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From the Department of Epidemiology and Public Health, University College London, UK.
Address for correspondence: Andrew Steptoe, Department of Epidemiology and Public Health, University College London, 1-19 Torrington Place, London WC1E 6BT, UK. Tel: (44) 20 7679 1804 Fax: (44) 20 7916 8542 E-mail: a.steptoe{at}ucl.ac.uk
| ABSTRACT |
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MATERIALS AND METHODS: Data were analyzed from 227 men and women aged 47 to 59 years from the Whitehall II epidemiological cohort. A psychosocial adversity and vulnerability index (PAVIX) was constructed from high scores on measures of job demands, neighborhood stress, and financial strain, low emotional support, limited social networks, low active coping, and low sense of control.
RESULTS: The measures making up the PAVIX were relatively independent of one another. Scores on the PAVIX were greater in lower SEP participants, and in single, separated, or divorced than married participants. The PAVIX was positively associated with psychological distress, depression, hopelessness, sleep problems, hostility, low self-esteem and loneliness, independently of age, sex, SEP, and marital status. There were no associations with health behaviors, but relationships were observed with glycohemoglobin, plasma fibrinogen, plasma viscosity, and body mass (women), that were again independent of covariates. Individuals with high PAVIX scores also reported impaired health-related quality of life.
DISCUSSION: The accumulated burden of life stress coupled with limited protective psychosocial resources is associated with adverse psychological, biological, and quality of life outcomes. This integrated approach to the investigation of psychosocial factors may prove valuable in understanding etiological processes.
Key Words: psychosocial factors, stress, socioeconomic position, quality of life, coronary heart disease.
Abbreviations: SEP = socioeconomic position;; BMI = body mass index;; CRP = C-reactive protein.
| INTRODUCTION |
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Combining psychosocial measures relevant to chronic disease is not new, because different sources of stress have been aggregated to assess the influence of cumulative adversity in previous studies (5,6). For example, Evans and English (7) recently assessed an array of physical stressors such as noise and crowding, and interpersonal stressors like family conflict and community violence, in children from low- and middle-income families. The extension of this approach to include both cumulative adversity and unfavorable psychosocial resource profiles has been more limited, although there are instances in which measures of life stress have been combined with social supports or coping strategies to assess stress buffering effects (8,9). The evidence that vulnerability factors such as low social support act in a buffering capacity is equivocal (10), so we decided to create a single index incorporating both measures of exposure to adversity and the absence of protective social and psychological resources.
This study involved middle-age employed men and women, and this dictated the ways in which adversity and vulnerability factors were operationalized. Exposure to chronic adversity was assessed by combining markers of potential stress from three sourceshigh job demands, financial strain, and neighborhood stress. Each of these has individually been related to biological risk factors, impaired quality of life, and increased incidence of serious disease outcomes (11,12). We reasoned that the impact of these adversities would be accentuated if they are combined with a lack of protective social and psychological resources. Both emotional support and social networks are associated with favorable biological risk profiles and survival in prospective studies (13). Consequently, low emotional support and limited social networks constitute vulnerability factors. Evidence relating psychological characteristics with objective health outcomes is less conclusive. However, it is widely acknowledged that coping responses are critical to adjustment to life stress (5,14). Aspinwall and Taylor (15) have argued that proactive coping facilitates accommodation to the hazards of everyday life, and that an active, problem-solving approach to the management of stressors may be generally more adaptive than avoidant coping strategies. Another relevant psychological characteristic is fatalism, or strong beliefs in the play of chance. Low perceived control is a determinant of heightened stress responsivity and poor adaptation (16). We therefore reasoned that low preferences for active coping, and strong beliefs in chance, are psychological vulnerability factors.
The main objective of this research was to determine whether a combined index of the burden of adversity and vulnerability would be a useful analytic tool for the investigation of psychosocial factors and health. A psychosocial adversity and vulnerability index (PAVIX) was constructed by summing high ratings of job demands, financial strain, neighborhood stress, and chance beliefs, and low scores on measures of emotional support, social networks, and active coping responses. We examined the composition of the index to determine whether particular measures or combinations of measures were selectively represented among participants with high scores, or whether each measure was equally represented. We predicted that scores on the PAVIX would be greater in people of lower SEP, since a number of the individual constituents have previously been associated with SEP (17,18).
The relationship between the PAVIX and the following four classes of outcome was investigated: (1) psychological well-being. It was predicted that a higher burden of psychosocial adversity and vulnerability would be positively associated with heightened perceived stress, distress as measured with standardized psychiatric measures, sleep problems, and with psychological characteristics that might in turn compromise health, including low self esteem, greater loneliness and hostility; (2) health behavior. If behavioral factors are responsible in part for the impact of negative life experiences on health, then PAVIX scores should be positively related to smoking, alcohol consumption and lack of physical activity; (3) biological risk factors. We hypothesized that scores on the PAVIX would be positively associated with body mass, waist-to-hip ratio, glycohemoglobin (an index of impaired glucose homeostasis), markers of vascular inflammation (fibrinogen and C-reactive protein), and rheological measures implicated in hemostasis (plasma viscosity and blood viscosity); and (4) health-related quality of life. It was hypothesized that the PAVIX be positively associated with impaired quality of life in multiple domains.
Low SEP is associated with several of these outcome variables (1921). The relationship between vulnerability and adversity and the four sets of outcomes were therefore adjusted for SEP as defined by occupation, so as to evaluate independent associations.
| MATERIALS AND METHODS |
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Measures of Psychosocial Adversity and Vulnerability
The psychosocial adversity and vulnerability index (PAVIX) consisted of three measures of chronic stress (job demands, financial strain, and neighborhood stress), and four measures of psychosocial resources (emotional social support, social network size, sense of control, and use of active coping).
Job demands were assessed with a measure developed from the demand/control model, as described by Bosma et al. (24). Four items (eg, "Do you have to work very intensively?") were administered, each of which was rated on a 4-point scale ranging from 0 (often) to 3 (never/almost never). Scores were converted to a scale from 0 to 100, in which 100 indicates maximum demands. The Cronbach
for the scale in this study was 0.70.
Financial strain was assessed with an adaptation of a widely used economic strain measure (25). This measure assesses difficulty paying ones bills, being able to replace items such as furniture or a car when needed, and being able to provide for ones family in terms of food, clothing, and medical care. Eight items were presented, with response options ranging from 1 = no difficulty to 3 = very great difficulty (Cronbach
=0.86).
Neighborhood stress was measured with the neighborhood problems scale, an inventory assessing exposure to community-wide stressors (26). Participants were asked to indicate the degree to which 10 neighborhood conditions (eg, litter in the streets, noise from traffic) constituted a problem, with ratings ranging from 1 = not a problem to 3 = serious problem. The internal consistency of the scale in the present sample was 0.74.
Emotional social support and social networks were both measured using the Close Persons Questionnaire (27). For emotional support, respondents were asked to designate the single individual to whom they had felt closest over the previous 12 months, and then to rate a series of statements concerning the support provided by this relationship on 4-point scales from not at all to a great deal. Eight items contributed to the emotional support scale (eg, "How much in the past 12 months did this person make you feel good about yourself?" Cronbach
=0.86), with higher scores indicating greater support. Social networks were measured with a series of questions concerning contact with family, friends, and relatives. Respondents were given points toward a social isolation score if they lived alone, if they had no relatives outside their household, never visited or were never visited by relatives or friends, or had no relatives or friends who they saw at least once per month. These scores could range from 0 (no social isolation) to 3 (maximum isolation); 46.6% of participants had social isolation scores of 1 to 3, so they were designed as the high social isolation group.
Sense of control was assessed using the chance locus of control scale developed by Levenson (28). This consisted of eight items (eg, "To a great extent my life is controlled by accidental happenings") rated on 6-point scales ranging from 0 (strongly disagree) to 5 (strongly agree). The alpha for the scale was 0.76. Ratings could range from 0 to 40, with higher scores indicating greater belief in chance control.
Active coping was measured with the four-item active coping scale from the COPE inventory of coping strategies (29). Each item (eg, "I concentrate my efforts on doing something about it") was rated on a 4-point scale ranging from 1 (never) to 4 (always). Average scores were calculated (range: 14), with higher values indicating greater use of active coping (Cronbach
= 0.71).
Additional Psychosocial Measures
Subjective SEP was assessed with the "ladder" measure described by Adler et al. (30). Participants were shown a drawing of a ladder with 10 rungs, representing where people stand in society. They were told that at the top of the ladder are the people who are best offthose who have the most money, most education, and best jobs. At the bottom are the people who are the worst off, have the least money, least education, and the worst jobs or no job. They were asked to place themselves on the rung on which they felt that they stood.
Perceived stress was assessed with the 10 item Perceived Stress scale (31). Respondents were asked how they had thought or felt over the past month, and each item (eg, "How often have you felt that you were on top of things?") was rated on a 5-point scale ranging from 0 = never to 4 = very often. Ratings were summed so that scores could range form 0 to 40 (Cronbach
= 0.87).
Psychological distress was assessed with the General Health Questionnaire 30 (GHQ 30), a well-established screening questionnaire for psychiatric disorder suitable for population studies (32). The Cronbach
in the present sample was 0.93. The standard scoring system was used, so scores could range 0 to 30, with higher scores indicating greater distress. To assess specific associations with depressive symptoms, we used the method described by Stansfeld et al (33) of selecting four items from the GHQ 30 that are also present in the depression subscale of the GHQ 28, scoring them on a Likert scale from 1 to 4. The Cronbach
for this GHQ depression scale was 0.89.
Hopelessness was assessed with the two-item scale used in the Kuopio study (34). Each item (eg, "The future to me seems to be hopeless, and I cannot believe that things are changing for the better"), each of which was scored on a 5-point scale from absolutely disagree to absolutely agree. Ratings were averaged to generate a hopelessness score ranging from 1 to 5.
Sleep problems were assessed with the sleep problems scale described by Jenkins et al. (35). This consists of four items, assessing how often in the past month the individual has woken up several times in the night, had trouble staying asleep etc. There were six response options, ranging from 0 = not at all to 5 = 22 to 31 days. The total was computed, so scores could range from 0 to 20. The measure has been used extensively in previous research on healthy populations and patient groups. The Cronbach
in the present sample was 0.73.
Self-esteem was measured with the 10 item Rosenberg scale (36). Items were rated on a 4-point scale, and scores could range from 0 to 30 with higher ratings indicating greater self-esteem. The Cronbach
was 0.89.
Cynical hostility was assessed with a 22-item version of the Cook-Medley scale (37). The scale primarily taps cognitive components of hostility including negative beliefs about and attitudes toward others, including cynicism and hostile attributions. Scores could range from 0 to 22, with higher ratings indicating greater hostility. The Cronbach
for this scale was 0.83.
Loneliness was assessed with the revised UCLA Loneliness scale (38). This consists of 20 items (eg, "I feel that no one knows me really well"), and participants were asked to rate how often they felt that way on a scale from 1 = never to 4 = often. Ratings were summed to produce a total score ranging from 20 (low) to 80 (high). The internal consistency in this study was 0.91.
Biobehavioral Measures and Quality of Life
The measures of health behavior were based on those used in earlier reports from the Whitehall II study (17). Participants were asked whether they were current smokers and a dichotomous score was used to indicate smoking status. Alcohol intake was measured by the number of servings of spirits, wine, and beer consumed in the past week. Physical activity was assessed with two measures. First, participants were asked how many times per week they engaged in vigorous activity of sufficient intensity to make them breathless. Second, total walking time was computed from separate estimates of walking on weekdays and the weekends.
Physical measurements included height, weight, and waist and hip circumference, assessed with standard methods (23). Waist-to-hip ratio and body mass index (BMI) were computed. Information concerning hormone replacement treatment was collected from women.
Measures from plasma were taken from blood drawn after 30 minutes of rest. Venous blood samples were collected in citrated (0.109 mol/L; 9:1 v:v) and K2-EDTA (1.5 mg/ml) tubes, centrifuged at room temperature, and the supernatant plasma was snap frozen at -70°C within 1 hour. Plasma glycohemoglobin was assayed using boronate affinity chromatography, a combination of boronate affinity, and liquid chromatography at a laboratory that conforms with the Diabetes Control and Complications Trial (DCCT) standardized method (39). Clottable fibrinogen was measured from citrated frozen samples by an automated Clauss assay in a MDA-180 coagulometer (Organon Teknika, Cambridge, UK) using the manufacturers reagents and the International Fibrinogen Standard (40). Hematocrit was assessed immediately after each blood sample was drawn using a microhematocrit centrifuge and reader (Hawksley Gelman, Lancing, Sussex, UK).
C-reactive protein was detected using a sensitive, two-site ELISA with antibodies from Dako diagnostics (Ely, Cambs, UK), as detailed previously (41). The interassay and intraassay coefficients of variation (CV) were less than 10%. Plasma viscosity was measured in the K2-EDTA samples using a semi-automated capillary viscometer (Coulter) at 37°C. Blood viscosity was calculated from hematocrit and plasma viscosity as described by Lowe et al. (42).
Quality of life was assessed using the short form 36 Health Survey (SF-36). Normative data for the general UK population are available (43), and the measure has also been applied to the complete Whitehall II cohort (20). Seven dimensions of functioning were assessed: physical functioning or activities of daily living, role impairment owing to physical problems, role impairment caused by emotional problems, social functioning, mental health, general perceptions of health, and vitality or energy. Scores were coded and transformed to a scale in which 0 = worst possible health and 100 = best possible health.
Procedure
Psychosocial measures were completed before the laboratory session, and took approximately 30 minutes to complete. Participants attended individually either in the morning or afternoon for the laboratory session. They were instructed not to have drunk any caffeinated beverages or to have smoked for at least 2 hours before the testing, and not to have consumed alcohol or exercised on the evening before or the day of testing. Those who had recently or currently had from any minor illness, or had used over-the-counter antiinflammatory or antihistamine medication over the previous 2 days, were rescheduled. After anthropometric measurement, a venous cannula was inserted and the participant rested quietly for 30 minutes. A blood sample then was drawn for analysis of inflammatory, hemostatic, and rheological markers.
Statistical Analysis
Complete data for all seven components of the PAVIX were available for 227 participants, so analyses were restricted to these individuals. They did not differ from participants with missing data in age, sex, or grade of employment. The PAVIX was constructed by dividing scores on each of the seven constituent measures by median split into high and low categories, except for social isolation which was categorized as detailed. The division points for the scales were as follows: job demands (6675), financial strain (89), neighborhood stress (1314), emotional support (2324), chance control (1516), and active coping (2.52.75). The negative categories were then summed; one unit was added to the PAVIX for high job demands, high financial strain, high neighborhood stress, social isolation, low emotional support, high chance control beliefs, and low use of active coping methods. Each individual had a single score between 0 and 7 on the PAVIX, with higher scores reflecting greater burden of psychosocial adversity and lack of psychosocial resources.
Associations between the burden of psychosocial adversity, objectively defined SEP, and sex, were assessed by comparing PAVIX scores for participants in the higher, intermediate, and lower grade of employment groups, and by comparing men and women using analysis of variance. Associations with subjective SEP were assessed by correlating PAVIX scores with ladder ratings, and by comparing PAVIX scores in individuals in the three tertiles of ladder ratings using analysis of variance. For the remaining analyses, participants were divided on the basis of PAVIX scores into low (02), medium (3, 4), and high (57) categories. These three categories were then compared on psychosocial, biobehavioral, anthropometric, and quality of life measures using analysis of variance for linear trends and
2 as appropriate. Sex was included as a factor in all analyses, so as to assess possible interactions between sex and PAVIX category. The pattern of statistical findings was similar when the PAVIX was modeled as a continuous variable in regression analyses. The categorical results are presented here as being more readily comprehensible. Plasma viscosity results were skewed, log-transformed before analysis, and geometric means are presented. Factors known to be associated with biological risk markers were included as covariates, as detailed in the Results section.
The possibility that associations between PAVIX scores and outcomes could be caused by the dominant influence of one particular component was tested in two ways. First, we assessed the extent to which high scores on each component contributed to the total PAVIX measure. Second, when associations between the PAVIX and any of the principle dependent variables was significant, analyses were repeated with each of the component measures removed in turn from the composite PAVIX. If the removal of any one of the seven components made a difference to the pattern of results, this would indicate that this component was primarily responsible for associations with the outcome in question. Data are presented as means ± standard error of the mean (SEM).
| RESULTS |
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Psychosocial Adversity and Vulnerability Index
Mean scores on the PAVIX averaged 3.2 and were normally distributed, including the full possible range from 0 to 7. Most (115 or 50.7%) participants reported high scores on three or four of the measures of adversity and vulnerability, so they were classified into the medium PAVIX category. Thirty-six (15.9%) had scores of 5 to 7, and 76 (33.5%) had fewer than three high scores, so they were allocated to the low PAVIX category. PAVIX scores did not vary with age or sex.
The averages of each component measure for participants in the low, medium, and high PAVIX categories are shown in Table 1. As expected, there were significant linear effects for all seven measures [F (2, 221) = 7.23 to 33.4, all p< 0.001]. Participants in the high PAVIX category reported greater job demands, financial strain, and neighborhood stress, less emotional support, greater social isolation, stronger beliefs in chance, and less use of active coping than respondents in the lower PAVIX categories. All seven components were equally represented at each level of the total PAVIX. For example, the proportion of high PAVIX (57) respondents who scored above the median for each component measure was as follows: high job demands 25.6%, high financial strain 24.2%, high neighborhood stress 27.9%, low emotional support 27.7%, high social isolation 28.4%, strong beliefs in chance 27.8%, and little use of active coping 28.7%. The proportion of low PAVIX (02) participants who scored below the median for the component measures was: low job demands 24.4%, low financial strain 18.5%, low neighborhood stress 18.0%, high emotional support 16.8%, low social isolation 14.7%, weak beliefs in chance 15.7%, and extensive use of active coping 9.9%. The seven components were relatively independent of one another; correlations ranged from -0.21 to +0.20, with the highest negative association being between financial strain and active coping, and the highest positive association between neighborhood stress and chance beliefs. The internal consistency of the PAVIX was low (
= 0.12), reflecting the independence of the components.
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Scores on the ladder measure of subjective SEP averaged 6.61, and ranged from 1 to 9.5. Ladder SEP ratings were negatively correlated with PAVIX scores (r= -0.25, p< 0.001). When ladder SEP ratings were divided into tertiles, the mean PAVIX score was 3.57 ± 0.18, 3.27 ± 0.17, and 2.93 ± 0.15 across the low, medium, and high subjective SEP groups [F (1, 220) = 3.68, p= 0.008]. Thus the burden of psychosocial adversity and vulnerability was associated with both objective and subjective indices of socioeconomic position.
PAVIX scores differed with marital status [F (2, 227) = 11.7, p< 0.001]. Mean scores were lower for married participants (2.93) compared with those who were single (4.05) or divorced/separated/widowed (3.65); 32.5% of the single and 20.6% of the divorced/separated/widowed were in the high PAVIX category, compared with 11.4% of the married participants (
2 = 5.80, p= 0.016). These patterns did not differ in men and women.
Psychological Factors
The associations between scores on the adversity and vulnerability index and psychological factors are summarized in Table 2. Age, sex, grade of employment, and marital status were included as covariates. The three PAVIX categories differed on all measures of psychological distress, including the perceived stress scale [F (2, 220) = 33.0, p< 0.001], the GHQ 30 [F (2, 220) = 6.09, p= 0.003], the GHQ depression scale [F (2, 220) = 6.60, p< 0.001], and the hopelessness scale [F (2, 219) = 4.45, p= 0.003]. For all measures, psychological distress was greatest in the highest PAVIX category, and least in participants with low PAVIX scores. These effects remained significant in analyses of the PAVIX in which each of the components was omitted in turn from the composite measure. High levels of adversity and vulnerability were also associated with low self-esteem, greater hostility, and greater loneliness [F (2, 220) = 8.98, 5.29, and 16.9, respectively, p< 0.001]. It therefore appears that the cumulative burden of adversity and vulnerability was associated with psychological distress and a profile of unfavorable psychological characteristics independently of age, sex, socioeconomic status, and marital status. There were no interactions between PAVIX category and sex in these analyses.
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Biobehavioral Factors
The proportions of participants with low, medium, and high PAVIX scores who smoked were 7.9%, 11.4%, and 5.6%, respectively (p= 0.92), indicating that the index was not associated with cigarette smoking. Participants had drunk an average of 9.60 servings of alcohol over the past week (range: 055), but this was not related to PAVIX scores; the mean number of servings adjusted for age and grade of employment was 9.64, 9.67, and 8.81 for low, medium, and high PAVIX categories respectively [F (2, 219) = 0.11, p= 0.68). The number of minutes walking per week was 346.9 (range 02520 min), and averaged 354.7, 354.2, and 268.1 in the low, medium, and high PAVIX categories [F (2, 217) = 1.24, p= 0.17]. The number of episodes of vigorous physical activity sufficient to get out of breath over the past week averaged 1.5 ± 0.2, and was also not related to PAVIX scores.
The analyses of BMI and waist circumference both showed interactions between PAVIX category and sex [F (2, 219) = 3.78 and 4.11, respectively, p< 0.025]. However, the differences in waist circumference were no longer significant after body mass index was taken into account, and there were no differences in waist-hip ratio. In the case of BMI, an association with PAVIX category was present in women but not men. In women, BMI (adjusted for age and grade of employment) averaged 24.1, 25.4, and 27.0 in the low, medium, and high PAVIX categories [F (2, 99) = 3.23, p= 0.013]. The association was not significant in men (mean BMI 26.2, 25.6, and 24.9 for the three categories).
There was a significant linear difference across PAVIX categories in glycohemoglobin [F (2, 216) = 2.52, p= 0.037]. Glycohemoglobin levels were positively associated with the adversity and vulnerability index, independently of age, sex, grade of employment, BMI, and smoking status (Table 3). A similar positive relationship was recorded for plasma fibrinogen [F (2, 214) = 7.75, p< 0.001], with an average difference of 0.40 g/L (95% CI: 0.200.61) between lowest and highest PAVIX categories, after adjustment for covariates. Both these associations remained significant when each component of the PAVIX was omitted in turn from the composite score.
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Health-Related Quality of Life
The results for the seven scales of the SF 36 included in this study are detailed in Table 4. There was no association between the PAVIX and role impairment because of physical problems. But for the other six scales, there were significant linear effects across the PAVIX categories, with lower quality-of-life ratings in those experiencing greater psychosocial burdens [F (2, 220) = 3.9215.5]. These effects were independent of age, sex, grade of employment, and marital status. The associations between the six SF 36 scales and the PAVIX remained significant when each component of the PAVIX was removed in turn from the composite score.
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| DISCUSSION |
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It is important to note that the index of psychological adversity and vulnerability had low interitem correlations and low internal consistency, indicating that the components were relatively independent. We did not, for example, find that individuals reporting high financial strain or neighborhood stress were particularly socially isolated or lacking in emotional support. Each of the items was equally represented in the high, medium, and low categories of the combined index. We also tested whether any single component of the PAVIX had a dominant influence on associations with psychological distress, impaired quality of life and biological risk, by performing analyses with each component of the composite index removed in turn.
The relationship between the PAVIX and SEP was as hypothesized. People with less privileged positions in society experience greater chronic stress from diverse sources, and have fewer protective psychological and social resources. The association was apparent using both objective and subjective indices of SEP. The overall pattern was expected, because lower SEP has previously been associated with a greater financial strain, greater neighborhood stress, social isolation, low emotional support, and low sense of control (17,26,46). Although job demands are generally rated as greater in low status work, in the Whitehall II cohort it is the higher grade civil servants who report greater job demands (17). In the light of these associations between the burden of adversity and vulnerability and SEP, all other analyses controlled for objective socioeconomic position, to determine whether the PAVIX was independently related to outcome variables.
Interestingly, the burden of adversity and vulnerability was similar in men and women in this cohort. Age was also unrelated to the PAVIX, but the narrow age range (4759 years) may be an explanation. We had anticipated that divorced, separated, or widowed participants might report greater vulnerability and adversity, because these life experiences are known to lead to strain and loss of resources (45). But single participants also had higher PAVIX scores on the psychosocial adversity and vulnerability index. The explanation is not clear. Single people lack the possibility of social support through marriage, and difficulty in establishing a life partnership might increase perceived adversity, but a selection effect cannot be ruled out.
The hypotheses relating the burden of adversity and vulnerability with psychological stress and other psychological factors were generally confirmed. Individuals scoring high on the PAVIX had greater scores on the GHQ 30, the depression subscale of the GHQ, and Kuopio hopelessness scale (Table 2). It has recently been shown in the Whitehall II cohort that the GHQ 30 predicts increased 5-year incidence of self-reported coronary heart disease and new electrocardiographic abnormalities, independently of age, grade of employment, and health behaviors (48), while the hopelessness scale predicts the progression of subclinical atherosclerosis (34). The effects observed here may therefore be significant for cardiovascular as well as mental health outcomes. There were no interactions between gender and the PAVIX in these analyses, so we did not detect any tendency for men and women to react differently to chronic adversity.
Associations between the burden of adversity and vulnerability and psychological factors such as low self-esteem, hostility, and loneliness are interesting, because these factors have in turn been linked to disturbances in neuroendocrine and autonomic function, and to health outcomes (2,49). Because this study was cross-sectional, the causal pathways are uncertain. It is possible that chronic stress coupled with ineffective coping responses and social support deficits led to distress, lowered self-esteem, loneliness, and a cynical outlook on life. Equally plausibly, however, characteristics such as hostility and low self-esteem may increase exposure to sources of chronic stress and promote social isolation.
This study found no relationship between the burden of psychosocial adversity and vulnerability and health behaviors relevant to chronic disease risk including cigarette smoking, two measures of alcohol consumption and three measures of regular physical activity. The inference is that in this sample, associations between psychosocial factors and disease risk are unlikely to be mediated through behavioral pathways. The number of cigarette smokers was small, and this reduced the likelihood of observing associations. Variations in alcohol consumption and physical activity were large, so range restriction is unlikely to be the explanation for lack of effects. However, the measures of health behavior were not comprehensive, and it is possible that more comprehensive investigation would uncover associations. We also observed very limited associations between the PAVIX and anthropometric variables. The index was positively associated with body mass in women but not men, and there were no differences in waist-to-hip ratio after body mass and SEP had been taken into account. These results are not in agreement with the hypothesis that chronic stress causes abdominal obesity (50). The range of waist-to-hip ratio and body mass index was somewhat limited, and this will have reduced the possibility of observing associations.
By contrast, higher burden of adversity and vulnerability was associated with greater glycohemoglobin concentration (Table 3). Glycohemoglobin is an indicator of impaired glucose tolerance in nondiabetic populations, and has been shown to predict all cause and cardiovascular mortality independently of other risk factors (51). The observation of a positive association between glycohemoglobin and psychosocial adversity and vulnerability is consistent with the evidence relating other indices of glucose metabolism with locus of control and social support (52, 53). It should be noted that none of the participants in this study had levels of glycohemoglobin indicative of type 2 diabetes.
We hypothesized that the burden of psychosocial adversity and vulnerability would be positively associated with concentration of the acute phase reactant CRP, a marker of the inflammatory processes underlying atherosclerosis that has been shown in prospective studies to be a robust predictor of future coronary heart disease (54). No such association was observed. Similarly, we did not uncover consistent relationships between the PAVIX and inflammatory cytokines such as IL-6 (data not shown). By contrast, fibrinogen concentration was positively associated with the PAVIX. Fibrinogen is thought to heighten cardiac risk through increasing plasma and whole blood viscosity, infiltration of the arterial wall, stimulation of atherogenic cell proliferation, and promotion of platelet aggregation (54). The positive association between the PAVIX and plasma viscosity suggests that rheological mechanisms may be significant, because they act both on atherogenesis and thrombosis (55). Importantly, these associations were independent of SEP and factors such as smoking and body mass index. Although causal conclusions cannot be drawn, the findings are consistent with the notion that the burden of psychosocial adversity and vulnerability increases cardiovascular risk through disturbances in glucose metabolism and impairment of blood flow due to red cell aggregation and increased viscosity at low sheer rates.
In the final set of analyses, we demonstrated that the PAVIX was positively associated with low ratings on several dimensions of quality of life. These relationships persisted after adjustment for SEP which is also associated with impaired quality of life (20). The findings suggest that the experience of high levels of chronic stress coupled with limited psychosocial resources may have generalized effects on health and well-being, some of which may not be identified by the specific markers of psychological distress or biological risk measured in this investigation.
A major concern in these analyses was whether associations between the index of adversity and vulnerability and outcome variables were caused by the dominant influence of one particular component. For example, life stress and social relationships have been related to psychological well-being and biological risk factors in previous studies, so might be responsible for the effects observed here. However, we found that in the analyses of psychological well-being, sleep problems, glycohemoglobin, fibrinogen, and quality of life scales, no single component was necessary for associations to be observed. When each of the seven constituents was removed in turn from the composite PAVIX, statistical effects were unchanged. The one exception to this pattern was plasma viscosity, where it emerged that all components bar one (neighborhood stress) were necessary for significant associations to emerge. These subsidiary analyses therefore strengthen the argument that combining measures of adversity and vulnerability provides incremental information about psychosocial factors that is not supplied by analyses of separate components.
There are important limitations to this analysis. The study was performed with middle-age employed men and women of white European origin without known serious health problem or disability, so results may not generalize to other groups. The items included in the PAVIX were selected pragmatically from the range of variables collected in this study, and other markers might prove more sensitive in this or other samples. We decided to sum the factors rather than generate a measure of the balance between adversities and psychosocial vulnerabilities. However, it is plausible that a balance measure would provide further insight into the associations of psychosocial factors with risk indicators. The relatively homogenous nature of the population studied led to restricted variability in some outcome measures, and stronger associations might emerge in a broader population. Nonetheless, the results show a rather consistent pattern of negative psychological, biological, and quality of life outcomes in people experiencing a high cumulative burden of chronic adversity and psychosocial vulnerability. This approach may prove useful in future research through providing a more integrated perspective on the global experience of strain than is achieved by the measurement of single psychosocial factors.
| ACKNOWLEDGMENTS |
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Received for publication November 5, 2002.
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