Academic journal article Scandinavian Journal of Work, Environment & Health

Shift Workers Have Similar Leisure-Time Physical Activity Levels as Day Workers but Are More Sedentary at Work

Academic journal article Scandinavian Journal of Work, Environment & Health

Shift Workers Have Similar Leisure-Time Physical Activity Levels as Day Workers but Are More Sedentary at Work

Article excerpt

Almost one in five of all employees in Europe and the USA work in rotating shifts or during the night (1, 2). Due to increasing economic and social demands, shift work is currently an inherent part of modern society. However, accumulating evidence indicates that shift work imposes an increased risk for metabolic disturbances, such as alterations in body weight, glycaemia and lipids (3-5), and several chronic diseases, such as breast cancer, type II diabetes, and cardiovascular disease (6-9).

To alleviate these adverse health effects of shift work, there is a need for insight into the mechanisms underlying this relationship. To date, the causal mechanisms linking shift work and health outcomes are not well understood, but they appear to be multifactorial. Lifestyle behaviors, such as physical inactivity, have been hypothesized but so far untested as one of the underlying mechanisms of adverse health effects of shift work (10). Therefore, it is important to understand differences in physical activity patterns between day and shift workers.

The findings of previous studies on the relation between shift work and physical activity were mixed, and thus inconclusive. Some studies observed that shift workers were less physically active than day workers (11-13). It has been suggested that this may be because shift workers are more fatigued and have less time to be physically active or are unable to participate in organized sport activities than day workers (14, 15). In contrast, other studies observed no difference between day and shift workers (16-19) or observed that shift workers were more physically active (20, 21). These studies (12, 13, 16-20) on shift work and physical activity often lack adjustment for relevant confounders, such as age and gender, and have mainly relied on self-reported physical activity. Self-reports are prone to bias and less reliable than objective methods for assessing physical activity (22-24). Moreover, self-reports do not provide activity patterns in detail, such as time spent in different durations of sitting, standing, and walking (25). In addition, most previous studies did not describe occupational physical activity (12, 18, 19, 21) or distinguish between occupational and leisure-time physical activity among shift workers (11), while shift work may influence occupational physical activity in a different way than leisure-time physical activity (26). For example, time constraints to participate in organized sport activities may decrease leisuretime physical activity, whereas different work tasks between day work and night shifts may be related to different occupational physical activity patterns (14, 15). Thus, detailed information about overall and specified physical activity behaviors (eg, duration and intensity of activity) of shift workers in comparison with day workers is currently lacking. In addition, there is increasing attention for sedentary behavior as an independent (ie, independent from physical activity) risk factor for metabolic disturbances and chronic diseases (27). Knowledge about sedentary behavior across shift work groups is therefore also of importance and has hardly been studied yet.

To evaluate differences in sedentary behavior and physical activity between day and shift workers, it is important to comprehensively capture the complex pattern of sedentary behavior and physical activity using objective measurement instruments. For this purpose, exposure variation analysis has recently been proposed as it includes all important dimensions of physical activity while reducing its complexity (25).

The aim of this study was to compare patterns of objectively measured leisure-time and occupational physical activity and sedentary behavior between day and shift workers. We hypothesized that shift workers have lower leisure-time and occupational physical activity and higher sedentary levels than day workers.

Methods

Population

We used data from the two Danish studies: the New method for Objective Measurements of physical Activity in Daily living (NOMAD) (28) and the Danish Physical ACTivity cohort with Objective measurements (DPhacto) (29). …

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