useful for interdisciplinary research, prevention, treatment, and rehabilitation. Summary of Background Data Attempts to study and prevent disability resulting from LBP have been hampered by the use of inadequate classifications of LBP. Methods Current classifications of LBP were critically reviewed, and criteria for a useful classification system are described. The disabling process is organized in eight consecutive phases determined by the presence and duration of work disability. Results The proposed eight-phase classification is based primarily on the presence and duration of work-disability rather than on clinical categories. It takes into account the developmental and social character of disability. The simplicity, reliability, and expandability of the model allow for its interdisciplinary use in research and intervention. Conclusion The prevention of disabling back pain requires an interdisciplinary approach. For this purpose, other than purely biomedical classifications of LBP are needed. The authors propose an eight-phase classification system primarily based on the duration of work disability and that takes into account other biomedical, developmental, and social characteristics of work-disability resulting from LBP.

Workplace conditions, socioeconomic status, and the risk of mortality and acute myocardial infarction: the Kuopio Ischemic Heart Disease Risk Factor Study.

OBJECTIVES This study investigated whether the association between workplace conditions and the risk of all-cause and cardiovascular mortality and acute myocardial infarction differed by socioeconomic status. METHODS Prospective data were used to examine these associations in 2297 Finnish men, with adjustment for prevalent diseases and biological, behavioral, and psychosocial covariates, and stratified by employment status and workplace social support. RESULTS Elevated age-adjusted relative hazards for all-cause mortality were found for men who reported high demands, low resources, and low income; high demands, high resources, and low income; and low demands, high resources, and low income. Similar patterns were found for cardiovascular mortality. In contrast, elevated age-adjusted relative hazards for acute myocardial infarction were observed only in men who reported high demands, low resources, and low income. These results did not differ by level of workplace social support or employment status. CONCLUSIONS The negative effects of workplace conditions on mortality and of myocardial infarction risk depended on income level and were largely mediated by known risk factors.

Doctor proactive communication, return-to-work recommendation, and duration of disability after a workers' compensation low back injury

Althoughdoctors are increasingly evaluated on the basis of return-to-work (RTW)outcomes, the effect of doctor–patient communication about the workplaceand RTW after an occupational injury has received little research attention.The effect of patient-reported doctor communication on duration of disabilitywas examined retrospectively in a 3-year cohort of 325 claimants with alost-time low back injury. Although doctor proactive communication wasassociated with a greater likelihood of RTW during the acute phase (<30days of disability), this effect disappeared when injury and workloadcharacteristics were taken into account. A positive RTW recommendation wasassociated with about a 60% higher RTW rate during the subacute/chronic phase(>30 days of disability) only. Prospective studies are needed to confirmthis effect. The impact of physician communication on RTW is largelyconfounded by injury and workplacefactors.

Objective stress factors, accidents, and absenteeism in transit operators : a theoretical framework and empirical evidence

The authors used observational job analysis as a conceptually based technique to measure stress factors unbiased by worker appraisal with 81 transit driving tasks on 27 transit lines. Stressor dimensions included work barriers that interfere with task performance due to poor technical-organizational design, time pressure, time binding (autonomy over time management), and monotonous conditions. Line-specific average stressor values were assigned to 308 transit operators who mainly worked the particular line. Logistic regression analyses showed associations for high work barriers and sickness absences (odds ratio [OR] = 3.8, p = .05). There were elevated risks for work accidents for high time pressure operators (OR = 4.0, p = .04) and for the medium time-binding group (OR = 3.3, p = .04) and significant (alpha = .20) unadjusted interaction terms for barriers and time pressure in predicting accidents and absences, and barriers and time binding in predicting absences. Findings suggest guaranteed rest breaks and flexible timing for accident prevention and removal of work barriers for reducing absenteeism.

Physical Workload and Ergonomic Factors Associated With Prevalence of Back and Neck Pain in Urban Transit Operators

Study Design. Back and neck pain was studied crosssectionally in 1,449 urban transit drivers by linking medical data, self‐reported ergonomic factors, and company records on job history. Objectives. The goal was to examine the relation between physical workload, ergonomic factors, and the prevalence of back and neck pain. Summary of Background Data. Researchers, to date, have not found an independent effect of ergonomic factors on back and neck pain while accounting for the effects of past and current physical workload. Methods. Self‐reported ergonomic factors, vehicle type, physical workload (measured as duration of driving), height, weight, age, and gender were analyzed in relation to back and neck pain, using multivariable logistic regression models. Results. Physical workload showed a positive dose‐response relation with back and neck pain after controlling for vehicle type, height, weight, age, and gender. The odds ratio for 10 years of driving was 3.43. Additional adjustment for ergonomic factors decreased this odds ratio to 2.55. Six out of seven ergonomic factors were significantly related to the prevalence of back and neck pain after adjustment for age, gender, height, weight, and physical workload. Problems with adjusting the seat had the largest effect (odds ratio = 3.52). Women had back and neck pain twice as frequently as men. Conclusion. The results support the hypothesis of a causal role of physical workload for the development of back and neck pain. Ergonomic factors partially mediated the risk of back and neck pain associated with driving, suggesting a potential for prevention of back and neck pain by ergonomic redesign of transit vehicles. Elevated risks for back and neck pain for female drivers were not explained by anthropometric and ergonomic factors.

Prolonged standing at work and hospitalisation due to varicose veins: a 12 year prospective study of the Danish population.

Background: Recent studies suggest that prolonged standing at work is associated with the development of diseases of varicose veins (VV). Aims: To assess the risk of hospitalisation due to VV in the lower extremities prospectively in workers standing or walking at least 75% of their time at work. Methods: A representative random sample of 9653 working age adults was drawn from the Central Population Register of Denmark in 1991. Of these, 8664 accepted to be interviewed by telephone (response rate 90%). Respondents (2939 men and 2708 women) were 20–59 years old and employed in 1990. Risk ratios for VV were estimated by log-linear Poisson regression models separately for men and women with adjustment for smoking status, body mass index (BMI), heavy lifting, and, for females only, number of children at baseline. Results: During 12 years of follow up, 40 hospitalisations due to VV were observed among the men and 71 among the women. For employees with jobs that require prolonged standing or walking compared to all other employees, the relative risk was 1.75 (95% CI 0.92 to 3.34) for men and 1.82 (95% CI 1.12 to 2.95) for women. The pooled estimate of the relative risk was 1.78 (95% CI 1.19 to 2.68). The aetiological fraction of prolonged standing or walking at work was estimated as 22.5% for men and 22.6% for women. Conclusions: This prospective study confirms that prolonged standing at work constitutes an excess risk of hospital treatment due to varicose veins and accounts for more than one fifth of all cases of working age.

Effort-reward imbalance and incidence of low back and neck injuries in San Francisco transit operators

Objectives: Effort–reward imbalance (ERI) has been associated with musculoskeletal disorders in cross-sectional and case–control studies, but no longitudinal studies have been published yet. The effect of ERI on the incidence of compensated low back and neck injuries was examined in a 7.5-year follow-up study among 1179 San Francisco transit operators. Methods: Data from medical examination and a survey on working conditions and health were linked to administrative workers’ compensation databases. HRs for first low back and first neck injury were calculated with multivariate Cox regression models. Additional analyses accounted for severity of injury based on medical diagnosis. Results: A 1 SD increase in ERI was associated with compensated low back (HR 1.13, 95% CI 1.02 to 1.26) and neck injuries (HR 1.14, 95% CI 1.02 to 1.27) after adjusting for gender, age, height, weight, years of professional driving, weekly driving hours, vehicle type, ergonomic problems, pain at baseline and job strain. The highest quartile of ERI showed an HR of 1.32 (95% CI 0.94 to 1.86) for low back injuries and an HR of 1.66 (95% CI 1.16 to 2.38) for neck injuries after adjustment for all covariates. The associations between ERI and low back injury were stronger for more severe injuries (HR 1.23, 95% CI 1.03 to 1.46 for a 1 SD increase in ERI) than for less severe injuries (HR 1.11, 95% CI 0.96 to 1.28). For neck injuries, stronger relationships were found for less severe injuries (HR 1.15, 95% CI 1.02 to 1.29) than for more severe injuries (HR 1.10, 95% CI 0.86 to 1.41). Conclusions: ERI is associated with low back and neck injuries in San Francisco transit operators independently of individual worker characteristics, physical workload, ergonomic problems, baseline pain and job strain. Effect sizes differ by injury severity.

A randomised controlled trial evaluating an alternative mouse and forearm support on upper body discomfort and musculoskeletal disorders among engineers

Objectives: The aim of this intervention study was to determine the effects of an alternative mouse and/or a forearm support board on the change in upper body discomfort scores and the development of incident musculoskeletal disorders. Methods: This randomised controlled intervention trial followed 206 engineers for one year. Participants were randomised to receive (1) a conventional mouse only, (2) an alternative mouse only, (3) a forearm support board, or (4) an alternative mouse plus forearm support board. Outcome measures included weekly upper body discomfort scores and incident musculoskeletal disorders. Results: During the study, 42 participants were diagnosed with an incident musculoskeletal disorder. The group that received the forearm support board experienced a reduction in their right upper extremity discomfort (beta-coefficient −0.35, 95% CI −0.67 to −0.03) in comparison to those who did not receive a forearm board. The group that received the alternative mouse had a protective, but non-significant (p = 0.20), effect on incident cases of right upper extremity musculoskeletal disorders (HR 0.57, 95% CI 0.24 to 1.34) and a non-significant reduction in neck/shoulder discomfort (beta-coefficient −0.23, 95% CI −0.056 to 0.10) in comparison to those who received a conventional mouse. Conclusions: In engineers who use a computer for more than 20 h per week, a forearm support board may reduce right upper extremity discomfort attributed to computer use.

1st place, PREMUS best paper competition: workplace and individual factors in wrist tendinosis among blue-collar workers – the San Francisco study

OBJECTIVE Workplace studies have linked hand/wrist tendinosis to forceful and repetitive hand exertions, but the associations are not consistent. We report findings from a prospective study of right wrist tendinosis among blue-collar workers. METHODS Workers (N=413) at four industries were followed for 28 months with questionnaires and physical examinations every 4 months to identify incident cases of right wrist tendinosis. Exposure assessment of force and repetition were based on field measurements and video analysis to determine repetition rate and the percent time (% time) in heavy pinch (>1 kg-force) or power grip (>4 kg-force). All exposure variables were measured at the level of the individual and task. For workers responsible for >1 task, a time-weighted average exposure was calculated based on task hours per week. A proportional hazards model was used to assess the relationship between exposures and incidence of wrist tendinosis. RESULTS During the 481 person-years of follow-up, there were 26 incident cases of right wrist tendinosis [incidence rate (IR) 5.40 cases per 100 person-years]. Adjusting for age, gender, and repetition, wrist tendinosis was associated with % time spent in heavy pinch [hazard ratio (HR) 5.01, 95% CI 1.27-19.79). Composite exposure measure American Conference of Industrial Hygienists Threshold Limit Value (ACGIH-TLV) for hand activity level (HR 3.95, 95% CI 1.52-10.26) was also associated with the outcome for the medium-exposure group using video-based total repetition rate. CONCLUSIONS The workplace factors predicting wrist tendinosis were time-weighted average values of % time spent in heavy pinch and the ACGIH-TLV for Hand Activity Level. The % time spent in power grip was not a significant predictor, nor were any measures of repetition. An exposure-response relationship was observed for the % time spent in heavy pinch. These findings may improve programs for preventing occupational wrist tendinosis.

Stroke among male professional drivers in Denmark, 1994–2003

Objectives: (1) To estimate the relative risk of stroke among various groups of professional drivers; (2) to determine if any excess risk should be attributed to infarction or haemorrhage; (3) to estimate the relative risk ratio for stroke among professional drivers living in Greater Copenhagen compared to those living outside the metropolis. Methods: A cohort of 6285 bus drivers, 4204 car, taxi, and van drivers, and 25 879 heavy truck and lorry drivers were followed up for hospital admission due to stroke and sub-diagnoses in the period 1994–2003. Using hospital admission for all economically active men as the standard, the standardised hospitalisation ratios (SHR) were calculated, taking age and county into consideration. Results: There was a high SHR for stroke among all groups of professional drivers (SHR = 132; 95% CI 121–141). Among car, taxi, and van drivers the SHR was 157 (95% CI 132–189), among bus drivers it was 139 (95% CI 119–163), and among heavy truck and lorry drivers it was 124 (95% CI 113–136). The excess risk for all groups of professional drivers was highest for cerebrovascular infarction (SHR = 139; 95% CI 124–155) and lowest for non-traumatic intracranial haemorrhage (SHR = 113; 95% CI 96–133). The excess risks for all groups were significantly higher for cerebrovascular infarction than for non-traumatic intracranial haemorrhage (relative risk ratio (RRR) 1.23; 95% CI 1.01–1.51). The RRR of stroke among drivers in the metropolitan area compared to rural areas was 1.13 (95% CI 0.94–1.36). The RRR for stroke among car, taxi, and van drivers compared to drivers of heavy trucks and of lorries was 1.28 (95% CI 1.03–1.57). Conclusion: All groups of professional drivers are at increased risk of stroke. The excess risk is more due to cerebral infarctions than to non-traumatic intracranial haemorrhage. The risk of stroke is higher among drivers carrying passengers than among drivers carrying goods.