Making the shift work: Changes in, interventions for, and factors associated with, health behaviours in shift working populations.

Shift work is associated with increased chronic disease risk. Shift work may impact health behaviours both directly, and indirectly through displacement of sleep, eating and physical activity opportunities due to work schedules. Suboptimal health behaviours, particularly inadequate sleep, insufficient physical activity and suboptimal dietary intake, are modifiable risk factors for chronic disease. To date, our understanding of these health behaviours in shift workers, and crucially the factors associated with these behaviours, is limited. Defining the onset and course of suboptimal health behaviours in shift workers may provide a useful intervention point to implement strategies at both the individual and workplace levels. Therefore the current thesis aimed to: 1) determine what is currently known about health behaviours in shift workers over time by investigating existing studies, 2) examine the effect of interventions on chronic disease risk factors in shift workers, 3) assess the onset and course of potential changes in health behaviours and associated factors, during the first 12 months of shift work, and 4) develop and validate a metric for measurement of psychosocial factors associated with health behaviours in shift workers. To investigate longitudinal health behaviours in shift workers a scoping review of existing literature was conducted. The scoping review of 15 studies highlighted the limited availability of research on dietary intake and physical activity in shift workers. There were significant between-study variations in sample characteristics, study duration, frequency of follow ups and behavioural measures utilised, making it challenging to draw consistent conclusions across the limited literature. The existing evidence suggests that shift workers may experience stable, but inadequate sleep. Furthermore, the very limited evidence regarding other behaviours indicates that shift workers may become less active over time and have suboptimal dietary intake, such as increased saturated fat intake. Finally, there was no evidence of existing longitudinal studies that consider all three behaviours concurrently. These findings suggest a need for longitudinal studies to examine all three health behaviours robustly and concurrently. To analyse the efficacy of interventions on chronic disease risk factors in shift workers a systematic review was undertaken. A total of 65 publications reported interventions for chronic disease risk factors, including health behaviours, in shift workers. Existing interventions can be grouped in four categories: schedule change, controlled light exposure, behavioural interventions and complementary therapies. Meta-analysis showed that interventions resulted in significant improvements to objective and subjective sleep, biomedical risk factors (e.g.e.g., Body Mass Index (BMI) and blood pressure) and perceived health status. These effects varied in direction and magnitude by both intervention type (e.g.e.g., schedule change, controlled light etc.) and by outcome of interest (e.g.e.g., sleep, BMI, blood pressure). Furthermore, despite insufficient studies to conduct meta-analysis, qualitative collation suggests that interventions, particularly those based on existing behavioural models, may result in positive changes to health behaviours. Given observational studies show that health behaviours may become suboptimal over time and interventions may improve risk factors in shift workers, it is necessary to examine whether these health behaviours change in response to the onset of shift work. To examine the effect of onset of shift work on health behaviours and associated factors, we sampled four cohorts of South Australian Paramedic Interns (n=19) during their internship training using a pre-shift work baseline, and then quarterly across their first 12 months of employment. Paramedic interns had a significant decline in sleep quality during the first 12 months of shift work, which was more pronounced in both female and older interns. Some components of dietary intake improved while others remained suboptimal but stable. Increases in leisure time physical activity, particularly for those with sufficient baseline physical activity, were also observed. Finally, health risk perception significantly increased over the first 12 months of shift work. These findings indicate that some health behaviours may be adversely impacted during the first 12 months of shift work, but there are large variations based on baseline behaviours and individual characteristics. For this reason, there is a need to better understand factors associated with health behaviours to better support workers. To understand factors associated with health behaviours, a metric was developed and validated to measure psychosocial determinants of health behaviours in shift workers. Following literature review, expert panel review, and cognitive interviews with shift workers, the developed Health Belief Model for Shift Workers (HBM-SW) Scale was piloted to an online sample (n=153). The HBM-SW showed acceptable validity and reliability. The HBM-SW showed that psychosocial determinants were associated with sleep quality, sleep duration, dietary intake and physical activity. The HBM-SW scale may be useful for the development and implementation of future strategies to support health behaviours in shift workers. Together the present body of work provides new knowledge of health behaviours and their associated factors in shift workers. The current thesis highlights a need for future studies which concurrently examine sleep, dietary intake and physical activity in shift workers, and future avenues for interventions which may be implemented, with input from shift workers, at an individual and workplace level in future to better support individual’s health outcomes.