Elsevier

Applied Nursing Research

Volume 26, Issue 1, February 2013, Pages 24-31
Applied Nursing Research

Original Article
The relationship between shift work and body mass index among Canadian nurses

https://doi.org/10.1016/j.apnr.2012.10.001Get rights and content

Abstract

Aim

The aim of this study was to examine the relationship between shift schedule and body mass index (BMI) among a sample of Canadian Nurses.

Background

Higher BMI values have been reported for employees working non-standard shifts compared to those working a regular daytime schedule. Little is known about the pathways through which shift work is associated with higher BMI.

Methods

This study was a secondary analysis of a sample from National Survey on the Work and Health of Nurses (N = 9291).

Results

We found a small, but statistically significant, difference in BMI scores across shift schedule categories with higher BMI scores reported among female nurses working night or mixed shift schedules, compared with those working a regular daytime schedule. Adjustment for working conditions and employer supported facilities did not attenuate the association between shift work and BMI scores.

Conclusions

The potential public health importance of this relationship requires further investigation given the small, but statistically significant, differences observed in this sample.

Introduction

The health effects of non-standard shift work are gaining increasing attention, in particular in relation to the development of cancer and cardiovascular disease (Costa, 2003, Knutsson and Boggild, 2000, Wang et al., 2011). A proposed pathway linking shift work to each of these diseases is via higher rates of obesity among shift workers (Fritschi et al., 2011, van Drongelen et al., 2011). The exact mechanisms linking shift work to obesity are still developing, but proposed pathways include reduced leisure time physical activity, increases in alcohol consumption, difficulty in maintaining a healthy diet or increased consumption of energy-dense foods to combat fatigue, and reduced amount and/or quality of sleep (Antunes et al., 2010, Lowden et al., 2010, Marshall et al., 2008, Wong et al., 2010). There is also some evidence of a selection effect, where respondents with higher BMI values select into shift work preferentially (Nabe-Nielsen, Garde, Tuchsen, Hogh, & Diderichsen, 2008). Shift work has also been associated with increased levels of smoking (van Amelsvoort, Schouten, & Kok, 2004), which is not commonly associated with obesity.

Workplace health promotion is a potential avenue for addressing obesity. Advantages to the employer include lower absenteeism, and lower medical costs (Finkelstein, Fiebelkorn, & Wang, 2005). A recent systematic review identified six practices where there was some evidence of effectiveness in preventing and/or controlling obesity in the workplace (Archer et al., 2011). These were: enhanced access to opportunities for physical activity combined with health education; exercise prescriptions (a planned physical activity regime given to an individual); multi-component educational practices (health education combined with exercise prescriptions); weight loss competitions and incentives; and behavioural practices such as participation in workshops focused on the development of skills such as goal setting, both with and without incentives (Archer et al., 2011). However, none of the studies included in this review concentrated specifically on the effect of health promotion programs on reducing the prevalence of obesity among shift workers compared to employees working a regular shift. It may be that such interventions are impractical or more difficult to implement for shift workers.

The objectives of this study are to address two research gaps. We wish to examine the relative contribution of health behaviours, psychosocial working conditions, and employer supported facilities in mediating the relationship between shift schedule and body mass index (BMI) among a sample of Canadian nurses. Second, we examine if the relationship between shift work and BMI differs among nurses who have employer supported facilities available to them versus those that do not.

We have the following series of hypotheses related to these objectives:

  • 1.

    Non-regular shift schedules will be associated with higher BMI scores;

  • 2.

    Non-regular shift work will be associated with increased smoking and alcohol consumption, and a poorer psychosocial work environment;

  • 3.

    Non-regular shift work will be associated with a lower prevalence of employer supported facilities for physical activity or healthy eating;

  • 4.

    Health behaviours, psychosocial work environment and non-presence of employer supported facilities will mediate the relationship between non-regular shift work and increased BMI; and

  • 5.

    The relationship between shift work and BMI will differ for respondents with access to employer supported facilities from those that do not, with smaller differences in BMI across shift work groups among respondents with access to physical activity facilities and healthy eating options.

Section snippets

Methods

This study was a secondary analysis of the National Survey of the Work and Health of Nurses (NSWHN), a national, cross-sectional survey conducted in 2005 in all 10 Canadian provinces and three territories, by Statistics Canada, together with the Canadian Institute for Health Information and Health Canada (Statistics Canada, 2009). Briefly, the survey collected information on nurses who were registered with a provincial nursing college, association or council, and either working as a nurse or

Results

Table 1 presents levels of BMI scores across our main independent variables (levels of BMI across other study variables are available from authors on request). Levels of BMI were statistically higher among respondents working night or mixed shift schedules than among day workers, although the differences in mean BMI scores were within one point across all shift schedule categories. Differences in BMI scores were also observed across our potential mediating variables. Higher levels of job strain

Discussion

The objective of this study was to examine the relationship between shift schedule and BMI, and investigate the role of health behaviours, psychosocial working conditions, and employer supported facilities as mediators in this relationship. We had proposed a series of five hypotheses of which two were supported, one was partially supported and two were not supported. We found a small, but statistically significant difference in BMI scores across shift schedule categories, after adjustment for a

Conclusions

In this representative sample of Canadian nurses we found that night and mixed shift schedules were associated with small, but potentially important elevation in BMI among female nurses. The relationship between shift schedule and BMI is not mediated by differences in working conditions, employer supported facilities or health behaviours that are traditionally thought to be associated with weight gain, although we did observe that drinking less than once a month was associated with night shift

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