Is a JEM an informative exposure assessment tool for night shift work

In this issue of Occupational and Environmental Medicine , Fernandez et al 1 investigate the role of maternal night shift work in occurrence of urogenital anomalies in offspring. The authors inferred potential exposure to night shift work by applying a job-exposure matrix (JEM)2 to mothers’ recorded occupations in the Australian Perinatal Registry. This study’s assessment of night shift work across various occupations, with nurses reported separately from other types of workers, adds valuable knowledge on a rarely studied outcome. The authors acknowledge that the lack of individual-level information on shift schedules precluded their ability to assess differences in duration and/or intensity of night shift work, which may variably interfere with reproductive function and recommend ‘investigation in a sample with more detailed exposure information’. This is an important recommendation given the widely recognised complexity of assessing exposures in epidemiological studies of night shift work.3 ‘Night shift work’ refers to work that occurs during the regular sleeping hours of the general population.3 As such, it is not an exposure in the traditional sense, but rather a proxy for a complex combination of exposures and circumstances leading to circadian disruption.4 In addition to a wide variety of schedule characteristics, these include light at night (LAN), phase shift, sleep disturbances, disrupted social behaviours and personal habits and other workplace hazards, many of which are strongly inter-related. Moreover, personal characteristics …