930 resultados para Arithmetic mean


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Acute mental stress induces a significant increase in plasma interleukin (IL)-6 levels as a possible mechanism for how psychological stress might contribute to atherosclerosis. We investigated whether the IL-6 response would habituate in response to a repetitively applied mental stressor and whether cortisol reactivity would show a relationship with IL-6 reactivity. Study participants were 21 reasonably healthy men (mean age 46+/-7 years) who underwent the Trier Social Stress Test (combination of a 3-min preparation, 5-min speech, and 5-min mental arithmetic) three times with an interval of 1 week. Plasma IL-6 and free salivary cortisol were measured immediately before and after stress, and at 45 and 105 min of recovery from stress. Cortisol samples were also obtained 15 and 30 min after stress. Compared to non-stressed controls, IL-6 significantly increased between rest and 45 min post-stress (p=.022) and between rest and 105 min post-stress (p=.001). Peak cortisol (p=.034) and systolic blood pressure (p=.009) responses to stress both habituated between weeks one and three. No adaptation occurred in diastolic blood pressure, heart rate, and IL-6 responses to stress. The areas under the curve integrating the stress-induced changes in cortisol and IL-6 reactivity were negatively correlated at visit three (r=-.54, p=.011), but not at visit one. The IL-6 response to acute mental stress occurs delayed and shows no adaptation to repeated moderate mental stress. The hypothalamus-pituitary-adrenal axis may attenuate stress reactivity of IL-6. The lack of habituation in IL-6 responses to daily stress could subject at-risk individuals to higher atherosclerotic morbidity and mortality.

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OBJECTIVE: Acute mental stress elicits blood hypercoagulability. Following a transactional stress model, we investigated whether individuals who anticipate stress as more threatening, challenging, and as exceeding their coping skills show greater stress reactivity of the coagulation activation marker D-dimer, indicating fibrin generation in plasma. METHODS: Forty-seven men (mean age 44 +/- 14 years; mean blood pressure [MBP] 101 +/- 12 mm Hg; mean body mass index [BMI] 26 +/- 3 kg/m(2)) completed the Primary Appraisal Secondary Appraisal (PASA) scale before undergoing the Trier Social Stress Test (combination of mock job interview and mental arithmetic task). Heart rate, blood pressure, plasma catecholamines, and D-dimer levels were measured before and after stress, and during recovery up to 60 minutes poststress. RESULTS: Hemodynamic measures, catecholamines, and D-dimer changed across all time points (p values <.001). The PASA "Stress Index" (integrated measure of transactional stress perception) correlated with total D-dimer area under the curve (AUC) between rest and 60 minutes poststress (r = 0.30, p = .050) and with D-dimer change from rest to immediately poststress (r = 0.29, p = .046). Primary appraisal (combined "threat" and "challenge") correlated with total D-dimer AUC (r = 0.37, p = .017), D-dimer stress change (r = 0.41, p = .004), and D-dimer recovery (r = 0.32, p = .042). "Challenge" correlated more strongly with D-dimer stress change than "threat" (p = .020). Primary appraisal (DeltaR(2) = 0.098, beta = 0.37, p = .019), and particularly its subscale "challenge" (DeltaR(2) = 0.138, beta = 0.40, p = .005), predicted D-dimer stress change independently of age, BP, BMI, and catecholamine change. CONCLUSIONS: Anticipatory cognitive appraisal determined the extent of coagulation activation to and recovery from stress in men. Particularly individuals who anticipated the stressor as more challenging and also more threatening had a greater fibrin stress response.

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CONTEXT: There is strong evidence for a physiological hyperreactivity to stress in systemic hypertension, but data on associated or potentially moderating psychological factors are scarce. OBJECTIVE: The objective of the study was to identify psychological correlates of physiological stress reactivity in systemic hypertension. DESIGN: This was a cross-sectional, quasi-experimentally controlled study. Study participants underwent an acute standardized psychosocial stress task combining public speaking and mental arithmetic in front of an audience. SETTING: The study was conducted in the population in the state of Zurich, Switzerland. SUBJECTS: Subjects included 22 hypertensive and 26 normotensive men (mean +/- sem 44 +/- 2 yr). MAIN OUTCOME MEASURES: We assessed the psychological measures social support, emotional regulation, and cognitive appraisal of the stressful situation. Moreover, we measured salivary cortisol and plasma epinephrine and norepinephrine before and after stress and several times up to 60 min thereafter as well as blood pressure and heart rate. RESULTS: We found poorer hedonistic emotional regulation (HER) and lower perceived social support in hypertensives, compared with normotensives (P < 0.01). Compared with normotensives, hypertensives showed higher cortisol, epinephrine, and norepinephrine secretions after stress (P < 0.038) as well as higher systolic and diastolic blood pressure (P < 0.001). Cortisol reactivity and norepinephrine secretion were highest in hypertensive men with low HER (P < 0.05). In contrast, hypertensives with high HER did not significantly differ from normotensives in both cortisol and norepinephrine secretion after stress. Epinephrine secretion was highest in hypertensives with low social support but was not different between hypertensives with high social support and normotensives. CONCLUSIONS: The findings suggest that both low social support and low HER are associated with elevated stress hormone reactivity in systemic hypertension.

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BACKGROUND: Integrity of the abdominal aortic aneurysm (AAA) neck is crucial for the long-term success of endovascular AAA repair (EVAR). However, suitable tools for reliable assessment of changes in small aortic volumes are lacking. The purpose of this study was to assess the intraobserver and interobserver variability of software-enhanced 64-row computed tomographic angiography (CTA) AAA neck volume measurements in patients after EVAR. METHODS: A total of 25 consecutive patients successfully treated by EVAR underwent 64-row follow-up CTA in 1.5-mm collimation. Manual CTA measurements were performed twice by three blinded and independent readers in random order with at least a 4-week interval between readings. Maximum and minimum transverse aortic neck diameters were measured twice on two different levels within the proximal neck. Volumetry of the proximal aortic neck was performed by using dedicated software. Variability was calculated as 1.96 SD of the mean arithmetic difference according to Bland and Altman. Two-sided and paired t tests were used to compare measurements. P values <.05 were considered to indicate statistical significance. RESULTS: Intraobserver agreement was excellent for dedicated aneurysmal neck volumetry, with mean differences of less than 1 mL (P > .05), whereas it was poor for transverse aortic neck diameter measurements (P < .05). However, interobserver variability was statistically significant for both neck volumetry (P < .005) and neck diameter measurements (P < .015). CONCLUSIONS: The reliability of dedicated AAA neck volumetry by using 64-row CTA is excellent for serial measurements by individual readers, but not between different readers. Therefore, studies should be performed with aortic neck volumetry by a single experienced reader.

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OBJECTIVE: The purpose of our study was to evaluate the efficacy of CT histogram analysis for further characterization of lipid-poor adenomas on unenhanced CT. MATERIALS AND METHODS: One hundred thirty-two adrenal nodules were identified in 104 patients with lung cancer who underwent PET/CT. Sixty-five nodules were classified as lipid-rich adenomas if they had an unenhanced CT attenuation of less than or equal to 10 H. Thirty-one masses were classified as lipid-poor adenomas if they had an unenhanced CT attenuation greater than 10 H and stability for more than 1 year. Thirty-six masses were classified as lung cancer metastases if they showed rapid growth in 1 year (n = 27) or were biopsy-proven (n = 9). Histogram analysis was performed for all lesions to provide the mean attenuation value and percentage of negative pixels. RESULTS: All lipid-rich adenomas had more than 10% negative pixels; 51.6% of lipid-poor adenomas had more than 10% negative pixels and would have been classified as indeterminate nodules on the basis of mean attenuation alone. None of the metastases had more than 10% negative pixels. Using an unenhanced CT mean attenuation threshold of less than 10 H yielded a sensitivity of 68% and specificity of 100% for the diagnosis of an adenoma. Using an unenhanced CT threshold of more than 10% negative pixels yielded a sensitivity of 84% and specificity of 100% for the diagnosis of an adenoma. CONCLUSION: CT histogram analysis is superior to mean CT attenuation analysis for the evaluation of adrenal nodules and may help decrease referrals for additional imaging or biopsy.

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Rationale: To provide a better understanding of cognitive functioning, motor outcome, behavior and quality of life after childhood stroke and to study the relationship between variables expected to influence rehabilitation and outcome (age at stroke, time elapsed since stroke, lateralization, location and size of lesion). Methods: Children who suffered from stroke between birth and their eighteenth year of life underwent an assessment consisting of cognitive tests (WISC-III, WAIS-R, K-ABC, TAP, Rey-Figure, German Version of the CVLT) and questionnaires (Conner's Scales, KIDSCREEN). Results: Twenty-one patients after stroke in childhood (15 males, mean 11;11 years, SD 4;3, range 6;10-21;2) participated in the study. Mean Intelligence Quotients (IQ) were situated within the normal range (mean Full Scale IQ 96.5, range IQ 79-129). However, significantly more patients showed deficits in various cognitive domains than expected from a healthy population (Performance IQ p = .000; Digit Span p = .000, Arithmetic's p = .007, Divided Attention p = .028, Alertness p = .002). Verbal IQ was significantly better than Performance IQ in 13 of 17 patients, independent of the hemispheric side of lesion. Symptoms of ADHD occurred more often in the patients' sample than in a healthy population (learning difficulties/inattention p = .000; impulsivity/hyperactivity p = .006; psychosomatics p = .006). Certain aspects of quality of life were reduced (autonomy p = .003; parents' relation p = .003; social acceptance p = .037). Three patients had a right-sided hemiparesis, mean values of motor functions of the other patients were slightly impaired (sequential finger movements p = .000, hand alternation p = .001, foot tapping p = .043). In patients without hemiparesis, there was no relation between the lateralization of lesion and motor outcome. Lesion that occurred in the midst of childhood (5-10 years) led to better cognitive outcome than lesion in the very early (0-5 years) or late childhood (10-18 years). Other variables such as presence of seizure, elapsed time since stroke and size of lesion had a small to no impact on prognosis. Conclusion: Moderate cognitive and motor deficits, behavioral problems, and impairment in some aspects of quality of life frequently remain after stroke in childhood. Visuospatial functions are more often reduced than verbal functions, independent of the hemispheric side of lesion. This indicates a functional superiority of verbal skills compared to visuospatial skills in the process of recovery after brain injury. Compared to the cognitive outcome following stroke in adults, cognitive sequelae after childhood stroke do indicate neither the lateralization nor the location of the lesion focus. Age at stroke seems to be the only determining factor influencing cognitive outcome.

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The goal of the Bernese periacetabular osteotomy is to correct the deficient acetabular coverage in hips with developmental dysplasia to prevent secondary osteoarthrosis. We determined the 20-year survivorship of symptomatic patients treated with this procedure, determined the clinical and radiographic outcomes of the surviving hips, and identified factors predicting poor outcome. We retrospectively evaluated the first 63 patients (75 hips) who underwent periacetabular osteotomy at the institution where this technique was developed. The mean age of the patients at surgery was 29 years (range, 13-56 years), and preoperatively 24% presented with advanced grades of osteoarthritis. Four patients (five hips) were lost to followup and one patient (two hips) died. The remaining 58 patients (68 hips) were followed for a minimum of 19 years (mean, 20.4 years; range, 19-23 years) and 41 hips (60%) were preserved at last followup. The overall mean Merle d'Aubigné and Postel score decreased in comparison to the 10-year value and was similar to the preoperative score. We observed no major changes in any of the radiographic parameters during the 20-year postoperative period except the osteoarthritis score. We identified six factors predicting poor outcome: age at surgery, preoperative Merle d'Aubigné and Postel score, positive anterior impingement test, limp, osteoarthrosis grade, and the postoperative extrusion index. Periacetabular osteotomy is an effective technique for treating symptomatic developmental dysplasia of the hip and can maintain the natural hip at least 19 years in selected patients. LEVEL OF EVIDENCE: Level III, prognostic study.

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OBJECTIVE: To assess whether stress further increases hypercoagulation in older individuals. We investigated whether acute stress-induced changes in coagulation parameters differ with age. It is known that hypercoagulation occurs in response to acute stress and that a shift in hemostasis toward a hypercoagulability state occurs with age. However, it is not yet known whether acute stress further increases hypercoagulation in older individuals, and thus may increase their risk for cardiovascular disease (CVD). METHODS: A total of 63 medication-free nonsmoking men, aged between 20 and 65 years (mean +/- standard error of the mean = 36.7 +/- 1.7 years), underwent an acute standardized psychosocial stress task combining public speaking and mental arithmetic in front of an audience. We measured plasma clotting factor VII activity (FVII:C), fibrinogen, and D-dimer at rest, immediately, and 20 minutes after stress. RESULTS: Increased age predicted greater increases in fibrinogen (beta = 0.26, p = 0.041; DeltaR(2) = 0.05), FVII:C (beta = 0.40, p = .006; DeltaR(2) = 0.11), and D-dimer (beta = 0.51, p < .001; DeltaR(2) = 0.18) from rest to 20 minutes after stress independent of body mass index and mean arterial blood pressure. General linear models revealed significant effects of age and stress on fibrinogen, FVII:C, and D-dimer (main effects: p < .04), and greater D-dimer stress reactivity with older age (interaction age-by-stress: F(1.5/90.4) = 4.36, p = .024; f = 0.33). CONCLUSIONS: Our results suggest that acute stress might increase vulnerability in the elderly for hypercoagulability and subsequent hemostasis-associated diseases like CVD.

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Psychosocial stress might increase the risk of atherothrombotic events by setting off an elevation in circulating levels of the proinflammatory cytokine interleukin (IL)-6. We investigated the effect of aspirin and propranolol on the responsiveness of plasma IL-6 levels to acute psychosocial stress. For 5 days, 64 healthy subjects were randomized, double-blind, to daily oral aspirin 100mg plus long-acting propranolol 80 mg, aspirin 100mg plus placebo, long-acting propranolol 80 mg plus placebo, or placebo plus placebo. Thereafter, all subjects underwent the 13-min Trier Social Stress Test, which combines a preparation phase, a job interview, and a mental arithmetic task. Plasma IL-6 levels were measured in blood samples collected immediately pre- and post-stress, and 45 min and 105 min thereafter. The change in IL-6 from pre-stress to 105 min post-stress differed between subjects with aspirin medication and those without (p =0.033; eta p2=0.059). IL-6 levels increased less from pre-stress to 105 min post-stress (p <0.027) and were lower (p =0.010) at 105 min post-stress in subjects with aspirin than in subjects without aspirin. The significance of these results was maintained when controlling for gender, age, waist-to-hip ratio, mean arterial blood pressure, and smoking status. Medication with propranolol was not significantly associated with the stress-induced change in IL-6 levels. Also, aspirin and propranolol did not significantly interact in determining the IL-6 stress response. Aspirin but not propranolol attenuated the stress-induced increase in plasma IL-6 levels. This suggests one mechanism by which aspirin treatment might reduce the risk of atherothrombotic events triggered by acute mental stress.

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Clinical assessments after Total Knee Arthroplasty (TKA) show persisting pain after implantation in over 20% of patients. Impingement of soft tissue around the knee, due to imprecise geometry of the tibial implant, can be one reason for persisting ailment. Two hundred and thirty seven MRI scans were evaluated using an active contour detection algorithm (snake) to obtain a high-resolution mean anatomical shape of the tibial plateau. Differences between female and male, older and younger (40) and left and right averaged shapes were determined. The shapes obtained were asymmetric throughout. Absolute differences between the subgroups fell short of inter-individual variations represented by calculated one-sigma confidence intervals. Our results indicate that a differentiation in TKA tibial plateau design by gender, age, or side is of minor relevance.

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Blood coagulation activation might be one mechanism linking acute mental stress with coronary events. We investigated the natural habituation of coagulation responses and recovery to short-term mental stress. Three times with one-week intervals, 24 men (mean age 47 +/- 7 years) underwent the same 13-min stressor (preparation, job interview, mental arithmetic). During each visit venous blood was obtained four times (baseline, immediately post-stress, 45 min of recovery, 105 min of recovery). Eight blood coagulation parameters were measured at weeks one and three. Acute stress provoked increases in von Willebrand factor antigen, fibrinogen, clotting factor FVII activity (FVII:C), FVIII:C, FXII:C (p's < or = 0.019), and D-dimer (N.S.). All coagulation parameters experienced full recovery except FVIII:C (p = 0.022). Stress did not significantly affect activated partial thromboplastin time and prothrombin time. At all time points FVIII:C and FXII:C levels were significantly higher at week one compared to week three (p's < or = 0.041). Before catheter insertion, systolic blood pressure (p = 0.001) and heart rate (p = 0.026) were relatively higher at week one. Unlike the magnitude of systolic blood pressure response to stress (p = 0.007) and of cortisol recovery from stress (p = 0.002), the magnitude of all coagulation responses to stress and the recovery from stress were similar in week one and week three. Sympathetic activation with anticipatory stress best explained increased baseline activity in FVIII and FXII at week one. An incapacity of the coagulation system to adapt to stress repeats is perhaps a consequence of evolution, but might also contribute to increased coronary risk in some individuals, particularly in those with cardiovascular diseases.

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OBJECTIVE: Vital exhaustion and depression are psychosocial risk factors of coronary artery disease. A hypercoagulable state in response to acute psychosocial stress contributes to atherothrombotic events. We aimed to investigate the hypothesis that vital exhaustion and depression correlate with stress-induced changes in the hypercoagulability marker D-dimer. METHODS: Thirty-eight healthy and nonsmoking school teachers (mean age 50+/-8 years, 55% women) completed the nine-item Maastricht Vital Exhaustion Questionnaire and the seven-item depression subscale of the Hospital Anxiety and Depression Scale. Within 1 week, subjects twice underwent the Trier Social Stress Test (i.e., preparation phase, mock job interview, and mental arithmetic that totaled 13 min). Plasma D-dimer levels were determined at five time points during the protocol. RESULTS: Vital exhaustion (P=.022; eta(2)=.080) and depressive symptoms (P=.011; eta(2)=.090) were associated with stress-induced changes in D-dimer levels over time controlling for sex and age. Elevated levels of vital exhaustion (r=-.46, P=.005) and of depression (r=-.51, P=.002) correlated with reduced D-dimer increase from pre-stress to immediately post-stress. Also, elevated vital exhaustion (r=.34, P=.044) and depression (r=.41, P=.013) were associated with increase (i.e., attenuated recovery) of D-dimer levels between 20 and 45 min post-stress. Controlling for stress hormone and blood pressure reactivity did not substantially alter these results. CONCLUSION: The findings suggest an attenuated immediate D-dimer stress response and delayed recovery of D-dimer levels post-stress with elevated vital exhaustion and depressive symptoms. In particular, the prolonged hypercoagulability after stress cessation might contribute to the atherothrombotic risk previously observed with vital exhaustion and depression, even at subclinical levels.