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ORIGINAL ARTICLES |
From the Department of Anthropology, University of Hawaii at Hilo, Hilo, Hawaii (D.E.B., P.S.M.); and the Institute for Primary and Preventative Health Care and Decker School of Nursing, Binghamton University, Binghamton, New York (G.D.J.).
Address correspondence reprint requests to Daniel E. Brown, PhD, Department of Anthropology, University of Hawaii at Hilo, 200 W. Kawili Street, Hilo, HI 96720-4091. E-mail: dbrown{at}hawaii.edu
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ABSTRACT |
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Methods: Premenopausal women who were either full-time teachers in public schools (teachers; N = 92) or nurses or nurse’s aides (nurses; N = 55) in East Hawaii who were not currently taking antihypertensive medication had ambulatory blood pressure (BP) and urinary catecholamine excretion measured over an approximate 4-hour period at work and home and over an approximate 8-hour period overnight. The women also filled out the Job Content Questionnaire (JCQ).
Results: The nurses had significantly lower scores on the "decision latitude" subscale of the JCQ. After controlling for the effects of ethnicity, age, body mass index, JCQ subscale scores, smoking habits, and menopausal status in regression analyses, the nurses also had significantly higher mean systolic and diastolic BP both in work and home settings and higher mean rates of both norepinephrine and epinephrine excretion in all daily settings (p < .05). There were no significant ethnic differences in scores on the JCQ subscales, but Asian-Americans had significantly higher systolic BP in all daily settings and higher diastolic BP overnight (p < .05) than Euro-Americans.
Conclusions: These results suggest that among professional women, physiological stress responses are significantly greater when occupation-related decision latitude is low (nurses) than when it is high (teachers). The physiological response to stress is carried over into the home and overnight settings when occupation-related decision latitude is low (nurses). Individual scores on the JCQ were not significantly related to physiological measures in this study, however. Inclusion of contrasting occupations may be necessary to properly evaluate the relationships between individually reported job strain and heightened physiological stress responses in studies of working women.
Key Words: job strain • ambulatory blood pressure • epinephrine • norepinephrine • stress • women
Abbreviations: JCQ = Job Content Questionnaire; BMI = body mass index; BP = blood pressure.
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INTRODUCTION |
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Elevated ambulatory blood pressure (BP) has been found in men with individually perceived job strain (written responses to the JCQ) (4,5), but the evidence for this effect among women is inconsistent (6,7). Light et al. (8), Curtis et al. (9), and Brown et al. (7,10) did not find a significant association between reported job strain and ambulatory BP. However, some ambulatory BP measures were significantly associated with job strain in studies by Van Egeren (11), Theorell et al. (12), Blumenthal et al. (13), and Laflamme et al. (14). Part of the variation in results of the studies on women may be the result of the fact that only individual perception and not occupational characteristics are being considered in the measure of job strain. In evaluating the studies of job strain and ambulatory blood pressure in women, we have suggested (7) that reported job strain might contribute to elevating ambulatory BP but that ethnicity and/or socioeconomic factors may modify, mask, or abrogate the effect. More recent studies confirm that ethnicity influences the relationship between reported job strain and physiological measures of stress (15) and that there are ethnic differences in perceived job stress (for example, Asian American physicians report higher stress than Euro-American colleagues (16)).
The connection between job strain and elevated BP (and subsequently the risk for cardiovascular disease) is thought to be mediated by an elevation in catecholamines (17). Few studies have examined the relationship between job strain and urinary catecholamine excretion rates, and the findings from those that have (7,10,18–20) are somewhat inconclusive with regard to the proposed link, often suggesting that elevated catecholamine levels are related to stress at work, but not necessarily to indices of job strain from the JCQ. The disparity in findings among these studies may again be related to the fact that the subjects in the studies are often from a single or several related occupations and of differing ethnicity, which may affect the variability of reported job strain by the JCQ.
In separate studies conducted in Hawaii, we have examined work and lifestyle stress in two groups of professional working women whose occupations differ with regard to decision latitude: nurses and nurse’s aides, a group often characterized as having both high psychological demand and low decision authority, and thus high job strain; and school teachers employed in public schools, a group usually characterized as having both high psychological demand and decision authority, and thus less job strain (2,21). These studies also examined differences between European-American and Asian-American groups (Filipino-American in the nurses and nurse’s aides study, Japanese-American in the teachers study). In examining the separate occupational groups, no significant relationship between job strain and physiological stress measures was observed ((7,10) Brown, unpublished data), but there were differences in response by ethnic group. The job strain findings may be biased, as noted previously, because the studies have involved single occupational groups, and thus there may not have been sufficient variability in the reports of job strain to detect associations. We therefore analyze results obtained from studies on the two Hawaii occupational groups here. We hypothesize that the nurses and nurse’s aides will report greater job strain and have higher ambulatory BP than the school teachers.
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METHODS |
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Subjects
Participants in the nurse and nurse’s aide study were full-time professional nurses or nurse’s aides who worked on the day shift in either Hilo Medical Center or Hilo Life Care Center, were premenopausal, not pregnant, not taking antihypertensive medication, and had body mass indices (BMIs) under 32 kg/m2. The subjects in the teachers study were full-time professional teachers in the public schools in East Hawaii, who were also not pregnant, not taking antihypertensive medication, and had BMIs below 32 kg/m2. At the selected healthcare facilities or schools, all women who fit these criteria were asked to participate. In the nurse and nurse’s aide study, five women who met the criteria refused to participate. In the teachers study, the total number of women who met the eligibility criteria was not enumerated; thus, it was not possible to establish participation rates, but it is likely that these rates varied from school to school based on recruitment methods permitted by each school’s administration.
As previously noted, the studies include Asian-American and Euro-American groups. The nurse and nurse’s aide study included Filipino-Americans (N = 35; 6 RNs, 9 LPNs, and 20 nurse’s aides) and Euro-Americans (N = 23; 16 RNs, 3 LPNs, and 4 nurse’s aides), whereas the teacher study included Japanese-Americans (N = 92) and Euro-Americans (N = 58). The nurses and nurse’s aides had greater variation in professional status, whereas all individuals in the teacher study were full-time, professional teachers. The Filipino-American nurses and nurse’s aides included a large number of women who were born in the Philippines and migrated to the United States (86%). The Japanese-American sample was primarily of women who were third- (71%) or fourth- (19%) generation Americans. In answering the question, "How American in lifestyle are you?" the Filipino-Americans averaged a score of 4.9, whereas the Japanese-Americans averaged a score of 6.6 on a scale of 1 to 10. Thus, the Japanese-Americans are a more Americanized group than the Filipino-Americans. Other characteristics of the two samples are shown in Table 1. As indicated, the women in the nurse and nurse’s aide study sample are significantly younger and less likely to drink alcohol on a regular basis than the teacher study sample.
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Procedures
All women underwent an anthropometric battery within a week of the BP monitoring period. Measurements included stature and weight, and BMI was computed. The participants also filled out a series of questionnaires at this time, which included the JCQ (24) and other questionnaires that ascertained birth date, menopausal status, and ethnicity, among other information. Scores on the "psychological demand" and "decision latitude" subscales of the JCQ were computed.
On the day of monitoring, participants were fitted with a SpaceLabs 90207 ambulatory BP monitor (SpaceLabs, Redmond, WA), an oscillometric device that has been validated in previous studies (25). Monitors were initialized according to each participant’s anticipated wake–sleep schedule for the coming 24 hours. The monitor was calibrated by use of a "T" connector between the monitor and a mercury column with three consecutive readings agreeing to within 5 mm Hg required for both diastolic and systolic BP. Participants were familiarized with the monitors at this time. The monitors measured BP every 15 minutes during selected waking hours and every 30 minutes during sleep over a 24-hour period.
Participants were also instructed in the collection of timed urine samples, each collected in bottles containing 0.5 g sodium metabisulfite. A "work" sample was collected over approximately 4 hours starting at the beginning of work with the bladder emptied at the "start" time and all voidings collected, including a final one at the end of the timed period. Project staff picked up this sample from the subject during her lunch period at work. Similarly, an approximately 4-hour "home" sample was collected once the woman arrived at home for the evening; the time of this sample varied slightly as a result of the different schedules of the women and varying time at home before sleep. A final "overnight" sample was started beginning at bedtime and was completed on waking the next morning (the final voiding in the "home" sample began the time period for the overnight sample; all later voidings during the night and the first voiding on waking were included in this sample). The home and overnight samples were picked up by project staff at the workplace before the participant began work the next morning.
Urine samples were measured for volume and aliquots were frozen at –70°C. These samples were then analyzed for norepinephrine and epinephrine concentrations using HPLC with electrochemical detection (26). Urine samples were mixed with internal standards, buffer, water, and alumina, and the alumina was washed by means of a water-jet vacuum pump that aspirated waste. The catecholamines were eluted with H2PO4 and then mixed with tetrasodium EDTA, tripotassium citrate, and sodium octyl sulfonate. This mixture was injected into the HPLC column using a mobile phase of tetrasodium EDTA, sodium octyl sulfonate, and KH2PO4 with 12% acetonitrile. Standards were run along with unknowns to determine concentrations of catecholamines. In analyses, catecholamines were expressed as the rate of excretion (ng/min) over each time period computed by multiplying the concentration by the urine production rate (mL/min).
For both occupational studies, each participant’s BP readings were averaged over the time spent at work, home, or during sleep. Only the work time corresponding to the urine collection time was included. Home and sleep averages were similarly computed over the time that urine was collected for catecholamine analyses.
Analysis
Regression analyses were used to examine occupational group differences in JCQ subscales along with the contributions of ethnicity, age, BMI, menopausal status, and smoking habits. A backward elimination technique was used in which all variables were included in the model, and then the variable that provided the least predictive power was removed (p > .1 for removal). Similar regression analyses were undertaken to examine occupational group differences in physiological measures using the same variables noted in the first regression analysis but adding the two JCQ subscales as additional independent variables. Regression analyses examining the effect of length of time in the occupational group on subscales of the JCQ and physiological measures were carried out using age as another predictor variable. No significant association between length of time in profession and either the two subscales of the JCQ or any physiological measure was noted when findings were adjusted for multiple comparisons. For all analyses, the level for rejection of the null hypothesis was set at p < .05.
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RESULTS |
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Table 3 shows results of regression analyses involving mean BP in three daily settings. Scores on the two subscales of the JCQ, menopausal status and smoking habits, were not significantly related to BP in any setting. Occupational group was significantly related to systolic and diastolic BP in the work and home settings with nurses having higher BP. Significant ethnic differences in systolic BP were present in all settings with Asian-Americans having relatively higher systolic BP. Asian-Americans also had significantly higher diastolic BP in the overnight setting than Euro-Americans.
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Results of similar regression analyses involving mean catecholamine excretion rates in three daily settings are shown in Table 4. There are significant contributions from occupational group for both epinephrine and norepinephrine in all daily settings. Scores on the two JCQ subscales and menopausal status were not significantly related to catecholamine excretion rate in any setting. Ethnicity was not a significant contributor to catecholamine excretion rate variation in any setting.
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The regression analyses for physiological measures were redone separately by ethnic group with occupational group, age, and BMI included as predictor variables. As seen in Table 5A, among Asian-Americans, occupational group is a significant predictor of the physiological variables. Age is also a significant predictor of BP among Asian-Americans, but in most cases, BMI is not. Among Euro-Americans, as shown in Table 5B, occupational group is a weaker predictor of the physiological measures, but BMI is a significant predictor of BP in all settings.
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DISCUSSION |
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It has been noted that the imputation method of assigning job strain based on occupational title is problematic when applied to the psychological demand component of job strain, because there is greater variability for this variable within a given occupational title (2). This may help explain why no significant differences were found in the JCQ psychological demand subscale between the nurse and nurse’s aide study sample and the teacher study sample. However, there were also no significant associations between scores on the psychological demand subscale of the JCQ and physiological measures of stress at work. The two occupational groups have both been characterized as having high psychological demand, although they differ in reported decision latitude (21). Hence, it may be that the pooled sample represents a group with greater variability in decision latitude, which may help explain the greater association of this component of job strain with physiological measures.
There is also a difference in occupational task and qualification variability between the two groups. The teacher sample is relatively homogeneous, all employed full-time in public schools, and all requiring college degrees for their employment. Among the nurses study sample, nurse’s aides have little in the way of educational requirements, and LPNs and RNs differ considerably in the amount of education required for their employment. Job characteristics also differ for these three types of healthcare workers. There is no significant difference among these three types of nurses in their scores on the subscales of the JCQ (analyses of variance), and there are no differences among the three job types for catecholamine excretion rates. However, LPNs have significantly higher overnight BP than RNs (analysis of variance: for systolic BP, F = 5.43, p < .01, Bonferroni post hoc tests: LPN > RN, nurse’s aides not significantly different from either professional nurse; for diastolic BP, F = 3.74, p < .05, Bonferroni post hoc tests: LPN > RN, nurse’s aides not significantly different from either professional nurse). The sample size for these job types among the nursing group is too small to permit a full understanding of reasons for the overnight BP differences, particularly because there are no significant differences among the nursing job types in physiological measures during working hours.
The occupational differences in stress response may be related to the general nature of the jobs themselves. Nurses are generally perceived as having high-stress jobs (29,30). Nurses deal with critical health situations on a daily basis, and although teachers have a great deal of responsibility for the lives of their students, this is usually not perceived in a life or death manner. It is of interest here that among the professional nurses, significantly elevated diastolic BP was found during times when they were passing out medications (22), an activity in which mistakes could have dire consequences. The nurses sample in this study worked at large institutions (either in the main hospital in the Hilo region and the largest nursing home in the region), which have rigid occupational hierarchies and taking "orders" is the norm. Teachers also work in large institutions, but they have considerable autonomy within their classrooms.
Some of the findings here may be a consequence of the particular ethnic mix of people in the two occupational groups. Ethnic differences have been found in relationships between job strain, specifically low decision latitude, and both elevated BP reactivity and norepinephrine excretion levels (15). In this study, the nurse study sample consisted of Filipino-Americans and Euro-Americans, whereas the teacher study sample consisted of Japanese-Americans or Euro-Americans. When analyses were repeated separately for Euro-American and Asian-American ethnic groups, respectively, Asian-Americans showed greater occupational group differences than Euro-Americans; the nurse study sample had significantly higher catecholamine excretion rates and higher BP than did the teachers. However, the greater occupational group differences among Asian-Americans in this report may be explained by the ethnic differences among Asians in the two groups: mostly immigrant Filipino-Americans among the nurses and primarily third- and fourth-generation Japanese-Americans among the teachers. Finally, there may well be ethnic differences in culturally based expectations about job-based autonomy. Traditional Japanese culture is highly stratified, and people expect to take and give orders at many different social levels (31,32). It is unclear to what degree this has changed in the third- and fourth-generation Japanese-Americans in this sample. Euro-Americans certainly are known to have expectations of great independence and autonomy relative to people in many other cultural groups. Filipino-Americans in Hawaii derive from diverse cultural groups in the Philippines, so generalizations are particularly difficult to make, but it may be reasonable to suggest that their attitudes about autonomy fall somewhere between the expectations of the other two ethnic groups. Thus, the response to differing levels of decision latitude may well vary in people from diverse cultural backgrounds, and these differences may have affected the results reported here.
Finally, the finding of higher mean BP, and particularly elevated nighttime BP, among the Asian-American sample has been reported on previously for the teacher study sample (33). This supports findings from several studies in which samples from populations at high risk for hypertension and stroke had significantly lower nighttime dipping of BP. This includes studies of black (34,35) and Asian (36) populations.
Expansion of this study to examine the effects on physiological measures of stress from occupations with different patterns of psychological demand and decision latitude is needed. For example, in the current study, both occupations had similar psychological demand but differed in decision latitude. Thus, our findings of occupational differences refer only to decision latitude. Comparison of occupations with similar decision latitude but variable psychological workload would permit observation of the effects of the latter subscale.
The inclusion of proximate, physiological measures in the study of job strain allows better understanding of the mechanisms by which job strain is linked to greater cardiovascular disease risk. Furthermore, the ethnic differences that are noted here both in perceived job strain and in the physiological measures, particularly BP, suggests that future studies must take precautions to account for these differences in the study design and interpretation of results.
This work was supported by grants from the National Institutes of Health (No. S06-GM08073-29) and from the American Heart Association, Hawaii Affiliate.
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NOTES |
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Received for publication December 20, 2004; revision received March 20, 2006.
DOI:10.1097/01.psy.0000222356.71315.8e
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-methylnoradrenaline, noradrenaline, and adrenaline in plasma using high-performance liquid chromatography with electrochemical detection. J Chromatogr 1981;224:507–12.[CrossRef]This article has been cited by other articles:
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  D. R. Smith and P. A. Leggat An international review of tobacco smoking research in the nursing profession, 1976-2006 Journal of Research in Nursing, March 1, 2007; 12(2): 165 - 181. [Abstract] [PDF]
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