This paper systematically reviews the scientific literature on the effects of individual and work-related factors on the Work Ability Index (WAI). Studies on work ability published from 1985 to 2006 were identified through a structured search in PubMed, and Web of Science. Studies were included if the WAI was used as measure of work ability and if quantitative information was presented on determinants of work ability. In total, 20 studies were included with 14 cross-sectional studies and six longitudinal studies. Factors associated with poor work ability, as defined by WAI, were lack of leisure-time vigorous physical activity, poor musculoskeletal capacity, older age, obesity, high mental work demands, lack of autonomy, poor physical work environment, and high physical work load. The WAI is associated with individual characteristics, lifestyle, demands at work, and physical condition. This multifactorial nature of work ability should be taken into account in health promotion programmes aimed at maintaining and promoting the participation of the labour force and improvement of the performance at work.

The goal of the study was to assess the test-retest reliability of the Work Ability Index (WAI) questionnaire. Reliability was tested using a test-retest design with a 4 week interval between measurements. Valid data were collected among 97 elderly construction workers aged 40 years and older. We analysed the test-retest reliability of the WAI score itself (range 7-49 points) and classification in one of the four WAI categories based on this score: poor (7-27 points); moderate (28-36 points); good (37-43 points); and excellent work ability (44-49 points). Exactly the same WAI score on both measurements was reported by 25% of the subjects and 95% of the individual differences between measurements were found to be <6.86 points (two times standard deviation). Despite the individual changes between measurements, no significant difference was reported in the mean WAI score at group level between test and retest measurements (40.4 versus 39.9). The percentage of observed agreement for the classification of subjects in one of the four WAI categories on both measurements equalled 66%. The results of this study provided evidence of an acceptable test-retest reliability of the classification of subject's work ability by means of the WAI questionnaire. At group level, the mean WAI score and classification into WAI categories were found to be a stable measure over a 4 week interval. These results give additional support for the applicability of the questionnaire in occupational health research and the daily practice of occupational health care.

In the coming decades, demographic, economic and social changes will result in an increased proportion of elderly persons in the workforce in most industrialized countries. This trend is causing growing interest in the problems of the aging worker in current employment. The objective of this particular paper is to provide more insight into the impact of aging on the balance between physical work capacity and physical workload. To this end, the scientific literature in the field is reviewed and ordered by means of a specific conceptual model of "aging and physical workload". A progressive decline in physical work capacity, characterized by diminished aerobic capacity and muscular capacity, has consistently been reported. However, inter-individual differences appear to be considerable. The question of whether there are systematic differences in physical work demands between younger and older workers within occupations has been answered vaguely. Conflicting results in this matter bring into discussion the role of the actual working method as one of the determinants of the physical workload. An age-related imbalance between physical workload and physical work capacity is suggested to result in a chronic overload, increasing the risk of long-term health effects such as musculoskeletal complaints and disorders. For many aging workers in physically demanding occupations, extreme physical workloads, increasing the risk of disease or disablement, are still reported. The multiconceptual study of aging and physical workload in the present paper reveals several possibilities for preventive measures. However, as information is still lacking, additional research is needed, in particular on the onset and development of long-term effects on health in relation to age and work demands.

Objectives: This study analysed the association between gender and upper extremity musculoskeletal complaints, among the general working population and in various occupational groups. The hypothesis was tested whether the higher risk for women in the general working population for these complaints could partly be explained by dierences in the distribution of men and women in occupations with dierent risks for the onset of upper extremity musculoskeletal complaints. Methods: The data for this study came from cross-sectional questionnaire data from 16,874 employees categorised in 21 dierent occupational classes. Associations between gender and complaints of the upper extremities were analysed for the total study sample and for each occupational class separately. An adjustment was made for the variable`occupational class' in the ®nal model in order to study the impact of occupational gender segregation on gender dierences in upper extremity complaints in the working population. Results: In the total study sample, signi®cantly higher risks of complaints of the neck, shoulder, elbow, and wrist among the women were observed. Within many occupational classes, women reported signi®cantly higher risks than did men, in particular for complaints of the neck and shoulder. Adjustment for occupational class showed increased risks for female workers for complaints of the neck, shoulder, elbow, and wrist, hence, rejecting our hypothesis on occupational gender segregation as an explanation for the higher risks for upper extremity complaints among women in the general working population. Conclusions: This study con®rmed the presence of gender dierences in upper extremity musculoskeletal complaints among the working population and in many occupational classes, with female workers having the higher risk. The results, however, do not lend support to a dierential occupational exposure theory as an explanation for the higher risks for these complaints among women in the general working population. Careful consideration of gender in¯uence in ergonomic epidemiological studies is recommended.

Objectives: This cross-sectional study was performed in order to elucidate the relationship of musculoskeletal complaints with age, gender and physically demanding work in the Netherlands. Methods: Questionnaire data of male (n 36 756) and female (n 7730) employees, gathered as part of periodical occupational health surveys among active workers in the Netherlands, were strati®ed for age, gender, and type of work demands. For each strati®ed group prevalence rates (PR) were calculated for complaints of the back, neck, upper and lower extremities. Moreover, prevalence rate dierences (PRD) were estimated as an absolute eect measure of exposure to various types of physical work demands, with active employees in mentally demanding work acting as a reference population. Results: Musculoskeletal complaints among workers in physically demanding occupations were found to increase with age for both sexes. For several complaints, substantially higher rates were reported for women than for men, with a relatively high number of complaints observed among the older female workers (around 40% for complaints of back, upper and lower extremities). Signi®cant PRDs were present in particular for employees in heavy physically demanding occupations and in jobs with mixed mental and physical work demands. Conclusions: With the ageing of the workforce in mind, these ®ndings stress the need for implementation of preventive measures. Special attention towards the susceptible group of female employees, the elderly age groups in particular, seems justi®ed. In order to clarify the combined eects of age and physical work demands on musculoskeletal complaints, additional studies are required.

Objectives: Building on Karasek's model of job demands and control (JD-C model), this study examined the effects of job control, quantitative workload, and two occupation specific job demands (physical demands and supervisor demands) on fatigue and job dissatisfaction in Dutch lorry drivers. Methods: From 1181 lorry drivers (adjusted response 63%) self reported information was gathered by questionnaire on the independent variables (job control, quantitative workload, physical demands, and supervisor demands) and the dependent variables (fatigue and job dissatisfaction). Stepwise multiple regression analyses were performed to examine the main effects of job demands and job control and the interaction effect between job control and job demands on fatigue and job dissatisfaction. Results: The inclusion of physical and supervisor demands in the JD-C model explained a significant amount of variance in fatigue (3%) and job dissatisfaction (7%) over and above job control and quantitative workload. Moreover, in accordance with Karasek's interaction hypothesis, job control buffered the positive relation between quantitative workload and job dissatisfaction. Conclusions: Despite methodological limitations, the results suggest that the inclusion of (occupation) specific job control and job demand measures is a fruitful elaboration of the JD-C model. The occupation specific JD-C model gives occupational stress researchers better insight into the relation between the psychosocial work environment and wellbeing. Moreover, the occupation specific JD-C model may give practitioners more concrete and useful information about risk factors in the psychosocial work environment. Therefore, this model may provide points of departure for effective stress reducing interventions at work. I n many sectors of industry, the nature of work has changed considerably over the past decades.1 2 Important changes concern making work more flexibile, the entry of the 24 hour economy, mechanisation, automation, and the appliance of information and communication technology. In general, these changes have resulted in a decreased exposure to physical and chemical agents and an increased exposure to psychosocial risk factors. In the road transport industry, for instance, the entry of the 24 hour economy has been accompanied by an increased demand for just in time deliveries leading to an intensification of the work of lorry drivers.3 Furthermore, the appliance of communication technology has led to a decreased feeling of independence and tighter time schedules for these workers. 4 These changes in the nature of work have gone hand in hand with an increased attention in occupational health research directed at the investigation of the relation between psychosocial work factors and health and wellbeing. Several occupational stress models have been postulated that can serve as a theoretical frame for this category of studies. Without doubt, the most influential and successful is the model of job demands and control (JD-C model) described by Karasek and Theo...

Objectives-To examine changes in musculoskeletal complaints over four years in groups of employees relative to age and work demands. Methods-Repeated questionnaire data of male employees in heavy physical work (exposed group, n=7324) and mental work (control group, n=4686), stratified for age (20-9, 30-9, 40-9, 50-9), were analysed. For each employee, data on the occurrence of musculoskeletal complaints from two surveys with a mean interval of around four years were available. Changes in prevalences over the follow up interval were analysed. Proportions of new, recovered, and chronic cases as well as those free of complaints at both surveys were studied. Results-For most complaints, there were significantly greater increases in prevalences in the exposed group compared with the control group over the follow up interval particularly within the group aged 40-9 for back, neck, and several sites of the upper and lower limbs. The 20-9 year age group also had significantly greater changes for several musculoskeletal complaints. Within the oldest age group (50-9) exposure to heavy physical work demands only affected changes in prevalences of neck and upper arm complaints. After four years in the cohort free of complaints at the start of the follow up the group aged 40-9 had the highest prevalence of complaints of the back, neck, and the upper and lower limbs. occupations." Most of these surveys were limited to cross sectional data, offering weak evidence for causality due to uncertainty over the time of exposure and bias by a health related selection of employees.Longitudinal studies are considered to be more appropriate for studying the combined effects of aging and exposure to physical work demands on the development of musculoskeletal complaints, even though these studies also have their specific problems.5 Published data on these kinds of studies are scarce. In a four year follow up study of Tuomi et al,6 an increase from 36% to 50% in prevalence of musculoskeletal diseases was reported among male employees in physically demanding jobs compared with a change from 25% to 38% among those in mentally demanding jobs.These findings, however, were based on only one particular age group, employees aged 45 or older.It might be suggested that several age related factors are responsible for an increased risk of developing musculoskeletal complaints with advancing age for employees in physically demanding occupations: (a) biological changes with age-for example, degenerative changes of the intervertebral discs7; (b) the age related increase in number of years of exposure to harmful work demands;2 8 and (c) a gradual change in the balance between physical workload and physical work capacity as a result of a declining physical work capacity with age not compensated for by adaptations in tasks and working conditions.9 10 With this in mind, differences in the development of musculoskeletal complaints between age groups may be expected over a follow up interval of several years.

Objectives-The main objective is to describe the potential health and work problems of the aging employees in the Dutch working population. In this way, we can identify groups at extra risk of specific health problems.Methods-In The Netherlands, occupational health services gather questionnaire data about work and health as part of periodical occupational health surveys (POHSs). These data from the POHSs of complaints about health and working conditions, aggregated into occupational groups and age categories, are used to provide indications for groups at extra risk of specific health problems. These problems are assessed by overviews of the relation between age and complaints about health and working conditions. Results-Alnost all of the health questions show an increase in health complaints with increasing age. White collar workers, especially the high grade white collar workers, usually have lower complaint percentages on health questions than blue collar workers. Female employees have relatively high complaint percentages on the health questions. Differences between occupational groups in the complaints about work and working conditions reflect the differences in work demands and exposure. The relation between age and work complaints is generally inconsistent and weak. The complaint percentages on work questions of female employees tend to be equal to or lower than those of the male employees. Conclusions-The absence of a clear increase of work complaints with advancing age in the presence of a decrease in health and working capacity may be explained by a selective turnover in the working population, especially in demanding occupations. To enhance the work participation of older employees it may be necessary to reduce the work demands and to increase decision latitude. (Occup Environ Med 1996;53:51-57)