https://doi.org/10.4082/kjfm.2017.38.2.86 • Korean J Fam Med 2017;38:86-92
Original Article eISSN: 2092-6715
The Association Between Shift Work and Health Behavior: Findings from the Korean National Health and Nutrition Examination Survey Myung-Ji Bae, Yun-Mi Song*, Jin-Young Shin, Bo-Young Choi, Jung-Hyun Keum, Eun-Ae Lee Department of Family Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
Background: Shift workers are increasing worldwide, and various negative health effects of shift work have been reported. This study aimed to evaluate the relationship between shift work and health behavior. Methods: This cross-sectional study included a total of 11,680 Korean adults (6,061 men and 5,619 women) aged ≥20 years old who participated in the Fifth Korean National Health and Nutrition Examination Survey, 2010–2012. Multiple logistic regression analysis was performed to evaluate the association between shift work and health behavior after adjusting for covariates. Results: In men, shift work was associated with an increased risk of inadequate sleep (odds ratio [OR], 1.18; 95% confidence interval [CI], 1.00 to 1.40) compared to day work. In women, shift work was associated with an increased risk of smoking (OR, 1.73; 95% CI, 1.34 to 2.22) and inadequate sleep (OR, 1.24; 95% CI, 1.05 to 1.47) compared to day work. In an age-stratified subgroup analysis, female shift workers aged ≥50 years old demonstrated an increased risk of smoking (OR, 5.55; 95% CI, 3.60 to 8.55), alcohol consumption (OR, 2.22; 95% CI, 1.53 to 3.23), and inadequate sleep (OR, 1.50; 95% CI, 1.10 to 2.05) compared to female day workers. Conclusion: Shift work is associated with worse health behavior, and this is most evident in women aged ≥50 years. Targeted strategies to reduce the negative health effects of shift work should be implemented, with consideration of shift workers’ demographic characteristics. Keywords: Alcohol Abuse; Health Behavior; Sleep Disorders; Smoking; Work Schedule Tolerance
Received: March 4, 2016, Revised: June 13, 2016, Accepted: June 27, 2016 *Corresponding Author: Yun-Mi Song Tel: +82-2-3410-2442, Fax: +82-2-3410-0388, E-mail: [email protected]
Copyright © 2017 The Korean Academy of Family Medicine This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
www.kjfm.or.kr 87
Myung-Ji Bae, et al. • Shift Work and Health Habits
Introduction
Methods
Over the last few decades, globally, the number of shift workers has in-
1. Study Subjects
creased rapidly to keep pace with the increasingly complex societal
This study utilized data from the fifth Korean National Health and Nu-
need for services and operations to be provided around the clock
trition Examination Survey (KNHANES V). The survey was conducted
ceaselessly.1) The Korean working condition survey reported that the
on a nationwide basis, in a representative sample of South Korean
proportion of employees involved in shift work increased from 7.2% in
adults and children, using a complex, multi-stage probability sample
2006 to 10.9% in 2010. In this survey, the most commonly reported
design, from 2010 to 2012. The survey consisted of three parts: the
shift work type was the regular two-shift (38.6%), followed by regular
health interview survey, the health examination survey, and the nutri-
three-shifts (23.9%), 24-hour rotating shift (14.0%), irregular two-shift
tion survey health examination to examine the participants’ health
(5.7%), fixed shift (5.5%), weekday split-shift (3.6%), irregular three-
conditions, socio-demographic characteristics, health behaviors, and
2,3)
shift (2.9%), and others (5.8%).
nutritional status.21-23) Of the 25,534 participants of the KNHANES V,
Owing to the global increase in shift work, its effect on health has
participants aged 20 minutes and at a frequency of ≥3 times
from Asian countries.17,18) Up to now, several Korean studies have eval-
per week. Moderate exercise was defined as activities such as low-
uated the relationship between smoking and working conditions or
speed swimming, tennis (doubles), volleyball, badminton, table ten-
employment status such as permanent or temporary placements,
nis, or manual labor involving light loads, for >30 minutes and ≥5 times
the United States or in the European countries
19,20)
overall work intensity, and weekly working hours.
however, these
per week. A low-intensity exercise was defined as walking or commut-
Korean studies not include shift workers.
ing for >30 minutes, ≥5 times per week. Participants who performed
Therefore, in the present study, we evaluated the association be-
vigorous, moderate, or low-intensity exercises were included in the
tween shift work and health behaviors such as smoking, alcohol con-
‘physical activity’ group, while the remaining were included in the
sumption, exercise, and the adequacy of sleep time in the Korean pop-
‘physical inactivity’ group.
ulation using data from the fifth the Korean National Health and Nutri-
Previous studies have reported that a sleep duration of 7 to 8 hours
tion Examination Survey.
per day is associated with lower risk of obesity, hypertension, diabetes, myocardial infarction, cerebral vascular accidents, and reduced risk of
https://doi.org/10.4082/kjfm.2017.38.2.86
88 www.kjfm.or.kr
Myung-Ji Bae, et al. • Shift Work and Health Habits
injuries and errors.7) With this reference value, we categorized partici-
erage working hours per week, education level, income level, and mar-
pants into two sleep groups: adequate sleep group (7 to 8 hours per
ital status were included in the model as covariates. Analyses were per-
day), or inadequate sleep group (≤6 hours or ≥9 hours), respectively.
formed for all participants, and also separately for men and women.
Based on the highest level of education attained, participants were
To assess the effect of age on the association between shift work and
categorized as ‘middle school or lower,’ ‘high school,’ and ‘college or
health behavior, we repeated the multiple logistic regression analyses
higher.’
based on three age strata (20–39, 40–49, and 50 years), with adjust-
The monthly average family equivalent income was calculated as
ment for average working hours per week, education level, income
total household income divided by the square root of the number of
level, and marital status. The effect of age on the association between
household members. Participants’ income level was classified based
work type and health behavior was assessed by including an interac-
on monthly average family equivalent income quartiles: 1st (lowest),
tion term (work type*age group) in the multiple logistic regression
2nd, 3rd, and 4th (highest).
models.
Married participants who were currently living with spouse were
All analyses were conducted using IBM SPSS software for Windows
classified into the ‘with spouse’ group while never married, divorced,
ver. 21.0 (IBM Corp., Armonk, NY, USA). P-values
Original Article eISSN: 2092-6715
The Association Between Shift Work and Health Behavior: Findings from the Korean National Health and Nutrition Examination Survey Myung-Ji Bae, Yun-Mi Song*, Jin-Young Shin, Bo-Young Choi, Jung-Hyun Keum, Eun-Ae Lee Department of Family Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
Background: Shift workers are increasing worldwide, and various negative health effects of shift work have been reported. This study aimed to evaluate the relationship between shift work and health behavior. Methods: This cross-sectional study included a total of 11,680 Korean adults (6,061 men and 5,619 women) aged ≥20 years old who participated in the Fifth Korean National Health and Nutrition Examination Survey, 2010–2012. Multiple logistic regression analysis was performed to evaluate the association between shift work and health behavior after adjusting for covariates. Results: In men, shift work was associated with an increased risk of inadequate sleep (odds ratio [OR], 1.18; 95% confidence interval [CI], 1.00 to 1.40) compared to day work. In women, shift work was associated with an increased risk of smoking (OR, 1.73; 95% CI, 1.34 to 2.22) and inadequate sleep (OR, 1.24; 95% CI, 1.05 to 1.47) compared to day work. In an age-stratified subgroup analysis, female shift workers aged ≥50 years old demonstrated an increased risk of smoking (OR, 5.55; 95% CI, 3.60 to 8.55), alcohol consumption (OR, 2.22; 95% CI, 1.53 to 3.23), and inadequate sleep (OR, 1.50; 95% CI, 1.10 to 2.05) compared to female day workers. Conclusion: Shift work is associated with worse health behavior, and this is most evident in women aged ≥50 years. Targeted strategies to reduce the negative health effects of shift work should be implemented, with consideration of shift workers’ demographic characteristics. Keywords: Alcohol Abuse; Health Behavior; Sleep Disorders; Smoking; Work Schedule Tolerance
Received: March 4, 2016, Revised: June 13, 2016, Accepted: June 27, 2016 *Corresponding Author: Yun-Mi Song Tel: +82-2-3410-2442, Fax: +82-2-3410-0388, E-mail: [email protected]
Copyright © 2017 The Korean Academy of Family Medicine This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
www.kjfm.or.kr 87
Myung-Ji Bae, et al. • Shift Work and Health Habits
Introduction
Methods
Over the last few decades, globally, the number of shift workers has in-
1. Study Subjects
creased rapidly to keep pace with the increasingly complex societal
This study utilized data from the fifth Korean National Health and Nu-
need for services and operations to be provided around the clock
trition Examination Survey (KNHANES V). The survey was conducted
ceaselessly.1) The Korean working condition survey reported that the
on a nationwide basis, in a representative sample of South Korean
proportion of employees involved in shift work increased from 7.2% in
adults and children, using a complex, multi-stage probability sample
2006 to 10.9% in 2010. In this survey, the most commonly reported
design, from 2010 to 2012. The survey consisted of three parts: the
shift work type was the regular two-shift (38.6%), followed by regular
health interview survey, the health examination survey, and the nutri-
three-shifts (23.9%), 24-hour rotating shift (14.0%), irregular two-shift
tion survey health examination to examine the participants’ health
(5.7%), fixed shift (5.5%), weekday split-shift (3.6%), irregular three-
conditions, socio-demographic characteristics, health behaviors, and
2,3)
shift (2.9%), and others (5.8%).
nutritional status.21-23) Of the 25,534 participants of the KNHANES V,
Owing to the global increase in shift work, its effect on health has
participants aged 20 minutes and at a frequency of ≥3 times
from Asian countries.17,18) Up to now, several Korean studies have eval-
per week. Moderate exercise was defined as activities such as low-
uated the relationship between smoking and working conditions or
speed swimming, tennis (doubles), volleyball, badminton, table ten-
employment status such as permanent or temporary placements,
nis, or manual labor involving light loads, for >30 minutes and ≥5 times
the United States or in the European countries
19,20)
overall work intensity, and weekly working hours.
however, these
per week. A low-intensity exercise was defined as walking or commut-
Korean studies not include shift workers.
ing for >30 minutes, ≥5 times per week. Participants who performed
Therefore, in the present study, we evaluated the association be-
vigorous, moderate, or low-intensity exercises were included in the
tween shift work and health behaviors such as smoking, alcohol con-
‘physical activity’ group, while the remaining were included in the
sumption, exercise, and the adequacy of sleep time in the Korean pop-
‘physical inactivity’ group.
ulation using data from the fifth the Korean National Health and Nutri-
Previous studies have reported that a sleep duration of 7 to 8 hours
tion Examination Survey.
per day is associated with lower risk of obesity, hypertension, diabetes, myocardial infarction, cerebral vascular accidents, and reduced risk of
https://doi.org/10.4082/kjfm.2017.38.2.86
88 www.kjfm.or.kr
Myung-Ji Bae, et al. • Shift Work and Health Habits
injuries and errors.7) With this reference value, we categorized partici-
erage working hours per week, education level, income level, and mar-
pants into two sleep groups: adequate sleep group (7 to 8 hours per
ital status were included in the model as covariates. Analyses were per-
day), or inadequate sleep group (≤6 hours or ≥9 hours), respectively.
formed for all participants, and also separately for men and women.
Based on the highest level of education attained, participants were
To assess the effect of age on the association between shift work and
categorized as ‘middle school or lower,’ ‘high school,’ and ‘college or
health behavior, we repeated the multiple logistic regression analyses
higher.’
based on three age strata (20–39, 40–49, and 50 years), with adjust-
The monthly average family equivalent income was calculated as
ment for average working hours per week, education level, income
total household income divided by the square root of the number of
level, and marital status. The effect of age on the association between
household members. Participants’ income level was classified based
work type and health behavior was assessed by including an interac-
on monthly average family equivalent income quartiles: 1st (lowest),
tion term (work type*age group) in the multiple logistic regression
2nd, 3rd, and 4th (highest).
models.
Married participants who were currently living with spouse were
All analyses were conducted using IBM SPSS software for Windows
classified into the ‘with spouse’ group while never married, divorced,
ver. 21.0 (IBM Corp., Armonk, NY, USA). P-values
