Chronobiology International, 2015; 32(2): 262–269 ! Informa Healthcare USA, Inc. ISSN: 0742-0528 print / 1525-6073 online DOI: 10.3109/07420528.2014.965826
ORIGINAL ARTICLE
Weekend work and depressive symptoms among Korean employees Hye-Eun Lee1, Hyoung-Ryoul Kim1, Jung-Ok Kong1,2, Tae-Won Jang1, Jun-Pyo Myong1, Jung-Wan Koo1, and Inah Kim3 1
Department of Occupational and Environmental Medicine, College of Medicine, The Catholic University of Korea, Seoul, Republic of Korea, 2Department of Preventive Medicine, Graduate School of Medicine, Kangwon National University, Chuncheon, Korea, and 3Department of Occupational and Environmental Health, Yonsei University Graduate School of Public Health, Seoul, Korea
The purpose of this study was to quantify the association between weekend work and depressive symptoms in a representative sample of Korean employees. Subjects were 29 171 employees of companies in Korea. Data were obtained as part of the 2011 Korean Working Conditions Survey. Depressive symptoms were measured as a score of 7 on the World Health Organization Well-being Index. The association between weekend work and depressive symptoms was quantified using logistic regression, controlling for sociodemographic and work-related factors including the number of hours worked per week and stratified by gender. The prevalence of depressive symptoms was higher in employees who reported working at least one weekend day in the past month than in employees who reported working no weekend days in the past month. After controlling for confounders, including the number of hours worked per week, 1–4 days of weekend work in the past month (odds ratio [95% confidence interval] of 1.36 [1.18–1.57] in males and 1.32 [1.12–1.58] in females) and44 days of weekend work in the past month (odds ratio [95% confidence interval] of 1.45 [1.19–1.78] in males and 1.36 [1.07–1.73] in females) were significantly associated with depressive symptoms. Weekend work was related with a significant increase in the prevalence of depressive symptoms in Korean workers. Keywords: Depression, weekend work, work schedule
INTRODUCTION
and time available to spend with family and socialize with friends, neighbors and the local community (Zeytinoglu & Cooke, 2006). The attitude towards weekend work in Korea is quite different from that in Western countries, where a standard working schedule is 8 h per day with no work on the weekend. It is only recently that 2 days off work at the weekend has become widely accepted in Korea. Legislation on a 5-day workweek was first introduced by the Labor Standard Act in 2004 (Park et al., 2012). Though it had many exceptions, the regulation prescribed 40 h per week as standard working hours. The legislation was expanded in stages and has been applied to all workplaces regardless of company size since July 2011. Although official data on the frequency of weekend work in Korea are not yet available, it is clear that there has been a trend over the past 10 years towards a decrease in the number of people working on a Saturday and Sunday, reflecting more widespread acceptance of the 5-day
Work schedules include the pattern of days worked each week, the pattern of hours worked each day, the number of hours worked each week, and the flexibility of working hours (Staines & Pleck, 1984). Issues associated with work schedules, including daily working hours, rest days per week, paid annual leave and protection for night workers and part-time workers, are the main interests of workforces and labor policy makers. There has been a trend to consider not only recovery from fatigue but also work-life balance when arranging work schedules. The International Labor Organization proposed five dimensions of ‘‘decent working time’’, namely that work schedules should be healthy, family friendly, promote gender equality, advance enterprise productivity and facilitate worker choice and influence (Messenger, 2004). Weekend work is unsocial and can be troubling to a worker’s personal life because it influences leisure time
Submitted May 28, 2014, Returned for revision September 10, 2014, Accepted September 11, 2014
Correspondence: Tae-Won Jang, Department of Occupational and Environmental Medicine, College of Medicine, The Catholic University of Korea, 222 Banpo-Daero, Seocho-Gu, Seoul, 137-701, Republic of Korea. Tel: +82.2-2258-6270. Fax: +82.2-2258-6691. E-mail: [email protected]
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Weekend work and depressive symptoms workweek legislation. However, Korean workers still work long hours compared to workers of other OECD countries (OECD, 2012) and half of the Korean workers work more than 48 h per week (Park et al., 2012); therefore, it is likely that there are still many employees who work on weekends in Korea. Numerous studies have investigated the relation between working hours or shiftwork and adverse health conditions including coronary heart disease (Virtanen et al., 2012), metabolic syndrome (Kobayashi et al., 2012; Mohebbi et al., 2012), accidents (Wagstaff & Sigstad Lie, 2011), sleep disturbances (Virtanen et al., 2009), health behaviors (Nabe-Nielsen et al., 2011), and breast cancer (Ijaz et al., 2013); however, the majority of these studies focused on shiftwork or long working hours. There have been few studies that have examined the effect of weekend work on adverse health conditions. Weekend work was a significant risk factor for cardiovascular mortality in a Hungarian population (Kopp et al., 2006) and several studies report a relation between weekend work and musculoskeletal symptoms in nurses (Lipscomb et al., 2002; Trinkoff et al., 2006). There are also reports of an association between weekend work and weight gain (Magee et al., 2010) and mental health (Kopp et al., 2008). In Asia, where long working hours and weekend work are widespread, only one study has been conducted on the effects of weekly rest days on health (Itani et al., 2013) and no studies have directly addressed the effects of weekend work on health. Importance of depression has been increasing in the aspect of disease burden in Korea (Lee et al., 2013). In the working population, depression can play an extremely important role in increasing sickness absence and work disability (Henderson et al., 2011; Kessler et al., 2006). Risk factors for depression include biological, demographic, and psychosocial factors (Holzel et al., 2011). Psychosocial work characteristics as risk factors for depression or depressive symptoms have been studied extensively in the work environment (Bonde, 2008). Besides work-related psychosocial factors, several studies have reported associations between working hours or shiftwork and depressive symptoms (Driesen et al., 2010, 2011; Kim et al., 2013a; Virtanen et al., 2011). However, to our knowledge, the impact of weekend work on mental health has not been studied. Weekend work and depression might be associated through several pathways. The physical and psychological workload is associated with weekend work and the lack of recovery time. In Korea, weekend work is usually linked with long working hours and an intense workload. Long working hours have a negative effect on mental health (Kim et al., 2013a; Virtanen et al., 2011). Adequate recovery is needed to relieve fatigue related to occupational demand (Sluiter et al., 2003) and rest days decrease the physical and psychological workload and provide the opportunity to recover. The combination of weekend work and long working hours may exhaust !
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and frustrate workers, increasing the likelihood of depression. Negative social interaction and low social support are reportedly risk factors for depression (Hays et al., 1997; Klein et al., 1988). Weekend work affects time with family (Hook, 2012) and the quality of family life (Staines & Pleck, 1984). According to a study based on the 2005 European Working Conditions Survey performed by the European Foundation for the Improvement of Living and Working Conditions (Eurofound), in which data were collected from a representative sample of workers from 31 European countries, working on one or more Sundays per month was associated with poorer work-life balance (Wirtz et al., 2011). Work-life balance is an important predictor of mental health (Frone, 2000; Gropel & Kuhl, 2009). Weekend work can affect depression by disturbing the work-life balance. In this regard, gender could be an important confounding factor for an association between weekend work and depressive symptoms. Being female is a well-known risk factor for depression and female workers are most vulnerable to work-life imbalance, although the prevalence of weekend work is lower among female workers than among male workers (Wirtz et al., 2011). The aim of this study was to evaluate the relation between weekend work and depressive symptoms in a nationally representative sample of Korean employees. This study hypothesized that depressive symptoms are more prevalent in employees who work on weekends than in employees who do not.
SUBJECTS AND METHODS Subjects Data from the third Korean Working Conditions Survey (KWCS), which were obtained in 2011 from a representative sample of the working population in Korea, were used for analysis. The KWCS is part of a series of crosssectional surveys that are conducted regularly by the Korea Occupational Safety and Health Agency. The KWCS is a national survey that collects information on the individual, working conditions and physical and psychosocial health in an interview conducted by a professional surveyor. A more detailed description of the survey design, sampling method and the validity and reliability of the data can be found in a previous publication (Kim et al., 2013b). The 2011 KWCS included data on a sample of 50 032 subjects that was representative of both the employed and self-employed working population. In this study, we only included workers who were employed by a company (n ¼ 29 711 and 69.5% as weighted percentage), and excluded self-employed workers. Self-employed workers are expected to have different characteristics in terms of weekend work because they are not covered by the Labor Standard Act and they can arrange their own working time.
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Our study design conformed to international ethical standards (Portaluppi et al., 2010) and was approved by the Institutional Review Board of the Seoul St. Mary’s Hospital (approval ID: KC14QISI0245).
Measurement The answers to the questions ‘‘How many times did you work on Saturdays in the last 1 month?’’ and ‘‘How many times did you work on Sundays in the last 1 month?’’ were used to classify respondents according to the number of weekend days worked in the last month. Respondents were assigned to the weekend-work group if they answered ‘‘at least 1 Saturday per month’’ or ‘‘at least 1 Sunday per month’’. The weekend-work group was divided into two subgroups according to the total number of days worked on a Saturday or Sunday in over the last 1 month: 1–4 days of weekend work and 44days of weekend work. The following sociodemographic factors were evaluated: gender, age (530 years, 30–39 years, 40–40 years, 50–59 years, or 460 years), marital status, educational level (middle school or below, high school, or college or above), and income (51300 US dollars per month, 1300– 2299 US dollars per month, or 2300 US dollars per month).The following work-related factors were evaluated: regular or non-regular worker, occupation (manager, professional, clerk, sales worker, agricultural worker, craft and related trades, plant and machine operator, or elementary occupation), the number of hours worked per week (540, 40–48, 49–60, or 460), the company size (1–4 workers, 5–49 workers, 50–299 workers or 300 workers), and whether or not the job included night shift work. We defined non-regular workers as temporary employees with a contract period of shorter than 1 year. Depressive symptoms were used as the dependent variable and were evaluated using the World Health Organization Well-Being Index (WBI-5) (WHO, 1998), which was designed to measure psychological wellbeing, including depression. WBI-5 comprises five items reflecting the presence or absence of well-being over the last 2 weeks. These items are rated on a six-point scale ranging from zero (at no time) to five (all of the time), resulting in a maximum score of 25. A cut-off score of 57 was used to define depressive symptoms. This cut-off point is recommended to screen for major depressive disorders (Lo¨we et al., 2004). The validity of measuring depression using the WBI-5 has previously been evaluated (Krieger et al., 2014). Statistical analysis The sampling weights from the KWCS were used for analysis to make the findings nationally representative. Sociodemographic factors (gender, age group, marital status, education level, and income) and occupational factors (type of employment contract, occupation, number of hours worked per week, size of company, and presence or absence of nightshift work) were
compared across weekend work groups using the 2-test. A multiple logistic regression analysis was conducted to examine the associations between weekend work and depressive symptoms after stratification by gender. Multiple logistic regression analysis model 1 was adjusted for age, marital status, income, night shift work, type of employment contract, occupation, and company size. Multiple logistic regression analysis model 2 was adjusted for the number of hours worked per week, in addition to the factors listed for model 1. The significance level for all statistical analyses was p50.05 using a two-tailed test. SAS version 9.2 (SAS Institute, Cary, NC) was used for statistical analysis.
RESULTS There were 14 160 workers (40.7% of the study sample) who had not worked on a weekend day in the past month, 15,984 workers (46.0%) who had worked 1–4 weekend days in the past month, and 4639 workers (13.3%) who had worked 44 weekend days in the past month. The sociodemographic characteristics and work-related characteristics of the three groups are shown in Tables 1 and 2, with all numbers reflecting weighted frequencies. The gender distribution, age, marital status, education level and income level differed across the three weekend-workgroups (Table 1). The type of employment contract, the occupation, the number of working hours per week, the presence of night shift work and the company size also differed across the three weekend-work groups (Table 2). The prevalence of depressive symptoms in each of the three weekend work groups stratified by gender is shown in Table 3. In males and females, the prevalence of depressive symptoms was higher in those who had worked 1–4 or 4 4 weekend days in the past month than in those who had worked no weekend days in the past month. The associations between weekend work and depressive symptoms obtained from multiple logistic regression analyses stratified by gender are shown in Table 4. In males and females, after controlling for socio-demographic and work-related factors, the odds ratio (OR) for depressive mood was significantly higher in the weekend work group than in no-weekend groups. After also adjusting for the amount of time worked, the OR was still significantly high, but it was decreased slightly in males.
DISCUSSION The main finding of our study was that weekend work was associated with poor mental health in Korean workers, in accordance with a previous study (Kopp et al., 2008). The prevalence of depressive symptoms was higher in those who had worked on a weekend day in the past month than in those who had not. There was also a dose-response relation between weekend work Chronobiology International
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TABLE 1. Prevalence of weekend work according to sociodemographic characteristics.
Full samplea Gender Male 20 544 Female 14 239 Age (years) 530 7409 30–39 9869 40–49 9249 50–59 5884 460 2372 Marital status Not married 11 961 Married 22 822 Education Middle school 3730 High school 12 794 College 18 259 Incomec (US dollars permonth) 51300 10 358 1300–2300 12 752 2300 11 008
No days of weekend work in the past month7
1–4 Days of weekend work in the past month
44 Days of weekend work in the past month
7727 (37.6) 6433 (45.2)
10094 (49.1) 5889 (41.4)
2722 (13.2) 1917 (13.5)
50.0001
1367 1062 1112 826 272
(18.5) (10.8) (12.0) (14.0) (11.5)
50.0001
2811 4215 3853 2308 973
(37.9) (42.7) (41.7) (39.2) (41.0)
3232 4591 4283 2750 1127
(43.6) (46.5) (46.3) (46.7) (47.5)
pb
4689 (39.2) 9471 (41.5)
5184 (43.3) 10 799 (47.3)
2088 (17.5) 2551 (11.2)
50.0001
1371 (36.8) 3848 (30.1) 8941 (49.0)
1758 (47.1) 6507 (50.9) 7719 (42.3)
601 (16.1) 2438 (19.1) 1600 (8.8)
50.0001
4170 (40.3) 4485 (35.2) 5198 (47.2)
4330 (41.8) 6495 (50.9) 4881 (44.3)
1858 (17.9) 1772 (13.9) 929 (8.4)
50.0001
Data are n (% of row total). a All numbers reflect weighted frequencies rounded to the nearest whole number. b p from chi-square test. c Individual income after tax. TABLE 2. Prevalence of weekend work according to work-related factors.
Type of employment contract Regular Non-regular Occupation Manager Professional and related Clerk Service Sales worker Agricultural, forestry or fishery Craft and related trades Plant, machine operator or assembler Elementary occupation Soldier Working time (hours per week) 540 40–48 49–60 61 Night shift work No Yes Company size (number of workers) 1–4 5–49 50–299 300
Full samplea
No days of weekend work in the past month
1–4 Days of weekend work in the past month
44 Days of weekend work in the past month
25 881 8902
10 412 (40.2) 3748 (42.1)
12 239 (47.3) 3745 (42.1)
3229 (12.5) 1410 (15.8)
50.0001
650 6893 8168 3019 3547 126 3293 3731 5271 86
281 3194 5190 718 995 60 767 993 1900 63
(43.2) (46.3) (63.5) (23.8) (28.0) (47.8) (23.3) (26.6) (36.0) (73.1)
303 3223 2655 1229 1643 48 2122 2205 2534 22
(46.7) (46.8) (32.5) (40.7) (46.3) (38.1) (64.5) (59.1) (48.1) (25.2)
66 476 323 1071 909 18 404 534 837 1
(10.1) (6.9) (4.0) (35.5) (25.6) (14.1) (12.3) (14.3) (15.9) (1.7)
50.0001
3449 18 534 9656 3144
1980 10 147 1873 161
(57.4) (54.7) (19.4) (5.1)
913 7218 5979 1874
(26.5) (38.9) (61.9) (59.6)
557 1169 1805 1108
(16.1) (6.3) (18.7) (35.3)
50.0001
31 350 3433
13 726 (43.8) 435 (12.7)
3730 (11.9) 910 (26.5)
50.0001
1805 1875 587 229
50.0001
7974 17 311 5835 2523
2201 7490 2572 1339
(27.6) (43.3) (44.1) (53.1)
Data are n (% of row total) a All numbers reflect weighted frequencies rounded to the nearest whole number. b p from chi-square test !
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13 895 (44.3) 2089 (60.8) 3968 7947 2675 955
(49.8) (45.9) (45.8) (37.9)
(22.6) (10.8) (10.1) (9.1)
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H.-E. Lee et al. TABLE 3. Weighted frequency of depressive symptoms by weekend work according to gender. Gender
Weekend-work groupa
N
Depressive symptomsb
pc
Male
No weekend work 1–4 days of weekend work 44 days of weekend work Total
7727 10 094 2722 20 544
943 1808 507 3258
(12.2) (17.9) (18.6) (15.9)
5.0001
Female
No weekend work 1–4 days of weekend work 44 days of weekend work Total
6433 5889 1917 14 239
713 748 287 1748
(11.1) (12.7) (15.0) (12.3)
0.0014
a
Classified by number of days of work on a Saturday or Sunday in the last 1 month. Defined as World Health Organization well-being index score 7. c p from chi-square test. b
TABLE 4. Odds ratio and 95% confidence interval of depressive symptomsa according to weekend work obtained from multiple logistic regression. Gender
Weekend-work groupb
Model 1c
Model 2d
Male
No weekend work 1–4 days of weekend work 44 days of weekend work
1.00 1.43 (1.24–1.65) 1.58 (1.30–1.92)
1.00 1.36 (1.18–1.57) 1.45 (1.19–1.78)
Female
No weekend work 1–4 days of weekend work 44 days of weekend work
1.00 1.34 (1.13–1.58) 1.38 (1.09–1.74)
1.00 1.32 (1.12–1.58) 1.36 (1.07–1.73)
a
Defined as World Health Organization well-being index score 7. Classified by number of days of work on Saturday or Sunday in the last 1 month. c Model 1: Adjusted for age, marital status, income, type of employment contract, occupation, night shift work and company size. d Model 2: Adjusted for the variables included in Model 1 and number of hours worked per week. b
and depressive symptoms, with employees who reported 44days weekend work having the highest prevalence of depressive symptoms. After controlling for age, marital status, education, income, type of employment contract, night shift work, occupation, company size, and number of hours worked per week, weekend work was associated with depressive symptoms in both males and females. An explanation for the elevated ORs of depressive symptoms in weekend workers might be physical/ psychological workload and lack of recovery time (Kim et al., 2013a; Virtanen et al., 2011) because weekend work is closely linked with long working hours in Korea. In support of this hypothesis, the OR for depressive symptoms in males was decreased in multiple logistic regression model 2, which controlled for the number of hours worked per week, compared with the OR in model 1. This finding could explain the indirect effect of weekend work on depressive symptoms, i.e. long working hours are an intermediate factor. However, this was not the case in females, possibly because weekend work due to long working hours was more frequent in males than in females. Another explanation for the association between weekend work and depressive symptoms might be interference with the work-life balance (Frone, 2000; Gropel & Kuhl, 2009). Weekend work is unsocial. In people who work on Sundays, time off on a weekday reportedly cannot compensate for the interference with
social activity (Bittman, 2005). In a longitudinal panel study of nurses, emotional exhaustion was significantly lower after a short weekend rest than after a 2-day rest from work on weekdays (Drach-Zahavy & Marzuq, 2013). In our analysis, work-life balance could explain why there was still a significant association between weekend work and depressive symptoms after controlling for the number of hours worked per week. However, it was unable to clearly show that work-life balance was involved with the impact of weekend work on depressive symptoms. In this study, we found that about 60% of employed workers in Korea had worked on at least one weekend day in the last month. The prevalence of weekend work in Korean employees was higher than that reported for European workers, although there is a 6-year gap between the two surveys. In a study based on the 2005 European Working Conditions Survey, around half of all workers (49%) had worked at least one weekend day in the last month (Wirtz et al., 2011). In most Western countries, the amount of hours spent working has reduced since the Second World War, from approximately 2600 h per year prior to the war to 1400–1800 h per year in the 2000s and a 5-day workweek with 7–8 h of work per day is now traditional (Zeytinoglu & Cooke, 2006). Korea has undergone a dramatic industrialization since the 1960s before experiencing an economic crisis in the late 1990s, and has thus experienced a rapidly Chronobiology International
Weekend work and depressive symptoms changing in labor market over the past few decades. As a result, long working hours and atypical working pattern have been existing simultaneously. It has been less than 10 years since legislation was brought in to enforce a 5-day workweek as standard. The Korean Labor Standard Act defines standard working hours as 40 h per week, with extensions up to 52 h per week permitted with the worker’s consent. However, working on a Saturday or Sunday has not been subject to the regulation of the law in Korea. In other words, if a worker works 8 h on both Saturday and Sunday, he could work 68 h per week legally. This may explain why a considerable proportion of workers in Korea had worked on a least one weekend day in the past month. Policies aimed at increasing flexibility in the labor market were first introduced in Korea in the late 1990s, and a governmental policy for reducing working time for job sharing has recently been implemented. Dual labor market theory or core-periphery conceptualization is often used to explain weekend work (Zeytinoglu & Cooke, 2006). Zeytinoglu and Cooke suggested that ‘‘core’’ workers work full-time in good quality jobs during the traditional workweek and ‘‘peripheral’’ workers, such as part-time workers, arrange nonstandard jobs and work schedules that include weekend work. However, our results suggested that in Korea, the majority of employees working at the weekend are full-time workers performing extended work hours, rather than part-time workers performing regular work hours. In our study, 62% of the 4639 workers who had worked 44 weekend days in the past month worked more than 49 h per week, and only 12% worked less than 40 h per week. Our findings showed that the prevalence of weekend work was higher in men than in women. In Europe, the prevalence of Sunday work is nearly equal in men and women, but Saturday work remains more frequent in men than in women (Eurofound, 2012). It is possible that the gender gap in weekend work in Korea remains because the family role of men and women differs in Korean society. The high prevalence of weekend work in employees aged 530 years or460 years and in married employees could be explained by similar factors, and the worker’s role in the family seems to act as an important factor in the amount of weekend work performed. Weekend work was also prevalent in night shift workers, service workers and sale workers, which likely reflects the 7-day and 24-h society in Korea. In this study, depressive symptoms were more prevalent in male workers (15.9%) than in female workers (12.3%). This result is not in accordance with the finding that depression is more prevalent in females than in males. This is a cross-sectional study that analyzed an active working population, not the general population. It is likely that individuals with severe mental disorders had left the workplace. The healthy worker survival effect is reportedly stronger in males than in females (Lea et al., 1999). The prevalence of !
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depressive symptoms might be lower in female workers than in male workers because female workers have a stronger healthy worker effect. Similarly, the prevalence of depression, as measured by a questionnaire, was higher among male workers (11.6%) than among female workers (10.9%) in a French nationwide survey (Cohidon et al., 2012). Another reason for this difference might be the characteristics of the WBI-5. This questionnaire consists of five positive items such as ‘‘I have felt cheerful and in good spirits’’, while the majority of questionnaires designed to assess depression are composed of negative items. Women are more emotionally expressive than men, which might also influence the prevalence of depressive symptoms (Kring & Gordon, 1998).
Strengths and limitations This study was cross-sectional and therefore our data cannot be used to prove a causal effect of weekend work on mental health. The reverse causal association is possible, i.e. depressive symptoms, such as a low desire for social interaction, led to workers with such symptoms to undertake more weekend work. Another limitation is that we assessed weekend work and depressive symptoms using self-report, and biases involved in subjective report, such as recall bias, may have affected the results. We hypothesized that weekend work affects mental health by the higher physical/psychosocial workload and disturbing the work-life balance. However, we could not clearly show this pathway in our analysis. The current study reports secondary data analysis, which lacks certain information that might be needed to improve the analysis and to test all hypotheses of interest. For example, work-life balance is most important to workers who are married and have children; however, we did not consider whether workers had young children in our analyses. Regarding physical and psychosocial workload as a mediator between weekend work and depressive symptoms, we built two regression models, one which adjusted for the amount of hours worked per week and one which did not. The ORs were decreased when working time was added to the regression model, which implies that weekend work indirectly affects depressive symptoms. This is the largest study to date of the association between weekend work mental health in Korea. Data were obtained from a large and representative sample of Korean workers, making the results representative of Korea’s working population. Many studies exploring work-related risk factors for mental health mainly focused on psychosocial factors of work. A small number of studies investigated the effects of long working hours and shift work on depression or depressive symptoms. The present study is the first to have attempted to distinguish the effects of long working hours or night shift work and those of weekend work. An additional strength of this study is its strong control of
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the effects of long working hours, night shift work, and other potential explanatory factors. Our analysis supports a substantial effect of weekend work on mental health in Korean workers, and suggests that this was not fully explained by long working hours. It is important to consider the association between weekend work and mental health when designing a work schedule. As a risk factor for depressive symptoms, weekend work deserves attention because it may change. When weekend work is necessitated by long working hours, reducing working hours by providing days off at the weekend may be the best approach to improve the mental health of workers.
DECLARATION OF INTEREST This study was supported by the Korean Occupational Safety and Health Agency (KOSHA). The authors gratefully acknowledge support from KOSHA. The authors declare that they have no conflict of interest.
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Itani OY, Kaneita M, Ikeda S, et al. (2013). Associations of work hours and actual availability of weekly rest days with cardiovascular risk factors. J Occup Health. 55:11–20. Kessler RC, Akiskal HS, Ames M, et al. (2006). Prevalence and effects of mood disorders on work performance in a nationally representative sample of U.S. workers. Am J Psychiatry. 163: 1561–8. Kim IH, Kim S, Lim M, et al. (2013a). Working hours and depressive symptomatology among full-time employees: Results from the fourth Korean National Health and Nutrition Examination Survey (2007–2009). Scand J Work Environ Health. 39:515–20. Kim YS, Rhee KY, Oh MJ, Park J. (2013b). The validity and reliability of the second Korean working conditions survey. Saf Health Work. 4:111–16. Klein DN, Taylor EB, Dickstein S, Harding K. (1988). Primary earlyonset dysthymia: Comparison with primary nonbipolar nonchronic major depression on demographic, clinical, familial, personality, and socioenvironmental characteristics and shortterm outcome. J Abnorm Psychol. 97:387–98. Kobayashi T, Suzuki E, Takao S, Doi H. (2012). Long working hours and metabolic syndrome among Japanese men: A crosssectional study. BMC Public Health. 12:395. Kopp M, Skrabski A, Szanto Z, Siegrist J. (2006). Psychosocial determinants of premature cardiovascular mortality differences within Hungary. J Epidemiol Community Health. 60: 782–8. Kopp MS, Stauder A, Purebl G, et al. (2008). Work stress and mental health in a changing society. Eur J Public Health. 18: 238–44. Krieger T, Zimmermann J, Huffziger S, et al. (2014). Measuring depression with a well-being index: Further evidence for the validity of the WHO Well-Being Index (WHO-5) as a measure of the severity of depression. J Affect Disord. 156:240–4. Kring AM, Gordon HA. (1998). Sex differences in emotion: Expression, experience, and physiology. J Pers Soc Psychol. 74:686–703. Lea CS, Hertz-Picciotto I, Andersen A, et al. (1999). Gender differences in the healthy worker effect among synthetic vitreous fiber workers. Am J Epidemiol. 150:1099–106. Lee KS, Park JH. (2013). Burden of disease in Korea during 2000–10. J Public Health (Oxf). 36:225–34. Lipscomb JA, Trinkoff AM, Geiger-Brown J, Brady B. (2002). Workschedule characteristics and reported musculoskeletal disorders of registered nurses. Scand J Work Environ Health. 28: 394–401. Lo¨we B, Spitzer RL, Gra¨fe K, et al. (2004). Comparative validity of three screening questionnaires for DSM-IV depressive disorders and physicians’ diagnoses. J Affect Disord. 78: 131–40. Magee CA, Caputi P, Stefanic N, Iverson CD. (2010). Occupational factors associated with 4-year weight gain in Australian adults. J Occup Environ Med. 52:977–81. Messenger JC. (2004). Working time and workers’ preferences in industrialized countries: Finding the balance. New York: Routledge. Mohebbi I, Shateri K, Seyedmohammadzad M. (2012). The relationship between working schedule patterns and the markers of the metabolic syndrome: Comparison of shift workers with day workers. Int J Occup Med Environ Health. 25:383–91. Nabe-Nielsen K, Quist HG, Garde AH, Aust B. (2011). Shiftwork and changes in health behaviors. J Occup Environ Med. 53: 1413–17. OECD. (2012). Average annual hours actually worked per worker. Available from: http://stats.oecd.org/ [last accessed 30 Jul 2013]. Park J, Kwon OJ, Kim Y. (2012). Long working hours in Korea: Results of the 2010 Working Conditions Survey. Ind Health. 50: 458–62. Chronobiology International
Weekend work and depressive symptoms Portaluppi F, Smolensky MH, Touitou Y. (2010). Ethics and methods for biological rhythm research on animals and human beings. Chronobiol Int. 27:1911–29. Sluiter JK, deCroon EM, Meijman TF, Frings-Dresen HM. (2003). Need for recovery from work related fatigue and its role in the development and prediction of subjective health complaints. Occup Environ Med. 60:i62–70. Staines GL, Pleck HJ. (1984). Nonstandard work schedules and family life. J Appl Psychol. 69:515–23. Trinkoff AM, Le R, Geiger-Brown J, et al. (2006). Longitudinal relationship of work hours, mandatory overtime, and on-call to musculoskeletal problems in nurses. Am J Ind Med. 49:964–71. Virtanen M, Ferrie JE, Singh-Manoux A, et al. (2011). Long working hours and symptoms of anxiety and depression: A 5-year followup of the Whitehall II study. Psychol Med. 41:2485–94. Virtanen M, Ferrie JE, Gimeno D, et al. (2009). Long working hours and sleep disturbances: The Whitehall II prospective cohort study. Sleep. 32:737–45.
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Virtanen M, Heikkila K, Jokela M, et al. (2012). Long working hours and coronary heart disease: A systematic review and meta– analysis. Am J Epidemiol. 176:586–96. Wagstaff AS, Sigstad Lie AJ. (2011). Shift and night work and long working hours – A systematic review of safety implications. Scand J Work Environ Health. 37:173–85. WHO. (1998). Wellbeing measures in health care: The Depcare Project: Report on a WHO Meeting, Stockholm, Sweden, 12–13 February 1998. København: World Health Organization Regional Office for Europe. Wirtz A, Nachreiner F, Rolfes K. (2011). Working on Sundays-effects on safety, health, and work-life balance. Chronobiol Int. 28: 361–70. Zeytinoglu IU, Cooke BG. (2006). Who is working at weekends? Determinants of regular weekend work in Canada. In: Boulin JY, Lallement M, Messenger JC, Michon F, eds. Decent working time – New trends, new issues. Geneva: International Labour Organization, pp. 395–416.
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ORIGINAL ARTICLE
Weekend work and depressive symptoms among Korean employees Hye-Eun Lee1, Hyoung-Ryoul Kim1, Jung-Ok Kong1,2, Tae-Won Jang1, Jun-Pyo Myong1, Jung-Wan Koo1, and Inah Kim3 1
Department of Occupational and Environmental Medicine, College of Medicine, The Catholic University of Korea, Seoul, Republic of Korea, 2Department of Preventive Medicine, Graduate School of Medicine, Kangwon National University, Chuncheon, Korea, and 3Department of Occupational and Environmental Health, Yonsei University Graduate School of Public Health, Seoul, Korea
The purpose of this study was to quantify the association between weekend work and depressive symptoms in a representative sample of Korean employees. Subjects were 29 171 employees of companies in Korea. Data were obtained as part of the 2011 Korean Working Conditions Survey. Depressive symptoms were measured as a score of 7 on the World Health Organization Well-being Index. The association between weekend work and depressive symptoms was quantified using logistic regression, controlling for sociodemographic and work-related factors including the number of hours worked per week and stratified by gender. The prevalence of depressive symptoms was higher in employees who reported working at least one weekend day in the past month than in employees who reported working no weekend days in the past month. After controlling for confounders, including the number of hours worked per week, 1–4 days of weekend work in the past month (odds ratio [95% confidence interval] of 1.36 [1.18–1.57] in males and 1.32 [1.12–1.58] in females) and44 days of weekend work in the past month (odds ratio [95% confidence interval] of 1.45 [1.19–1.78] in males and 1.36 [1.07–1.73] in females) were significantly associated with depressive symptoms. Weekend work was related with a significant increase in the prevalence of depressive symptoms in Korean workers. Keywords: Depression, weekend work, work schedule
INTRODUCTION
and time available to spend with family and socialize with friends, neighbors and the local community (Zeytinoglu & Cooke, 2006). The attitude towards weekend work in Korea is quite different from that in Western countries, where a standard working schedule is 8 h per day with no work on the weekend. It is only recently that 2 days off work at the weekend has become widely accepted in Korea. Legislation on a 5-day workweek was first introduced by the Labor Standard Act in 2004 (Park et al., 2012). Though it had many exceptions, the regulation prescribed 40 h per week as standard working hours. The legislation was expanded in stages and has been applied to all workplaces regardless of company size since July 2011. Although official data on the frequency of weekend work in Korea are not yet available, it is clear that there has been a trend over the past 10 years towards a decrease in the number of people working on a Saturday and Sunday, reflecting more widespread acceptance of the 5-day
Work schedules include the pattern of days worked each week, the pattern of hours worked each day, the number of hours worked each week, and the flexibility of working hours (Staines & Pleck, 1984). Issues associated with work schedules, including daily working hours, rest days per week, paid annual leave and protection for night workers and part-time workers, are the main interests of workforces and labor policy makers. There has been a trend to consider not only recovery from fatigue but also work-life balance when arranging work schedules. The International Labor Organization proposed five dimensions of ‘‘decent working time’’, namely that work schedules should be healthy, family friendly, promote gender equality, advance enterprise productivity and facilitate worker choice and influence (Messenger, 2004). Weekend work is unsocial and can be troubling to a worker’s personal life because it influences leisure time
Submitted May 28, 2014, Returned for revision September 10, 2014, Accepted September 11, 2014
Correspondence: Tae-Won Jang, Department of Occupational and Environmental Medicine, College of Medicine, The Catholic University of Korea, 222 Banpo-Daero, Seocho-Gu, Seoul, 137-701, Republic of Korea. Tel: +82.2-2258-6270. Fax: +82.2-2258-6691. E-mail: [email protected]
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Weekend work and depressive symptoms workweek legislation. However, Korean workers still work long hours compared to workers of other OECD countries (OECD, 2012) and half of the Korean workers work more than 48 h per week (Park et al., 2012); therefore, it is likely that there are still many employees who work on weekends in Korea. Numerous studies have investigated the relation between working hours or shiftwork and adverse health conditions including coronary heart disease (Virtanen et al., 2012), metabolic syndrome (Kobayashi et al., 2012; Mohebbi et al., 2012), accidents (Wagstaff & Sigstad Lie, 2011), sleep disturbances (Virtanen et al., 2009), health behaviors (Nabe-Nielsen et al., 2011), and breast cancer (Ijaz et al., 2013); however, the majority of these studies focused on shiftwork or long working hours. There have been few studies that have examined the effect of weekend work on adverse health conditions. Weekend work was a significant risk factor for cardiovascular mortality in a Hungarian population (Kopp et al., 2006) and several studies report a relation between weekend work and musculoskeletal symptoms in nurses (Lipscomb et al., 2002; Trinkoff et al., 2006). There are also reports of an association between weekend work and weight gain (Magee et al., 2010) and mental health (Kopp et al., 2008). In Asia, where long working hours and weekend work are widespread, only one study has been conducted on the effects of weekly rest days on health (Itani et al., 2013) and no studies have directly addressed the effects of weekend work on health. Importance of depression has been increasing in the aspect of disease burden in Korea (Lee et al., 2013). In the working population, depression can play an extremely important role in increasing sickness absence and work disability (Henderson et al., 2011; Kessler et al., 2006). Risk factors for depression include biological, demographic, and psychosocial factors (Holzel et al., 2011). Psychosocial work characteristics as risk factors for depression or depressive symptoms have been studied extensively in the work environment (Bonde, 2008). Besides work-related psychosocial factors, several studies have reported associations between working hours or shiftwork and depressive symptoms (Driesen et al., 2010, 2011; Kim et al., 2013a; Virtanen et al., 2011). However, to our knowledge, the impact of weekend work on mental health has not been studied. Weekend work and depression might be associated through several pathways. The physical and psychological workload is associated with weekend work and the lack of recovery time. In Korea, weekend work is usually linked with long working hours and an intense workload. Long working hours have a negative effect on mental health (Kim et al., 2013a; Virtanen et al., 2011). Adequate recovery is needed to relieve fatigue related to occupational demand (Sluiter et al., 2003) and rest days decrease the physical and psychological workload and provide the opportunity to recover. The combination of weekend work and long working hours may exhaust !
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and frustrate workers, increasing the likelihood of depression. Negative social interaction and low social support are reportedly risk factors for depression (Hays et al., 1997; Klein et al., 1988). Weekend work affects time with family (Hook, 2012) and the quality of family life (Staines & Pleck, 1984). According to a study based on the 2005 European Working Conditions Survey performed by the European Foundation for the Improvement of Living and Working Conditions (Eurofound), in which data were collected from a representative sample of workers from 31 European countries, working on one or more Sundays per month was associated with poorer work-life balance (Wirtz et al., 2011). Work-life balance is an important predictor of mental health (Frone, 2000; Gropel & Kuhl, 2009). Weekend work can affect depression by disturbing the work-life balance. In this regard, gender could be an important confounding factor for an association between weekend work and depressive symptoms. Being female is a well-known risk factor for depression and female workers are most vulnerable to work-life imbalance, although the prevalence of weekend work is lower among female workers than among male workers (Wirtz et al., 2011). The aim of this study was to evaluate the relation between weekend work and depressive symptoms in a nationally representative sample of Korean employees. This study hypothesized that depressive symptoms are more prevalent in employees who work on weekends than in employees who do not.
SUBJECTS AND METHODS Subjects Data from the third Korean Working Conditions Survey (KWCS), which were obtained in 2011 from a representative sample of the working population in Korea, were used for analysis. The KWCS is part of a series of crosssectional surveys that are conducted regularly by the Korea Occupational Safety and Health Agency. The KWCS is a national survey that collects information on the individual, working conditions and physical and psychosocial health in an interview conducted by a professional surveyor. A more detailed description of the survey design, sampling method and the validity and reliability of the data can be found in a previous publication (Kim et al., 2013b). The 2011 KWCS included data on a sample of 50 032 subjects that was representative of both the employed and self-employed working population. In this study, we only included workers who were employed by a company (n ¼ 29 711 and 69.5% as weighted percentage), and excluded self-employed workers. Self-employed workers are expected to have different characteristics in terms of weekend work because they are not covered by the Labor Standard Act and they can arrange their own working time.
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Our study design conformed to international ethical standards (Portaluppi et al., 2010) and was approved by the Institutional Review Board of the Seoul St. Mary’s Hospital (approval ID: KC14QISI0245).
Measurement The answers to the questions ‘‘How many times did you work on Saturdays in the last 1 month?’’ and ‘‘How many times did you work on Sundays in the last 1 month?’’ were used to classify respondents according to the number of weekend days worked in the last month. Respondents were assigned to the weekend-work group if they answered ‘‘at least 1 Saturday per month’’ or ‘‘at least 1 Sunday per month’’. The weekend-work group was divided into two subgroups according to the total number of days worked on a Saturday or Sunday in over the last 1 month: 1–4 days of weekend work and 44days of weekend work. The following sociodemographic factors were evaluated: gender, age (530 years, 30–39 years, 40–40 years, 50–59 years, or 460 years), marital status, educational level (middle school or below, high school, or college or above), and income (51300 US dollars per month, 1300– 2299 US dollars per month, or 2300 US dollars per month).The following work-related factors were evaluated: regular or non-regular worker, occupation (manager, professional, clerk, sales worker, agricultural worker, craft and related trades, plant and machine operator, or elementary occupation), the number of hours worked per week (540, 40–48, 49–60, or 460), the company size (1–4 workers, 5–49 workers, 50–299 workers or 300 workers), and whether or not the job included night shift work. We defined non-regular workers as temporary employees with a contract period of shorter than 1 year. Depressive symptoms were used as the dependent variable and were evaluated using the World Health Organization Well-Being Index (WBI-5) (WHO, 1998), which was designed to measure psychological wellbeing, including depression. WBI-5 comprises five items reflecting the presence or absence of well-being over the last 2 weeks. These items are rated on a six-point scale ranging from zero (at no time) to five (all of the time), resulting in a maximum score of 25. A cut-off score of 57 was used to define depressive symptoms. This cut-off point is recommended to screen for major depressive disorders (Lo¨we et al., 2004). The validity of measuring depression using the WBI-5 has previously been evaluated (Krieger et al., 2014). Statistical analysis The sampling weights from the KWCS were used for analysis to make the findings nationally representative. Sociodemographic factors (gender, age group, marital status, education level, and income) and occupational factors (type of employment contract, occupation, number of hours worked per week, size of company, and presence or absence of nightshift work) were
compared across weekend work groups using the 2-test. A multiple logistic regression analysis was conducted to examine the associations between weekend work and depressive symptoms after stratification by gender. Multiple logistic regression analysis model 1 was adjusted for age, marital status, income, night shift work, type of employment contract, occupation, and company size. Multiple logistic regression analysis model 2 was adjusted for the number of hours worked per week, in addition to the factors listed for model 1. The significance level for all statistical analyses was p50.05 using a two-tailed test. SAS version 9.2 (SAS Institute, Cary, NC) was used for statistical analysis.
RESULTS There were 14 160 workers (40.7% of the study sample) who had not worked on a weekend day in the past month, 15,984 workers (46.0%) who had worked 1–4 weekend days in the past month, and 4639 workers (13.3%) who had worked 44 weekend days in the past month. The sociodemographic characteristics and work-related characteristics of the three groups are shown in Tables 1 and 2, with all numbers reflecting weighted frequencies. The gender distribution, age, marital status, education level and income level differed across the three weekend-workgroups (Table 1). The type of employment contract, the occupation, the number of working hours per week, the presence of night shift work and the company size also differed across the three weekend-work groups (Table 2). The prevalence of depressive symptoms in each of the three weekend work groups stratified by gender is shown in Table 3. In males and females, the prevalence of depressive symptoms was higher in those who had worked 1–4 or 4 4 weekend days in the past month than in those who had worked no weekend days in the past month. The associations between weekend work and depressive symptoms obtained from multiple logistic regression analyses stratified by gender are shown in Table 4. In males and females, after controlling for socio-demographic and work-related factors, the odds ratio (OR) for depressive mood was significantly higher in the weekend work group than in no-weekend groups. After also adjusting for the amount of time worked, the OR was still significantly high, but it was decreased slightly in males.
DISCUSSION The main finding of our study was that weekend work was associated with poor mental health in Korean workers, in accordance with a previous study (Kopp et al., 2008). The prevalence of depressive symptoms was higher in those who had worked on a weekend day in the past month than in those who had not. There was also a dose-response relation between weekend work Chronobiology International
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TABLE 1. Prevalence of weekend work according to sociodemographic characteristics.
Full samplea Gender Male 20 544 Female 14 239 Age (years) 530 7409 30–39 9869 40–49 9249 50–59 5884 460 2372 Marital status Not married 11 961 Married 22 822 Education Middle school 3730 High school 12 794 College 18 259 Incomec (US dollars permonth) 51300 10 358 1300–2300 12 752 2300 11 008
No days of weekend work in the past month7
1–4 Days of weekend work in the past month
44 Days of weekend work in the past month
7727 (37.6) 6433 (45.2)
10094 (49.1) 5889 (41.4)
2722 (13.2) 1917 (13.5)
50.0001
1367 1062 1112 826 272
(18.5) (10.8) (12.0) (14.0) (11.5)
50.0001
2811 4215 3853 2308 973
(37.9) (42.7) (41.7) (39.2) (41.0)
3232 4591 4283 2750 1127
(43.6) (46.5) (46.3) (46.7) (47.5)
pb
4689 (39.2) 9471 (41.5)
5184 (43.3) 10 799 (47.3)
2088 (17.5) 2551 (11.2)
50.0001
1371 (36.8) 3848 (30.1) 8941 (49.0)
1758 (47.1) 6507 (50.9) 7719 (42.3)
601 (16.1) 2438 (19.1) 1600 (8.8)
50.0001
4170 (40.3) 4485 (35.2) 5198 (47.2)
4330 (41.8) 6495 (50.9) 4881 (44.3)
1858 (17.9) 1772 (13.9) 929 (8.4)
50.0001
Data are n (% of row total). a All numbers reflect weighted frequencies rounded to the nearest whole number. b p from chi-square test. c Individual income after tax. TABLE 2. Prevalence of weekend work according to work-related factors.
Type of employment contract Regular Non-regular Occupation Manager Professional and related Clerk Service Sales worker Agricultural, forestry or fishery Craft and related trades Plant, machine operator or assembler Elementary occupation Soldier Working time (hours per week) 540 40–48 49–60 61 Night shift work No Yes Company size (number of workers) 1–4 5–49 50–299 300
Full samplea
No days of weekend work in the past month
1–4 Days of weekend work in the past month
44 Days of weekend work in the past month
25 881 8902
10 412 (40.2) 3748 (42.1)
12 239 (47.3) 3745 (42.1)
3229 (12.5) 1410 (15.8)
50.0001
650 6893 8168 3019 3547 126 3293 3731 5271 86
281 3194 5190 718 995 60 767 993 1900 63
(43.2) (46.3) (63.5) (23.8) (28.0) (47.8) (23.3) (26.6) (36.0) (73.1)
303 3223 2655 1229 1643 48 2122 2205 2534 22
(46.7) (46.8) (32.5) (40.7) (46.3) (38.1) (64.5) (59.1) (48.1) (25.2)
66 476 323 1071 909 18 404 534 837 1
(10.1) (6.9) (4.0) (35.5) (25.6) (14.1) (12.3) (14.3) (15.9) (1.7)
50.0001
3449 18 534 9656 3144
1980 10 147 1873 161
(57.4) (54.7) (19.4) (5.1)
913 7218 5979 1874
(26.5) (38.9) (61.9) (59.6)
557 1169 1805 1108
(16.1) (6.3) (18.7) (35.3)
50.0001
31 350 3433
13 726 (43.8) 435 (12.7)
3730 (11.9) 910 (26.5)
50.0001
1805 1875 587 229
50.0001
7974 17 311 5835 2523
2201 7490 2572 1339
(27.6) (43.3) (44.1) (53.1)
Data are n (% of row total) a All numbers reflect weighted frequencies rounded to the nearest whole number. b p from chi-square test !
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13 895 (44.3) 2089 (60.8) 3968 7947 2675 955
(49.8) (45.9) (45.8) (37.9)
(22.6) (10.8) (10.1) (9.1)
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H.-E. Lee et al. TABLE 3. Weighted frequency of depressive symptoms by weekend work according to gender. Gender
Weekend-work groupa
N
Depressive symptomsb
pc
Male
No weekend work 1–4 days of weekend work 44 days of weekend work Total
7727 10 094 2722 20 544
943 1808 507 3258
(12.2) (17.9) (18.6) (15.9)
5.0001
Female
No weekend work 1–4 days of weekend work 44 days of weekend work Total
6433 5889 1917 14 239
713 748 287 1748
(11.1) (12.7) (15.0) (12.3)
0.0014
a
Classified by number of days of work on a Saturday or Sunday in the last 1 month. Defined as World Health Organization well-being index score 7. c p from chi-square test. b
TABLE 4. Odds ratio and 95% confidence interval of depressive symptomsa according to weekend work obtained from multiple logistic regression. Gender
Weekend-work groupb
Model 1c
Model 2d
Male
No weekend work 1–4 days of weekend work 44 days of weekend work
1.00 1.43 (1.24–1.65) 1.58 (1.30–1.92)
1.00 1.36 (1.18–1.57) 1.45 (1.19–1.78)
Female
No weekend work 1–4 days of weekend work 44 days of weekend work
1.00 1.34 (1.13–1.58) 1.38 (1.09–1.74)
1.00 1.32 (1.12–1.58) 1.36 (1.07–1.73)
a
Defined as World Health Organization well-being index score 7. Classified by number of days of work on Saturday or Sunday in the last 1 month. c Model 1: Adjusted for age, marital status, income, type of employment contract, occupation, night shift work and company size. d Model 2: Adjusted for the variables included in Model 1 and number of hours worked per week. b
and depressive symptoms, with employees who reported 44days weekend work having the highest prevalence of depressive symptoms. After controlling for age, marital status, education, income, type of employment contract, night shift work, occupation, company size, and number of hours worked per week, weekend work was associated with depressive symptoms in both males and females. An explanation for the elevated ORs of depressive symptoms in weekend workers might be physical/ psychological workload and lack of recovery time (Kim et al., 2013a; Virtanen et al., 2011) because weekend work is closely linked with long working hours in Korea. In support of this hypothesis, the OR for depressive symptoms in males was decreased in multiple logistic regression model 2, which controlled for the number of hours worked per week, compared with the OR in model 1. This finding could explain the indirect effect of weekend work on depressive symptoms, i.e. long working hours are an intermediate factor. However, this was not the case in females, possibly because weekend work due to long working hours was more frequent in males than in females. Another explanation for the association between weekend work and depressive symptoms might be interference with the work-life balance (Frone, 2000; Gropel & Kuhl, 2009). Weekend work is unsocial. In people who work on Sundays, time off on a weekday reportedly cannot compensate for the interference with
social activity (Bittman, 2005). In a longitudinal panel study of nurses, emotional exhaustion was significantly lower after a short weekend rest than after a 2-day rest from work on weekdays (Drach-Zahavy & Marzuq, 2013). In our analysis, work-life balance could explain why there was still a significant association between weekend work and depressive symptoms after controlling for the number of hours worked per week. However, it was unable to clearly show that work-life balance was involved with the impact of weekend work on depressive symptoms. In this study, we found that about 60% of employed workers in Korea had worked on at least one weekend day in the last month. The prevalence of weekend work in Korean employees was higher than that reported for European workers, although there is a 6-year gap between the two surveys. In a study based on the 2005 European Working Conditions Survey, around half of all workers (49%) had worked at least one weekend day in the last month (Wirtz et al., 2011). In most Western countries, the amount of hours spent working has reduced since the Second World War, from approximately 2600 h per year prior to the war to 1400–1800 h per year in the 2000s and a 5-day workweek with 7–8 h of work per day is now traditional (Zeytinoglu & Cooke, 2006). Korea has undergone a dramatic industrialization since the 1960s before experiencing an economic crisis in the late 1990s, and has thus experienced a rapidly Chronobiology International
Weekend work and depressive symptoms changing in labor market over the past few decades. As a result, long working hours and atypical working pattern have been existing simultaneously. It has been less than 10 years since legislation was brought in to enforce a 5-day workweek as standard. The Korean Labor Standard Act defines standard working hours as 40 h per week, with extensions up to 52 h per week permitted with the worker’s consent. However, working on a Saturday or Sunday has not been subject to the regulation of the law in Korea. In other words, if a worker works 8 h on both Saturday and Sunday, he could work 68 h per week legally. This may explain why a considerable proportion of workers in Korea had worked on a least one weekend day in the past month. Policies aimed at increasing flexibility in the labor market were first introduced in Korea in the late 1990s, and a governmental policy for reducing working time for job sharing has recently been implemented. Dual labor market theory or core-periphery conceptualization is often used to explain weekend work (Zeytinoglu & Cooke, 2006). Zeytinoglu and Cooke suggested that ‘‘core’’ workers work full-time in good quality jobs during the traditional workweek and ‘‘peripheral’’ workers, such as part-time workers, arrange nonstandard jobs and work schedules that include weekend work. However, our results suggested that in Korea, the majority of employees working at the weekend are full-time workers performing extended work hours, rather than part-time workers performing regular work hours. In our study, 62% of the 4639 workers who had worked 44 weekend days in the past month worked more than 49 h per week, and only 12% worked less than 40 h per week. Our findings showed that the prevalence of weekend work was higher in men than in women. In Europe, the prevalence of Sunday work is nearly equal in men and women, but Saturday work remains more frequent in men than in women (Eurofound, 2012). It is possible that the gender gap in weekend work in Korea remains because the family role of men and women differs in Korean society. The high prevalence of weekend work in employees aged 530 years or460 years and in married employees could be explained by similar factors, and the worker’s role in the family seems to act as an important factor in the amount of weekend work performed. Weekend work was also prevalent in night shift workers, service workers and sale workers, which likely reflects the 7-day and 24-h society in Korea. In this study, depressive symptoms were more prevalent in male workers (15.9%) than in female workers (12.3%). This result is not in accordance with the finding that depression is more prevalent in females than in males. This is a cross-sectional study that analyzed an active working population, not the general population. It is likely that individuals with severe mental disorders had left the workplace. The healthy worker survival effect is reportedly stronger in males than in females (Lea et al., 1999). The prevalence of !
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depressive symptoms might be lower in female workers than in male workers because female workers have a stronger healthy worker effect. Similarly, the prevalence of depression, as measured by a questionnaire, was higher among male workers (11.6%) than among female workers (10.9%) in a French nationwide survey (Cohidon et al., 2012). Another reason for this difference might be the characteristics of the WBI-5. This questionnaire consists of five positive items such as ‘‘I have felt cheerful and in good spirits’’, while the majority of questionnaires designed to assess depression are composed of negative items. Women are more emotionally expressive than men, which might also influence the prevalence of depressive symptoms (Kring & Gordon, 1998).
Strengths and limitations This study was cross-sectional and therefore our data cannot be used to prove a causal effect of weekend work on mental health. The reverse causal association is possible, i.e. depressive symptoms, such as a low desire for social interaction, led to workers with such symptoms to undertake more weekend work. Another limitation is that we assessed weekend work and depressive symptoms using self-report, and biases involved in subjective report, such as recall bias, may have affected the results. We hypothesized that weekend work affects mental health by the higher physical/psychosocial workload and disturbing the work-life balance. However, we could not clearly show this pathway in our analysis. The current study reports secondary data analysis, which lacks certain information that might be needed to improve the analysis and to test all hypotheses of interest. For example, work-life balance is most important to workers who are married and have children; however, we did not consider whether workers had young children in our analyses. Regarding physical and psychosocial workload as a mediator between weekend work and depressive symptoms, we built two regression models, one which adjusted for the amount of hours worked per week and one which did not. The ORs were decreased when working time was added to the regression model, which implies that weekend work indirectly affects depressive symptoms. This is the largest study to date of the association between weekend work mental health in Korea. Data were obtained from a large and representative sample of Korean workers, making the results representative of Korea’s working population. Many studies exploring work-related risk factors for mental health mainly focused on psychosocial factors of work. A small number of studies investigated the effects of long working hours and shift work on depression or depressive symptoms. The present study is the first to have attempted to distinguish the effects of long working hours or night shift work and those of weekend work. An additional strength of this study is its strong control of
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the effects of long working hours, night shift work, and other potential explanatory factors. Our analysis supports a substantial effect of weekend work on mental health in Korean workers, and suggests that this was not fully explained by long working hours. It is important to consider the association between weekend work and mental health when designing a work schedule. As a risk factor for depressive symptoms, weekend work deserves attention because it may change. When weekend work is necessitated by long working hours, reducing working hours by providing days off at the weekend may be the best approach to improve the mental health of workers.
DECLARATION OF INTEREST This study was supported by the Korean Occupational Safety and Health Agency (KOSHA). The authors gratefully acknowledge support from KOSHA. The authors declare that they have no conflict of interest.
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