Key Words: ambulatory blood pressure, diurnal blood pressure variation, work stress, home stress, working women

Transcription

1 499 Original Article The Influence of Work- and Home-Related Stress on the Levels and Diurnal Variation of Ambulatory Blood Pressure and Neurohumoral Factors in Employed Women Kazuomi KARIO, Gary D. JAMES, RoseMerie MARION, Mustafa AHMED, and Thomas G. PICKERING The purpose of this study was to examine the effects of self-reported perceived stress at work and home on the levels, variation and co-variation of ambulatory blood pressure (BP), pulse rate (PR) and urinary catecholamine, cortisol, and aldosterone excretion measured at work, home and during sleep in women employed outside the home. The subjects of the study were 134 women (mean age years, range 18 to 64 years) who were employed in managerial, technical or clerical positions at the same work place. Perceived stress at work and home was self-reported on a scale from 0 (low) to 10 (high). BP, PR and the urinary rates of excretion of epinephrine, norepinephrine, cortisol and aldosterone were averaged in the daily work environment from 11 AM to 3 PM, in the daily home environment from approximately 6 PM to 10 PM, and during sleep from approximately 10 PM to 6 AM the following morning. The results showed that systolic and diastolic BP (SBP and DBP) and the rates of urinary catecholamine, cortisol, and aldosterone excretion measured in the work environment were significantly higher than corresponding measurements taken in the home environment. SBP measured at work was also positively correlated with the difference in perceived stress between work and home ( p 0.05). PR ( p 0.001) and the rate of urinary norepinephrine excretion ( p 0.05) measured in the home environment were positively correlated with stress at home. When the subjects were divided into groups based on whether the work or home environment was perceived to be most stressful, women reporting greater stress at work (n 85) had higher work SBP ( p 0.005), work DBP ( p 0.05), and sleep SBP ( p 0.005) than women who perceived the home environment to be more stressful (n 34). There were no differences in the urinary hormonal excretion rates between these perceived-stress groups. Among women with greater perceived stress at home, the home-stress score was positively correlated with sleep SBP level (r 0.310, p 0.05), its variation (SD of sleep SBP: r 0.402, p 0.01) and home pulse rate (r 0.414, p 0.01). These findings suggest that among employed women, work stress may increase ambulatory BP levels throughout the day, while home stress may induce additional sympathetic activation at home. In addition, they also show that among employed women who perceive greater stress at home than at work, higher home stress levels may also elevate sleep BP levels. (Hypertens Res 2002; 25: ) Key Words: ambulatory blood pressure, diurnal blood pressure variation, work stress, home stress, working women From the Integrative and Behavioral Cardiology Program, Zena and Michael A. Wiener Cardiovascular Institute, Mount Sinai School of Medicine, New York, USA, Decker School of Nursing and the Institute for Primary and Preventive Health Care, Binghamton University-State University of New York, Binghamton, USA, and Hypertension Center, Weil Medical College of Cornell University-New York Presbyterian Hospital, New York, USA. This study was supported by a grant (No. HL47540) from the National Heart, Lung and Blood Institute, USA. Address for Reprints: Kazuomi Kario, M.D., Ph.D., Department of Cardiology, Jichi Medical School, Yakushiji, Minamikawachi-machi, Kawachi-gun, Tochigi , Japan. kkario@jichi.ac.jp Received January 30, 2002; Accepted in revised form March 12, 2002.

2 500 Hypertens Res Vol. 25, No. 4 (2002) Introduction Average daily ambulatory blood pressure (BP) and its diurnal variation are influenced by changes in posture, mood, activity and sleep quality (1 4). Stress experienced during the day has also been reported to have an association with high BP as well as cardiovascular disease through its effects on the levels and activity of the hormones of the hypothalamuspituitary-adrenal axis and autonomic nervous system (5 7). Stress arising from the work setting strongly influences ambulatory blood pressure levels. Several researchers have demonstrated a positive association between job strain (a combination of high demands at work with low decision latitude or control) (8) and high ambulatory BP (ABP) levels in cross-sectional (9 11) and prospective studies (12, 13). These associations have been found mostly in men. However, the fact that job strain may not affect women does not necessarily mean that employment-related stressors do not have an impact on women s BP. Studies of normotensive women working in clerical and technical jobs found that women who perceived greater stress at work than home on the day they were studied had higher ambulatory systolic BP (SBP) levels during work than women who perceived more or equal stress at home on the study day and that the higher work BP values were associated with a greater proportional change in sleep-to-work catecholamine excretion (14, 15). The results of a subsequent study indicate that increased effort expended on coping with job demands may also have a large impact on women s BP at work (16). A growing number of studies show that not only ABP levels but also the patterns of diurnal BP variation are of clinical relevance (17 21), and that various factors are closely related to ABP variation (22 32). Because the perceptions of daily stress play an important role in determining these levels and variations, there is an increasing need to understand the role of stress perceptions on the inter-relationships of stress-related vasoactive hormone levels and BP variation. Therefore, the purpose of this study was to evaluate the relationships among perceived stress (at work and home), ABP, pulse rate (PR) and vasoactive hormones (epinephrine, norepinephrine, cortisol and aldosterone) in women employed outside the home. Subjects Subjects and Methods The subjects of this study were 134 healthy women, aged from 18 to 64 years. They were employed in various managerial, technical or clerical jobs at a major medical center in New York City. All worked a day shift (i.e., 9 AM 5 PM). The women were volunteers who had never been previously diagnosed with hypertension. They had to meet several criteria to be eligible for study. Subjects were excluded if they Table 1. had cardiovascular disease or diabetes mellitus, were on prescription drug therapy of any kind, were pregnant or obese (defined as having greater than 40% of body mass as fat as determined from skinfold measurements), or exhibited significant premenstrual syndrome symptoms (as defined by clinical treatment for same). Each signed an informed consent form approved by the Institutional Review Board of Cornell University Medical Center prior to participation. Selected demographic characteristics of the study subjects are shown in Table 1. Procedures Selected Characteristics of Study Sample (N 134) Characteristic X SD Age (years) BMI (kg/m 2 ) Ethnicity (%) White 42 Black 27 Asian/Hispanic 31 Married (%) 41 With children (%) 46 Menstrual status (%) Follicular phase 55 Luteal phase 36 Postmenopausal 09 Perceived stress score Work Home Total Menstrual status on the day the subject was studied. The procedures used to collect the data for this study are similar to those reported by James et al (15). At the beginning of their workday (between 8AM and 9AM) the subjects arrived at the Hypertension Center, where they completed several questionnaires, had anthropometric measurements taken and were fitted with a Spacelabs (Redmond, USA) ambulatory monitor. This device has been previously described and validated (33). The monitor was calibrated to a mercury column, and was considered accurate when 5 consecutive readings agreed to within 5 mmhg with simultaneous auscultated measurements taken by a trained technician using a stethoscope placed just distal to the BP cuff (34). The monitor was programmed to take readings every 15 min from 8 AM to 10 PM and every 30 min from 10 PM to 8 AM the following day. Just prior to the monitor hook-up, body composition was assessed from six skinfold thicknesses and circumferences around the upper arm, waist and chest. Height, weight and frame size (small, medium and large) were also measured. Demographic data, medical history and information concern-

3 Kario et al: Ambulatory Blood Pressure and Stress in Women 501 ing life and daily stress were also collected at this time. The body mass index was calculated as weight (kg)/ [height (m)] 2. Following the hook-up, the subjects were given a 3-l polyethylene bottle and instructed on the collection of urine for the assay of several hormones (see below). After all the procedures were completed, the subjects went to work. The length of time required to complete the procedures was about 40 min. Approximately 1 to 2 h after completion of the ambulatory monitor hook-up procedures (at approximately 11 AM), the subjects were called at their workplace by the project nurse and asked to go to the bathroom and empty their bladder. They were told not to collect this urine specimen, but to collect all subsequent urine for the next 4 h and to bring the collection back to the Hypertension Center. The time of the call was recorded by the nurse and represented the beginning of the work period for the purpose of this study. Then, just prior to 3 PM (the end time for the 4-h urine collection at work) the subjects were again contacted at their work place to remind them to return their collected urine to the Hypertension Center. Upon arriving at the Center, the subjects were requested to go to the bathroom and empty their bladder one final time in their work polyethylene bottle. The time of this last collection was recorded and represented as the end of the work period. At this time, the subjects were given two additional 3-l polyethylene bottles for urine collections at home in the evening, and for the following morning (overnight). They were instructed that when they arrived home (at approximately 6 PM), they were to urinate (but not collect the specimen) and note the time. This was the start of their home period. They were told to then collect all their urine samples until they went to bed (at approximately 10 PM), following the same procedure as they had followed at work. The last urination before going to bed (sleep), was collected in the home bottle and the time was recorded. This time represented the end of the home period and the beginning of the overnight (sleep) period. Finally, the subjects were instructed to collect their first urination upon awakening in the morning (at approximately 6 AM) into the remaining empty polyethylene bottle, noting the time. This time denoted the end of the sleep period. These home and sleep urine samples were returned to the Hypertension Center, along with the blood pressure monitor in the morning following the final urine collection. The times were checked and the subjects were interviewed to verify the times. Based on the urine collection times, three contrasting daily environments were defined: work (11 AM to 3 PM), home (approximately 6PM to 10PM) and sleep (approximately 10 PM to 6 AM). The timed urine samples were collected in 0.5 g of sodium metabisulfite (35). The total volume of each sample was measured (to the nearest ml) and the length of time of the collection (to the nearest min) was recorded when the urine specimens were returned. Three 5-ml aliquots were taken from each sample and frozen to 30ºC immediately after collection and prior to the hormonal assays. Epinephrine and norepinephrine were assayed in the Clinical Research Center Laboratory at the Weill Medical College of Cornell University using HPLC with electrochemical detection (36). Cortisol was determined using a solid phase 125 I radioimmunoassay (37) and aldosterone was also quantified by radioimmunoassay (38). Cortisol and aldosterone were assayed in the SCOR Laboratory of the Hypertension Center of the Medical College. For the analysis, the catecholamines, cortisol and aldosterone levels were expressed as rates of excretion. The rates of catecholamine excretion (ng/min) were calculated by multiplying the measured concentration (ng/ml) by the urine production rate (ml/min). Similar calculations were also made for the cortisol and aldosterone measures, but with the rates of excretion being expressed as µg/24 h. In order to compare the BP and PR values with the average excretion rates in each environment, the mean pressures at work (11 AM to 3 PM), home (approximately 6 PM to 10 PM), and during sleep (approximately 10 PM to 6 AM) were calculated. On average, there were 15 measurements per urine collection period. Before calculating the means, artifactual BP readings were removed from further analysis by inspection based on previously published criteria (39). The average awake BP was also calculated from the total number of pressures taken during the day while awake, not just those taken during the work and home urine collection periods. Assessment of Perceived Stress The perception of the stressfulness of the work and home environments on the day of study was evaluated using a score from 0 (low) to 10 (high) as in our previous work (14, 15). The subjects were asked to report their perceived stress only for the periods over which urine was collected at work and home. The total stress score was defined as the sum of the work and home scores, and a work home stress difference was determined by subtracting the home score from the work score. To determine the effects of the pattern of experienced daily stress on the biological parameters, the total number of subjects were divided into two groups based on the difference in the reported perceived stress scores, as in our previous work (14, 15). The groups were designated workstressed (work-stress score home-stress score; n 85) and home-stressed (work-stress score home-stress score; n 34) in the analysis. While there was a marked difference in the average work- and home-stress scores between the 2 groups (by definition), it is interesting to note that there was no difference in the total daily stress scores. Statistical Analysis All results are presented as the mean SD. Comparison between the work- and home-stressed groups was made using

4 502 Hypertens Res Vol. 25, No. 4 (2002) Table 2. Blood Pressure, Pulse Rate and Hormonal Levels in Different Daily Settings (N 134) Characteristic Daily setting Work Home Awake Sleep Ambulatory SBP (mmhg) , Ambulatory DBP (mmhg) , Ambulatory pulse rate (bpm) Urinary epinephrine (ng/min) 4.5 ( ) 2.5 ( ), NA 1.1 ( ) Urinary norepinephrine (ng/min) 23 (12 43) 19 (9.1 38), NA 9.8 (5.1 19) Urinary cortisol (µg/24 h) 23 (11 48) 10 (4.3 23), NA 17 (8.2 35) Urinary aldosterone (µg/24 h) 5.5 (2.4 13) 2.9 ( ) NA 2.5 ( ) Geometric means (95% confidence interval) are shown for the urinary measures. p vs. sleep values. p 0.01, p vs. work values using paired Student s t-test. NA, not available. Table 3. Demographic Comparisons between the Work- Stressed (N 85) and Home-Stressed (N 49) Women Characteristic X SD Work-stressed Home-stressed Age (years) Body mass index (kg/m 2 ) Ethnicity (%) White Black Others (Asian or Hispanic) Status of marriage and children (%) Married With children Single with children Managerial work (%) Stress score Work Home Total Menstrual status (%) Follicular phase Luteal phase Postmenopause Research professor, medical record coordinator, health administrator, laboratory coordinator, system manager, clinical psychologist, manager, or physician. p Table 4. Blood Pressure, Pulse Rate and Hormonal Comparisons between the Work-Stressed (N 85) and Home- Stressed (N 49) Women Characteristic X SD Work-stressed Home-stressed Systolic BP (mmhg) Work Home Sleep Diastolic BP (mmhg) Work Home Sleep Pulse rate (bpm) Work Home Sleep Urine epinephrine (ng/min) Work 4.5 ( ) 4.6 (2.1 10) Home 2.7 ( ) 2.3 ( ) Sleep 1.2 ( ) 1.0 ( ) Urine norepinephrine (ng/min) Work 21 (11 42) 25 (15 42) Home 18 (8.7 37) 19 (9.7 39) Sleep 9.7 (5.1 19) 9.9 (5.4 18) Urine cortisol (µg/24 h) Work 21 (10 45) 26 (12 54) Home 11 (4.3 26) 9.0 (4.4 18) Sleep 17 (7.8 38) 17 (9.0 30) Urine aldosterone (µg/24 h) Work 5.6 (2.5 13) 5.4 (2.1 14) Home 2.9 ( ) 2.8 ( ) Sleep 2.6 ( ) 2.3 ( ) Geometric mean (95% confidence interval) of urinary measures are shown. p 0.05, p Student s t-tests. Comparison among the different periods within the same group was made using the paired Student s t-test. Pearson s coefficients were calculated to determine associations among the variables. Correlations were evaluated in the total sample and by stress group. Partial correlations adjusting for stress perception were also calculated to evaluate the mediating effects of these variables on the associations between the hormones and BPs or PRs. Multiple linear regression analysis was used to test the difference in the slope of the relationship of BP, PR, and hormones to stress (home or work) between the work-stressed and homestressed groups. Differences and associations were considered statistically significant at p 0.05.

5 Kario et al: Ambulatory Blood Pressure and Stress in Women 503 Table 5. Correlations between Perceived Stress Scores and Blood Pressure, Pulse Rate and the Hormones 1 among the Work- Stressed Women (N 85) Parameters Work-stress Home-stress Total stress Work home score score score score difference 2 Systolic BP Work Home Sleep Diastolic BP Work Home Sleep Pulse rate Work Home Sleep Urinary epinephrine Work Home Sleep Urinary norepinephrine Work Home Sleep Urinary cortisol Work Home Sleep Urinary aldosterone Work Home Sleep Before calculation of the correlation coefficients, the urinary hormonal measures were log-transformed. 2 The work home stress score difference was calculated as the work-stress score minus the home-stress score. p 0.05, p Total Group Results Table 2 shows the average levels of ABP and the urinary hormone excretion rates during the work-, home-, awakeand sleep-periods in the total group of women. As indicated, ambulatory SBP and diastolic BP (DBP) levels and the rates of catecholamine, cortisol, and aldosterone during the work period were significantly higher than those during the home period. In examining the correlations among theses measures in the group as a whole, work SBP correlated positively with the work home stress score difference (r 0.180, p 0.05), while home PR correlated with the absolute home-stress score (r 0.278, p 0.001). The rate of norepinephrine excretion was positively correlated with the absolute homestress score (r 0.190, p 0.05). Home PR was positively correlated with excretions of norepinephrine (r 0.199), epinephrine (r 0.174), and cortisol (r 0.218) (all p 0.05), after controlling for the effects of perceived home stress. Finally, there were no significant correlations between ABP and the rates of urinary hormone excretion. Work-Stressed vs. Home-Stressed Groups Tables 3 and 4 compare selected demographic characteristics, ABP levels and hormone excretion rates between the work-stressed and home-stressed groups. As indicated, there were no significant differences between the stress groups in the proportion of women of different ethnicity, women with children or married women. Work SBP ( p 0.005) and DBP ( p 0.05) and sleep SBP ( p 0.005) were significantly higher in the work-stressed group, while there were no significant differences in the levels of urinary hormone levels during each period (work, home, and sleep) between the two groups. Associations of Perceived Stress with ABP and Urinary Hormones Tables 5 and 6 show the correlations between stress with ABP and urinary hormone levels in the work-stressed group and the home-stressed group. In the work-stressed group, the home-stress score was positively correlated with sympathetic parameters (PR, urinary catecholamine excretion rate) during the home period, while the work-stress score had had no association with any of the parameters measured (Table 5). However, after controlling for the effect of home stress,

6 504 Hypertens Res Vol. 25, No. 4 (2002) Table 6. Correlations between the Perceived Stress Scores and Blood Pressure, Pulse Rate and Hormones 1 among the Home- Stressed Women (N 49) Parameters Work-stress Home-stress Total stress Work home score score score score difference 2 Systolic BP Work Home Sleep Diastolic BP Work Home Sleep Pulse rate Work Home Sleep Urinary epinephrine Work Home Sleep Urinary norepinephrine Work Home Sleep Urinary cortisol Work Home Sleep Urinary aldosterone Work Home Sleep Before calculation of correlation coefficients, the data of urinary measures were log-transformed. 2 The work home stress score difference was calculated as the work-stress score minus the home-stress score. p 0.05, p home PR showed a significant positive correlation with excretion of norepinephrine (r 0.231) and cortisol (r 0.221) (both p 0.05). In the home-stressed group, home-stress scores were positively correlated with the sleep SBP level (r 0.310, p 0.05) and home PR (r 0.414, p 0.01), while work-stress scores again had no association with any of the parameters measured (Table 6). Multiple linear regression analysis revealed that the slope of the relationship between the work home score difference and sleep SBP level between the work-stressed and home-stressed groups was significant ( p 0.036). Blood Pressure Variability Further analysis evaluating the relationship between BP variability and perceived stress showed that the total stress score was positively correlated with the SD of the ambulatory awake SBP (r 0.170, p 0.05), and that perceived work stress was positively correlated with ambulatory awake DBP (r 0.251, p 0.01). In the work-stressed group, the work home stress difference was negatively correlated with the SD of home SBP (r 0.251, p 0.05), while in the home-stressed group, the home-stress score was positively associated with the SD of sleep SBP (r 0.402, p 0.01) and with the SD of sleep DBP (r 0.323, p 0.05). Discussion The results show that the pattern of perceived stress during the day is related to the level and variation of ABP measured at work, home and during sleep in women employed outside the home. In addition, the pattern of perceived stress also affects the relationship between vasoactive hormone levels and BP. Overall work BPs were slightly higher than home BPs, and the rates of excretion of the catecholamines, cortisol, and aldosterone were also higher at work than at home. The higher catecholamine levels may partly reflect higher sympathetic activation while at work than at home among the women studied. Previous studies have reported that catecholamine levels decreased sharply after leaving work, while in working women, the levels increased or did not change after work, suggesting that home stress may still continue to affect sympathetic activation at home (40, 41). It is unclear whether work stress was higher or home stress was lower in our study population when compared with these previously reported populations. The highly stressful work environment in New York City which would lead to a greater disparity between the work and home environments may partially explain the difference in results between our study and those

7 Kario et al: Ambulatory Blood Pressure and Stress in Women 505 employing populations in Sweden (40) or North Carolina (41). However, these differences in neurohumoral factors between work and home periods may partly reflect diurnal changes in these factors, because the time of the work urine collection (11 AM to 3 PM) may include morning surges in cortisol and aldosterone (42). Work SBP was significantly positively correlated with the work home stress score difference. When the subjects were divided into work- and home-stressed groups according to the perceived stress score, work SBP and DBP and sleep SBP were significantly higher in the former group than in the latter group, while there were no significant differences in neurohumoral factors between the two groups. Thus, perceived work stress may increase the ABP during work in women, as we found in our earlier studies (14, 15). In contrast, in our previous study, among women who perceived work as more stressful, there was a positive association between the change in catecholamine excretion and the change in ABP from either work or home to sleep (15). Among the women in the present study, no relationship between ABP and catecholamine levels was found. The home-stress score was positively associated with home PR ( p 0.001) and the home urinary norepinephrine excretion rate ( p 0.05), suggesting that sympathetic activation at home is related to perceived home stress. The association between home PR and catecholamine excretion was essentially unaffected by controlling for the effect of home stress, which suggests that home stress has a similar effect on both measures. Furthermore, in the home-stressed group, the home-stress score was positively correlated with the sleep SBP level (r 0.310, p 0.05) and its variation (SD of sleep SBP: r 0.402, p 0.01). This may indicate that stress perceived at home several hours before sleep may affect sleep quality. We previously found that sleep BP was positively associated with sleep physical activity assessed by actigraphy (4). Because there is a positive association between poor sleep quality (frequent arousal) determined by polysomnography and increased sleep physical activity detected by actigraphy, actigraphs are now widely used to assess sleep quality (43). We recently found that sleep BP was positively correlated with the sleep/awake activity ratio calculated from objective physical activity assessed using actigraphy (4). This result indicates that nocturnal BP is partly determined by sleep quality. Thus, perceived home stress may have a carryover effect that increases sleep BP levels by decreasing sleep quality. Increased variation of SBP may also reflect an increased change of sleep status, which in turn may reflect poor sleep quality. In studies like the present one, which attempt to examine the association between psychological stress and biological variables, precise assessment of the degree of stress is difficult, since it relies on the subjective reporting of different subjects. To minimize this problem, we used a relative classification of stress (a work-stressed and a home-stressed group) based on the ratio of the work-stress to the homestress scores. There was no significant difference in the total stress score (the home-stress plus the work-stress scores) between the home-stressed and work-stressed groups. No control ABPs were measured under the non-stressed condition or different stress conditions in this cross-sectional study. In addition, because of the relatively small size and select nature of the sample of women in this study, caution should be used in extrapolating the results to the general population. 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