Carel T. J. Hulshof

Self-reported back pain in tractor drivers exposed to whole-body vibration

SummaryA postal questionnaire on symptoms of ill health and exposure to whole-body vibration was completed by 577 workers (response rate 79%) who were employed in certain functions by two companies 11 years before. The relation between the occupational history of driving vibrating vehicles (mainly agricultural tractors) and back pain has been analyzed. The prevalence of reported back pain is approximately 10% higher in the tractor drivers than in workers not exposed to vibration. The increase is mainly due to more pain in the lower back and more pain lasting at least several days. A vibration dose was calculated by assigning each vehicle driven a vibration magnitude, estimated on the base of vibration measurements. The prevalence of back pain increases with the vibration dose. The highest prevalence odds ratios are found for the more severe types of back pain. These prevalence odds ratios do not increase with the vibration dose. This might be due to health-related selection which is more pronounced for severe back pain than for back pain in general. The two components of the vibration dose, duration of exposure and estimated mean vibration magnitude, have also been considered separately. Back pain increases with duration of exposure but it does not increase with the estimated mean magnitude of vibration. This is probably due to the inaccuracy of this estimate. The higher prevalence of back pain in tractor drivers might be (partly) caused by whole-body vibration, but prolonged sitting and posture might also be of influence.

Self-reported Back Pain in Fork-lift Truck and Freight-container Tractor Drivers Exposed to Whole-body Vibration

To study the long-term health effect of whole-body vibration, a questionnaire on symptoms of ill health was mailed to 242 drivers and a reference group of 210 workers from six harbor companies (response 81%). Vehicles driven were fork-lift trucks and freight-container tractors. Vibration level during a representative working period (vector sum of the frequency weighted acceleration in the x-, y-, and z-directions) was 0.8 m/sec2 for the fork-lift trucks and 1.0 m/sec2 for the freight-container tractors. Only the results concerning self-reported symptoms of the back are described. Of the young (<35 years), shortterm-exposed drivers, 68% reported that they had back pain regularly vs. only 25% of the reference group of comparable age. With increasing age, the difference in the prevalence of self-reported regular back pain between the drivers and the reference group disappeared. Driving during the 5 years preceding the onset of symptoms seemed to increase the risk of back pain, whereas earlier exposure did not.

Effectiveness of measures and implementation strategies in reducing physical work demands due to manual handling at work

OBJECTIVES The purpose of this study was to determine whether workplace smoking policy was associated with respiratory health effects among food and beverage servers. METHODS Data were obtained from a postal survey of hospitality workers. The participation rate for the questionnaire was 73.9% of those contacted. Current smokers were excluded from the analysis. Adjustment for differences between groups in age, gender, ex-smoker versus never smoker status, home exposure environmental tobacco smoke, childhood asthma, mail versus telephone questionnaire, and hours worked per week was done using logistic regression. A subset of 88 nonsmokers underwent laboratory evaluation, including spirometry and hair nicotine analysis. RESULTS The prevalence of irritant and respiratory symptoms among 383 nonsmokers was consistently higher among the participants from premises where smoking was permitted without restrictions on the workplace. In comparison with those from facilities where smoking was prohibited, the highest adjusted odds ratios (OR) were for chronic phlegm for those working where smoking was permitted (OR 8.5 95% confidence interval (95% CI) 2.4-30.0] or where there were partial smoking restrictions (OR 5.7 95% CI 1.7-19.4). Lung function was not reduced apart from the ratio between forced expiratory volume in 1 second and forced vital capacity, which was lower for workers from facilities where smoking was permitted. Hair nicotine levels were lowest for workers from facilities where smoking was prohibited. CONCLUSIONS The results suggest that occupational exposure to environmental tobacco smoke, determined through smoking policies, can adversely affect the respiratory health of nonsmokers who work in the food and beverage service industry.

Back disorders in crane operators exposed to whole-body vibration

SummaryIn The Netherlands so far little research has been carried out to investigate the health effects of exposure to whole-body vibration at work. In a retrospective (10-year) follow-up study, the incidence of permanent work disabilities in crane operators exposed to vibration was compared to that of a control group. The emphasis in this presentation is on disablement because of back disorders. Among the crane operators with more than 5 years of exposure to vibration, more disability due to back trouble occurred than in the control group. The incidence density ratio (IDR) exceeded 2 for disability because of degeneration of the intervertebral disc, after adjustment for age, nationality, shift work and calendar year. With increasing years of exposure, the risk ratio for disability because of intervertebral disc disorders also increased. The risk ratio for a disability pension due to disease of the intervertebral disc for crane operators with more than 5 years of exposure was almost 3 compared to the control group. A combination of exposure to whole-body vibration, an unfavorable posture, and climatic conditions is responsible for the development of these health effects.

Evaluation research in occupational health services: general principles and a systematic review of empirical studies.

OBJECTIVES: To study the nature and extent of evaluation research in occupational health services (OHSs). METHODS: Literature review of evaluation research in OHSs. On the basis of a conceptual model of OHS evaluation, empirical studies are categorised into aspects of input, process, output, outcome, and OHS core activities. RESULTS: Many methods to evaluate OHSs or OHS activities exist, depending on the objective and object of evaluation. The amount of empirical studies on evaluation of OHSs or OHS activities that met the non-restrictive inclusion criteria, was remarkably limited. Most of the 52 studies were more descriptive than evaluative. The methodological quality of most studies was not high. A differentiated picture of the evidence of effectiveness of OHSs arises. Occupational health consultations and occupational rehabilitation are hardly studied despite much time spent on the consultation by occupational physicians in most countries. The lack of effectiveness and efficiency of the pre-employment examination should lead to its abandonment as a means of selection of personnel by OHSs. Periodic health monitoring or surveillance, and education on occupational health hazards can be carried out with reasonable process quality. Identification and evaluation of occupational health hazards by a workplace survey can be done with a high output quality, which, however, does not guarantee a favourable outcome. CONCLUSIONS: Although rigorous study designs are not always applicable or feasible in daily practice, much more effort should be directed at the scientific evaluation of OHSs and OHS instruments. To develop evidence-based occupational health care the quality of evaluation studies should be improved. In particular, process and outcome of consultation and rehabilitation activities of occupational physicians need to be studied more.

Long-term sick leave and disability pensioning due to back disorders of tractor drivers exposed to whole-body vibration

SummaryIn a historical 11-year follow-up study, disability pensioning and the incidence of the first sick leave of 4 weeks or longer due to back disorders has been investigated in a group of drivers exposed to whole-body vibration (WBV), mainly of agricultural tractors. The reference group comprised workers not or only slightly exposed to WBV from the same and another company. The vibration exposure of the tractor drivers was roughly around the ISO-2631 fatigue-decreased proficiency limit. The incidence of a first long-term sick leave due to back disorders was 3 per 100 person-years in tractor drivers and 2 per 100 person-years in the entire reference group. However, the incidence was not substantially increased in tractor drivers when the referents comprised only those working at the same company, suggesting selection bias. The highest relative risk (ca. 3) was found for long-term sick leave due to intervertebral disc disorders and this risk seemed to increase with the received WBV dose. That especially the incidence of intervertebral disc disorders increased, agrees well with findings in other studies. Data on disability pensioning due to back disorders are too scarce to be conclusive, but a trend towards younger disablement in tractor drivers is evident. Exposure to WBV, together with twisted posture and prolonged sitting, are considered to be responsible for the increased incidences observed in tractor drivers.

A search strategy for occupational health intervention studies.

Background: As a result of low numbers and diversity in study type, occupational health intervention studies are not easy to locate in electronic literature databases. Aim: To develop a search strategy that facilitates finding occupational health intervention studies in Medline, both for researchers and practitioners. Methods: A gold standard of articles was created by going through two whole volumes of 19 biomedical journals, both occupational health specialty and non-occupational health journals. Criteria for occupational health intervention studies were: evaluating an intervention with an occupational health outcome and a study design with a control group. Each journal was searched independently by two of the authors. Search terms were developed by asking specialists and counting word frequencies in gold standard articles. Results: Out of 11 022 articles published we found 149 occupational health intervention studies. The most sensitive single terms were work*[tw] (sensitivity 71%, specificity 88%) and effect*[tw] (sensitivity 75%, specificity 63%). The most sensitive string was (effect*[tw] OR control*[tw] OR evaluation*[tw] OR program*[tw]) AND (work*[tw] OR occupation*[tw] OR prevention*[tw] OR protect*[tw]) (sensitivity 89%, specificity 78%). The most specific single terms were “occupational health”[tw] (sensitivity 22%, specificity 98%) and effectiveness[tw] (sensitivity 22%, specificity 98%). The most specific string was (program[tw] OR “prevention and control”[sh]) AND (occupational[tw] OR worker*[tw]) (sensitivity 47%, specificity 98%). Conclusion: No single search terms are available that can locate occupational health intervention studies sufficiently. The authors’ search strings have acceptable sensitivity and specificity to be used by researchers and practitioners respectively. Redefinition and elaboration of keywords in Medline could greatly facilitate the location of occupational health intervention studies.

Low back pain in drivers exposed to whole body vibration: analysis of a dose–response pattern

Objective: Analysis of a dose–response pattern between exposure to whole body vibration (WBV) and low back pain (LBP) in a group of drivers. Methods: This study assessed individual factors, work-related risk factors, various LBP outcome measures and LBP disability in a group of drivers (n = 571) approached at baseline (T0), as well as the WBV magnitude of a representative sample of their vehicles (n = 49), at T0 and at 1-year follow-up (T1). Data were collected using a self-administered questionnaire and actual field measurements according to ISO 2631-1. The magnitude and duration of vibration exposure and a variety of daily and cumulative WBV-exposure measures were calculated for each driver. Results: 229 drivers (40.1%) completed both questionnaires (T0 and T1). The magnitude of WBV was comparable over time. Depending on the LBP outcome, various individual factors (marital status, back trauma and smoking) and work-related risk factors (previous job with heavy physical loading, lifting, bending and the physical risk index) related significantly to onset (all, p<0.05). After adjusting for these contributing factors, the study found a significant trend (an increase in odds ratios of developing LBP with an increase in WBV exposure) for driving-related LBP with daily driving time (p<0.03), and the cumulative measures total hours of exposure (p<0.01), root sum of squares at total dose (p<0.05) and root sum of quads at total dose (p<0.01). No significant trend was found for 12-month LBP. No analysis on a possible dose–response pattern could be derived for either LBP intensity or LBP disability, due to low prevalence. Conclusion: The investigation found a dose–response pattern between WBV exposure and driving-related LBP. No indication of a dose–response pattern was found between WBV exposure and 12-month LBP. Although this dose–response pattern is only an indication, these findings imply that WBV exposure might contribute to the onset of driving-related LBP.

Measurement error of waist circumference: Gaps in knowledge

OBJECTIVE It is not clear whether measuring waist circumference in clinical practice is problematic because the measurement error is unclear, as well as what constitutes a clinically relevant change. The present study aimed to summarize what is known from state-of-the-art research. DESIGN To identify the magnitude of the measurement error of waist circumference measurements from the literature, a search was conducted in PubMed from 1975 to February 2011. RESULTS The measurement error may vary between 0·7 cm and 15 cm. Taking a realistic range of measurable waist circumference into account (60-135 cm), we argue that a short-term clinically relevant change in waist circumference of 5 % may lie between 3·0 and 6·8 cm and a maintained clinically relevant change of 3 % between 1·8 and 4·1 cm. CONCLUSIONS Based on these results, we conclude it may be difficult to distinguish clinically relevant change from measurement error in individual subjects, due to the large measurement error and unclear definition of clinically relevant change. More research is needed to address these gaps in knowledge. To minimize measurement error, we recommend using a uniform measurement protocol, training and repeated measurements.

Development and evaluation of a quality assessment instrument for occupational physicians.

OBJECTIVES: To develop and apply a method for assessing the quality of the process of occupational health care for individual patients. METHODS: The scientific literature was studied to develop a method to assess the quality of the process of occupational rehabilitation for workers with low back pain. The method was applied to health care and university workers with low back pain who were rehabilitated by their occupational physicians. RESULTS: Assessment of quality of care is regarded as a four step approach. Firstly, guidelines should be developed and implemented. Secondly, indicators for quality and criteria to demarcate good and deviant quality were derived from the guidelines. Thirdly, a method for data collection was chosen. Finally, quality was scored. For occupational rehabilitation, there was some deviance from the guidelines for most cases, especially in continuity of care with a deviant rate of 47%. Other indicators deviated from 1.4%-17.4%. Occupational physicians agreed on the relevance of the indicators and criteria, but for three indicators they evaluated the criteria as too rigid. They did not agree with their own performance scores in 66% of the deviant cases. CONCLUSION: Assessing the quality of the process of occupational health care with this method is an asset to present methods, but more specific criteria are needed for a more sensitive assessment.