A Six Year Prospective Study of Fibrinogen and Other Risk Factors Associated with Mortality in Stable Claudicants

A total of 333 patients with stable intermittent claudication at recruitment were followed up for 6 years to determine risk factors associated with subsequent mortality. Cardiovascular diseases were the underlying cause of death in 78% of the 114 patients who died. The strongest independent predictor of death during the follow-up period was the plasma fibrinogen level, an increase of 1 g/l being associated with a nearly two-fold increase in the probability of death within the next 6 years. Age, low ankle/brachial pressure index and a past history of myocardial infarction also increased the probability of death during the study period. The plasma fibrinogen level is a valuable index of those patients with stable intermittent claudication at high risk of early mortality. The results also provide further evidence for the involvement of fibrinogen in the pathogenesis of arterial disease.

Antithrombin III and arterial disease

Cross-sectional studies suggest that both low and high antithrombin III levels are associated with the risk of arterial disease, principally ischaemic heart disease (IHD). The prospective relation between antithrombin III and subsequent death from arterial disease has been investigated in 893 men in the Northwick Park Heart Study. Antithrombin III levels were directly correlated with high rather than low levels of factor VII activity and of plasma fibrinogen. There were more deaths from arterial disease in the low and high thirds of the antithrombin III distribution than in the middle third.

Strenuous exercise, plasma fibrinogen, and factor VII activity

OBJECTIVE

To assess the effect of physical activity on plasma fibrinogen and factor VII activity and thus on the risk of ischaemic heart disease.

DESIGN

Cross sectional survey.

SETTING

Ten group practices in the Medical Research Council's General Practice Research Framework.

PATIENTS

3967 men aged 45-69 attending screening clinics for the thrombosis prevention trial.

METHODS

Structured interview to elicit the intensity and frequency of physical exercise during past month. Measurement of fibrinogen, factor VII activity, cholesterol concentration, blood pressure, and other indices of ischaemic heart disease risk.

RESULTS

Strenuous exercise was associated with significantly lower fibrinogen concentrations than mild exercise, implying a difference of about 15% in the risk of ischaemic heart disease. Strenuous exercise was also associated with lower cholesterol concentrations. More frequent strenuous exercise was associated with lower factor VII activity.

CONCLUSIONS

With the recognition of plasma fibrinogen as a strong index of ischaemic heart disease risk the results of this and other studies suggest a pathway through which the protective effect of strenuous exercise may partly be mediated and they provide doctors and patients with a valuable incentive towards prevention, particularly in those whose risk of ischaemic heart disease is substantially due to raised fibrinogen concentrations.

Predictors of mortality and disability in stroke

The increasingly accurate prediction of survival and functional recovery in patients with stroke will be of value in planning both their individual management and the health and social services needed. To establish the independent predictive effects of a range of personal and clinical characteristics, data on 900 patients admitted to Northwick Park Hospital with stroke were analysed by stepwise multiple regression. Older patients who lose consciousness at the outset and show signs of multiple neurological deficits, abnormal pupils, and conjugate deviation of the eyes are more likely to die within a year than those without these characteristics. Those who survive the acute episode and are discharged alive are more likely to die within a year if they are old and have sensory loss with severe physical disability. Older female patients who are incontinent, lose consciousness at the onset of stroke, sustain extensive motor deficits in combination with other neurological deficits, and have residual disabilities from previous strokes are particularly likely to be severely disabled on discharge from hospital. Routinely collected clinical data enable useful forecasts about mortality and disability after stroke. The accuracy of these forecasts can probably be improved further.

Community studies of the health service implications of low back pain

STUDY DESIGN

Retrospective study using primary care physician case notes and a self-report questionnaire on the same randomly selected population sample.

OBJECTIVES

To assess the prevalence, management, and outcomes of low back pain in the community, comparing, in the same random sample of registered patients, self-report questionnaire data and primary care physicians' records.

SUMMARY OF BACKGROUND DATA

The financial and resource implications of low back pain are extensive. Data on consultations, investigations, and the management of low back pain are fragmentary and there are no comparisons estimating prevalence from case notes and self-report.

METHODS

A retrospective study of prevalence, management, referral, and outcome covering the previous 12 months was carried out in three general practices using case notes and a self-report postal questionnaire on a sample of 900 patients over 18 years.

RESULTS

Lifetime prevalence of low back pain was 62%. Annual prevalence was 48%, with 16% reporting low back pain at the time of report. Twenty-four percent consulted their primary care physician for low back pain, of whom 17% were referred to a hospital specialist. The annual consultation rate of patients with low back pain was similar to the rate for patients with chronic conditions. The activities of daily living were restricted in less than half, with few taking sick leave. The general health status of those reporting recent low back pain was significantly lower than those not reporting low back pain. Most felt that low back pain was self-limiting and would not consult health professionals for future episodes. There were substantial discrepancies between case notes recorded at consultation with the primary care physician and self-report regarding consultation and investigations.

CONCLUSIONS

Prevalence rates were comparable with those reported in other studies. The significant discrepancies between data sources suggest patient recall bias or underrecording in case notes. The low consultation rate, time off, and day-to-day disability indicate that most episodes are self-limiting.

Lipid and lipoprotein concentrations in 1604 men and women in working populations in north-west London

Serum lipid and lipoprotein concentrations in men and women vary with age, and so-called "normal" limits should take account of this. Serum cholesterol, triglyceride, and phospholipid concentrations were measured in 1027 men and 577 women in five working populations in north-west London, and lipoprotein electrophoresis and quantitative analyses of lipoprotein concentrations were also performed. In men the best fit between serum cholesterol, triglycerides, and phospholipids, on the one hand, and age, on the other, was given by a curvilinear relationship expressed as a quadratic regression. In women the best fit was given by a linear regression. White men had higher serum cholesterol and triglyceride concentrations than Black men, and these differences were reflected in the distributions of the lipoproteins. There were no differences between values in White and Black women. Young women on oral contraceptives had lipid concentrations similar to those of older women not on these preparations. These data suggest that the adoption of concentrations of serum cholesterol (275-300 mg/100 ml (7-1-7-8 mmol/l) and triglycerides (175-200 mg/100 ml (2-0--2-3 mmol/l) recommended by a recent report on the prevention of coronary disease as limits above which special attention should be given to the management of hyperlipidaemia could result in as few as 2% of younger men or as many as 31% of older men being selected for treatment.

Randomized controlled trial of low dose warfarin in the primary prevention of ischaemic heart disease in men at high risk: design and pilot study

We report the pilot stage of a double-blind randomized controlled trial of low dose warfarin in the primary prevention of ischaemic heart disease (IHD) in men at high risk. The first objective was to see if levels of factor VII coagulant activity, VIIc, could be reduced without undue difficulty from a mean level of about 115% to about 70% (the level in patients on conventional warfarin doses being about 30%). This was accomplished with a mean daily dose of 4.6 mg warfarin. The international normalized ratio (INR) corresponding to a VIIc value of 70% was about 1.5. The second objective was to assess the risk of bleeding associated with the intended level of anticoagulation. There was no significant excess in the number of actively treated men ever reporting nose bleeds, possible haematuria, rectal bleeding or bruising, although there may have been an increase in the frequency of rectal bleeding in men who did report this symptom. The third objective was to establish the willingness of patients to take part in a trial of this kind. Of those invited to the initial screening examination, 72% attended. Of those invited to enter the treatment phase of the trial, 71% did so. Compliance with trial treatment was at a very high level. The rate of withdrawal from randomized treatment was within acceptable limits, at about 15% over a three- or four-year period. The scientific case for a full trial is strong and the pilot trial shows that it could be accomplished.

Mean cell volume in a working population: the effects of age, smoking, alcohol and oral contraception

The effects of mean cell volume (MCV) of age, smoking habit, alcohol consumption, menopausal status, and use of oral contraceptives have been studied as appropriate in 1596 white men and 892 white women in working populations in North-West London. In men, increasing age, smoking and alcohol consumption each make an independent contribution to MCV. In women, the effect of smoking is similar to that in men; the effect of alcohol is less obvious, possibly because of the low stated alcohol intake in women. The effect of alcohol on MCV in the population studied is not as marked as in hospital patients who admit to excessive alcohol consumption; this may partly be due to differences in methods of eliciting intake. There is a small increase in MCV following the menopause. Women on oral contraceptives show a rise in MCV with increasing age; this is not seen in women not on oral contraceptives. There is a strong inverse association between MCV and red blood cell count, which may be part of a mechanism to ensure constant oxygen carrying capactiy.

Gemfibrozil Reduces Plasma Prothrombin Fragment F1+2 Concentration, a Marker of Coagulability, in Patients with Coronary Heart Disease

The effects of gemfibrozil on several indices of haemostatic activity were explored in male patients with coronary heart disease (CHD). Sixty-three of 71 patients completed a crossover study in which gemfibrozil 1,200 mg/day and matching placebo were each taken in randomised order for 2 months in a doubleblind manner, separated by a 2-month washout period. Serum cholesterol decreased by an average (95% confidence interval) of 12 (9 to 15)% and non-fasting triglyceride concentration by 43 (34 to 51)% during active treatment. Plasma prothrombin fragment Fi + 2 concentration, a marker of the in vivo rate of generation of thrombin, was 25 (12 to 37)% lower on average while on gemfibrozil than during the placebo phase. Factor VII coagulant activity (VIIC) and antigen concentration, and fibrinopeptide A concentration were not influenced by gemfibrozil in the group overall. However, the VIIC response appeared to be dependent upon the untreated cholesterol level. Hypercholesterolaemic men (cholesterol >6.5 mmol/1) experienced a significant reduction in VIIC averaging 6% of standard during active therapy. Other effects of gemfibrozil were a 5 (2 to 9)% increase in plasma fibrinogen by a gravimetric method, an 11 (8 to 13)% increase in platelet count, and a 6 (2 to 10)% reduction in white cell count. The reduced incidence of CHD following gemfibrozil therapy in hyperlipidaemic patients may arise in part through a reduction in procoagulant activity and thus the risk of an occlusive coronary thrombosis.

Increased factor VII coagulant activity in the rabbit following diet-induced hypercholesterolaemia. Evidence for increased conversion of VII to alpha VIIa and higher flux within the coagulation pathway

Factor VII coagulant activity (VIIc) is considerably higher in rabbits fed a 1% cholesterol-supplemented diet than in rabbits fed a standard diet. This increase was statistically significant 4-6 days from the beginning of treatment and rose to about 300% during the 100 days of treatment. Treatment is also associated with a 20-fold increase in plasma cholesterol concentration with the major fraction of excess cholesterol associated with the very low and intermediate density lipoprotein fractions. In both groups of rabbits, the direction and extent of variation in VIIc generally coincided with variation in cholesterol, so that over time there were significant and positive correlations between plasma cholesterol concentration in both the rabbits fed the standard diet and the rabbits fed the cholesterol-supplemented diet. The increase in VIIc was due to a higher proportion of the more active alpha VIIa in the plasma of hypercholesterolaemic rabbits rather than to an increase in the concentration of the single-chain protein. The plasma concentration of factor X and prothrombin had increased in the hypercholesterolaemic rabbits by 10 days from the beginning of treatment and both proteins were maintained at 150-200% of the concentrations in the plasma of rabbits fed the standard diet. However, these differences were only seen when the factor X and prothrombin were assayed using synthetic substrates. The specific coagulation assays for these two factors revealed no differences between the groups of animals up to 100 days.

Extra-Cranial Bleeding and Other Symptoms due to Low Dose Aspirin and Low Intensity Oral Anticoagulation

Data from the early stages of the thrombosis prevention trial (TPT) have been used to establish and quantify the risk of extracranial bleeding due to low dose aspirin (75 mg) and low intensity oral anticoagulation with warfarin (international normalised ratio, INR, 1.5) singly or in combination, in men aged between 45 and 69 who are at high risk of ischaemic heart disease (IHD). The design of the trial is factorial, the four treatments being combined low dose aspirin and low intensity anticoagulation (WA), low intensity anticoagulation alone (W), low dose aspirin alone (A) and double placebo treatment (P). The trial is being carried out through the Medical Research Council’s General Practice Research Framework, with participating practices throughout the United Kingdom. Results are based on the first 3,667 men entered. The risk of major gastrointestinal bleeding due to active treatment is probably about 1 in 500 man-years of treatment, there currently being no difference between the three active regimes (WA, W, A). Intermediate and minor bleeding episodes occur more frequently with WA than with W or A on their own, the excess being mainly due to minor nose bleeds and bruises. In turn, both W and A on their own cause more such minor episodes than placebo treatment, P. There is no evidence that any of the three active regimes increases the risk of peptic ulceration, nor do they increase reports of indigestion. Aspirin increases reports of constipation and reduces reports of blurred vision. Minor bleeding occurs less frequently in smokers than in non-smokers but is not influenced by age. The antithrombotic regimes used are feasible and acceptable. So far, combined treatment and treatment with warfarin alone are not associated with more frequent serious hazards than low dose aspirin on its own, a regime that is increasingly used in clinical practice. The results provide a measure of reassurance for further trials of low intensity oral anticoagulation with warfarin alone or in combination with low dose aspirin.

Systematically missing confounders in individual participant data meta-analysis of observational cohort studies

One difficulty in performing meta-analyses of observational cohort studies is that the availability of confounders may vary between cohorts, so that some cohorts provide fully adjusted analyses while others only provide partially adjusted analyses. Commonly, analyses of the association between an exposure and disease either are restricted to cohorts with full confounder information, or use all cohorts but do not fully adjust for confounding. We propose using a bivariate random-effects meta-analysis model to use information from all available cohorts while still adjusting for all the potential confounders. Our method uses both the fully adjusted and the partially adjusted estimated effects in the cohorts with full confounder information, together with an estimate of their within-cohort correlation. The method is applied to estimate the association between fibrinogen level and coronary heart disease incidence using data from 154 012 participants in 31 cohorts.† Copyright © 2009 John Wiley & Sons, Ltd.

Use of Repeated Blood Pressure and Cholesterol Measurements to Improve Cardiovascular Disease Risk Prediction: An Individual-Participant-Data Meta-Analysis

The added value of incorporating information from repeated blood pressure and cholesterol measurements to predict cardiovascular disease (CVD) risk has not been rigorously assessed. We used data on 191,445 adults from the Emerging Risk Factors Collaboration (38 cohorts from 17 countries with data encompassing 1962-2014) with more than 1 million measurements of systolic blood pressure, total cholesterol, and high-density lipoprotein cholesterol. Over a median 12 years of follow-up, 21,170 CVD events occurred. Risk prediction models using cumulative mean values of repeated measurements and summary measures from longitudinal modeling of the repeated measurements were compared with models using measurements from a single time point. Risk discrimination (C-index) and net reclassification were calculated, and changes in C-indices were meta-analyzed across studies. Compared with the single-time-point model, the cumulative means and longitudinal models increased the C-index by 0.0040 (95% confidence interval (CI): 0.0023, 0.0057) and 0.0023 (95% CI: 0.0005, 0.0042), respectively. Reclassification was also improved in both models; compared with the single-time-point model, overall net reclassification improvements were 0.0369 (95% CI: 0.0303, 0.0436) for the cumulative-means model and 0.0177 (95% CI: 0.0110, 0.0243) for the longitudinal model. In conclusion, incorporating repeated measurements of blood pressure and cholesterol into CVD risk prediction models slightly improves risk prediction.

Long-term effects of hemostatic variables on fatal coronary heart disease: 30-year results from the first prospective Northwick Park Heart Study (NPHS-I)

BACKGROUND

The long-term associations of established risk factors for coronary heart disease (CHD), for example cholesterol, are well known, but not for the less familiar hemostatic variables.

OBJECTIVES

To establish whether associations between hemostatic variables and CHD first identified nearly three decades ago have persisted long-term.

METHODS

The first Northwick Park Heart Study (NPHS-I) recruited 2167 white men and 941 white women, average age at entry 48 years, on whom measures of factor (F) VII activity (VIIc) and plasma fibrinogen were carried out, both at entry and at follow-up approximately 6 years later.

RESULTS

During a median follow-up of 29 years, 231 male and 36 female CHD deaths were recorded from notifications by the Office for National Statistics. VIIc at recruitment was significantly related to CHD mortality, corrected rate ratio, RR, per 1 SD increase 1.56 (95% CI 1.29, 1.88) in men and RR 1.78 (95% CI 1.17, 2.72) in women. Recruitment fibrinogen was also strongly related to CHD mortality in men, RR 1.63 (95% CI 1.33, 1.99) but not in women, RR 0.75 (95% CI 0.40, 1.43). The associations persisted after controlling for confounders and were confirmed using 6-year follow-up measurements and in analyses omitting deaths within 10 years of recruitment.

CONCLUSIONS

The hemostatic system contributes to CHD mortality, and its effect is stable over time. For VIIc, the effect was similar in men and women, while for fibrinogen it appeared to be present only in men.

Sources of Variability in Coagulation Factor Assays

Estimates of the components of variation of a number of coagulation factor assays are presented and are compared with those for other haematological and biochemical variables. They have been derived from a study in which fourteen volunteers gave blood samples approximately bi-monthly for three years. The systematic between-batch variation w7as generally only a small component of the total variation. However, the proportion of the total variation due to differences between people ranged from about 15% in the case of two measures of antithrombin III to about 85% for cholesterol and haemoglobin. For factor VII activity and fibrinogen, the figure was just over 70%. These estimates of the components of variation are not generally available in the literature. In view of the increasing interest in the role of coagulation factors in the pathogenesis of arterial disease, estimates of this kind are needed both for the interpretation of observed relationships as well as for planning sample sizes for future studies.

Psychological characteristics and fatal ischaemic heart disease

OBJECTIVE

To determine the relation between psychological characteristics and subsequent fatal ischaemic heart disease (IHD) events.

DESIGN

Prospective study of participants in the Northwick Park heart study (NPHS) recruited between 1972 and 1978 and followed up for fatal events until 1997.

SETTING

Three occupational groups in north west London.

SUBJECTS

1408 white men without a history of myocardial infarction aged 40-64 years at entry who completed a Crown-Crisp experiential index form (CCEI).

MAIN OUTCOME MEASURE

Fatal IHD during follow up.

RESULTS

A one point increase in the score on the obsessionality/obsessional neurosis subscale was associated with a relative risk of fatal IHD of 1.08 (95% confidence interval (CI) 1.02 to 1.15). For the functional somatic complaint subscale the relative risk was also 1.08 (95% CI 1.02 to 1.15). In the case of the total score the relative risk of fatal IHD was 1.28 (95% CI 1.09 to 1.50) for a 10 point increase. The associations were independent of age, social class, and known cardiovascular risk factors. In the case of phobic anxiety, which had previously been found to be associated with fatal IHD in NPHS, the association was evident in the first 10 years of follow up but overall the relative risk was only 1.07 (95% CI 0.99 to 1.15) for a one point increase in the score.

CONCLUSION

Scores on two of the subscales of the CCEI and the total score are significantly associated with fatal IHD on long term follow up independently of other known risk factors.

Relation between cigarette smoking and use of hormonal replacement therapy for menopausal symptoms

The aim of this study was to characterise new users of hormonal replacement therapy (HRT) for the relief of menopausal symptoms and to compare these women with never-users of HRT; 402 new users and 804 never-users were studied. Hot flushes were the most common symptom in both users and non-users and were the most frequent reason for prescribing HRT. The prevalence of menopausal symptoms in non-users of HRT was high although substantially lower than that in users. HRT users were more likely to be current cigarette smokers than were never-users. There was also, within smokers, a significant relation between the number of cigarettes smoked and the likelihood of using HRT. This relation between HRT use and smoking could result from an anti-oestrogen effect of smoking, intensifying menopausal symptoms. Of potential clinical relevance is the suggestion that a proportion of women using HRT may be doing so in order to alleviate smoking-induced symptoms. Users of HRT were also more likely to have used oral contraceptives than were never-users; this relation was probably behavioural.

Recent history of ischaemic heart disease and duodenal ulcer in doctors

Data are presented on the incidence of ischaemic (coronary) heart disease and duodenal ulcer among the several thousand male medical practitioners aged 35-64 holding immediate sickness benefit policies with the Medical Sickness Annuity and Life Assurance Society Limited. Three periods are considered: 1947-50, 1957-60, and 1961-5.The incidence of first clinical episodes of ischaemic heart disease in the doctors altered little between 1947-50 and 1957-60 but increased in 1961-5. Comparison of the late 1940s with the early 1960s shows a 60% rise of incidence at ages 45-54 but little change at other ages. Cases first presenting as "sudden" death increased between 1947-50 and 1961-5 by 111% at 45-54, and again changed little at 55-64. In two other occupational groups that have been studied-bus conductors and insurance salesmen-the increase of incidence was greater than for the doctors at 45-54 and it occurred also over 55 years of age. The increase from 1947-50 to 1961-5 in mortality during all episodes of ischaemic heart disease was the same in the doctors as in the male population of England and Wales at 45-54, but at 55-64 it was less.The results in the doctors are not due to alterations over the period in length of sickness absence, or underwriting policy, or of the nomenclature used on the certificates.Well-documented changes in the smoking habits of doctors may be partly responsible for what appears to have been a relatively favourable experience of ischaemic heart disease from 1947-50 to 1961-5, especially at ages 55-64.Incidence of duodenal ulcer at ages 35-64 declined steadily in this population of doctors from 1947-50 to 1961-5. The decline is very likely to be real.

The Women's international study of long-duration oestrogen after menopause (WISDOM): a randomised controlled trial

BACKGROUND

At the time of feasibility work and final design of the trial there was no randomised control trial evidence for the long-term risks and benefits of hormone replacement therapy. Observational studies had suggested that long term use of estrogen was likely to be associated, amongst other things, with reduced risks of osteoporosis and ischaemic heart disease and increased risks of breast and endometrial cancer. Concomitant use of progestogens had been shown to protect against endometrial cancer, but there were few data showing how progestogen might affect estrogen actions on other conditions. Disease specific risks from observational studies suggested that, overall, long-term HRT was likely to be beneficial. Several studies showed that mortality from all causes was lower in HRT users than in non-users. Some secondary cardiovascular prevention trials were ongoing but evidence was also required for a range of outcomes in healthy women. The WISDOM trial was designed to compare combined estrogen and progestogen versus placebo, and estrogen alone versus combined estrogen and progestogen. During the development of WISDOM the Women's Health Initiative trial was designed, funded and started in the US.

DESIGN

Randomised, placebo, controlled, trial.

METHODS

The trial was set in general practices in the UK (384), Australia (94), and New Zealand (24). In these practices 284175 women aged 50-69 years were registered with 226282 potentially eligible. We sought to randomise 22300 postmenopausal women aged 50 - 69 and treat for ten years. The interventions were: conjugated equine estrogens, 0.625 mg orally daily; conjugated equine estrogens plus medroxyprogesterone acetate 2.5/5.0 mg orally daily; matched placebo. Primary outcome measures were: major cardiovascular disease, osteoporotic fractures, breast cancer and dementia. Secondary outcomes were: other cancers, all cause death, venous thromboembolism and cerebro-vascular disease.

RESULTS

The trial was prematurely closed during recruitment following publication of early results from the Women's Health Initiative. At the time of closure, 56583 had been screened, 8980 entered run-in, and 5694 (26% of target of 22,300) randomised. Those women randomised had received a mean of one year of therapy, mean age was 62.8 years and total follow-up time was 6491 person years.

DISCUSSION

The WISDOM experience leads to some simple messages. The larger a trial is the more simple it needs to be to ensure cost effective and timely delivery. When a trial is very costly and beyond the resources of one country, funders and investigators should make every effort to develop international collaboration with joint funding.