Job hassles and cardiovascular reaction patterns among urban bus drivers

Forty-six bus drivers took pan in a longitudinal field study of cardiovascular reactions to urban driving. "Job hassles" were recorded by observers using a standardized list of stress-related events in traffic and on the bus. Measures of blood pressure, heart rate, and ratings of perceived mental strain were obtained after each route segment. Intraindividual correlations between psychophysiological recordings and job hassles were calculated and submitted to cluster analysis. Two reaction patterns were identified, 1 characterized by consistently, although modestly, positive associations between the frequency of job hassles and psychophysiological reactions, the other characterized by a low association between the frequency of hassles and indicators or psychophysiological arousal. The former group displayed significantly higher blood pressure and mental strain ratings in the unwinding phase after work than did the latter group of workers. The results are discussed in terms of rate or "unwinding" after exposure to stressful conditions.

Comparisons of ambulatory blood pressure monitoring and repeated office measurements in primary care

BACKGROUND

The accuracy of office blood pressure (BP) readings is questionable because of blood pressure variability and measurement errors. The primary aim of this study was to determine the number of office visits required to optimize the estimation of usual blood pressure in older adults in primary care.

METHODS

Ambulatory blood pressure monitoring was used to define usual blood pressure in an observational study of 75 randomly selected family practice patients. Each subject made six visits for office BP measurements and had 24-hour ambulatory BP monitoring done twice. Mean office BP, based on one through six visits, was compared with mean ambulatory BP.

RESULTS

The sample consisted of 29 men and 46 women; 18 were black and 57 were white. Twenty-one subjects were taking antihypertensive medication. The mean age +/- 1/standard deviation (SD) was 60 (+/- 8) years. The correlation between mean office BP and mean ambulatory BP rose with the number of visits averaged, with most of the gain obtained within 3 visits. The maximal correlation for 24-hour ambulatory BP was r = .85/.75 (systolic/diastolic) (P < .01). However, even when using average office BP over six visits to estimate mean ambulatory BP, a discrepancy of > or = 10 mm Hg between estimated and observed ambulatory BP levels persisted in 18% to 20% of subjects.

CONCLUSIONS

Readings from at least three office visits should be averaged to estimate usual blood pressure. It should be noted, however, that important discrepancies between estimated and observed mean ambulatory BP persist even after readings taken over six visits. Ambulatory BP monitoring probably provides unique information about usual blood pressure that cannot be captured by repeated office BP readings.

Associations of ankle-brachial index with clinical coronary heart disease, stroke and preclinical carotid and popliteal atherosclerosis: the Atherosclerosis Risk in Communities (ARIC) Study

The resting ankle-brachial index (ABI) is a non-invasive method to assess the patency of the lower extremity arterial system and to screen for the presence of peripheral occlusive arterial disease. To determine how the ABI is associated with clinical coronary heart disease (CHD), stroke, preclinical carotid plaque and far wall intimal-medial thickness (IMT) of the carotid and popliteal arteries, we conducted analyses in 15 106 middle-aged adults from the baseline examination (1987-1989) of the Atherosclerosis Risk in Communities (ARIC) Study. The prevalence of clinical CHD, stroke/transient ischemic attack (TIA) and preclinical carotid plaque increased with decreasing ABI levels, particularly at those of < 0.90. Individuals with ABI < 0.90 were twice as likely to have prevalent CHD as those with ABI > 0.90 (age-adjusted odds ratio (OR) ranging from 2.2 (95% CI: 1.0-5.1) in African-American men to 3.3 (95% CI: 2.1-5.0) in white men). Men with ABI < 0.90 were more than four times as likely to have stroke/TIA as those with ABI > 0.90 (age-adjusted OR: 4.2 (95% CI: 1.8-9.5) in African-American men and 4.9 (95% CI: 2.6-9.0) in white men). In women the association was weaker and not statistically significant. Among those free of clinical cardiovascular disease, individuals with ABI < or = 0.90 had statistically significantly higher prevalence of preclinical carotid plaque compared to those with ABI > 0.90 (age-adjusted ORs ranging from 1.5 (95% CI: 1.0-1.9) in white women to 2.6 (95% CI: 1.0-6.6) in african-american men). The ABI was also inversely associated with far wall IMT of the carotid arteries (in both men and women) and the popliteal arteries (in men only). The associations of ABI with clinical CHD, stroke, preclinical carotid plaque and IMT of the carotid and popliteal arteries were attenuated and often not statistically significant after further adjustment for LDL cholesterol, cigarette smoking, hypertension and diabetes. These data demonstrate that low ABI levels, particularly those of < 0.90, are indicative of generalized atherosclerosis.

Noise, physiology, and human performance: the potential role of effort

Thirty-three male college students ages 18-31 were assigned to 2 levels of noise exposure and worked at 2 levels of effort while calculating the Norinder arithmetic task (M. Frankenhaeuser & U. Lundberg, 1977). As hypothesized, noise increased heart rate, norepinephrine, and cortisol only under high effort. Blood pressure did not change significantly. Reaction time slowed significantly under noise only when effort was low. Both self-report and epinephrine level confirmed the effort manipulation and showed that it was orthogonal to noise levels. These data support the adaptive costs hypothesis and have practical implications for industry. These implications include trade-offs of productivity and worker health, which may be dependent on management style.

Variation of common carotid artery elasticity with intimal-medial thickness: the ARIC Study. Atherosclerosis Risk in Communities

The Atherosclerosis Risk in Communities (ARIC) study is a prospective investigation of the etiology and natural history of atherosclerosis and cardiovascular disease in four U.S. communities. The purpose of this work is to investigate the relationship between common carotid artery elasticity and intimal-medial thickness (IMT) in the four race-gender groups represented in the ARIC cohort. Noninvasive ultrasonic methods were used to measure IMT and the [systolic minus diastolic] diameter change (DC) of the left common carotid artery in 10,920 black and white, men and women between the ages of 45 and 64 y. The relationship between DC and IMT and IMT2 was examined after adjustment of DC for age, height, diastolic diameter, diastolic blood pressure and linear and quadratic terms for pulse pressure. This adjusted value of DC was used as an index of elasticity of the common carotid artery in the ARIC cohort with larger values of adjusted DC implying a more elastic vessel. The general behavior of adjusted DC with increasing IMT was observed to be qualitatively similar in all four race-gender groups. Adjusted DC remained nearly constant or increased slightly for values of IMT between approximately 0.4 and 0.8 mm, up to approximately the 90th percentile of IMT, and then decreased above the 90th percentile of IMT. Common carotid artery elasticity, defined as adjusted DC, varies with increasing IMT in the ARIC cohort in a manner consistent with results from previous studies in animals and human subjects addressing the variation of several elasticity indices with atherosclerotic involvement and risk factor exposure in the aorta, and brachial and radial arteries. Our results suggest that thicker common carotid artery walls in middle-aged U.S. populations are no stiffer than thinner walls, except for the thickest 10% of arteries. Since the distal common carotid artery frequently contains atheromatous plaques in this population, the lack of change in stiffness, indeed, the reduction in stiffness per unit thickness, may reflect the various stages of early common carotid atherosclerosis most often found in this population. These are characterized more by destruction of arterial wall structural elements than by changes such as widespread or circumferential sclerosis, which would strengthen and stiffen the artery.

Sex-specific associations of magnetic resonance imaging-derived intra-abdominal and subcutaneous fat areas with conventional anthropometric indices. The Atherosclerosis Risk in Communities Study

Accurate measurement of central fat patterning is difficult to obtain by conventional anthropometry. Direct measurement of intra-abdominal fat area by magnetic resonance imaging, while accurate, is impractical for large-scale observational studies. This report examines the sex-specific associations of conventional anthropometric indices with intra-abdominal fat and subcutaneous fat areas measured by magnetic resonance imaging. A total of 157 volunteers (97 men and 60 women) aged 48-68 years of predominately white ethnicity had intra-abdominal fat and subcutaneous fat areas measured as part of the Atherosclerosis Risk in Communities (ARIC) Study. Weight, body mass index, waist circumference, waist : hip ratio, and subscapular skinfold thickness were measured or calculated by a standardized protocol. On average, women had a lower intra-abdominal fat area than men (109.5 cm2 vs. 152.9 cm2) but a higher mean subcutaneous fat area (287.8 cm2 vs. 214.6 cm2). After adjustment for age, intra-abdominal fat area was quadratically associated with body mass index, waist circumference, weight, and subscapular skinfold thickness in men; in women, these associations were best modeled by a positive linear equation. Waist : hip ratio was linearly related to intra-abdominal fat area in both sexes. In general, anthropometric measures predicted lower percentages of the total variance in intra-abdominal fat area for men than for women. For subcutaneous fat area, all anthropometric indices were linearly associated and predicted more of the variance in subcutaneous fat area than in intra-abdominal fat area. These results indicate that among men, greater intra-abdominal fat deposition rates occur at relatively low body weights and fat is more uniformly deposited at higher weights. Women appear to deposit intra-abdominal fat at a constant rate as they gain weight, even after menopause. The authors conclude that when waist circumference or body mass index is used as a surrogate for intra-abdominal fat area in men, a quadratic term should be included in the analysis as a predictor variable. Subcutaneous fat area can be estimated well by linear measures commonly employed in epidemiologic studies.

Population-based study of heart rate variability and prevalent myocardial infarction. The Atherosclerosis Risk in Communities Study

Clinically based studies have indicated that patients who have suffered myocardial infarction (MI) exhibit lower heart rate variability (HRV). Such associations have not been reported at the population level. To investigate whether MI is related to lower HRV in the general population, the authors examined a stratified random sample of 2,243 men and women aged 45-64 years, of whom 260 had had MI and 1,983 were free of any coronary heart disease manifestations. All were part of the biracial cohort of the Atherosclerosis Risk in Communities study sampled from four United States communities. Resting, 2-minute supine heart rate data were analyzed using spectral analysis to estimate high-frequency (0.16-0.35 Hz) and low-frequency (0.025-0.15 Hz) spectral powers as conventional indices of HRV. The mean levels of high-frequency powers were 1.02 and 1.23 (beats/min)2 for MI and non-MI groups, respectively (P < .05), and the low-frequency means were 2.46 and 3.11 (beats/min)2 for MI and non-MI groups, respectively (P < .01). Age, race, and sex-adjusted odds ratios (95% confidence interval) of lower high-frequency and low-frequency powers contrasting MI to non-MI individuals were 1.52 (range, 1.09-2.10) and 1.54 (range, 1.12-2.10), respectively. After adjustment for use of beta-blocker medication, the odds ratios (95% confidence interval) were 1.26 (range, 0.88-1.81) and 1.22 (range, 0.87-1.69) for lower high-frequency and low-frequency powers, respectively. The findings from this first population-based study of prevalent MI and HRV provide support for an inverse association between MI and lower HRV. However, adjusting for beta-blocker use eliminates the statistical association. These findings confirm that impaired HRV is found in individuals with prevalent MI, even when drawn as a sample of community-dwelling individuals. This impaired HRV may contribute to the increased risk of subsequent cardiovascular events previously observed in survivors of acute MI. The cross-sectional data also suggest that use of beta-blockers diminishes the odds of lower HRV associated with MI.

Survival of patients undergoing renal replacement therapy in one center with special emphasis on racial differences

This study compared racial differences in end-stage renal disease (ESRD) in 550 patients starting renal replacement therapy at a large academic dialysis center between January 1, 1990, and December 31, 1993, with follow-up through December 31, 1994. Patient groups were compared with respect to cause of ESRD, comorbid factors at the start of dialysis therapy, choice of modality, transplantation rate, and survival. Fifty-eight percent of the patients were white and 42% were African-American. There was a similar distribution of causes of ESRD between races. African-American patients were less likely to choose peritoneal dialysis as initial therapy (11.6% v 29.3%; P < 0.001) and were less likely to change dialysis modality. Transplantation rates were significantly different between African-American and white patients (9.3% v 27.6%; P < 0.001). African-Americans less frequently received living-related, living-nonrelated, and cadaveric renal transplants. Given differences in transplantation rates and in survival of transplanted patients versus patients on dialysis, survival analysis was performed without censoring for transplantation. A multivariate Cox proportional hazards model was formed, and the following were identified as being significant independent predictors of survival: age, race, age-race interaction, serum albumin at the start of dialysis, activity level at the start of dialysis, and presence of congestive heart failure and cancer. Age had little effect on survival among African-American patients, while it was a significant predictor of survival in white patients. In the group of patients starting dialysis before the age of 30 years, African-American patients had a significantly increased mortality risk compared with white patients. However, white patients older than 50 years had a higher mortality risk; this risk difference increased with age. Racial differences in mortality among older white patients could not be explained by differences in comorbid conditions, transplantation rates, or withdrawal from dialysis.

Role of social class in excess black stroke mortality

BACKGROUND AND PURPOSE

It has been suggested that a substantial proportion of the excess stroke mortality among black Americans may be attributable to relatively lower socioeconomic status (SES) in this group. In this report we provide the first quantitative estimates of the proportion of excess black stroke mortality attributable to SES for a large population-based cohort.

METHODS

We used data from the National Longitudinal Mortality Study for persons 45 years and older (73,400 white men, 87,528 white women, 6522 black men, and 8816 black women). Sex-specific proportional hazards model were used to estimate excess black stroke mortality with and without adjustment for education and income (measures of SES). The contribution of SES to the excess black stroke risk was estimated from the difference in regression coefficients for race in these models.

RESULTS

In men, low SES was associated with increased stroke mortality (P < or = .0001) and accounted for 14% to 46% of the excess black stroke risk (P < .05). However, we could find no association between SES and stroke mortality in women, and SES did not account for a significant proportion of the excess stroke mortality in black women.

CONCLUSIONS

Although SES proved to account for a statistically significant proportion of excess male black stroke mortality, overall SES explained less than one quarter of the observed excess between ages 45 and 65. In women, SES did not significantly reduce the estimated excess black stroke mortality. Although SES may be playing a role in excess black stroke mortality, a substantial proportion of the excess appears attributable to other sources, including cerebrovascular risk factors that are unrelated to SES, unmeasured lifestyle influences, social resources, and genetic factors.

Evaluation of magnetic resonance imaging for quantification of intraabdominal fat in human beings by spin-echo and inversion-recovery protocols

We evaluated two magnetic resonance imaging (MRI) methods, spin echo and inversion recovery (IR), for quantification of intraabdominal fat in a subgroup of participants from the Atherosclerosis Risk in Communities (ARIC) Study. Both methods were used previously to quantify visceral fat, and the IR but not the spin echo method has been validated by comparison with computed tomography in human beings. In the present study, the reliability of both methods was excellent: reliability coefficients comparing two readers on the same scan were 0.9574 for IR (n = 158) and 0.9254 for spin echo (n = 47) when random effects models with log-transformed data were used. A comparison of visceral fat areas in 47 subjects with both IR and spin echo indicated that IR gave a slightly higher mean area than did spin echo: 134.9 compared with 129.8 cm2. However, a mixed-model analysis of variance (ANOVA) of the log-transformed data showed no statistical difference between either method or readers in the comparison of IR and spin echo. These data suggest that the IR and spin echo protocols evaluated in this communication are comparable with one another and reliable for estimation of intraabdominal fat.

Is the stroke belt disappearing? An analysis of racial, temporal, and age effects

BACKGROUND AND PURPOSE

The stroke risk among white residents of the coastal plain of North Carolina, South Carolina, and Georgia (the "Stroke Belt") has been reported to be between 1.3 and 2.0 times the national average. In this study we examined (1) whether a similar excess risk exists for blacks in this region, (2) whether this regional excess stroke risk has decreased over time, and (3) whether the regional excess risk is consistent across ages from 45 to more than 85 years.

METHODS

Using data from the Compressed Mortality File, we estimated the annual relative stroke mortality risk for black and white men and women in a region of 153 coastal plain counties and compared these rates to those for the remainder of the United States.

RESULTS

The relative geographic excess risk of stroke death was similar for black residents and white residents of the Stroke Belt for both men and women. Despite the decline in stroke mortality, the relative increased risk of stroke death in the region has remained constant from 1968 to 1991; however, the pattern of excess risk across age differed significantly between race/sex groups.

CONCLUSIONS

These data show that the Stroke Belt continues to exist for blacks and whites and for men and women. Although the specific causes of the Stroke Belt remain unknown, the public health impact is staggering, with a greater than 40% excess risk of stroke mortality and more than 1200 excess stroke deaths annually.

Teaching With Entertainment Films: An Empathetic Focus

In an effort to bridge the gap in learning in the affective domain, nurse educators must understand and develop meaningful teaching strategies. Specific strategies designed to facilitate cognitive understanding of the affective response can be found in entertainment films. The findings of this study suggest that the use of entertainment films with guidance is effective in teaching empathetic responses. The continued study of the complex phenomenon in developing an understanding of the many variables that comprise not only the experience of empathy, but also the transference of the experience into helping interventions.

Arterial wall thickness is associated with prevalent cardiovascular disease in middle-aged adults. The Atherosclerosis Risk in Communities (ARIC) Study

BACKGROUND AND PURPOSE

This study was done to assess the relationship between prevalent cardiovascular disease and arterial wall thickness in middle-aged US adults.

METHODS

The association of preexisting coronary heart disease, cerebrovascular disease, and peripheral vascular disease with carotid and popliteal intimal-medial thickness (IMT) (measured by B-mode ultrasound) was assessed in 13,870 black and white men and women, aged 45 to 64, during the Atherosclerosis Risk in Communities (ARIC) Study baseline examination (1987 through 1989). Prevalent disease was determined according to both participant self-report and measurements at the baseline examination (including electrocardiogram, fasting blood glucose, and medication use).

RESULTS

Across four race and gender strata, mean carotid far wall IMT was consistently greater in participants with prevalent clinical cardiovascular disease than in disease-free subjects. Similarly, the prevalence of cardiovascular disease was consistently greater in participants with progressively thicker IMT. The greatest differences in carotid IMT associated with prevalent disease were observed for reported symptomatic peripheral vascular disease (0.09 to 0.22 mm greater IMT in the four race-gender groups).

CONCLUSIONS

These data document the substantially greater arterial wall thickness observed in middle-aged adults with prevalent cardiovascular disease. Both carotid and popliteal arterial IMT were related to clinically manifest cardiovascular disease affecting distant vascular beds, such as the cerebral, peripheral, and coronary artery vascular beds.

Relations of intimal-medial thickness among sites within the carotid artery as evaluated by B-mode ultrasound. ARIC Investigators. Atherosclerosis Risk in Communities

BACKGROUND AND PURPOSE

B-mode ultrasound is a widely used technique for the clinical and epidemiological assessment of carotid atherosclerosis. This article describes the relation between arterial intimal-medial thickness (IMT) at different sites within the extracranial carotid artery.

METHODS

IMT was measured by B-mode real-time ultrasound as an index of atherosclerotic involvement in the extracranial carotid arteries as part of the population-based Atherosclerosis Risk in Communities (ARIC) study. The relation between IMT at different sites was described by correlation coefficients and percentile regression techniques based on between 4034 and 9386 pairs of measurements (variation in sample size depending on the paired sites).

RESULTS

Increased IMT at one site was associated with increased IMT at other sites. The correlation between right and left IMT at the same anatomic location in the carotid artery ranged from .34 to .49; the correlation at different anatomic locations in the carotid artery on the same side ranged from .25 to .43. The distribution of IMT, described by the percentiles of IMT at the inference site as a function of IMT at the index site, showed constricted percentiles of IMT at the inference site for small IMT at the index site and an increase in the spread of percentiles with increasing IMT.

CONCLUSIONS

Although increased carotid IMT at one site is positively associated with thickened walls at other carotid sites, the ability to accurately predict wall thickness at a site given the wall thickness at other sites is modest. The general association between sites supports the systemic nature of atherosclerosis, while the lack of tight agreement between sites supports the focal nature of the atherosclerotic process.

Dietary fat intake and carotid artery wall thickness: the Atherosclerosis Risk in Communities (ARIC) Study

Associations between atherosclerosis and dietary fat and cholesterol have been demonstrated in numerous animal experiments. The relation between these dietary components and atherosclerosis has not previously been reported in a population-based study among human beings. The associations of dietary fat and cholesterol with carotid artery wall thickness (atherosclerosis) were investigated in a population-based study, the Atherosclerosis Risk in Communities (ARIC) Study, from 1987 to 1989. Participants were 2,095 black women, 5,146 white women, 1,318 black men and 4,589 white men, aged 45-64 years, recruited from four US communities: Jackson, Mississippi; Forsyth County, North Carolina; Washington County, Maryland; and Minneapolis, Minnesota. Habitual diet was assessed with a food frequency questionnaire. Wall thickness was measured with B-mode ultrasound. After adjustment for age and energy intake, animal fat, saturated fat, monounsaturated fat, cholesterol, and Keys' score were positively related to wall thickness, while vegetable fat and polyunsaturated fat were inversely related to wall thickness. These associations persisted after further adjustment for smoking and hypertension and were consistent across the four race and sex groups. Thus, elements of habitual dietary intake were consistently associated with carotid artery wall thickness, compatible with their putatively atherogenic and antiatherogenic properties.

Working on the hot seat: urban bus operators

City bus operators suffer elevated health risks and striking levels of absenteeism and medical disability that may be related to occupational stress. This article provides a critical overview of findings on urban bus drivers' health status, paying particular attention to aspects of the physical and psychosocial job environment that may cause ill health. Methodological shortcomings in the research are discussed and preliminary ideas for salutagenic interventions are proposed.

A prospective reevaluation of transient ischemic attacks as a risk factor for death and fatal or nonfatal cardiovascular events

BACKGROUND AND PURPOSE

Transient ischemic attack (TIA) is generally considered a risk factor for death and cardiovascular events. This assumption is based on comparisons of the survival of the TIA population with that of the general population. Such comparisons may provide biased estimates of the risk associated with TIA because the general population is usually more healthy than TIA patients.

METHODS

Using a prospective case-control study design, we report the comparison of a TIA population (n = 280) and a control group (n = 399) with a comparable cardiovascular risk factor burden. Proportional hazards analysis was used to compare survival time and time to fatal or nonfatal stroke and/or myocardial infarction for the two study groups. Comparisons were made without adjustment for risk factors and after adjustment for age, race, sex, and major cardiovascular risk factors.

RESULTS

Before adjustment for age-race-sex or risk factors, TIA proved to be a risk factor for early mortality, stroke, and myocardial infarction (P < .05). Adjustment for age-race-sex disparities between the case and control groups explained much of the differences in mortality, as the hazard ratio was reduced from 2.2 to 1.4. However, adjustment for age-race-sex or age-race-sex and risk factors did not markedly reduce the role of TIA as a risk factor for stroke or myocardial infarction.

CONCLUSIONS

Although TIA proved to be a risk factor for stroke or myocardial infarction, it apparently plays a smaller role in the risk of death.

Social support lowers cardiovascular reactivity to an acute stressor

This study examined whether social support can reduce cardiovascular reactivity to an acute stressor. College students gave a speech in one of three social conditions: alone, in the presence of a supportive confederate, or in the presence of a nonsupportive confederate. Systolic and diastolic blood pressure were measured at rest, before the speech, and during the speech. While anticipating and delivering their speech, supported and alone subjects exhibited significantly smaller increases in systolic and diastolic blood pressures than did nonsupported subjects. Supported subjects also exhibited significantly smaller increases in systolic blood pressure than did alone subjects before and during the speech. Men had higher stress-related increases in blood pressures than did women; but gender did not moderate the effects of social support on cardiovascular reactivity. These results provide experimental evidence of potential health benefits of social support during acute stressors.

Household crowding and social support: a quasiexperimental analysis

People often cope with crowded living conditions by socially withdrawing from their housemates. This coping strategy may overgeneralize, influencing social interactions with others outside the home. In a stressful laboratory situation, Ss from crowded homes, in comparison with uncrowded counterparts, are less likely to seek support from a confederate and rate the confederate as less supportive. Moreover, Ss from crowded homes are less likely to offer support to a confederate in need. These differences in social interaction behaviors appear to be attributable to crowded residents' social withdrawal.

Carotid artery intimal-medial thickness distribution in general populations as evaluated by B-mode ultrasound. ARIC Investigators

BACKGROUND AND PURPOSE

B-mode ultrasound is a widely used technique for the clinical and epidemiological assessment of carotid atherosclerosis. This article provides a description of the distribution of carotid atherosclerosis in the general population.

METHODS

Intimal-medial arterial wall thickness was measured by B-mode real-time ultrasound as an index of atherosclerotic involvement in the extracranial carotid arteries as part of the population-based Atherosclerosis Risk in Communities (ARIC) study. The distribution was described by race-sex strata, in which 759 to 4952 individuals were imaged depending on strata and location in the carotid system.

RESULTS

Median wall thickness ranged between 0.5 and 1 mm at all ages; fewer than 5% of ARIC participants had values exceeding 2 mm. Individuals tended to have a larger wall thickness in the carotid bifurcation than in the common carotid artery. Internal carotid artery values were more variable, with higher proportions of both large and small wall thicknesses than in the common carotid. The proportion of individuals with a large wall thickness was greatest at the bifurcation and smallest at the common carotid artery. Men had uniformly larger wall thickness than women. Cross-sectional analysis suggests that age-related increases in wall thickness average approximately 0.015 mm/y in women and 0.018 mm/y in men in the carotid bifurcation, 0.010 mm/y for women and 0.014 mm/y for men in the internal carotid artery, and 0.010 mm/y in both sexes in the common carotid artery.

CONCLUSIONS

Estimates provided for wall thickness percentiles can serve as "nomograms" by age, race, and sex.

Household crowding and social support: a quasiexperimental analysis

People often cope with crowded living conditions by socially withdrawing from their housemates. This coping strategy may overgeneralize, influencing social interactions with others outside the home. In a stressful laboratory situation, Ss from crowded homes, in comparison with uncrowded counterparts, are less likely to seek support from a confederate and rate the confederate as less supportive. Moreover, Ss from crowded homes are less likely to offer support to a confederate in need. These differences in social interaction behaviors appear to be attributable to crowded residents' social withdrawal.

Physiological deactivation after two contrasting tasks at a video display terminal: learning vs repetitive data entry

Two contrasting 90 min VDT work situations were simulated in the laboratory: (1) a machine-paced, repetitive data entry task; and (2) a stimulating, self-paced learning task with successive feedback. Thirty non-smoking male students (20-34 years), without previous experience of VDT work, participated individually in each condition on two consecutive days (balanced order) and in a task-free baseline condition. Self-reports and successive measurements (ambulatory recordings) of systolic and diastolic blood pressure and heart rate were obtained during work and during a subsequent 60 min period of deactivation. Urine samples were obtained after each period for the determination of catecholamines and cortisol. In the baseline condition, measurements were obtained at corresponding times of the day. As expected, the data entry task was associated with self-reports of boredom, irritation, and unpleasantness; the learning task wtih alertness, interest, and ability to concentrate. Similar elevations of physiological measurements occurred in both work situations. However, differences between conditions were found after work. Following data entry, deactivation was slower in five of the six variables (significant for epinephrine).

Composition and biological activity of chromium-pyridine carboxylate complexes

Coordination complexes of chromium (Cr) and two pyridine carboxylate isomers, nicotinate (nic) and picolinate (pic) were synthesized and analyzed. Cr mono and dinicotinate complexes were formed with 1:1 and 1:2 ratios of Cr3+ and nic at pH 7.5. Cr dinicotinate was the only complex formed from a 1:3 ratio of Cr3+ and nic. Mono, di, and tri picolinate complexes were formed with 1:1, 1:2, and 1:3 ratios of Cr3+ and pic at pH 7.5. Cr is coordinated with nic through the carboxyl carbon while Cr is coordinated with pic through both the pyridine nitrogen and the carboxyl carbon. Cr dinicotinate enhanced insulin activity in isolated adipose tissue. None of the other complexes were active in this assay system. In contrast, Cr tripicolinate, which is lipophilic, increased glucose uptake by skeletal muscle cultures but none of the other complexes were effective. In addition, dietary supplements of Cr tripicolinate increased rate of lean body mass development in humans and decreased hemoglobin glycation in aging rats. None of the other complexes was effective in these in vivo assays. The results of this investigation prove that the chemical properties of Cr nic and Cr pic complexes differ markedly. The chemical differences result in a vast difference in the biological action of the complexes.