László, Krisztina D. MSc; Kopp, Mária S. MD, PhD
There is increasing and suggestive evidence to support that adverse psychosocial circumstances at work are associated with an increased risk for poor health, including mental health morbidity,1 cardiovascular diseases2,3 and musculoskeletal disorders.4 It has been suggested that work stress may also affect women’s gynaecological functioning, specifically pregnancy outcomes,5 length and volume of menstrual flow,6 regularity and length of menstrual cycle6–9 and primary dysmenorrhoea.10–12
Evaluation of potential risk factors for menstrual disorders, including work-related ones, has generally focused on three aspects of menstrual dysfunction namely on anovulation, inadequate luteal phase, and amenorrhea.13 Despite the high prevalence of dysmenorrhoea and the plausibility of the relationship, little attention has been paid to the association between work-related stress and menstrual pain. The results of the few existing studies in this area are inconclusive. Christiani et al,10 Wang et al11 and László et al12 have found stress at work to be associated with dysmenorrhoea, whereas neither Gordley et al,14 nor Chung et al15 found a relationship between these factors. However, most of these studies, including our previous investigation,12 did not adopt a theoretical framework to define work stress and measured this factor using a single item. This may limit the validity of the exposure assessment and thus the result of the studies.
Siegrist16 proposed that work stress may be defined as an imbalance between efforts spent and rewards received at work. This non-symmetric exchange may be maintained in circumstances: a) when the employee has no alternative choice in the labor market, b) for strategic reasons (eg, expecting future gains), and c) when the employee is characterized by a motivational pattern of excessive work-related overcommitment which prevents to accurately assess the cost-gain relationship.16 Work stress according to this definition has been investigated widely and has been found to be a consistent predictor of several health outcomes.17,18 However, to the best of our knowledge no study analyzing the relationship between the effort-reward imbalance model and painful menstruation has been published.
Identification of modifiable risk factors for dysmenorrhoea is important because the condition affects a large proportion of women of reproductive age.11,19–22 Between 30% and 90% of women report to experience pain at menses,23–25 whereas 10% to 20% of women report such severe pain that they are unable to perform their work or have to miss school.25–27 Besides influencing mood and quality of life, dysmenorrhoea reduces the work capacity and productivity of women who suffer from this problem. The costs this menstrual disorder causes to the society are huge; according to estimations made for the United States they vary between 94 and 308 million USD/d missed.28
Therefore, the aim of this study was to investigate whether job stress defined as an imbalance between efforts and rewards at work and overcommitment are associated with menstrual pain.
Analyses for the present study were based on data from the Hungarostudy Epidemiological Panel 2006, a follow-up of the Hungarostudy 2002 nation-wide representative survey. The baseline data collection took place in 2002 and involved 12,668 subjects (refusal rate 17.7%) who were representative for the adult population of Hungary according to age, sex, and sub-region. The sampling and data collection procedure of the Hungarostudy 2002 baseline survey has been described in detail elsewhere.12 Eight thousand eight persons from those interviewed in 2002 gave an informed consent to participate in a follow-up study. A total of 7321 persons (91.4%) could be traced at the follow-up 4 years later in the frame of the Hungarostudy Epidemiological Panel 2006. Of these subjects 318 (4.3%) were reported to have deceased, 1738 (23.7%) refused to participate in the study and 741 (10.1%) were not in adequate condition to complete the interview (eg, due to illness, drunkenness), resulting in 4524 subjects being interviewed29 of whom 2688 were women.
Because of the nature of the phenomenon investigated, analysis for the present study were restricted to a part of this follow-up sample, ie, to women who were employed in 2006 at the time of the survey and who reported not to be post-menopausal or pregnant. An additional 75 women were excluded due to missing data on menstrual pain, resulting in 821 women being finally included in the present analysis.
The study was approved by the Ethics Committee of the Semmelweis University in Budapest.
Assessment of Work Stress.
Work stress was measured using an abbreviated version of the Effort-Reward Imbalance Questionnaire.16,30 The questionnaire, validated in Hungary by Salavecz et al,31 contains 15 items. The three items of the Effort scale inquire about time pressure, frequent interruptions and disturbances, and increasing demands on the job. The Reward scale includes six statements which refer to job promotion prospects, undesirable changes in the work situation, job insecurity, respect and monetary gratification. Answers to these scales consist of two parts. First, respondents answer whether they are exposed to different stress factors and if yes they indicate to what extent these are a source of distress for them. The overcommitment scale consists of six items and assesses the “inability to withdraw from work obligations.”31 Answers to the items of this scale are given on a 4-point Likert scale ranging from “strongly disagree” to “strongly agree.” Scale values were obtained by summing the scores on the individual items. Higher scores indicate higher efforts, rewards and overcommitment, respectively.
The Hungarian abbreviated version of the questionnaire proved to be a valid instrument for measuring work stress, to have a similar factorial structure and internal consistency to that of the original.31 Cronbach alpha coefficients in the validation study based on data from our survey were 0.77 for the Effort and Reward scales and 0.80 in the case of the Overcommitment scale.31
Ascertainment of Covariates.
Occupational class was categorized as a) un-, semi-, or skilled worker, b) clerk, c) professional, and d) supervisor or manager. Personal and mother’s education was classified into three levels: less than high school, completion of high school, and college/university. Marital status was classified as living versus not living in a partnership. Self-reports about unsuccessfully trying to conceive for at least 1 year and previous miscarriage were recorded. Answers to the item regarding the number of children were dichotomised into with and without children, in order to obtain a proxy measure for parity status. Smoking was categorized as never, former, or current smoker. Weight and height were recorded, and body-mass index (BMI) was calculated by dividing the weight with the square of the height value (kg/m2). Given the non-linear relationship between BMI and dysmenorrhoea, women were divided into three groups: those with BMI <18.5 were considered to be underweight, those having a BMI between 18.5 and 25 were considered as having normal weight, whereas those with a BMI >25 were regarded as being overweight or obese. Physical activity was determined by combining answers to the questions: “How often do you engage in sport activities (eg, swimming, jogging, cycling, playing football, aerobic etc)?” and “How often do you engage in physical activities other than sports, eg, gardening, construction work etc, when your heart beats intensively for at least 10 minutes?” Answer possibilities were: “never,” “less then once a week,” “once a week,” and “more than once a week.” Women who engaged less than once a week in any of these activities were considered to be physically inactive.
Depressive symptoms were assessed using an abbreviated version of the Beck Depression Inventory.32–34 The 9-item questionnaire asks participants to rate the intensity of their depressive symptoms on a scale ranging from 1 to 4. In our study, the Cronbach α coefficient was 0.87, indicating good internal consistency of the scale.
Negative affect, ie, “the tendency to experience negative emotions across time and situations” was measured at baseline (in 2002) with a shortened, 5-item version of the negative affect subscale of the type D Scale developed by Johan Denollet.35,36 Responses were given on a 4-point Likert scale ranging from “not at all characteristic” to (0) “fully characteristic.”3 The Cronbach alpha coefficient in our study was 0.84.
Assessment of Menstrual Pain.
The existence of menstrual pain was assessed by asking the participants the following question: “Does menstrual pain limit your daily activity? (No/yes).”
The imbalance between efforts and rewards at work was calculated as the ratio between the effort and reward scores weighed by the number of items in each scale. Characteristics of women with and without limiting menstrual pain were compared by t-tests for independent samples in the case of continuous variables with normal distribution, whereas Mann-Whitney U tests were used for variables with skewed distribution. Categorical data were compared by χ2 test. Un- and multi-adjusted binary logistic models were performed to examine the association between effort-reward imbalance and overcommitment at work and painful menstruation. The two work stress variables, age, depressive symptoms, and negative affectivity were introduced as continuous variables in these models, whereas all the other covariates were treated as categorical data. A threshold of P < 0.05 was established in order to consider an association significant. Statistical analyses were conducted using SPSS 13.0 for Windows.
Painful menstruation that limited daily activity was characteristic of 165 women, which represented 20.1% of those included in the analysis. Comparative data on age, occupational class, own and mother’s education, marital status, parity, unsuccessfully trying to conceive for at least 1 year, previous miscarriage, smoking, BMI, physical activity, depressive symptoms, negative affectivity, and work stress of the women with and without limiting menstrual pain are presented in Table 1. Women suffering from painful menstruation were on average somewhat younger than those not reporting such problems (P = 0.09) and were less likely to have given birth to a child (P = 0.04). The proportion of un-, semi- or skilled workers, of clerks, professionals and supervisors was 47.2%, 9.0%, 15.8%, and 28.0% in the group with dysmenorrhoea and 57.8%, 4.6%, 15.6%, and 22.1% in the group without painful menses, respectively. Seventeen percent of dysmenorrhoeal women reported to have tried unsuccessfully to conceive for at least 1 year compared to 13% of women without menstrual pain (P = 0.059). Women with painful menses were leaner (P = 0.047), reported higher negative affectivity (P = 0.03), lower rewards (P = 0.005), higher overcommitment (P = 0.006), slightly higher depressive symptoms scores (P = 0.08) and somewhat higher imbalance between efforts and rewards at work (P = 0.05). Own and mother’s education, marital status, history of miscarriage, smoking, physical activity and efforts at work did not differ significantly between the two groups.
Table 2 presents the results of the un- and multivariable-adjusted logistic regression analysis, conducted to investigate the association between characteristics of the psychosocial work environment and painful menstruation. In unadjusted analysis effort-reward imbalance was associated with an increased risk of dysmenorrhoea, the odds ratios (OR) and the 95% confidence intervals (95% CI) being 1.46 (1.09 to 1.94). A one point increase on the overcommitment score was associated with a 7% increase in the risk of dysmenorrhoea (OR [95% CI]: 1.07 [1.02 to 1.12]). Adjustment for potential confounding factors, ie, age, occupational class, own and mother’s education, marital status, parity, unsuccessfully trying to conceive for at least 1 year and previous miscarriage resulted in a stronger association between effort-reward imbalance (OR [95% CI]: 1.52 [1.12 to 2.06]) and painful menstruation and similar association between overcommitment and the outcome. Adding depressive symptoms to this model reduced the risk of dysmenorrhoea associated with effort-reward imbalance to 1.44 (95% CI: [1.05 to 1.97]). Further adjustment for behavioral risk factors, ie, smoking, physical activity, and BMI did not alter the results considerably.
We conducted additional analysis when we added negative affectivity to model 2. We found no evidence for confounding from this factor, the OR (95% CI) for the association between effort-reward imbalance and dysmenorrhoea was 1.46 (1.07 to 2.00) and 1.07 (1.02 to 1.13) for the overcommitment-menstrual pain relationship.
The objective of the present study was to investigate whether a stressful work environment predicts menstrual pain. We found that high effort-reward imbalance and overcommitment were associated with an increased risk for dysmenorrhoea, relationship which persisted after adjustment for demographic, socioeconomic, gynaecological, behavioral and mental health factors.
Our findings are in line with previous studies conducted by Christiani et al10 and Wang et al11 which found a positive association between work stress and the risk of dysmenorrhoea. Findings from the present study complement and extend the results of our previous investigations showing that low control at work, low job security and low social support were associated with menstrual pain among Hungarian working women.12 However, compared to our previous study in which work stress was assessed using single items instead of a validated questionnaire,12 the current investigation uses a theory-based and widely accepted definition of work stress and measures it by means of a validated questionnaire. Furthermore, in contrast to our previous study12 we were now able to take into account a wider range of potential confounders for the association between work stress and dysmenorrhoea.
Potential Explanations for the Association Between Work Stress and Dysmenorrhoea
So far, knowledge regarding explanations for the link between work stress and dysmenorrhoea is very limited. Factors that may confound the relationship between job stress and menstrual pain may be primarily related to age, parity, socioeconomic position, personality, previous gynaecological, and psychological morbidity.37 However, these factors could not explain in our study the observed association between work stress and painful menstruation.
Proposed physiological linking mechanisms between stress and dysmenorrhoea involve excessive and prolonged activation of the hypothalamic-pituitary-adrenal axis, which in turn may lead to impaired follicular development.11 Through its effects on progesterone, impaired follicular development may influence the activity of prostaglandins which induce myometrial contractions resulting in uterine ischemia and pain.11 This hypothesis is supported by a recent study conducted by Park and Watanuki38 which found a higher sympathetic nervous system activity and greater responsivity to stressors in women with dysmenorrhoea compared with healthy controls. This difference was not confined only to the menstrual phase, but was observed in the non-painful follicular phase of the menstrual cycle as well. The authors argue that these findings imply that dysmenorrhoeal women may be affected by stressors other than pain per se as compared to controls.38
It could be hypothesized that proinflammatory cytokines may also contribute to the explanation of the link between work stress and dysmenorrhoea. Chronic stress is now known to increase inflammatory activity.39,40 A study conducted by Yeh et al41 found higher levels of the interleukin-6 cytokine in women suffering from menstrual pain compared to controls non-reporting such problem, even after adjustment for covariates.41
Furthermore, it is plausible that mental health does not act only as a confounder in the relationship between work stress and dysmenorrhoea, but also as a potential mediator of this association. High job stress is known to increase the risk of mental health morbidity,1 which in turn is positively related to painful menses.37 We found a 13% reduction in the regression coefficient for the association between the effort-reward imbalance and painful menstruation when adjusting for depressive symptoms, suggesting that this factor may moderately contribute to the explanation of the investigated association.42 Whether it acts as a confounder or it is on the intermediary path between work stress and dysmenorrhoea or both needs to be investigated in future studies with longitudinal design.
Furthermore, it could be hypothesized that behavioral risk factors may also mediate between work stress and primary dysmenorrhoea. Effort-reward imbalance at work has been found to be positively associated with smoking status and smoking intensity,43 with low physical activity44 and with BMI.45 In other studies the risk of dysmenorrhoea was higher among smokers compared to non-smokers37 and among those having extremes of BMI compared to persons with normal weight.46 Physical activity may reduce the risk of dysmenorrhoea by improving blood flow at the pelvic level and by stimulating the release of beta endorphins, which act as non-specific analgesics.47 However, despite the theoretical plausibility of mediation from behavioral factors we found that the association between work stress and dysmenorrhoea was not influenced by health behavior.
Strengths and Limitations of the Study
To the best of our knowledge this study is one of the first ones to investigate in a large, nation-wide survey the association between job stress and dysmenorrhoea. Most of the previous studies in this area focused on employees in specific occupations, eg, nurses,15 cotton mill workers,10 textile mill workers,11 air-force workers14 etc, which limited the possibilities to generalize the findings to other occupational or socioeconomic categories. Furthermore, in contrast to most of the previous investigations in this area, the definition of work stress in our study was theory-based and work stress was assessed with a validated questionnaire.
The limitations of our study need to be addressed as well. Though reverse causality, ie, that women with dysmenorrhoea would be more likely to be selected in jobs with high work stress is not plausible, as in most observational studies we can not exclude the possibility of residual confounding. However, a remaining confounder would have to be associated with both work stress and menstrual pain and generally unrelated to confounding factors already included in our multivariate analyses.
Secondly, since the Hungarostudy Epidemiological Panel 2006 was not primarily designed to investigate menstrual disturbances, no data on contraceptive methods such as oral contraceptives or intrauterine devices was available. Confounding from these factors is, however, not likely; the use of these contraceptives is not likely to influence women’s levels of job stress. However, the possibility that these factors eventually mediate between work stress and dysmenorrhoea can not be excluded. It is plausible that overcommitted women or those having low work rewards, specifically job insecurity, undesirable future changes in the work situation or low salaries, would be less willing to become pregnant and therefore prefer these more secure contraceptive methods. Both oral contraceptives37 and the levonorgestrel-intrauterine system48 have been shown to reduce the risk of painful menses.
Similarly, no data on parity status was collected. When considering a proxy for this variable, ie, the question on the number of children, we might have excluded those parous women whose children had died.
In conclusion, our results indicate that an imbalance between efforts and rewards and overcommitment at work are associated with dysmenorrhoea. The relationship between work-related psychosocial factors and painful menstruation needs to be further investigated to determine factors that may explain this relationship. If a causal relationship between work stress and dysmenorrhoea is supported by future studies, workplace stress management programs aiming to reduce stress at work might attenuate the negative effects of this menstrual disorder and will reduce the costs burdening society.
This study was supported by the OTKA TS-40889/2002, OTKA TS-049785/2004, OTKA K 73754/2008, the ETT-100/2006, the NKFP 1/002/2001, and NKFP 1b/020/2004 grants.
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