Involvement of the hemostatic system in the insulin resistance syndrome. A study of 1500 patients with angina pectoris. The ECAT Angina Pectoris Study Group

Increased PAI activity and PAI-1 antigen occurring with an oral fat load: associations with PAI-1 genotype and plasma active TGF-beta levels

Whether the post-prandial lipemic response is linked to potentially pro-atherogenic and/or prothrombotic changes in plasminogen activator inhibitor (PAI) and transforming growth factor-beta (TGF-beta) is uncertain. The aim of our study was to determine whether PAI-1 antigen and PAI activity were elevated during post-prandial lipemia following a standard fat tolerance test. We also investigated changes in TGF-beta1 antigen and TGF-beta activity, to determine whether changes in TGF-beta activity were associated with changes in PAI measurements. Lastly, the influence of genotype at a common insertion/deletion polymorphism in the PAI-1 promoter on changes in PAI activity and PAI-1 antigen was examined. Fat tolerance tests were undertaken in 57 healthy middle-aged men to investigate associations between plasma concentrations of lipoproteins, PAI (antigen and activity) and TGF-beta. PAI-1 concentration increased by 76% after 8 h (P < 0.0001). PAI activity also increased by 64% (P = 0.0054) and TGF-beta activity decreased by 10% (P < 0.0001). Increases in PAI-I antigen and PAI activity varied markedly between individuals. To investigate these heterogeneous responses we examined whether genotype at the common insertion/deletion polymorphism of the PAI-1 promoter accounted for these differences. Individuals with at least one 4G (deletion) allele showed potentially pro-atherogenic changes in both PAI-1 and TGF-beta, compared to individuals who were homozygous for the 5G (insertion) allele. In conclusion, increased PAI and decreased TGF-beta activity occur during a fat tolerance test and this effect may be modulated by a common insertion/deletion polymorphism in the PAI-1 promoter.

Relationship of blood coagulation and fibrinolysis to vital exhaustion

OBJECTIVE

Acute physical and psychological stressors affect blood coagulation and fibrinolysis, but little is known about hemostatic factors associated with chronic psychological stress. Prolonged psychological stress may end in a state of vital exhaustion, which has been shown to be a risk factor for first myocardial infarction and recurrent events after coronary angioplasty. The present study tested the hypothesis that vital exhaustion resulting from chronic psychological stress is associated with impaired fibrinolytic capacity and increased coagulation factors.

METHODS

On the basis of a validated questionnaire and subsequent structured interview, a well-defined group of otherwise healthy exhausted men was recruited (N = 15) and compared with age-matched not-exhausted controls (N = 15). Fibrinolytic measures included tissue plasminogen activator (TPA) antigen and plasminogen activator inhibitor (PAI-1) activity, and as coagulation factors we examined factors VIIc, factor VIIIc, and fibrinogen. Control variables were: blood pressure, smoking status, triglycerides, cholesterol, and standard hematological measures. Samples were collected twice to correct for intraindividual fluctuations. Statistical analyses were performed using 2 x 2 mixed model analysis of variance with subsequent univariate testing.

RESULTS

Vital exhaustion was associated with significantly elevated levels of PAI-1 activity (p = .023). The higher PAI-1 activity in exhausted subjects (median = 13.0 U/ml vs. 6.0 U/ml) was not accounted for by smoking status or serum lipids. No significant differences were observed in TPA antigen, factor VIIc, factor VIIIc, and fibrinogen. The groups did not differ in blood pressure, smoking status, triglycerides, cholesterol, or standard hematological measures.

CONCLUSION

These data suggest a reduced fibrinolytic capacity in exhausted individuals. Therefore, the relationship between vital exhaustion and risk of myocardial infarction may be mediated in part by an imbalance between blood coagulation and fibrinolysis.

Liposuction in Dercum's disease: impact on haemostatic factors associated with cardiovascular disease and insulin sensitivity

OBJECTIVE

To study the impact of adipose tissue removal by liposuction on factors associated with increased risk of cardiovascular atherosclerotic disease within the coagulation and fibrinolytic system and glucose metabolism.

DESIGN, SETTING AND SUBJECTS

Liposuction was performed in 53 patients with Dercum's disease. The levels of fibrinogen, von Willebrand factor antigen (VWF:Ag) and plasminogen activator inhibitor type 1 activity (PAI-1) were measured preoperatively, and 2 weeks, 4 weeks and 3 months postoperatively. In a subsample of 10 patients, insulin sensitivity was determined before and 2-4 weeks after surgery using the 2-h euglycaemic hyperinsulinaemic clamp technique. The study was performed as a single-centre study.

MAIN OUTCOME MEASURE

Fibrinogen, PAI-1 and VWF:Ag levels, and glucose uptake before and after removal of adipose tissue.

RESULTS

Weight reduction was sustained throughout the follow-up period with a mean decrease from 90.7 to 86.6 kg (P < 0.0001). There was a slight increase in levels of coagulation factors 2 and 4 weeks postoperatively, probably in reaction to the surgical trauma. After 3 months the values had returned to preoperative levels except for PAI-1, which still showed a slight increase (P < 0.05). In the subsample of 10 patients, glucose uptake was improved (P < 0.05) from a short-term perspective after surgery.

CONCLUSION

Surgical removal of adipose tissue, without change in lifestyle, does not seem to improve the levels of coagulation and fibrinolytic factors associated with cardiovascular atherosclerotic disease, whereas glucose takeup may be facilitated and insulin sensitivity increases from a short-term perspective.

Hypertriglyceridemia, atherogenic dyslipidemia, and the metabolic syndrome

The importance of high serum cholesterol, especially a high level of low-density lipoprotein (LDL) cholesterol, as a risk factor for coronary artery disease is well established. Likewise, efficacy for decreasing risk for coronary artery disease by LDL-lowering therapy has recently been documented through clinical trials. However, many high-risk patients manifest elevated serum triglyceride levels, and the role of hypertriglyceridemia in causation of coronary artery disease remains to be elucidated. Nonetheless, there is growing evidence that hypertriglyceridemia is a marker for increased risk for coronary artery disease; in fact, it can serve as a marker for several atherogenic factors. These factors include increased concentrations of atherogenic triglyceride-rich lipoproteins; the atherogenic lipoprotein phenotype, or lipid triad; and the metabolic syndrome. The lipid triad consists of elevated serum triglycerides, small LDL particles, and low high-density lipoprotein (HDL) cholesterol. The metabolic syndrome includes the coexistence of the lipid triad, elevated blood pressure, insulin resistance (plus glucose intolerance), and a prothrombotic state. Many previous studies indicate that hypertriglyceridemia is strongly associated with all of these atherogenic factors. The clinical approach to treatment of patients with hypertriglyceridemia thus requires a broad-based strategy that includes reduction of atherogenic triglyceride-rich lipoproteins, reversal of the lipid triad, and favorable modification of the metabolic syndrome. The development of therapeutic regimens to effect these changes poses a challenge for future research on the problem of hypertriglyceridemia.

Estrogen replacement therapy and cardiovascular protection: lipid mechanisms are the tip of an iceberg

Cardiovascular disease remains a major cause of mortality among postmenopausal women. After menopause, atherogenesis is promoted by a number of metabolic and vascular changes. A multitude of observational clinical studies have come to the conclusion that estrogen replacement therapy (ERT) reduces cardiovascular risk by approximately 50% and that estrogen's favorable effects on the lipid profile can explain only 25-50% of the overall observed reduction. Estrogens are now known to have potent anti-atherogenic properties through lipid and non-lipid mechanisms; both will be highlighted in view of the recent literature. Estrogens induce favorable changes on lipids and lipoproteins, partly by increasing HDL-cholesterol and decreasing both LDL-cholesterol and lipoprotein (a). Non-lipid mechanisms of estrogen action include decreasing insulin resistance, serum fibrinogen, factor VII and plasminogen activator inhibitor-1 (PAI-1). Moreover, estrogens maintain endothelial cell integrity, decrease expression of adhesion molecules, lower systemic blood pressure, promote vasodilatation, decrease platelet aggregability, inhibit vascular smooth muscle cell proliferation, possess potent antioxidant and calcium antagonist activities, inhibit adrenergic responses and downregulate platelet and monocyte reactivity. Also mentioned are recent reports linking estrogen to the renin-angiotensin system, relaxin, serotonin and homocysteine. What was once thought of as a simple action is now being increasingly appreciated as a complex, multifaceted mechanism, which serves to prove that estrogen is a powerful cardiovascular agent.

The 4G/5G polymorphism of the plasminogen activator inhibitor gene is associated with the time course of progression to acute coronary syndromes

The 4G allele of the plasminogen activator inhibitor (PAI-I) gene is associated with increased PAI-I levels. Increased PAI-I levels have been reported to be associated with atherothrombotic events. However, the significance of the 4G/5G polymorphism of the PAI-I gene in the pathogenesis of ischemic heart diseases has not been determined. We assessed the 4G/5G polymorphism of the PAI-I gene in 500 subjects including 148 normal controls, 23 subjects with normal coronary arteries, 28 subjects with a paradoxical acetylcholine response, 97 subjects with angina pectoris (AP) and 204 subjects with myocardial infarction (MI). We assessed the length of time between the first anginal pain and the onset of acute coronary syndromes (ACS) in the AP and MI subjects. Subjects who developed ACS within 2 months from the first anginal pain were categorized to have a rapid progression to ACS, and subjects who had had stable anginal pain more than 2 months were placed in the non-ACS group. Subjects in the ACS group were younger than those in non-ACS group (P = 0.012) The frequency of the 5G/5G genotype of the PAI-I gene was lower in the ACS (0.228) than in the non-ACS group (0.093) (P = 0.003). Multiple logistic analyses revealed that a younger age (P = 0.028, odds ratio = 1.03) and the (4G/5G + 4G/4G) genotype of the PAI-I gene (P = 0.008, odds ratio = 2.68) were associated with the ACS group. We also assessed plasma PAI-I antigen levels in 78 subjects. Plasma PAI-I antigen levels in the non-ACS group were significantly lower than those in the ACS group (P = 0.050). Multiple regression analyses revealed that plasma PAI-I levels were determined by plasma insulin (P < 0.001) and the genotype of the PAI-I gene (P = 0.019). Higher plasma insulin levels and the (4G/5G + 4G/4G) genotype of the PAI-I gene were associated with higher plasma PAI-I levels. The 4G/5G polymorphism of the PAI-I gene influenced not only plasma PAI-I antigen levels but also the time course of the progression to ACS in patients with coronary atherosclerosis.

Social inequality in coronary risk: central obesity and the metabolic syndrome. Evidence from the Whitehall II study

This report describes the social distribution of central obesity and the metabolic syndrome at the Whitehall II study phase 3 examination, and assesses the contribution of health related behaviours to their distribution. Cross-sectional analyses were conducted utilising data collected in 1991-1993 from 4978 men and 2035 women aged 39-63 years who completed an oral glucose tolerance test. There was an inverse social gradient in prevalence of the metabolic syndrome. The odds ratio (95% confidence interval) for having the metabolic syndrome comparing lowest with highest employment grade was: men 2.2 (1.6-2.9), women 2.8 (1.6-4.8). Odds ratios for occupying the top quintile of the following variables, comparing lowest with highest grade, were, for waist-hip ratio: men 2.2 (1.8-2.8), women 1.6 (1.1-2.4); post-load glucose: men 1.4 (1.1-1.8), women 1.8 (1.2-2.6); triglycerides: men 1.6 (1.2-2.0), women 2.2 (1.5-3.3); fibrinogen: men 1.7 (1.4-2.3), women 1.9 (1.2-2.8). Current smoking status, alcohol consumption and exercise level made a small contribution (men 11%, women 9%) to the inverse association between socioeconomic status and metabolic syndrome prevalence. In conclusion, central obesity, components of the metabolic syndrome and plasma fibrinogen are strongly and inversely associated with socioeconomic status. Our findings suggest the metabolic syndrome may contribute to the biological explanation of social inequalities in coronary risk. Health related behaviours appear to account for little of the social patterning of metabolic syndrome prevalence.

Relation of serum cytokine concentrations to cardiovascular risk factors and coronary heart disease

OBJECTIVE

To determine whether serum concentrations of the cytokines tumour necrosis factor alpha (TNF alpha) and interleukin 6 (IL-6), which regulate C reactive protein, are associated with cardiovascular risk factors and prevalent coronary heart disease.

DESIGN

A population based cross sectional study.

SUBJECTS AND METHODS

198 men aged 50 to 69 years were part of a random population sample drawn from south London. Serum cytokine and C reactive protein concentrations were determined by enzyme linked immunosorbent assay. The presence of coronary heart disease was determined by Rose angina questionnaire and Minnesota coded electrocardiogram.

RESULTS

Serum TNF alpha concentrations were positively related to body mass index and Helicobacter pylori infection, but inversely related to alcohol consumption. IL-6 concentrations were positively associated with smoking, symptoms of chronic bronchitis, age, and father having a manual occupation. TNF alpha was associated with increased IL-6 and triglycerides, and reduced high density lipoprotein cholesterol. IL-6 was associated with raised fibrinogen, sialic acid, and triglycerides. ECG abnormalities were independently associated with increases in IL-6 and TNF alpha, each by approximately 50% (P < 0.05 for TNF alpha, P < 0.1 for IL-6). The corresponding increases in men with an abnormal ECG or symptomatic coronary heart disease were 28% for TNF alpha and 36% for IL-6 (P = 0.14 for TNF alpha and P < 0.05 for IL-6).

CONCLUSIONS

This study confirms that many of the phenomena with which C reactive protein is associated, are also associated with serum levels of cytokine, which may be the mechanism.

Central obesity, insulin resistance, syndrome X, lipoprotein(a), and cardiovascular risk in Indians, Malays, and Chinese in Singapore

STUDY OBJECTIVE

To examine the hypothesis that the higher rates of coronary heart disease (CHD) in Indians (South Asians) compared with Malays and Chinese is at least partly explained by central obesity, insulin resistance, and syndrome X (including possible components).

DESIGN

Cross sectional study of the general population.

SETTING

Singapore.

PARTICIPANTS

Random sample of 961 men and women (Indians, Malays, and Chinese) aged 30 to 69 years.

MAIN RESULTS

Fasting serum insulin concentration was correlated directly and strongly with body mass index (BMI), waist-hip ratio (WHR), and abdominal diameter. The fasting insulin concentration was correlated inversely with HDL cholesterol and directly with the fasting triglyceride concentration, blood pressures, plasminogen activator inhibitor 1 (PAI-1), and tissue plasminogen activator (tPA), but it was not correlated with LDL cholesterol, apolipoproteins B and A1, lipoprotein(a), (Lp(a)), fibrinogen, factor VIIc, or prothrombin fragment (F)1 + 2. This indicates that the former but not the latter are part of syndrome X. While Malays had the highest BMI, Indians had a higher WHR (men 0.93 and women 0.84) than Malays (men 0.91 and women 0.82) and Chinese (men 0.91 and women 0.82). In addition, Indians had higher fasting insulin values and more glucose intolerance than Malays and Chinese. Indians had lower HDL cholesterol, and higher PAI-1, tPA, and Lp(a), but not higher LDL cholesterol, fasting triglyceride, blood pressures, fibrinogen, factor VIIc, or prothrombin F1 + 2.

CONCLUSIONS

Indians are more prone than Malays or Chinese to central obesity with insulin resistance and glucose intolerance and there are no apparent environmental reasons for this in Singapore. As a consequence, Indians develop some but not all of the features of syndrome X. They also have higher Lp(a) values. All this puts Indians at increased risk of atherosclerosis and thrombosis and must be at least part of the explanation for their higher rates of CHD.

Risk for non-insulin-dependent diabetes in the normoglycaemic elderly is associated with impaired cognitive function

We studied cognitive function in normoglycaemic elderly subjects at different risk levels for developing non-insulin-dependent diabetes mellitus (NIDDM) and in patients with NIDDM. Risk for NIDDM was considered increased if both 2 h glucose and insulin values on oral glucose tolerance testing were higher than the median in normoglycaemic subjects, and low if the respective values were lower than the median. The increased risk group showed impairment on tests of immediate and delayed memory, attention, visuomotor speed and verbal fluency. Moreover, the increased risk group did not differ from patients with NIDDM on any cognitive tests. Our results suggest that increased risk for NIDDM is associated with widely affected cognitive function in the normoglycaemic elderly, highlighting the importance of healthy living habits.

Albuminuria is directly associated with increased plasma PAI-1 and factor VII levels in NIDDM patients

Increased plasma plasminogen activator inhibitor type 1 (PAI-1), coagulation factor VII (FVII) and fibrinogen levels have been recognized as risk factors for cardiovascular disease. Because a substantially high incidence of cardiovascular disease has been reported in diabetic patients with nephropathy compared with those without nephropathy, we measured plasma levels of PAI-1, FVII activity and fibrinogen in non-insulin-dependent diabetic patients (NIDDM) with normoalbuminuria (without nephropathy), microalbuminuria (incipient nephropathy) and macroalbuminuria (overt nephropathy). PAI-1 and FVII levels were significantly increased in NIDDM with overt nephropathy compared with NIDDM without nephropathy. Fibrinogen levels were comparable between the patients with normo-, micro- and macro-albuminuria. Univariate regression analysis indicated that PAI-1 and FVII levels were significantly correlated with the albumin excretion rate (AER) in urine. PAI-1, FVII and fibrinogen levels were significantly correlated with the degree of insulin resistance estimated by the steady state plasma glucose concentration (SSPG) during the continuous infusion of glucose, insulin and octreotide. PAI-1 levels were correlated with plasma triglyceride (TG) levels. Multiple regression analysis revealed that AER was significantly associated with PAI-1 and FVII levels, whereas TG lost significant correlation with PAI-1 when AER, SSPG and plasma TG were entered as independent variables. SSPG retained an independent correlation with fibrinogen, PAI-1 and FVII levels. These results suggest that elevated plasma levels of PAI-1 and FVII in NIDDM patients with nephropathy are directly associated with renal damage, whereas insulin resistance widely regulates hemostatic components in NIDDM patients, irrespective of the presence of nephropathy.

A novel G/A and the 4G/5G polymorphism within the promoter of the plasminogen activator inhibitor-1 gene in patients with deep vein thrombosis

Plasma plasminogen activator inhibitor-1 (PAI-1) level was observed to be associated with sequence variations at the PAI-1 locus. Therefore, PAI-1 gene promoter was screened for possibly new polymorphisms and to investigate the contribution of these sequence variations to PAI-1 levels in patients with deep vein thrombosis (DVT). DNA was isolated from blood of 83 consecutive unrelated patients (42 +/- 11 years old) and from 50 apparently healthy subjects of similar age and gender distribution. Six fragments covering DNA sequence- 1523 base pairs (bp) upstream from the start of PAI-1 gene transcription to +90 bp in the first exon, were amplified by polymerase chain reaction and analyzed by single-strand conformation polymorphisms. Two polymorphisms were found: a previously described 4G/5G deletion/insertion polymorphism -675bp upstream from the start of transcription and a novel G/A single base substitution polymorphism further upstream at -844 bp. The two polymorphisms were in strong linkage disequilibrium. Significant differences between patients and controls were observed neither for the frequencies of the 4G/5G alleles (0.60/0.40 and 0.59/0.41, respectively) nor for the frequencies of the G/A alleles (0.33/0.67 and 0.41/0.59, respectively). The distribution of both polymorphisms was similar in idiopathic and secondary DVT as well as in first and recurrent DVT. In patients association between the 4G/5G genotypes and PAI activity was observed, with the highest values in the 4G/4G genotype (13.3 U/mL), median values in the 4G/5G genotype (9.8 U/mL) and the lowest values in the 5G/5G genotype (2.0 U/mL). Despite the lack of association between the G/A genotypes and plasma PAI-1 levels, electrophoretic mobility shift assay showed specific binding of a nuclear protein from human vascular endothelial cells extracts to both the G and the A variant, suggesting functional importance of this novel G/A polymorphism in regulating the expression of PAI-1 gene.

Thrombogenic and fibrinolytic factors and cardiovascular risk in non-insulin-dependent diabetes mellitus

Disturbances of the haemostatic system may favour the development of vascular damage and the final occlusion events in the progress of coronary heart disease (CHD). It has been shown recently in epidemiological studies, that increased concentration of several factors, mainly fibrinogen, factor VII, von Willebrand factor (vWF), and the fibrinolytic variables plasminogen activator inhibitor 1 (PAI-1) and tissue plasminogen activator (t-PA), can be considered as risk factors for CHD. As morbidity and mortality through coronary atherosclerosis are higher in type 2 diabetic patients than in nondiabetic subjects and as insulin resistance represents a situation which favours the development of atherothrombosis, evaluation of the haemostatic factors which are recognized as risk factors may be interesting to consider in these situations. In fact, it has been shown that the fibrinolytic parameters PAI-1 and t-PA antigen are strongly related to the metabolic disorder of insulin resistance, whereas the link with fibrinogen, factor VII, and vWF remains weak. Many cross-sectional studies conducted in different populations have shown that PAI-1 and t-PA antigen (which represents t-PA/PAI-1 complexes) are strongly correlated with insulin, triglyceride, high-density lipoprotein (HDL) cholesterol, body mass index, walst-to-hip ratio and blood pressure, and that the improvement of insulin resistance improves in parallel the metabolic abnormalities and the concentration of the fibrinolytic parameters. Attempts at explaining the elevated PAI-1 and t-PA antigen levels in the insulin resistance syndrome have involved many clinical and in vitro studies, in which the role of insulin, insulin propeptides, very-low-density lipoprotein (VLDL) triglyceride, insulin resistance per se, glucose, and adipose tissue have successively been analysed and the main results of these studies are presented in this review. Due to recent experimental data from animal models of thrombosis, a pathogenic role of decreased fibrinolytic activity or increased PAI-1 levels can be proposed and could play a role in the development of vascular disease in subjects with Type 2 diabetes or insulin resistance.

Haemostatic parameters and vascular risk

Associations between increased plasma concentrations of the three haemostatic factors--fibrinogen, Factor VII and plasminogen activator inhibitor 1 (PAI-1)--and cardiovascular disease (CVD) have recently been demonstrated in epidemiological studies. The relative risk of CVD is increased by 2-3 times in subjects whose levels of fibrinogen fall within the upper third of the general distribution in comparison to those subjects who fall into the lower third; a positive correlation exists between increased Factor VII activity and cardiovascular mortality. Many studies have demonstrated that elevated levels of PAI-1 and tPA antigen are associated with CVD. Several studies have also shown that there are important associations between conventional risk factors for atherothrombosis and haemostatic factors. Fibrinogen levels are strongly linked with smoking, and Factor VII levels are linked with cholesterol, triglycerides and fat intake. PAI-1 and tPA antigen levels, on the other hand, are closely associated with insulin resistance. This paper discusses the principal genetic and environmental determinants of the plasma levels of each of these three haemostatic factors and relates them to the risk of developing CVD.

C reactive protein and its relation to cardiovascular risk factors: a population based cross sectional study

OBJECTIVE

To test the hypothesis that minor chronic insults such as smoking, chronic bronchitis, and two persistent bacterial infections may be associated with increases in C reactive protein concentration within the normal range and that variations in the C reactive protein concentration in turn may be associated with levels of cardiovascular risk factors and chronic coronary heart disease.

DESIGN

Population based cross sectional study.

SETTING

General practices in Merton, Sutton, and Wandsworth.

SUBJECTS

A random sample of 388 men aged 50-69 years from general practice registers. 612 men were invited to attend and 413 attended, of whom 25 non-white men were excluded. The first 303 of the remaining 388 men had full risk factor profiles determined.

INTERVENTIONS

Measurements of serum C reactive protein concentrations by in house enzyme linked immunosorbent assay (ELISA); other determinations by standard methods. Coronary heart disease was sought by the Rose angina questionnaire and Minnesota coded electrocardiograms.

MAIN OUTCOME MEASURES

Serum C reactive protein concentrations, cardiovascular risk factor levels, and the presence of coronary heart disease.

RESULTS

Increasing age, smoking, symptoms of chronic bronchitis, Helicobacter pylori and Chlamydia pneumoniae infections, and body mass index were all associated with raised concentrations of C reactive protein. C Reactive protein concentration was associated with raised serum fibrinogen, sialic acid, total cholesterol, triglyceride, glucose, and apolipoprotein B values. C Reactive protein concentration was negatively associated with high density lipoprotein cholesterol concentration. There was a weaker positive relation with low density lipoprotein cholesterol concentration and no relation with apolipoprotein A I value. C Reactive protein concentration was also strongly associated with coronary heart disease.

CONCLUSION

The body's response to inflammation may play an important part in influencing the progression of atherosclerosis. The association of C reactive protein concentration with coronary heart disease needs testing in prospective studies.

Childhood social circumstances and psychosocial and behavioural factors as determinants of plasma fibrinogen

BACKGROUND

High plasma fibrinogen concentration is associated with an increased risk of coronary heart disease. We have investigated associations between plasma fibrinogen and factors operating in childhood and in adulthood, including the psychosocial characteristics.

METHODS

In a cross-sectional study of Civil Servants in London, UK, 2095 men and 1202 women aged 45-55 years provided blood samples for fibrinogen measurement at the time of the Whitehall II study baseline. The participants completed a questionnaire on demographic characteristics, education, employment grade, parents' occupation, health behaviours, and work characteristics.

FINDINGS

Measures of childhood environment (adult height, father's social class, and participant's education) were inversely associated with adult plasma fibrinogen concentration in both sexes. Lower socioeconomic status (as shown by employment grade) was associated with higher fibrinogen concentrations, with differences from top to bottom grade of 0.22 g/L (95% Cl 0.13-0.31) in men and 0.37 g/L (0.18-0.56) in women (p<0.0001, both sexes). This association was not accounted for by measures of childhood circumstances. Control over work, assessed by personnel managers, was inversely related to fibrinogen in both sexes, and a similar relation was seen for self-rated control over work among men but not women. Men in the bottom third of the distribution for self-rated and externally assessed control over work had higher fibrinogen concentrations than those in the top third for both measures (difference 0.16 g//L [0.07-0.26]; p<0.001.) There was no difference between these extremes among women (0.02 g/L [0.16 to 0.19]). Current smokers had higher fibrinogen concentrations than non-smokers, and moderate alcohol consumers had lower concentrations than those who drank occasionally or never.

INTERPRETATION

Although our study was cross-sectional, it provides evidence that adult fibrinogen concentration is determined by factors operating throughout life. Fibrinogen may be a marker of the biological pathways that mediate the inverse socioeconomic gradient in coronary disease.

Glucose intolerance, hyperinsulinaemia and cognitive function in a general population of elderly men

Cognitive impairment is highly prevalent among the elderly. Subjects with disturbed glucose metabolism may be at risk of impaired cognitive function, as these disturbances can influence cognition through atherosclerosis, thrombosis and hypertension. We therefore studied the cross-sectional association of cognitive function with hyperinsulinaemia, impaired glucose tolerance and diabetes mellitus in a population-based cohort of 462 men aged 69 to 89 years. Cognitive function was measured by the 30-point Mini-Mental State Examination. Results were expressed as the rate ratio (95% confidence interval) of the number of erroneous answers given on the Mini-Mental State Examination by the index compared to the reference group. Compared to subjects with normal glucose tolerance, known diabetic patients had a rate ratio of 1.23 (1.04-1.46), newly-diagnosed diabetic patients of 1.16 (0.91-1.48) and subjects with impaired glucose tolerance of 1.18 (0.98-1.41), after adjustment for confounding due to age, occupation and cigarette smoking (p-trend = 0.01). Non-diabetic subjects in the highest compared to the lowest quartile of the area under the insulin curve had a rate ratio of 1.24 (1.03-1.50), after adjustment for confounding (p-trend = 0.02). The results did not change appreciably when potentially mediating factors, including cardiovascular diseases and risk factors associated with the insulin resistance syndrome, were taken into account. These results suggest that diabetes, as well as impaired glucose tolerance and hyperinsulinaemia in non-diabetic subjects are associated with cognitive impairment.

Pathophysiology of fibrinolysis

The observed association between abnormal fibrinolysis and a tendency toward bleeding or thrombosis demonstrates the (patho)physiological importance of the fibrinolytic system. Deficient fibrinolysis represents an important haemostatic abnormality associated with thrombosis. A decreased fibrinolytic activity may be due to a defective synthesis and/or release of tissue-type plasminogen activator (t-PA) from the vessel wall, to a deficiency or functional defect in the plasminogen or fibrinogen molecule or more frequently to increased levels of t-PA inhibitor. Alternatively, excessive fibrinolysis due to increased levels of t-PA, to alpha 2-antiplasmin deficiency or to plasminogen activator inhibitor-1 (PAI-1) deficiency, may result in bleeding tendency.

Fibrinolysis and atherosclerosis

The link between impaired fibrinolytic function and CHD has been reinforced considerably in the past couple of years. This has been achieved by a combination of epidemiological, clinical, cell biological and molecular biological studies. The molecular mechanisms for the identified associations between more established risk factors for atherosclerotic disease and impaired fibrinolytic function now need to be disentangled to promote the design of specific drugs that may pave the way for intervention. The possibility that some of the observed relations are epiphenomena should also not be disregarded. The concept of genotype-specific differences in the susceptibility of the individual to common metabolic disturbances needs to be examined in greater detail. Basic research on the role of fibrinolysis in atherosclerosis and its thrombotic complications should be given high priority, because the modulation of fibrinolytic function is likely to become an important approach to prevention.