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concepts and oxidative DNA damage in a sample of workers in Japan
Journal of Psychosomatic Research 66 (2009) 329 – 334
Short communication
Three job stress models/concepts and oxidative DNA damage in a sample of workers in Japan Akiomi Inoue a,⁎, Norito Kawakami a , Masao Ishizaki b , Masaji Tabata c , Masao Tsuchiya a,d , Miki Akiyama e,f , Akiko Kitazume f , Mitsuyo Kuroda a , Akihito Shimazu a a Department of Mental Health, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan Department of Social and Environmental Medicine (Hygiene), Kanazawa Medical University, Uchinada, Japan c Ishikawa Health Service Association, Kanazawa, Japan d Department of Epidemiology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan e Division of Nursing, Faculty of Healthcare, Tokyo Healthcare University, Tokyo, Japan f Department of Psychiatric Nursing, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan b
Received 14 May 2008; received in revised form 31 August 2008; accepted 25 September 2008
Abstract Objective: Three job stress models/concepts (the job demands– control [DC] model, the effort–reward imbalance [ERI] model, and organizational justice) have been linked to coronary heart disease (CHD) at work. In recent years, oxidative DNA damage has been identified as a new risk factor for CHD. However, evidence for the association between these job stressors and oxidative DNA damage is limited. The present cross-sectional study investigated the association between these job stress models/concepts and oxidative DNA damage as a possible mediator of the adverse health effects of job stress. Methods: A total of 166 male and 51 female workers of a manufacturing factory in Japan were surveyed using a mailed questionnaire regarding job stressors and demographic, occupational, and lifestyle variables. Urinary concentrations of 8-
hydroxy-2′-deoxyguanosine (8-OHdG), a biomarker of oxidative DNA damage, were also measured. Results: In male subjects, the urinary concentrations of 8-OHdG were significantly higher among the group with lower interactional justice, one of the two components of organizational justice; however, no association was observed with the DC model or the ERI model. In female subjects, high job demands/control ratio was significantly and positively associated with the urinary concentrations of 8-OHdG. Conclusion: Interactional justice among male workers and the DC model-based strain among female workers may be associated with increased urinary concentrations of 8-OHdG which possibly reflects oxidative DNA damage. © 2009 Elsevier Inc. All rights reserved.
Keywords: Coronary heart disease; Effort–reward imbalance model; Job demands–control model; Organizational justice; Urinary 8-OHdG
Introduction Job stressors have been recognized as one of major risk factors for coronary heart disease (CHD) [1]. Among others, three major theories or models of job stressor have been
⁎ Corresponding author. Department of Mental Health, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan. Tel.: +81 3 5841 3522; fax: +81 3 5841 3392. E-mail address: [email protected] (A. Inoue). 0022-3999/08/$ – see front matter © 2009 Elsevier Inc. All rights reserved. doi:10.1016/j.jpsychores.2008.09.016
identified and linked to CHD [2]: the job demands–control (DC) model [3], the effort–reward imbalance (ERI) model [4], and the organizational justice concept [5,6]. In the DC model, job strain defined as the combination of high job demands and low job control has been associated with risk for CHD [2]. The ERI at work, which focuses on a long-term macro-level excess of effort at work compared to work reward, has also been proposed as a risk factor for CHD [4]. The organizational justice concept includes two components: procedural justice which is fairness of the process and procedures used to make allocation decisions [7]; and
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interactional (relational) justice which captures the quality of interpersonal treatment people receive during the enactment of organizational procedures [8]. Low interactional justice at work has also been associated with an increased risk for CHD [5,6]. In recent years, oxidative DNA damage, which is often measured using urinary or leukocyte levels of 8-hydroxy-2′deoxyguanosine (8-OHdG) [9], has been identified as a new risk factor for CHD [10]. Thus, oxidative DNA damage may play a mediating role in linking job stressors to CHD. To date, no study has tested the association between these three job stress models/concepts and 8-OHdG, while a previous study partly addressed the association between workload and 8-OHdG measurements among female workers [11]. The present study was undertaken to investigate the crosssectional association between the three major job stress models/concepts and the levels of urinary 8-OHdG in a sample of workers in Japan. It is hypothesized that those who have high job strain, high ERI, or low organizational justice have high urinary concentrations of 8-OHdG.
Methods
The ERIQ consists of scales for extrinsic effort and reward at work. To define the high ERI group, two approaches were used [15]: (1) first, we defined those who had an effort/reward ratio of 1.0 or higher as high ERI; (2) second, because the prevalence of high ERI was reported to be relatively low in Japanese samples [19], we also classified the subjects into tertiles according to the effort/reward ratio. The OJQ consists of scales for procedural justice and interactional justice. The subjects were classified into tertiles in terms of procedural justice or interactional justice score. Measurement of urinary 8-OHdG At the health check-up, after fasting overnight, we collected urine samples from the subjects in the morning. The samples were immediately frozen and stored at −30°C, then sent to a central laboratory of the Mitsubishi Chemical Medience Corporation, Tokyo, Japan, to measure 8-OHdG using the enzyme-linked immunosorbent assay (ELISA) kit using the monoclonal antibody N45.1, adjusted for urinary creatinine concentrations. The intra-assay coefficient of variation for the measurement at the central laboratory was reported to be 9.6%. The urinary concentrations of 8-OHdG were almost normally distributed in the present sample.
Subjects Other covariates A cross-sectional study of employees of a manufacturing factory located in northern-central Japan was conducted in August 2007. A self-administered questionnaire survey and an on-site health check-up were conducted. All employees (N=302) were invited to participate in this study. A total of 244 participated in this study (response rate, 81%). Data from 217 workers (166 males and 51 females) without missing value on relevant variables were analyzed. The study procedure was approved by the Ethics Committees of the Graduate School of Medicine, The University of Tokyo, and Kanazawa Medical University. Assessment of job stressors Job stressors were measured by using, respectively, the Japanese version of the Job Content Questionnaire (JCQ) [12,13], the Effort-Reward Imbalance Questionnaire (ERIQ) [14,15], and the Organizational justice Questionnaire (OJQ) [16,17, Inoue et al., unpublished observations]. The JCQ includes scales for job demands and job control. We used two approaches to define the high job strain group [18]: (1) first, subjects were classified into four quadrant groups using the median scores for job demands and job control: high strain job (higher job demands and lower job control), active job (higher job demands and higher job control), passive job (lower job demands and lower job control), and low strain job (lower job demands and higher job control); (2) second, those in the highest tertile of the job demands/control ratio were defined as the high strain group.
Demographic (age, education, and marital status), occupational (occupational status, overtime in the past month, and a possible exposure to heavy metals at work), and lifestyle variables (body mass index [BMI], exercise, smoking, alcohol consumption, fruit consumption, vegetable consumption, and habitual supplement use) which could have an influence on oxidative stress [20] were assessed by using the self-administered questionnaire. Statistical analysis Analysis of variance (ANOVA) and analysis of covariance (ANCOVA) were employed to compare crude and adjusted average urinary concentrations of 8-OHdG with groups classified on the basis of each job stress model/concept. These analyses were conducted separately for males and females. In addition, similar analyses were conducted after excluding those (three males and three females) with concurrent chronic medical conditions which were previously reported to be associated with increased urinary 8OHdG levels [21]. The level of significance was .05 (twotailed). SPSS 14.0J for Windows was used for the statistical analyses.
Results Table 1 shows the subjects' characteristics and average scores for each job stressor scale by sex. Average scores for
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Table 1 Demographic characteristics, lifestyles, and job stressors among employees who participated in the study by sex Male (N=166) n (%) Age (years) Education (years) More than 12 12 or less Marital status Currently married Never married Divorced/widowed Occupation Manager White-collar Blue-collar Overtime in the past month (hours) Possible heavy metal exposure Yes No BMI (kg/m2) Exercise (times per week) Once or more Less than once Smoking Current smoker Past smoker Never smoker Alcohol consumption (drinks per months) More than 20 20 or less None Fruit consumption (times per week) Once or more Less than once Vegetable consumption (times per week) More than 3 times 3 times or less Habitual supplement use Yes No
Female (N=51) Average (S.D.)
n (%)
35.3 (9.2)
Average (S.D.) 36.4 (8.9)
68 (41.0) 98 (59.0)
19 (37.3) 32 (62.7)
107 (64.5) 57 (34.3) 2 (1.2)
31 (60.8) 17 (33.3) 3 (5.9)
16 (9.6) 36 (21.7) 114 (68.7)
– (0.0) 12 (23.5) 39 (76.5)
P .451 .744
.186
.049
28.8 (33.9)
16.7 (22.3)
.003 b.001
20.7 (2.9)
b.001 .256
– (0.0) 51 (100.0)
34 (20.5) 132 (79.5) 23.1 (3.6) 65 (39.2) 101 (60.8)
25 (49.0) 26 (51.0)
87 (52.4) 29 (17.5) 52 (30.1)
10 (19.6) 4 (7.8) 37 (72.5)
67 (40.4) 60 (36.1) 39 (23.5)
6 (11.8) 17 (33.3) 28 (54.9)
85 (51.2) 81 (48.8)
30 (58.8) 21 (41.2)
83 (50.0) 83 (50.0)
34 (66.7) 17 (33.3)
31 (18.7) 135 (81.3)
22 (43.1) 29 (56.9)
b.001
b.001
.423
.039
.001
Job stressor scale scores Job Content Questionnaire Job demands (12–48) Job control (24–96) Job demands/control ratio (0.125–2.000) Effort-Reward Imbalance Questionnaire Effort (6–30) Reward (11–55) Effort/reward ratio (0.20–5.00) Organizational Justice Questionnaire Procedural justice (1.00–5.00) Interactional justice (1.00–5.00)
job demands and job demands/control ratio were significantly higher, and average scores for job control were significantly lower among female subjects than male subjects. In male subjects, after adjusting for all the covariates, the urinary concentrations of 8-OHdG were significantly different among the groups classified on the basis of interactional justice (F [2, 145]=4.96, P=.008), with higher concentrations
32.7 (5.3) 65.7 (11.0) 0.51 (0.13)
34.7 (5.0) 60.7 (9.6) 0.58 (0.12)
.018 .004 b.001
14.4 (4.6) 42.0 (8.0) 0.68 (0.34)
15.6 (5.3) 41.9 (6.9) 0.73 (0.37)
.122 .930 .355
3.03 (0.71) 3.16 (0.88)
2.90 (0.67) 3.27 (0.77)
.254 .428
in the group with low interactional justice (Table 2). In female subjects, the urinary concentrations of 8-OHdG were significantly different among the groups classified on the basis of the job demands/control ratio (F [2, 32]=4.20, P=.024), with higher concentrations in the group with high job demands/control ratio, after adjusting for all the covariates. These results were unchanged for 163 males
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Table 2 Comparison of crude and adjusted average urinary concentrations of 8-OHdG (ng/mg creatinine) by groups classified on the basis of the job demands–control model, the effort–reward imbalance model, and organizational justice among Japanese male (N=166) and female (N=51) employees a
Job stressors
n
Crude
Demographic and occupational factors adjusted
Demographic, occupational, and lifestyle factors adjusted
Average (S.D.)
Average (S.E.) b
Average (S.E.) c
Males Job strain quadrants High strain job Active job Passive job Low strain job
29 52 47 38
7.99 (1.71) 8.14 (1.95) 8.22 (2.33) 7.78 (2.28) P=.788
7.68 (0.41) 8.12 (0.31) 8.24 (0.34) 8.00 (0.37) P=.722
7.73 (0.40) 8.06 (0.31) 8.27 (0.34) 8.02 (0.37) P=.775
Job demands/control ratio High (0.537–2.000) Medium (0.461–0.536) Low (0.125–0.460)
56 54 56
7.96 (1.72) 8.34 (2.31) 7.87 (2.22) P=.462
7.70 (0.29) 8.41 (0.29) 8.07 (0.29) P=.237
7.70 (0.29) 8.42 (0.28) 8.06 (0.29) P=.224
8.57 (1.85) 7.96 (2.13) P=.172
8.38 (0.42) 7.99 (0.18) P=.396
8.22 (0.41) 8.02 (0.17) P=.664
8.30 (1.80) 7.80 (2.32) 8.05 (2.13) P=.445
8.20 (0.28) 7.85 (0.28) 8.11 (0.29) P=.660
8.16 (0.28) 7.82 (0.28) 8.18 (0.28) P=.604
Effort/reward imbalance (effort/reward ratio) High (1.00–5.00) 26 Low (0.20–0.99) 140 Effort/reward tertiles (effort/reward ratio) High (0.711–5.000) 56 Medium (0.486–0.710) 56 Low (0.200–0.485) 54 Procedural justice Low (1.00–2.86) Medium (3.00–3.29) High (3.43–5.00)
61 45 60
8.16 (2.36) 7.84 (1.88) 8.11 (1.97) P=.716
8.25 (0.28) 7.75 (0.33) 8.08 (0.27) P=.533
8.21 (0.28) 7.83 (0.33) 8.03 (0.28) P=.770
Interactional justice Low (1.00–2.83) Medium (3.00–3.50) High (3.67–5.00)
51 60 55
8.75 (2.23) 7.89 (2.00) 7.59 (1.92) P=.012
8.76 (0.29) 7.85 (0.27) 7.62 (0.28) P=.014
8.81 (0.29) 7.80 (0.27) 7.63 (0.28) P=.008
Females Job strain quadrants High strain job Active job Passive job Low strain job
9 13 17 12
7.32 (2.29) 7.03 (1.53) 8.15 (3.17) 5.73 (1.47) P=.066
7.31 (0.84) 7.12 (0.67) 7.96 (0.63) 5.92 (0.90) P=.415
8.20 (0.87) 7.16 (0.67) 7.33 (0.62) 6.10 (0.89) P=.513
Job demands/control ratio High (0.601–2.000) Medium (0.521–0.600) Low (0.125–0.520)
18 17 16
8.09 (3.00) 6.91 (2.40) 6.34 (1.26) P=.097
8.34 (0.58) 6.79 (0.61) 6.21 (0.71) P=.063
8.46 (0.54) 6.50 (0.57) 6.38 (0.70) P=.024
7.04 (2.02) 7.17 (2.55) P=.874
6.80 (0.77) 7.24 (0.37) P=.617
7.51 (0.82) 7.06 (0.35) P=.643
7.92 (2.54) 7.03 (2.62) 6.50 (2.02) P=.230
7.85 (0.59) 6.82 (0.62) 6.76 (0.63) P=.358
8.04 (0.55) 6.82 (0.59) 6.59 (0.59) P=.175
6.70 (1.98) 7.98 (2.37) 6.78 (2.85) P=.228
6.99 (0.56) 7.92 (0.58) 6.52 (0.60) P=.256
7.25 (0.59) 7.80 (0.55) 6.34 (0.58) P=.196
Effort/reward imbalance (effort/reward ratio) High (1.00–5.00) 10 Low (0.20–0.99) 41 Effort/reward tertiles (effort/reward ratio) High (0.751–5.000) 17 Medium (0.513–0.750) 17 Low (0.200–0.512) 17 Procedural justice Low (1.00–2.71) Medium (2.86–3.14) High (3.29–5.00)
18 17 16
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Crude
Demographic and occupational factors adjusted
Demographic, occupational, and lifestyle factors adjusted
Average (S.D.)
Average (S.E.) b
Average (S.E.) c
6.81 (2.32) 6.82 (2.10) 7.68 (2.79) P=.475
6.89 (0.70) 6.73 (0.60) 7.70 (0.55) P=.466
7.52 (0.72) 6.66 (0.63) 7.35 (0.57) P=.670
Table 2 (continued)
Job stressors Interactional justice Low (1.00–2.83) Medium (3.00–3.67) High (3.83–5.00) a b c
n 13 18 20
One-way ANOVA was used for the comparison of crude average. ANCOVA was used for the comparison of adjusted average. Adjusted for age, education, marital status, occupational status, overtime, and possible heavy metal exposure. Additionally adjusted for BMI, exercise, smoking, alcohol consumption, vegetable consumption, fruit consumption, and habitual supplement use.
and 48 females after excluding respondents who had a current chronic medical condition (data available on request).
Discussion In male subjects, the urinary concentrations of 8-OHdG were greater in the group with lower interactional justice. This is consistent with previous findings of an increased risk for CHD among workers with lower interactional justice [5,6]. On the other hand, procedural justice was not significantly associated with the urinary concentrations of 8-OHdG among male subjects. Low interactional justice taps unfair treatment of workers by superiors and managers, which is more likely to cause chronic distress in the daily working life for workers than procedural justice, i.e., justice in procedures of decision making in a workplace. Interactional or procedural justice was not associated with the urinary concentrations of 8-OHdG among females. Interactional justice may cause greater distress particularly among male workers, who have a greater job commitment [22], and thus be more associated with urinary 8-OHdG among males. Neither job strain nor ERI was significantly associated with the urinary concentrations of 8-OHdG in males. However, in female subjects, high job demands/control ratio was significantly and positively associated with the urinary concentrations of 8-OHdG. A previous study also reported that perceived workload was associated with 8-OHdG levels in leukocytes in females, but not in males [11]. A task-oriented model, such as the DC model, may be more important for females in terms of increased urinary 8-OHdG, although a further study is required to clarify the gender difference. Possible limitations must be considered. First, the sample was relatively small in its size and from one particular manufacturing company in Japan. Furthermore, those who perceived they had greater job stress and chronic health conditions may have been less likely to participate in this study. Second, the observed differences were small, which may be casual. Third, the concentrations of 8-OHdG measured by single spot monitoring may not be a precise measure of the individual base levels [23]. The 8-OHdG measurement by ELISA was reported to have a crossreactivity with some other analogous compounds [24],
while the monoclonal antibody we used (N45.1) shows a minimal cross-reactivity only towards 8-sulfhydryl-G and 8OHG (less than 1%) [25]. Also, the urinary excretion rate of 8-OHdG is supposed to reflect repair process after DNA damage, but not DNA damage itself. The rates of DNA repair vs. rates of DNA damage should be investigated in future research. Fourth, job stressors were measured by selfreport. The subjects may refrain from answering the scales precisely. Fifth, personality, a high-fat diet, or medication may confound the findings. Finally, a causal relationship cannot be determined because of the cross-sectional nature of the study. A large-scale prospective study is needed to investigate a causal linkage between job stressors, oxidative DNA damage, and incidence of CHD. Acknowledgments The present study was supported by a Grant-in-Aid for Scientific Research (B) 2004-2007 (No. 16390170) from the Ministry of Education, Culture, Sports, Science, and Technology, Japan. References [1] Steenland K, Fine L, Belkic K, Landsbergis P, Schnall P, Baker D, Theorell T, Siegrist J, Peter R, Karasek R, Marmot M, Brisson C, Tuchsen F. Research findings linking workplace factors to CVD outcomes. Occup Med 2000;15:7–68. [2] Kivimäki M, Virtanen M, Elovainio M, Kouvonen A, Väänänen A, Vahtera J. Work stress in the etiology of coronary heart disease: a metaanalysis. Scand J Work Environ Health 2006;32:431–42. [3] Karasek R. Job demands, job decision latitude, and mental strain: implications for job redesign. Adm Sci Q 1979;24:285–311. [4] Siegrist J. Adverse health effects of high-effort/low-reward conditions. J Occup Health Psychol 1996;1:27–41. [5] Kivimäki M, Ferrie JE, Brunner E, Head J, Shipley MJ, Vahtera J, Marmot MG. Justice at work and reduced risk of coronary heart disease among employees. Arch Intern Med 2005;165:2245–51. [6] Elovainio M, Leino-Arjas P, Vahtera J, Kivimäki M. Justice at work and cardiovascular mortality: a prospective cohort study. J Psychosom Res 2006;61:271–4. [7] Thibaut J, Walker L. Procedural Justice: A Psychological Analysis. Hillsdale (NJ): Erlbaum, 1975. [8] Bies RJ, Moag JS. Interactional justice: communication criteria of fairness. In: Lewicki RJ, Sheppard BH, Bazerman MH, editors. Research on Negotiation in Organizations. vol. 1. Greenwich (Conn): JAI Press, 1986. pp. 43–55.
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[9] Kasai H, Nishimura S. Hydroxylation of deoxyguanosine at C-8 position by ascorbic acid and other reducing agents. Nucleic Acids Res 1984;12:2137–45. [10] Andreassi MG. Coronary atherosclerosis and somatic mutations: an overview of the contributive factors for oxidative DNA damage. Mut Res Rev Mut Res 2003;543:67–86. [11] Irie M, Asami S, Nagata S, Miyata M, Kasai H. Relationships between perceived workload, stress and oxidative DNA damage. Int Arch Occup Environ Health 2001;74:153–7. [12] Karasek R. Job Content Questionnaire and User's Guide. Lowell (Mass): University of Massachusetts at Lowell, 1985. [13] Kawakami N, Kobayashi F, Araki S, Haratani T, Furui H. Assessment of job stress dimensions based on the job demands–control model of employees of telecommunication and electric power companies in Japan: reliability and validity of the Japanese version of Job Content Questionnaire. Int J Behav Med 1995;2:358–75. [14] Tsutsumi A, Ishitake T, Peter R, Siegrist J, Matoba T. The Japanese version of the Effort-Reward Imbalance Questionnaire: a study in dental technicians. Work Stress 2001;15:86–96. [15] Siegrist J, Starke D, Chandola T, Godin I, Marmot MG, Niedhammer I, Peter R. The measurement of effort–reward imbalance at work: European comparisons. Soc Sci Med 2004;58:1483–99. [16] Moorman RH. Relationship between organizational justice and organizational citizenship behaviors: do fairness perceptions influence employee citizenship? J Appl Psychol 1991;76:845–55. [17] Elovainio M, Kivimäki M, Vahtera J. Organizational justice: evidence of a new psychosocial predictor of health. Am J Public Health 2002;92: 105–8.
[18] Landsbergis PA, Schnall PL, Warren K, Pickering TG, Schwartz JE. Association between ambulatory blood pressure and alternative formulations of job strain. Scand J Work Environ Health 1994;20: 349–63. [19] Tsutsumi A, Kayaba K, Nagami M, Miki A, Kawano Y, Ohya Y, Odagiri Y, Shimomitsu T. The effort–reward imbalance model: in Japanese working population. J Occup Health 2002;44:398–407. [20] Møller P, Wallin H, Knudsen LE. Oxidative stress associated with exercise, psychological stress and life-style factors. Chem Biol Interact 1996;102:17–36. [21] Kasai H. Analysis of form of oxidative DNA damage, 8-hydroxyguanosine, as a biomarker of cellular oxidative stress during carcinogenesis. Mutat Res 1997;387:147–63. [22] Baird JE, Zelin RC, Marxen DE. Gender differences in the job attitudes of accountants. Mid Am J Bus 1998;13:35–42. [23] Pilger A, Rüdiger HW. 8-Hydroxy-2′-deoxyguanosine as a marker of oxidative DNA damage related to occupational and environmental exposures. Int Arch Occup Environ Health 2006;80:1–15. [24] Cooke MS, Olinski R, Loft S, European Standards Committee on Urinary (DNA) Lesion Analysis (ESCULA). Measurement and meaning of oxidatively modified DNA lesions in urine. Cancer Epidemiol Biomarkers Prev 2008;17:3–14. [25] Toyokuni S, Tanaka T, Hattori Y, Nishiyama Y, Yoshida A, Uchida K, Hiai H, Ochi H, Osawa T. Quantitative immunohistochemical determination of 8-hydroxy-2′-deoxyguanosine by a monoclonal antibody N45.1: its application to ferric nitrilotriacetate-induced renal carcinogenesis model. Lab Invest 1997;76: 365–74.
Short communication
Three job stress models/concepts and oxidative DNA damage in a sample of workers in Japan Akiomi Inoue a,⁎, Norito Kawakami a , Masao Ishizaki b , Masaji Tabata c , Masao Tsuchiya a,d , Miki Akiyama e,f , Akiko Kitazume f , Mitsuyo Kuroda a , Akihito Shimazu a a Department of Mental Health, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan Department of Social and Environmental Medicine (Hygiene), Kanazawa Medical University, Uchinada, Japan c Ishikawa Health Service Association, Kanazawa, Japan d Department of Epidemiology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan e Division of Nursing, Faculty of Healthcare, Tokyo Healthcare University, Tokyo, Japan f Department of Psychiatric Nursing, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan b
Received 14 May 2008; received in revised form 31 August 2008; accepted 25 September 2008
Abstract Objective: Three job stress models/concepts (the job demands– control [DC] model, the effort–reward imbalance [ERI] model, and organizational justice) have been linked to coronary heart disease (CHD) at work. In recent years, oxidative DNA damage has been identified as a new risk factor for CHD. However, evidence for the association between these job stressors and oxidative DNA damage is limited. The present cross-sectional study investigated the association between these job stress models/concepts and oxidative DNA damage as a possible mediator of the adverse health effects of job stress. Methods: A total of 166 male and 51 female workers of a manufacturing factory in Japan were surveyed using a mailed questionnaire regarding job stressors and demographic, occupational, and lifestyle variables. Urinary concentrations of 8-
hydroxy-2′-deoxyguanosine (8-OHdG), a biomarker of oxidative DNA damage, were also measured. Results: In male subjects, the urinary concentrations of 8-OHdG were significantly higher among the group with lower interactional justice, one of the two components of organizational justice; however, no association was observed with the DC model or the ERI model. In female subjects, high job demands/control ratio was significantly and positively associated with the urinary concentrations of 8-OHdG. Conclusion: Interactional justice among male workers and the DC model-based strain among female workers may be associated with increased urinary concentrations of 8-OHdG which possibly reflects oxidative DNA damage. © 2009 Elsevier Inc. All rights reserved.
Keywords: Coronary heart disease; Effort–reward imbalance model; Job demands–control model; Organizational justice; Urinary 8-OHdG
Introduction Job stressors have been recognized as one of major risk factors for coronary heart disease (CHD) [1]. Among others, three major theories or models of job stressor have been
⁎ Corresponding author. Department of Mental Health, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan. Tel.: +81 3 5841 3522; fax: +81 3 5841 3392. E-mail address: [email protected] (A. Inoue). 0022-3999/08/$ – see front matter © 2009 Elsevier Inc. All rights reserved. doi:10.1016/j.jpsychores.2008.09.016
identified and linked to CHD [2]: the job demands–control (DC) model [3], the effort–reward imbalance (ERI) model [4], and the organizational justice concept [5,6]. In the DC model, job strain defined as the combination of high job demands and low job control has been associated with risk for CHD [2]. The ERI at work, which focuses on a long-term macro-level excess of effort at work compared to work reward, has also been proposed as a risk factor for CHD [4]. The organizational justice concept includes two components: procedural justice which is fairness of the process and procedures used to make allocation decisions [7]; and
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interactional (relational) justice which captures the quality of interpersonal treatment people receive during the enactment of organizational procedures [8]. Low interactional justice at work has also been associated with an increased risk for CHD [5,6]. In recent years, oxidative DNA damage, which is often measured using urinary or leukocyte levels of 8-hydroxy-2′deoxyguanosine (8-OHdG) [9], has been identified as a new risk factor for CHD [10]. Thus, oxidative DNA damage may play a mediating role in linking job stressors to CHD. To date, no study has tested the association between these three job stress models/concepts and 8-OHdG, while a previous study partly addressed the association between workload and 8-OHdG measurements among female workers [11]. The present study was undertaken to investigate the crosssectional association between the three major job stress models/concepts and the levels of urinary 8-OHdG in a sample of workers in Japan. It is hypothesized that those who have high job strain, high ERI, or low organizational justice have high urinary concentrations of 8-OHdG.
Methods
The ERIQ consists of scales for extrinsic effort and reward at work. To define the high ERI group, two approaches were used [15]: (1) first, we defined those who had an effort/reward ratio of 1.0 or higher as high ERI; (2) second, because the prevalence of high ERI was reported to be relatively low in Japanese samples [19], we also classified the subjects into tertiles according to the effort/reward ratio. The OJQ consists of scales for procedural justice and interactional justice. The subjects were classified into tertiles in terms of procedural justice or interactional justice score. Measurement of urinary 8-OHdG At the health check-up, after fasting overnight, we collected urine samples from the subjects in the morning. The samples were immediately frozen and stored at −30°C, then sent to a central laboratory of the Mitsubishi Chemical Medience Corporation, Tokyo, Japan, to measure 8-OHdG using the enzyme-linked immunosorbent assay (ELISA) kit using the monoclonal antibody N45.1, adjusted for urinary creatinine concentrations. The intra-assay coefficient of variation for the measurement at the central laboratory was reported to be 9.6%. The urinary concentrations of 8-OHdG were almost normally distributed in the present sample.
Subjects Other covariates A cross-sectional study of employees of a manufacturing factory located in northern-central Japan was conducted in August 2007. A self-administered questionnaire survey and an on-site health check-up were conducted. All employees (N=302) were invited to participate in this study. A total of 244 participated in this study (response rate, 81%). Data from 217 workers (166 males and 51 females) without missing value on relevant variables were analyzed. The study procedure was approved by the Ethics Committees of the Graduate School of Medicine, The University of Tokyo, and Kanazawa Medical University. Assessment of job stressors Job stressors were measured by using, respectively, the Japanese version of the Job Content Questionnaire (JCQ) [12,13], the Effort-Reward Imbalance Questionnaire (ERIQ) [14,15], and the Organizational justice Questionnaire (OJQ) [16,17, Inoue et al., unpublished observations]. The JCQ includes scales for job demands and job control. We used two approaches to define the high job strain group [18]: (1) first, subjects were classified into four quadrant groups using the median scores for job demands and job control: high strain job (higher job demands and lower job control), active job (higher job demands and higher job control), passive job (lower job demands and lower job control), and low strain job (lower job demands and higher job control); (2) second, those in the highest tertile of the job demands/control ratio were defined as the high strain group.
Demographic (age, education, and marital status), occupational (occupational status, overtime in the past month, and a possible exposure to heavy metals at work), and lifestyle variables (body mass index [BMI], exercise, smoking, alcohol consumption, fruit consumption, vegetable consumption, and habitual supplement use) which could have an influence on oxidative stress [20] were assessed by using the self-administered questionnaire. Statistical analysis Analysis of variance (ANOVA) and analysis of covariance (ANCOVA) were employed to compare crude and adjusted average urinary concentrations of 8-OHdG with groups classified on the basis of each job stress model/concept. These analyses were conducted separately for males and females. In addition, similar analyses were conducted after excluding those (three males and three females) with concurrent chronic medical conditions which were previously reported to be associated with increased urinary 8OHdG levels [21]. The level of significance was .05 (twotailed). SPSS 14.0J for Windows was used for the statistical analyses.
Results Table 1 shows the subjects' characteristics and average scores for each job stressor scale by sex. Average scores for
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Table 1 Demographic characteristics, lifestyles, and job stressors among employees who participated in the study by sex Male (N=166) n (%) Age (years) Education (years) More than 12 12 or less Marital status Currently married Never married Divorced/widowed Occupation Manager White-collar Blue-collar Overtime in the past month (hours) Possible heavy metal exposure Yes No BMI (kg/m2) Exercise (times per week) Once or more Less than once Smoking Current smoker Past smoker Never smoker Alcohol consumption (drinks per months) More than 20 20 or less None Fruit consumption (times per week) Once or more Less than once Vegetable consumption (times per week) More than 3 times 3 times or less Habitual supplement use Yes No
Female (N=51) Average (S.D.)
n (%)
35.3 (9.2)
Average (S.D.) 36.4 (8.9)
68 (41.0) 98 (59.0)
19 (37.3) 32 (62.7)
107 (64.5) 57 (34.3) 2 (1.2)
31 (60.8) 17 (33.3) 3 (5.9)
16 (9.6) 36 (21.7) 114 (68.7)
– (0.0) 12 (23.5) 39 (76.5)
P .451 .744
.186
.049
28.8 (33.9)
16.7 (22.3)
.003 b.001
20.7 (2.9)
b.001 .256
– (0.0) 51 (100.0)
34 (20.5) 132 (79.5) 23.1 (3.6) 65 (39.2) 101 (60.8)
25 (49.0) 26 (51.0)
87 (52.4) 29 (17.5) 52 (30.1)
10 (19.6) 4 (7.8) 37 (72.5)
67 (40.4) 60 (36.1) 39 (23.5)
6 (11.8) 17 (33.3) 28 (54.9)
85 (51.2) 81 (48.8)
30 (58.8) 21 (41.2)
83 (50.0) 83 (50.0)
34 (66.7) 17 (33.3)
31 (18.7) 135 (81.3)
22 (43.1) 29 (56.9)
b.001
b.001
.423
.039
.001
Job stressor scale scores Job Content Questionnaire Job demands (12–48) Job control (24–96) Job demands/control ratio (0.125–2.000) Effort-Reward Imbalance Questionnaire Effort (6–30) Reward (11–55) Effort/reward ratio (0.20–5.00) Organizational Justice Questionnaire Procedural justice (1.00–5.00) Interactional justice (1.00–5.00)
job demands and job demands/control ratio were significantly higher, and average scores for job control were significantly lower among female subjects than male subjects. In male subjects, after adjusting for all the covariates, the urinary concentrations of 8-OHdG were significantly different among the groups classified on the basis of interactional justice (F [2, 145]=4.96, P=.008), with higher concentrations
32.7 (5.3) 65.7 (11.0) 0.51 (0.13)
34.7 (5.0) 60.7 (9.6) 0.58 (0.12)
.018 .004 b.001
14.4 (4.6) 42.0 (8.0) 0.68 (0.34)
15.6 (5.3) 41.9 (6.9) 0.73 (0.37)
.122 .930 .355
3.03 (0.71) 3.16 (0.88)
2.90 (0.67) 3.27 (0.77)
.254 .428
in the group with low interactional justice (Table 2). In female subjects, the urinary concentrations of 8-OHdG were significantly different among the groups classified on the basis of the job demands/control ratio (F [2, 32]=4.20, P=.024), with higher concentrations in the group with high job demands/control ratio, after adjusting for all the covariates. These results were unchanged for 163 males
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Table 2 Comparison of crude and adjusted average urinary concentrations of 8-OHdG (ng/mg creatinine) by groups classified on the basis of the job demands–control model, the effort–reward imbalance model, and organizational justice among Japanese male (N=166) and female (N=51) employees a
Job stressors
n
Crude
Demographic and occupational factors adjusted
Demographic, occupational, and lifestyle factors adjusted
Average (S.D.)
Average (S.E.) b
Average (S.E.) c
Males Job strain quadrants High strain job Active job Passive job Low strain job
29 52 47 38
7.99 (1.71) 8.14 (1.95) 8.22 (2.33) 7.78 (2.28) P=.788
7.68 (0.41) 8.12 (0.31) 8.24 (0.34) 8.00 (0.37) P=.722
7.73 (0.40) 8.06 (0.31) 8.27 (0.34) 8.02 (0.37) P=.775
Job demands/control ratio High (0.537–2.000) Medium (0.461–0.536) Low (0.125–0.460)
56 54 56
7.96 (1.72) 8.34 (2.31) 7.87 (2.22) P=.462
7.70 (0.29) 8.41 (0.29) 8.07 (0.29) P=.237
7.70 (0.29) 8.42 (0.28) 8.06 (0.29) P=.224
8.57 (1.85) 7.96 (2.13) P=.172
8.38 (0.42) 7.99 (0.18) P=.396
8.22 (0.41) 8.02 (0.17) P=.664
8.30 (1.80) 7.80 (2.32) 8.05 (2.13) P=.445
8.20 (0.28) 7.85 (0.28) 8.11 (0.29) P=.660
8.16 (0.28) 7.82 (0.28) 8.18 (0.28) P=.604
Effort/reward imbalance (effort/reward ratio) High (1.00–5.00) 26 Low (0.20–0.99) 140 Effort/reward tertiles (effort/reward ratio) High (0.711–5.000) 56 Medium (0.486–0.710) 56 Low (0.200–0.485) 54 Procedural justice Low (1.00–2.86) Medium (3.00–3.29) High (3.43–5.00)
61 45 60
8.16 (2.36) 7.84 (1.88) 8.11 (1.97) P=.716
8.25 (0.28) 7.75 (0.33) 8.08 (0.27) P=.533
8.21 (0.28) 7.83 (0.33) 8.03 (0.28) P=.770
Interactional justice Low (1.00–2.83) Medium (3.00–3.50) High (3.67–5.00)
51 60 55
8.75 (2.23) 7.89 (2.00) 7.59 (1.92) P=.012
8.76 (0.29) 7.85 (0.27) 7.62 (0.28) P=.014
8.81 (0.29) 7.80 (0.27) 7.63 (0.28) P=.008
Females Job strain quadrants High strain job Active job Passive job Low strain job
9 13 17 12
7.32 (2.29) 7.03 (1.53) 8.15 (3.17) 5.73 (1.47) P=.066
7.31 (0.84) 7.12 (0.67) 7.96 (0.63) 5.92 (0.90) P=.415
8.20 (0.87) 7.16 (0.67) 7.33 (0.62) 6.10 (0.89) P=.513
Job demands/control ratio High (0.601–2.000) Medium (0.521–0.600) Low (0.125–0.520)
18 17 16
8.09 (3.00) 6.91 (2.40) 6.34 (1.26) P=.097
8.34 (0.58) 6.79 (0.61) 6.21 (0.71) P=.063
8.46 (0.54) 6.50 (0.57) 6.38 (0.70) P=.024
7.04 (2.02) 7.17 (2.55) P=.874
6.80 (0.77) 7.24 (0.37) P=.617
7.51 (0.82) 7.06 (0.35) P=.643
7.92 (2.54) 7.03 (2.62) 6.50 (2.02) P=.230
7.85 (0.59) 6.82 (0.62) 6.76 (0.63) P=.358
8.04 (0.55) 6.82 (0.59) 6.59 (0.59) P=.175
6.70 (1.98) 7.98 (2.37) 6.78 (2.85) P=.228
6.99 (0.56) 7.92 (0.58) 6.52 (0.60) P=.256
7.25 (0.59) 7.80 (0.55) 6.34 (0.58) P=.196
Effort/reward imbalance (effort/reward ratio) High (1.00–5.00) 10 Low (0.20–0.99) 41 Effort/reward tertiles (effort/reward ratio) High (0.751–5.000) 17 Medium (0.513–0.750) 17 Low (0.200–0.512) 17 Procedural justice Low (1.00–2.71) Medium (2.86–3.14) High (3.29–5.00)
18 17 16
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Crude
Demographic and occupational factors adjusted
Demographic, occupational, and lifestyle factors adjusted
Average (S.D.)
Average (S.E.) b
Average (S.E.) c
6.81 (2.32) 6.82 (2.10) 7.68 (2.79) P=.475
6.89 (0.70) 6.73 (0.60) 7.70 (0.55) P=.466
7.52 (0.72) 6.66 (0.63) 7.35 (0.57) P=.670
Table 2 (continued)
Job stressors Interactional justice Low (1.00–2.83) Medium (3.00–3.67) High (3.83–5.00) a b c
n 13 18 20
One-way ANOVA was used for the comparison of crude average. ANCOVA was used for the comparison of adjusted average. Adjusted for age, education, marital status, occupational status, overtime, and possible heavy metal exposure. Additionally adjusted for BMI, exercise, smoking, alcohol consumption, vegetable consumption, fruit consumption, and habitual supplement use.
and 48 females after excluding respondents who had a current chronic medical condition (data available on request).
Discussion In male subjects, the urinary concentrations of 8-OHdG were greater in the group with lower interactional justice. This is consistent with previous findings of an increased risk for CHD among workers with lower interactional justice [5,6]. On the other hand, procedural justice was not significantly associated with the urinary concentrations of 8-OHdG among male subjects. Low interactional justice taps unfair treatment of workers by superiors and managers, which is more likely to cause chronic distress in the daily working life for workers than procedural justice, i.e., justice in procedures of decision making in a workplace. Interactional or procedural justice was not associated with the urinary concentrations of 8-OHdG among females. Interactional justice may cause greater distress particularly among male workers, who have a greater job commitment [22], and thus be more associated with urinary 8-OHdG among males. Neither job strain nor ERI was significantly associated with the urinary concentrations of 8-OHdG in males. However, in female subjects, high job demands/control ratio was significantly and positively associated with the urinary concentrations of 8-OHdG. A previous study also reported that perceived workload was associated with 8-OHdG levels in leukocytes in females, but not in males [11]. A task-oriented model, such as the DC model, may be more important for females in terms of increased urinary 8-OHdG, although a further study is required to clarify the gender difference. Possible limitations must be considered. First, the sample was relatively small in its size and from one particular manufacturing company in Japan. Furthermore, those who perceived they had greater job stress and chronic health conditions may have been less likely to participate in this study. Second, the observed differences were small, which may be casual. Third, the concentrations of 8-OHdG measured by single spot monitoring may not be a precise measure of the individual base levels [23]. The 8-OHdG measurement by ELISA was reported to have a crossreactivity with some other analogous compounds [24],
while the monoclonal antibody we used (N45.1) shows a minimal cross-reactivity only towards 8-sulfhydryl-G and 8OHG (less than 1%) [25]. Also, the urinary excretion rate of 8-OHdG is supposed to reflect repair process after DNA damage, but not DNA damage itself. The rates of DNA repair vs. rates of DNA damage should be investigated in future research. Fourth, job stressors were measured by selfreport. The subjects may refrain from answering the scales precisely. Fifth, personality, a high-fat diet, or medication may confound the findings. Finally, a causal relationship cannot be determined because of the cross-sectional nature of the study. A large-scale prospective study is needed to investigate a causal linkage between job stressors, oxidative DNA damage, and incidence of CHD. Acknowledgments The present study was supported by a Grant-in-Aid for Scientific Research (B) 2004-2007 (No. 16390170) from the Ministry of Education, Culture, Sports, Science, and Technology, Japan. References [1] Steenland K, Fine L, Belkic K, Landsbergis P, Schnall P, Baker D, Theorell T, Siegrist J, Peter R, Karasek R, Marmot M, Brisson C, Tuchsen F. Research findings linking workplace factors to CVD outcomes. Occup Med 2000;15:7–68. [2] Kivimäki M, Virtanen M, Elovainio M, Kouvonen A, Väänänen A, Vahtera J. Work stress in the etiology of coronary heart disease: a metaanalysis. Scand J Work Environ Health 2006;32:431–42. [3] Karasek R. Job demands, job decision latitude, and mental strain: implications for job redesign. Adm Sci Q 1979;24:285–311. [4] Siegrist J. Adverse health effects of high-effort/low-reward conditions. J Occup Health Psychol 1996;1:27–41. [5] Kivimäki M, Ferrie JE, Brunner E, Head J, Shipley MJ, Vahtera J, Marmot MG. Justice at work and reduced risk of coronary heart disease among employees. Arch Intern Med 2005;165:2245–51. [6] Elovainio M, Leino-Arjas P, Vahtera J, Kivimäki M. Justice at work and cardiovascular mortality: a prospective cohort study. J Psychosom Res 2006;61:271–4. [7] Thibaut J, Walker L. Procedural Justice: A Psychological Analysis. Hillsdale (NJ): Erlbaum, 1975. [8] Bies RJ, Moag JS. Interactional justice: communication criteria of fairness. In: Lewicki RJ, Sheppard BH, Bazerman MH, editors. Research on Negotiation in Organizations. vol. 1. Greenwich (Conn): JAI Press, 1986. pp. 43–55.
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