The significance of work environment factors
A number of work-related factors have been studied in relation to sick leave, particularly physical/ergonomic factors such as heavy physical work, awkward work postures and repetitive work, psychosocial working conditions such as psychological job demands, job control and social support in the workplace, and organisational factors such as shift work. A comprehensive study of the causes of sick leave carried out in 2004 (29) found limited scientific evidence that physical working conditions – particularly heavy physical work – have an effect on sick leave, and moderate evidence of a causal connection with low job control (30). However, among people who were sick-listed due to back disorders, it was found that a number of factors had an effect, among them low job satisfaction (moderate documentation), low job control, and work involving heavy lifting or a bent/twisted working position (limited documentation) (31). Despite a great number of studies and well documented statistical associations between working conditions and sick leave, it was nevertheless concluded that the scientific documentation to support a causal relationship was generally limited, especially due to problems with selection or confounding (30). Even if the association between disease and certain working conditions is well documented, most people who suffer from a disease are not on sick leave, a fact which may contribute to the relatively weak documentation (32).
In Denmark a number of longitudinal studies have been conducted in which attempts have been made to reduce the weaknesses of earlier research (33). These studies have combined the use of data from questionnaires and records, and they have studied factors that impact on different stages of the sick leave process (34).
They estimated that the number of people taking more than six sick days per year could have been 40 per cent lower if everyone’s physical and psychosocial work environment had matched the standard of that enjoyed by the 10 per cent with lowest exposures (35). Other studies from Denmark have shown similar figures (36). Heavy physical work such as heavy lifting/carrying or pushing/pulling, and awkward work postures such as standing up/squatting or a bent /twisted neck/back, appear to be particularly important (37). Many psychosocial job factors appear to be important, such as job control (work autonomy), social support from supervisors, psychological job demands, predictability and role conflicts (33, 38). The results vary somewhat from study to study and between women and men, particularly with respect to psychosocial factors (33). The attributable proportion of sick leave was found to be higher for work-related factors than for life style factors such as smoking (26 per cent among women and 17 per cent among men) (39).
Social inequalities in health are well documented and working conditions have been shown to influence these differences (40). A Danish study found that physical and psychosocial working conditions could explain as much as 40 – 50 per cent of long-term sick leave differences between the highest and the lowest social classes (managers/academics and skilled/unskilled workers respectively), adjusted for life style and other factors (41).