Brief Cutting Edge Report
Obesity
EPIDEMIOLOGY/GENETICS
Association of Body Mass Index with Lifestyle and Rotating Shift Work in Japanese Female Nurses Yuki Tada1, Yukari Kawano1, Izumi Maeda1, Takahiro Yoshizaki2,3, Ayaka Sunami2, Yuri Yokoyama2, Harumi Matsumoto4, Azumi Hida1, Taiki Komatsu5, and Fumiharu Togo6
Objective: Higher body mass index (BMI) values have been reported in rotating shift workers compared with regular daytime workers. This study examines the relationship between work schedule and BMI, and considers whether lifestyle habits could explain the relationship. Methods: Japanese female nurses (1179 day workers and 1579 rotating shift workers, aged 20-59) were studied using self-administered questionnaires. The questionnaires assessed height, weight, and dietary intake, physical activity, and sleep (lifestyle) habits. Results: The BMI of shift workers was significantly higher than that of day workers. Shift workers consumed significantly higher amounts of sugar-sweetened beverages and slept for significantly shorter durations on nights between days on the day shift compared with day workers—factors which were also independently associated with higher BMI. In addition, multivariable linear regression coefficients for BMI showed a significant correlation with rotating shift work (b 5 0.051), after controlling for lifestyle habits. Conclusions: Higher consumption of sugar-sweetened beverages and shorter sleep duration were associated with rotating shift work and higher BMI. This should be taken into consideration in preventing obesity in real-life shift work situations. Other shift work-related factors, such as abnormal timing of meals and/or sleep, should also be identified. Obesity (2014) 22, 2489–2493. doi:10.1002/oby.20908
Introduction In the nursing profession, health problems may be caused by severe working conditions, such as shifting of the work schedule between the day and night (i.e., rotating shift work). Associations between rotating shift work and key risk factors for disease onset, such as a higher body mass index (BMI) have been suggested (1,2). Diet and physical activity are primary determinants of BMI (3). A previous study of dietary habits of female nurses and caregivers demonstrated that rotating shift workers consumed more sugarsweetened beverages and snacks than day workers (2). In addition, rotating shift work restricts participation in social and leisure activities and decreases opportunities for regular exercise (4). Furthermore, negative associations between sleep duration and BMI (5) or energy intake (6) have been reported. However, it is not clear
whether increasing BMI in rotating shift workers is caused by habitual dietary intake, physical activity, and/or sleep. Recent laboratory studies have shown that forced abnormal circadian timing of meals and/or sleep has adverse effects on the metabolism among subjects uninvolved in night work (7,8). However, it remains unclear whether day-night reversals and BMI are associated in reallife shift work situations. Therefore, the first purpose of this study is to determine the relationships between BMI, rotating shift work, and the quantity and quality of variables of lifestyle habits. The second purpose is to determine whether rotating shift work is associated with BMI after controlling for the effects of the selected quantity and quality of lifestyle habits on BMI to explore whether these factors could fully explain the relationship between rotating shift work and BMI.
1
Department of Nutritional Science, Faculty of Applied Bioscience, Tokyo University of Agriculture, Japan 2 Graduate School of Agriculture, Tokyo University of Agriculture, Japan 3 Faculty of Food and Nutritional Sciences, Toyo University, Japan 4 Healthcare Nutrition Course, Showagakuin junior college, Japan 5 School of Health Science, Department of Physical Therapy, Tokyo University of Technology, Japan 6 Educational Physiology Laboratory, Graduate School of Education, The University of Tokyo, Japan. Correspondence: Fumiharu Togo ([email protected]) and Yuki Tada ([email protected])
Funding agencies: This study was supported by grants from the Japan Society for the Promotion of Science (Grant-in-Aid for start-up 20800085, Scientific Research [C] 22500690). Disclosure: The authors declared no conflict of interest. Author contributions: YT, YK, TK, and FT designed the research; TY, AS, YY, HM, TK, and FT conducted the research; YT, IM, AH, and FT analyzed the data; YT, YK, and FT wrote the manuscript; YT and FT had primary responsibility for the final content. All the authors read and approved the final manuscript. Received: 26 May 2014; Accepted: 11 August 2014; Published online 23 September 2014. doi:10.1002/oby.20908
www.obesityjournal.org
Obesity | VOLUME 22 | NUMBER 12 | DECEMBER 2014
2489
Obesity
Rotating Shift Work and BMI in Female Nurses Tada et al.
TABLE 1 Demographic variables for day workers (DW) and rotating shift workers (SW)
Current work schedule
Age (yr) BMI (kg/m2)a
Obesity
EPIDEMIOLOGY/GENETICS
Association of Body Mass Index with Lifestyle and Rotating Shift Work in Japanese Female Nurses Yuki Tada1, Yukari Kawano1, Izumi Maeda1, Takahiro Yoshizaki2,3, Ayaka Sunami2, Yuri Yokoyama2, Harumi Matsumoto4, Azumi Hida1, Taiki Komatsu5, and Fumiharu Togo6
Objective: Higher body mass index (BMI) values have been reported in rotating shift workers compared with regular daytime workers. This study examines the relationship between work schedule and BMI, and considers whether lifestyle habits could explain the relationship. Methods: Japanese female nurses (1179 day workers and 1579 rotating shift workers, aged 20-59) were studied using self-administered questionnaires. The questionnaires assessed height, weight, and dietary intake, physical activity, and sleep (lifestyle) habits. Results: The BMI of shift workers was significantly higher than that of day workers. Shift workers consumed significantly higher amounts of sugar-sweetened beverages and slept for significantly shorter durations on nights between days on the day shift compared with day workers—factors which were also independently associated with higher BMI. In addition, multivariable linear regression coefficients for BMI showed a significant correlation with rotating shift work (b 5 0.051), after controlling for lifestyle habits. Conclusions: Higher consumption of sugar-sweetened beverages and shorter sleep duration were associated with rotating shift work and higher BMI. This should be taken into consideration in preventing obesity in real-life shift work situations. Other shift work-related factors, such as abnormal timing of meals and/or sleep, should also be identified. Obesity (2014) 22, 2489–2493. doi:10.1002/oby.20908
Introduction In the nursing profession, health problems may be caused by severe working conditions, such as shifting of the work schedule between the day and night (i.e., rotating shift work). Associations between rotating shift work and key risk factors for disease onset, such as a higher body mass index (BMI) have been suggested (1,2). Diet and physical activity are primary determinants of BMI (3). A previous study of dietary habits of female nurses and caregivers demonstrated that rotating shift workers consumed more sugarsweetened beverages and snacks than day workers (2). In addition, rotating shift work restricts participation in social and leisure activities and decreases opportunities for regular exercise (4). Furthermore, negative associations between sleep duration and BMI (5) or energy intake (6) have been reported. However, it is not clear
whether increasing BMI in rotating shift workers is caused by habitual dietary intake, physical activity, and/or sleep. Recent laboratory studies have shown that forced abnormal circadian timing of meals and/or sleep has adverse effects on the metabolism among subjects uninvolved in night work (7,8). However, it remains unclear whether day-night reversals and BMI are associated in reallife shift work situations. Therefore, the first purpose of this study is to determine the relationships between BMI, rotating shift work, and the quantity and quality of variables of lifestyle habits. The second purpose is to determine whether rotating shift work is associated with BMI after controlling for the effects of the selected quantity and quality of lifestyle habits on BMI to explore whether these factors could fully explain the relationship between rotating shift work and BMI.
1
Department of Nutritional Science, Faculty of Applied Bioscience, Tokyo University of Agriculture, Japan 2 Graduate School of Agriculture, Tokyo University of Agriculture, Japan 3 Faculty of Food and Nutritional Sciences, Toyo University, Japan 4 Healthcare Nutrition Course, Showagakuin junior college, Japan 5 School of Health Science, Department of Physical Therapy, Tokyo University of Technology, Japan 6 Educational Physiology Laboratory, Graduate School of Education, The University of Tokyo, Japan. Correspondence: Fumiharu Togo ([email protected]) and Yuki Tada ([email protected])
Funding agencies: This study was supported by grants from the Japan Society for the Promotion of Science (Grant-in-Aid for start-up 20800085, Scientific Research [C] 22500690). Disclosure: The authors declared no conflict of interest. Author contributions: YT, YK, TK, and FT designed the research; TY, AS, YY, HM, TK, and FT conducted the research; YT, IM, AH, and FT analyzed the data; YT, YK, and FT wrote the manuscript; YT and FT had primary responsibility for the final content. All the authors read and approved the final manuscript. Received: 26 May 2014; Accepted: 11 August 2014; Published online 23 September 2014. doi:10.1002/oby.20908
www.obesityjournal.org
Obesity | VOLUME 22 | NUMBER 12 | DECEMBER 2014
2489
Obesity
Rotating Shift Work and BMI in Female Nurses Tada et al.
TABLE 1 Demographic variables for day workers (DW) and rotating shift workers (SW)
Current work schedule
Age (yr) BMI (kg/m2)a
