摘要:

Insulin resistance is common in the general population and tends to cluster with glucose intolerance, dyslipidaemia and high blood pressure. The importance of the insulin-resistant phenotype for the assessment of cardiovascular risk and response to intervention is increasingly being recognized. Therefore, there is a need for an accurate and reproducible method for measuring insulin resistancein vivo. The euglycaemic insulin clamp is currently the best available standard technique. It provides steady-state measures of insulin action and is easily combined with a number of other investigative methods (tracer dilution, limb catheterization, indirect calorimetry, positron emission tomography and nuclear magnetic resonance scans). Whereas homeostatic model assessment uses fasting plasma glucose and insulin concentrations to derive indices of insulin sensitivity and secretion from a mathematical model, other techniques are based on the exogenous infusion of glucose or insulin, or both, either under steady-state (the insulin suppression test) or under dynamic conditions (insulin tolerance test, intravenous glucose-tolerance test with minimal model analysis, and constant infusion of glucose with model assessment).This article recalls the principles of insulin action, with special reference to the concept of clearance and the equivalence of different approaches to estimating this function. Merits and disadvantages of the various techniques are then concisely reviewed, with emphasis on their relative feasibilities and reliabilities. Recent developments and future trends are mentioned. Criteria for choice and some reference data are given to aid the clinical investigator.

ISSN:0263-6352    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Long-term blood pressure stability in humans is not affected by prolonged hypotensive drug therapy. After withdrawal of long-term hypotensive therapy from essential hypertensives, their blood pressures soon return to pre-treatment levels. Since the well-studied stabilizing systems all adapt to prevailing blood pressure levels, they cannot account for long-term stability of blood pressure.There is a parallel between trough blood pressure and the lower limit of cerebral autoregulation. Blood pressure goes down to a trough level once sleep has been established. This level is maintained for 3–4 h, with minor perturbations. For normal and hypertensive humans and rats, the level is almost the same as the lower limit of cerebral autoregulation. In essential hypertension the nocturnal fall of blood pressure and the lower limit for cerebral autoregulation could be set by atheromatous narrowing or occlusion of large cerebral arteries, especially those supplying the brain stem, from which the Cushing response is initiated. Constriction and maldevelopment of smaller cerebral arteries are probably the main causes of increased cerebrovascular resistance in spontaneously hypertensive rats (SHR). The structural difference between the two situations might explain the failure of prolonged hypotensive therapy to reduce the lower limit of cerebral autoregulation in humans, which it is able to achieve in young SHR.If trough blood pressure stability were the anchor which prevents casual blood pressures from drifting, a primary increase of cerebrovascular resistance would be a plausible explanation for essential hypertension. It could also make a major causal neurogenic contribution to hypertension in rat models, especially SHR and stroke-prone SHR.

ISSN:0263-6352    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Although the blood vessels are exposed to high pressures in hypertension, the main complications of hypertension (stroke and myocardial infarction) are paradoxically thrombotic rather than haemorrhagic. In keeping with Virchow's triad, patients with hypertension do demonstrate abnormalities of vessel wall (endothelial dysfunction or damage), blood constituents (abnormal levels of haemostatic factors, platelet activation and fibrinolysis) and blood flow (rheology and flow reserve), suggesting that hypertension does confer a prothrombotic or hypercoagulable state. These abnormalities appear to be related to target organ damage and long-term prognosis and are altered by treatment. The observation that satisfactory blood pressure reduction with non-drug intervention and with various classes of antihypertensive drugs does not lead to an equal reduction in heart attacks and strokes may be due in part to unfavourable effects on the hypercoagulable state in hypertension. Antihypertensive agents with particular benefits in reducing this hypercoagulable state would be likely to have additional advantages in reducing the occurrence of stroke and other thromboembolic events.J Hypertens16:913–916 © 1998 Lippincott-Raven Publishers.

ISSN:0263-6352    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

BackgroundThe greater than normal cardiovascular risk of hypertensive patients could be partly due to an impairment of hemostatic balance found in such individuals.ObjectiveTo examine the relationship between hemostatic variables and blood pressures in 1950 apparently healthy male participants in the prospective cardiovascular Münster study aged 40–65 years.MethodsBlood pressure and other variables were determined, including fibrinogen level, coagulation factor VII clotting activity, protein C level, antithrombin III level, plasminogen activator inhibitor-1 level, euglobulin fibrinolytic activity, and von Willebrand factor level.ResultsAge-adjusted mean values of coagulation factor VII clotting activity, plasminogen activator inhibitor-1 level, antithrombin III level, and protein C level in hypertensives and borderline hypertensives were significantly higher than those in normotensive men (e.g. for hypertensive versus normotensive men, coagulation factor VII clotting factor activity 111.5 versus 106.1%, plasminogen activator inhibitor-1 level 5.05 versus 3.22 arbitrary units/ml, and protein C level 111.1 versus 107.0%,P< 0.05–0.01). For most of the hemostatic variables we found positive bivariate correlations to blood pressure (P≤ 0.05). Exceptions were von Willebrand factor level (no correlation to blood pressure), and euglobulin fibrinolytic activity (a negative correlation to systolic blood pressure and no correlation to diastolic blood pressure). Significance persisted in the multiple logistic regression analysis with the exception of the relationships between systolic and diastolic blood pressures and fibrinogen level as well as euglobin fibrinolytic activity after adjustment for age. After adjustment for age and body mass index significance for relationships between systolic blood pressure and coagulation factor VII clotting activity as well as protein C level was also lost.ConclusionsWe conclude that the greater than normal cardiovascular risk of hypertensive patients is partly due to an imbalance in hemostasis.

ISSN:0263-6352    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

ObjectiveTo characterize relationships among blood pressure, pulse rate, vitamin C status and other protective and risk factors for older British people, from a national survey.DesignA cross-sectional analysis of survey data.SettingA population study, representative of mainland Britain.SubjectsAmong 914 people of both sexes living in the community, 373 were taking blood-pressure-lowering drugs and were therefore excluded from the analyses.InterventionsCompletion of an interview on health, lifestyle and dietary habits, recording of a 4-day dietary record, anthropometry and taking of a blood sample to determine haematological and biochemical status.Main outcome measuresSystolic and diastolic blood pressures, pulse rate, indices of micronutrient status including plasma ascorbate concentration, nutrient intake and haematology.ResultsPlasma ascorbate concentration was inversely correlated to systolic and diastolic blood pressures and pulse rate. Other covariates of blood pressure included age, sex, domicile, plasma retinol, fibrinogen and γ-tocopherol concentrations, erythrocyte count, prothrombin time and urine sodium: creatinine ratio. Covariates of pulse rate included sex, domicile, plasma fibrinogen and platelet count. Blood pressure was also correlated to intake of vitamin C.ConclusionsPlasma ascorbate concentration and intake of vitamin C are covariates of blood pressure in older people living in Britain. New intervention studies are now needed, to test for possible causalities.

ISSN:0263-6352    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

ObjectiveTo examine incidence of cancer and cancer mortality in relation to high blood pressure.DesignA longitudinal study of middle-aged men from a random population sample.SettingGöteborg, Sweden.SubjectsWe studied 7396 men aged 47–55 years without diagnosed cancer at baseline (1970–1973).Mainoutcome measures Incidence of cancer and mortality from cancer.ResultsBy the end of December 1992, 1401 men had been diagnosed with cancer at any site and 651 had died from cancer. Of the men in the highest fifth of the systolic blood pressure distribution (above 166 mmHg) 126 per 10 000 observation years were diagnosed with cancer at any site, compared with 91 per 10 000 in the lowest fifth [below 130 mmHg; relative risk after adjustment for age, smoking, body mass index, treatment for hypertension and leisure time physical activity 1.41 (95% confidence interval 1.19–1.68); P for trend 0.0001]. Of men in the highest fifth, 55 per 10 000 observation years died from cancer, compared with 42 in the lowest [adjusted relative risk 1.41 (1.09–1.82); P for trend 0.01]. Several types of tumour tended to be more common among men with hypertension, but only genito-urinary cancers [age-adjusted relative risk 1.39 (1.04–1.85)] and non-melanoma skin cancer [age-adjusted relative risk 1.98 (1.12–3.51)] were significantly so. Findings were similar for diastolic blood pressure and if data for the first 5 years of follow-up were excluded. There was an increase in risk of cancer also during the first 5 years [adjusted relative risk 1.80 (1.10–2.92) for systolic blood pressure and 1.77 (1.05–2.99) for diastolic blood pressure].ConclusionsWe found an excess risk of cancer and of death from cancer for men with high blood pressure. Although the increase in risk was comparatively modest, the findings are of public health importance, insofar as both hypertension and cancer are common conditions.

ISSN:0263-6352    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

ObjectivesTo investigate whether hypertension and the use of antihypertensive drugs are associated with mortality from cancer among women.DesignA prospective study of 11 075 women living in Utrecht, the Netherlands, aged 50–65 years at enrolment in a breast cancer screening project (DOM cohort). Women attended screening rounds between 1974 and 1985, during which blood pressure measurements were taken and information on drug use and smoking was ascertained. Since 1974 (median follow-up time 19 years) information on cause of death has been obtained from the patient's general practitioner. Hypertension was defined as a systolic blood pressure > 160 mmHg, a diastolic blood pressure > 95 mmHg, or current use of antihypertensive drugs. Cox regression analysis was used to investigate the association between hypertension (treated and untreated) and total and site-specific mortalities from cancer. The influences of systolic and diastolic blood pressures per 10 mmHg increase for women not using antihypertensive drugs were evaluated. Analyses were adjusted for age, smoking, and body mass index.ResultsIn total, 704 women died of cancer and 1633 women left the study area. Hypertensive women had a greater than normal (not statistically significant) total risk of mortality from cancer [hazard ratio (HR) 1.10, 95% confidence interval (CI) 0.93–1.31]. Risks for treated and untreated hypertensive women were similar. Cancer-site-specific analyses revealed a statistically significantly lower mortality from gastrointestinal cancers among untreated hypertensive women (HR 0.64, 95% CI 0.44–0.93), whereas mortality from lung cancer was more prevalent among these women (HR 2.50, 95% CI 1.37–4.59). Mortality from lymphatic and hematopoietic cancers for drug-treated hypertensive women was greater than normal (HR 2.11, 95% CI 1.04–4.28), as was mortality from cancers of the uterus, cervix, and ovary (HR 1.80, 95% CI 1.00–3.26).ConclusionThese results support the hypothesis that, if there is a link between blood pressure and cancer, it is likely to be positive and relatively small (+10%); and applies also to nondrug-treated women. The relation may apply for some types of cancer, but not for others.

ISSN:0263-6352    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

BackgroundThe possibility that calcium antagonists exert an anti-atherosclerotic action at least partly independently of the blood-pressure-lowering effect is supported by results of a large number of experimental studies and can now be investigated by quantitative β-mode ultrasound imagining of the carotid artery walls.DesignThe European Lacidipine Study on Atherosclerosis (ELSA) is a prospective, randomized, double-blind, multinational trial comparing effects of 4-year treatment based on the long-acting, highly lipophilic calcium antagonist lacidipine with those of treatment based on the β-blocker atenolol on the development of carotid artery wall alterations in patients (aged 45–75 years) with mild-to-moderate hypertension (systolic blood pressure 150–210 mmHg and diastolic blood pressure 95–115 mmHg). While the intervention study is progressing, this article summarizes baseline data obtained from the whole cohort of 2259 patients randomly allocated to treatment.MethodsBaseline ultrasound data were obtained from two replicate examinations performed shortly before random allocation to treatment by certified sonographers at 23 referral centres and read at the ultrasound coordinating centre at the Wake Forest University School of Medicine. Intima—media thickness was measured at up to 12 different sites in the carotid artery tree and expressed as the mean of the maxima at these sites (Mmax), the mean of the maxima at four sites in the distal common carotid artery and bifurcation (CBMmax) and the maximum intima—media thickness (Tmax). Baseline demographic and clinical measurements were performed by investigators in 410 peripheral clinical units and 24 h ambulatory blood pressure monitorings read and validated by members of a centralized unit at the University of Milan. The statistical analysis centre at the Technische Universität Mächen received and analysed all baseline data, by calculating means ± SD, medians and ranges and performing correlation (Spearman correlation coefficients) and multiple regression analyses.ResultsPrevalence of carotid artery wall alterations among the hypertensive patients randomly allocated to treatment in the ELSA was very high: 82% hadTmax> 1.3 mm (‘plaques’ according to protocol) and 17% hadTmax> 1.0 and < 1.3 mm (‘thickening’), with a median of two plaques per patient. We found significant correlations between ultrasound measurements and the following demographic and clinical variables: age, sex, systolic blood pressure and pulse pressure (both clinic and ambulatory), concentrations of total, high-density lipoprotein and low-density lipoprotein cholesterol and triglycerides, smoking habit and duration of hypertension. We found no significant correlation to diastolic blood pressure and glucose concentration. A multiple regression analysis indicated significant variables in the following rank order: age, 24 h ambulatory pulse pressure, sex, low-density lipoprotein cholesterol concentration, triglyceride concentration, smoking and clinic systolic blood pressure.ConclusionsAnalysis of baseline data from the ELSA has shown that there is an extremely marked prevalence of carotid artery wall alterations among mild-to-moderate, middle-aged hypertensive patients. In addition to age, systolic blood pressure and pulse pressure, particularly if they are accurately measured by ambulatory monitoring, play a major role, somewhat greater than those of sex, low-density lipoprotein cholesterol concentration and smoking, in influencing intima—media thickness.

ISSN:0263-6352    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

ObjectiveTo assess cognitive functions and their correlates for a dementia-free cohort of old patients with isolated systolic hypertension.DesignCross-sectional data from the randomization period of the European Trial in Elderly with Systolic Hypertension (Syst-Eur Vascular Dementia Project).SettingSixteen European countries and Israel.ParticipantsWe studied 2252 patients aged 60–100 years (mean 70).Main outcome measuresMini Mental State Examination (MMSE) and Spearman correlation of MMSE scores to demographic data or blood pressure.ResultsThe MMSE was successfully completed for 1474 women and 751 men. The baseline blood pressure averaged 173 ± 10/86 ± 6 mmHg (means ± SD). Median age at which education of patients at school had stopped was 15 years. Men and women who consumed alcohol (28%) had median intakes of 8 and 3 g/day, respectively. The median MMSE score was 29 (range 15–30). The maximum score of 30 was attained by 609 (30%) subjects. Fifty-nine (3%) patients had a MMSE score of 23 or less. The MMSE score decreased with advancing age (r= −0.21,P< 0.001). Both for men and for women, it was positively correlated to the level of education (r= 0.30 andr= 0.32,P< 0.001). For women after adjustment for age and the level of education, the score was correlated negatively to systolic blood pressure (r= −0.07,P< 0.05) but positively to intake of alcohol (r= 0.06,P< 0.05).ConclusionIn a cohort of elderly patients with isolated systolic hypertension, baseline cognitive function measured in terms of the MMSE score was high, probably due to selective recruitment of patients who were not clinically demented. Blood pressure was a weak contributor to cognitive status compared with age and level of education. Baseline cognitive function of women was negatively and independently correlated to systolic blood pressure.

ISSN:0263-6352    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

ObjectiveTo compare the predictive powers of self-measurement of blood pressure at home (home blood pressure measurement) and casual (screening) blood pressure measurement for mortality.DesignA prospective cohort study.Subjects and methodsWe obtained home and screening blood pressure measurements for 1789 subjects aged ≥ 40 years who were followed up for a mean of 6.6 years. The prognostic significance of blood pressure for mortality was determined by the Cox proportional hazards regression model adjusted for age, sex, smoking status, past history of cardiovascular disease, and the use of antihypertensive medication.ResultsWhen the home blood pressure values and the screening blood pressure values were simultaneously incorporated into the Cox model as continuous variables, only the average of multiple (taken more than three times) home systolic blood pressure values was significantly and strongly related to the cardiovascular mortality risk. The average of the two initial home blood pressure values was also better related to the mortality risk than were the screening blood pressure values.ConclusionsHome blood pressure measurement had a stronger predictive power for mortality than did screening blood pressure measurement for a general population. This appears to be the first study in which the prognostic significances of home and screening blood pressure measurements have been compared.

ISSN:0263-6352    

出版商:OVID    

年代:1998

数据来源: OVID