Atlanta, GA: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, R01-OH-008543, 2009 Mar; :1-15
Work organization and the psychosocial stresses of the workplace have received increasing attention in the past decade as potential contributors to ill-health. With the increase in participation in more physically demanding and socially challenging work roles has come a new interest in the effect of these stressors on reproduction, particularly on adverse pregnancy outcomes. Evidence suggests that some groups of pregnant workers may be at risk for premature delivery or small-for-gestational-age (SGA) births as a consequence of workplace stressors. Clear associations between occupational stressors and adverse pregnancy outcomes have been, to date, difficult to draw. Factors including study design, retrospective assessment of exposure, and choice of exposure measurement may be partially obscuring any association between work-related stress and pregnancy outcomes. The work here represents an important intersection of three important areas where significant gaps in knowledge exist, and where further understanding of exposures is important for the design of subsequent studies. The overall goals of this developmental and planning grant were to obtain preliminary data assessing two models of occupational stress during pregnancy, in particular measuring repeatedly and longitudinally across the course of pregnancy to evaluate the possibility that work stress may change across pregnancy. This proposal aims also to evaluate the use of the effort-reward imbalance (ERI) model, which has not been tested in pregnant workers or used in studies of pregnancy outcomes. As sufficient data do not exist on the measurement and range of these exposures during pregnancy, or in the US population of this age and gender, it is essential that the elements used in exposure assessment be carefully measured, both to obtain baseline values in early pregnancy, and to assess the degree to which these values may vary across the course of pregnancy. It was intended to inform subsequent studies to test (with sufficient power) the possibility that psychosocial stressors in the workplace exert an effect on pregnancy. The work here represents a necessary first step in the ability to test these hypothesized effects, and will assist in determining whether newer models of the psychosocial parameters of stress in the workplace might be useful in measuring an association with adverse pregnancy outcomes. As well, this work represents an initial assessment of whether changes in measured parameters of stress, or distinct trajectories over time, occur during the course of pregnancy. Principal aims of the study were: 1) To explore the use of newer instruments measuring occupational psychosocial stressors in pregnant women; specifically using the Effort-Reward Imbalance (ERI) model, with comparison to, and possible combination of features with, the Demand-Control (DC) model. 2) To evaluate the psychometric properties of the ERI in pregnancy, including reliability, and content validity. 3) To evaluate the construct validity of the stress scales, to enable their use in measuring occupational psychosocial strain in pregnancy. 4) To evaluate the possibility that occupational psychosocial stressor levels in working women change across the unique time period represented by pregnancy, assessing the direction and magnitude of this change. In summary several important findings were noted that reflect on the design of future relevant studies. The psychometric properties of the Effort-Reward Imbalance model were exceptionally good, with Crohnbach's alpha uniformly greater than 0.7 for all scales of the model; this contrasted with the scores for job control, which were under 0.4. This may reflect, as in our earlier work, the fact that the ERI model is of greater measurement validity in a service economy, contrasted with the Demand -Control model and its origins in an economy more weighted to manufacturing. Subject scores on the ERI model showed a decline across time during pregnancy, with a concomitant increase in job control (non-significant) and no change in effort-reward imbalance across pregnancy. The possibility of a critical period through which occupational psychosocial stressors act is given credence by these results. We find that correlations between intermediate outcome variables related to pregnancy outcomes (blood pressure, self-rated fatigue), and occupational psychosocial stressors are greatest and statistically significant (ranging from 0.35 to 0.59, p<0.01) at the second measurement wave, corresponding to mid-pregnancy and the timing of early fetal growth. In longitudinal models, intermediate outcome variables (self-rated fatigue) were significantly related to work overcommitment. We find much weaker correlations with occupational psychosocial variables and actual birth outcomes, especially birth weight, although this is not surprising since the study was not designed with sufficient size and power to specifically test this hypothesis. These results are in accord with a modest effect of overcommitment on the health of women subjects, and do point to the possibility that work characteristics may affect intermediate health endpoints that have modest consequences on fetal growth and development. Substantial differences in occupational characteristics between blacks and white/Hispanic subjects were found, consistent with the PI's prior work and which show lower values in blacks once adjusted for age and education. That these values are similar to whites, or higher, in Hispanics (and are persistently higher, or improve with adjustment for education) suggests differential access to higher-quality or less stressful work despite equivalent levels of education, and is likely in part explanatory of the findings of several past studies noting higher risk for adverse birth outcomes in college-educated black mothers versus both college-educated whites and blacks without a college degree. This may inform the design of future studies which should encompass measurement of factors such as economic barriers and discrimination that would provide potential explanatory data for both findings related to occupational trajectories and outcomes related to long-term differentials in health consequent to work factors. In summary, these findings from the R-21 Preliminary/Planning grant may be of substantial value in the planning of more formal targeted and larger scale studies that can be designed to measure the effect of working conditions and occupational psychosocial stressors on birth and perinatal outcomes.
John D. Meyer, Section of Occupational and Environmental Medicine, 263 Farmington Ave, MC-6210, Farmington, CT 06030-6210