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Biomedical subjects

T W Meade

Publications and source records attributed to T W Meade.

At least 199 records · Page 11Linked to original sources
PubMed1980

Haemostatic function and cardiovascular death: early results of a prospective study.

Components of the haemostatic system which may be involved in the pathogenesis of ischaemic heart disease (IHD) were measured in the Northwick Park Heart Study. Of 1510 white men aged 40-64 at recruitment, 49 have since died. 27 died from cardiovascular disease (IHD in all but 3), 18 from cancer, and 4 from other causes. The mean recruitment levels of factor VIIc, factor VIIIc, and fibrinogen were significantly higher in those who died of cardiovascular disease than in those who survived. The independent associations of factor VIIc and fibrinogen with cardiovascular death were at least as strong as the association of blood cholesterol with cardiovascular death. A clustering of two or three high clotting-factor values (factor VIIc, factor VIIIc, and fibrinogen) was present at recruitment in 63% of those who died of cardiovascular disease, compared with 23% of those who survived. The clotting-factor results appeared to be specific for cardiovascular disease: there was no evidence that high levels of factor VIIc, factor VIIIc, and fibrinogen were associated with death from cancer. The general epidemiology of factor VIIc, factor VIIIc, and fibrinogen is consistent with their having a role in the pathogenesis of IHD.

Adult↗
PubMed1980

Progestogens and cardiovascular reactions associated with oral contraceptives and a comparison of the safety of 50- and 30-microgram oestrogen preparations.

Progestogens probably have metabolic effects that may contribute to the increased risk of cardiovascular reactions associated with combined oestrogen-progestogen oral contraceptives. This possibility was investigated by a study of nearly 2000 reports to the Committee on Safety of Medicines from 1964 to 1977. The reports concerned preparations in which norethisterone acetate in doses of 1.0, 2.5, 3.0, or 4.0 mg was combined with 50 microgram of ethinyloestradiol and those in which levonorgestrel in doses of 150 or 250 microgram was combined with 30 microgram of ethinyloestradiol. Observed and expected numbers of reports were compared, using retail pharmacy purchase figures as a measure of the use of different preparations. There was a significant positive association between the dose of norethisterone acetate and deaths from stroke and ischaemic heart disease (IHD); this association was also found for all cases of these two conditions, fatal plus non-fatal. There were no associations of dose of norethisterone acetate with hypertension or venous thrombosis. The higher dose of levonorgestrel was associated with a possible excess of deaths, non-venous plus venous, and an excess of strokes. There was no association between dose of levonorgestrel and hypertension or venous thrombosis. The reports were also used to assess the relative safety of 30-microgram and 50-microgram oestrogen preparations. Those with 30 microgram of oestrogen were associated with significantly fewer reports of death and IHD (both fatal, and fatal plus non-fatal) than those with 50 microgram of oestrogen. In view of the large-scale move towards preparations with progressively lower oestrogen doses, there are no grounds for major changes in oral contraceptive practice. Within the range of preparations currently in use, however, there is a case for minimising the dose of progestogen to reduce the chances of thromboembolism.

Cardiovascular Diseases↗
PubMed1980

Unemployment and the disabled.

An analysis of Employment Services Division statistics show a close relationship between the levels of unemployment in the disabled rehabilitated at the Employment Rehabilitation Centres (ERCs) and the rates of unemployment in the general population in the whole of Great Britain (r = 0.90) or in the local areas of the Centres (r = 0.66). There is also a significant association between the levels of unemployment in 749 rehabilitees passing through one ERC and the rates of unemployment in their home areas. The results have practical implications for both the employment and medical rehabilitation services.

Disability Evaluation↗
PubMed1979

Haemostatic variables associated with diabetes and its complications.

To study the possible role of an "increased thrombotic tendency" in the vascular complications of diabetes several tests of haemostatic function were carried out on 91 men and 63 women with diabetes aged 35-54 years and the results compared with findings in 686 men and 393 women of the same age in the Northwick Park Heart Study. Mean values for factors VII and X, fibrinogen, and platelet adhesiveness were higher in the diabetics, but mean fibrinolytic activity and whole blood platelet counts were lower. Antithrombin III values were also higher in the diabetics, which may have constituted a protective response to other changes favouring the onset of vascular disease. Diabetics with retinopathy had higher factor VII and antithrombin III values, and those with proteinuria had higher values for factor VII, fibrinogen, and platelet adhesiveness than those without these complications. These findings suggest a potentially important association between a thrombogenic tendency and vascular disease in diabetes. Nevertheless, prospective data are needed to clarify whether the haemostatic abnormalities precede the onset of clinically manifest vascular complications or are a consequence of them.

Adult↗
PubMed1979

Characteristics affecting fibrinolytic activity and plasma fibrinogen concentrations.

As part of a study to determine the extent to which the haemostatic system is implicated in the onset of clinically manifest ischaemic heart disease, characteristics influencing fibrinolytic activity (FA) and plasma fibrinogen concentrations were examined in 1601 men aged 18-64 and 707 women aged 18-59 in several occupational groups in North-west London. In men FA noticeably decreased till the age of about 58, when there was a small rise. In women a small increase in FA between 18 and about 40 was followed by a slightly larger fall between 40 and 59. There was a pronounced negative association of FA with obesity. FA was significantly less in smokers than non-smokers, though the effect was not large. FA increased with alcohol consumption. FA in men appeared to be greatest in the lower social classes, and men on night shift had poorer FA than those on day work. FA was greater in women using oral contraceptives than in those not using these preparations. In both sexes FA increased with exercise, but there were no associations between any of the characteristics studied and the increase. Plasma fibrinogen concentrations increase with age and obesity, are higher in smokers than non-smokers, and fall with alcohol consumption. In women the concentrations are higher in those using oral contraceptives. The general epidemiology of FA and plasma fibrinogen concentrations suggests that they may well be implicated in the pathogenesis of ischaemic heart disease.

Adolescent↗
PubMed1979

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.

Adolescent↗
PubMed1979

Relationship of air temperature to various chemical, haematological, and haemostatic variables.

Results for biochemical and haematological variables have been correlated with data on atmospheric temperature in order to identify possible mechanisms through which low environmental temperature may increase mortality from myocardial infarction and cerebrovascular disease. With the exception of cholesterol, there were no associations in the case of several clinical chemistry variables, or of haemoglobin and related indices. With varying degrees of consistency among the sex and age groups studied, temperature was positively correlated with factor VII, antithrombin III, and cholesterol, and negatively correlated with fibrinolytic activity. The correlations were all low but may offer some clues to mechanisms whereby air temperature influences ischaemic heart and cerebrovascular disease mortality.

Adolescent↗
PubMed1979

Ischaemic heart disease mortality risks for smokers and non-smokers.

Although many studies have shown that smoking is associated with an increased risk of death from ischaemic heart disease (IHD), and that the increase appears to vary with age and amount smoked, there has been little formal specification or estimation of the relationship. In this paper two alternative models are tested, using data for different ages and levels of smoking from four major studies in three countries. One model explains 80% of the variation in mortality in terms of a positive linear function of the number of cigerettes smoked, the parameters of which decrease with age. We estimate that every cigerette smoked per day increases the risk of dying from IHD by as much as 35% at ages 35 to 44, reducing to 2% at ages 65 to 74. The risk attributable to smoking may account for more than 80% of IHD deaths of men aged 35 to 44, and 27% of those of men aged 45 to 64. Although the relative risk is highest for younger age groups, the absolute risk of death from IHD that is attributable to smoking increases with age. The evidence suggests that both are increasing with time.

Adult↗
PubMed1979

Repeatability and validity of a modified activities of daily living (ADL) index in studies of chronic disability.

In order to measure disability in a randomised controlled trial of different intensities of rehabilitation following stroke, a modification of existing methods has been developed; it makes use of 17 items of activities of daily living (ADL) which are rated on a three-point scale, and it has been subjected to tests of repeatability and validity. While some activities (e.g. use of taps, ascending or descending stairs) are either redundant or repetitive, others provide independent measures of disability. There was no significant inter-observer variability; the assessors disagreed on 78 (3.7%) out of a total of 2,125 paired observations. In a study of short-term within-patient variability, different scores were assigned on 49 (14.4%) out of a total of 340 observations made on two separate occasions. Minor differences (mainly in activities involving equipment e.g. cookers) emerged when scores obtained in hospital were compared with those obtained at home, but the two sets of scores were still highly correlated (r = 0.962. There was, however, considerable discrepancy between the hospital scores and those derived from the patients' own estimates of their activities at home, the latter falling below actual capabilities as indicated by the hospital scores. A clinical validation of the index showed a significant association between the hospital ADL scores and the extent of cerebral lesions determined by the number of neurological deficits. This modified ADL index is sufficiently repeatable and valid for the assessment of patients with moderate disability as a result of stroke and other chronic diseases; in most circumstances, it can probably be simplified to include only five or six items.

Activities of Daily Living↗
PubMed1979

Ethnic differences in blood pressure with observations on noradrenaline and renin. 1. A working population.

115 factory workers (62 white, 53 black) were studied with measurements of blood pressure, plasma noradrenaline concentration, and plasma renin activity. Blood pressure was higher in blacks than in whites. There were no ethnic differences in plasma noradrenaline, which increased with age, but was not related to blood pressure. Mean plasma renin activity was 55% lower in blacks than whites and this difference was not related to differences in sodium intake. There were no associations between renin and noradrenaline, or between renin and blood pressure.

Adult↗
PubMed1978

The effect of plasma fibrinogen levels on measures of fibrinolytic activity.

It has been claimed that lysis time methods may be inappropriate as measures of fibrinolytic activity on the grounds that they are largely determined by plasma fibrinogen levels. The dilute blood clot lysis time (DBCLT) has therefore been measured in 103 subjects; fibrinolytic activity (expressed as 100/DBCLT) has been compared with the fibrin plate area (FPA) lysed by the euglobulin fraction, the latter method being, of course, virtually independent of plasma fibrinogen. Plasma fibrinogen levels have also been measured; they ranged from 167 to 416 mg%. Results have been analysed by the technique of multiple regression. The incorporation of plasma fibrinogen levels in the regression equation relating 100/DBCLT to FPA does not result in a significant increase in the proportion of the variance in 100/DBCLT that can be explained. It is concluded that there is no evidence that DBCLT is influenced by plasma fibrinogen levels within the physiological range.

Female↗
PubMed1978

Automation of two-stage factor VIII assay.

Two automated methods for two-stage factor VIII assays have been compared with one another, and evaluated in practice. The Depex method records the clotting time when an electric circuit is completed by the formation of a fibrin thread across a hook-type electrode; the Electra method is based on an optical density technique of clot detection. The two methods gave comparable results for measured levels of factor VIII when haemophilic or "normal" plasmas were assayed. Results from the two methods in practice also suggest that both are valid at low and "normal" factor VIII levels. The Electra method is also probably suitable for assays of concentrates; however, the Depex method appears to give falsely high values in these circumstances, and experimental findings suggest that the reason may be that increased viscosity due to the high fibrinogen levels in factor VIII concentrates causes premature closure of the circuit between the two ends of the Depex electrode. The main advantage of the Depex method is that, provided 3 or 4 machines are available, a given number of assays can be completed more quickly than on Electra. The main advantages of Electra are that it is probably subject to less laboratory error than Depex, and that it is suitable for assaying concentrates as well as haemophilic and "normal" plasmas.

Automation↗
PubMed1978

Are racial differences in essential hypertension due to different pathogenetic mechanisms?

1. Plasma noradrenaline concentration and plasma renin activity were measured in a control, British, urban population (n = 115) in which blacks were matched for age and sex with whites. 2. Similar measurements were made in subjects with essential hypertension (77 white and 23 black), and 48 healthy normotensive white civil servants. 3. In controls blood pressure was significantly higher in blacks; it correlated with age in both races and with pulse rate in blacks. There were no significant racial differences in plasma noradrenaline which was positively correlated with age in both blacks and whites. Mean plasma renin activity was 55% lower in blacks, and this difference was not related to urinary sodium excretion. 4. In hypertensive subjects plasma noradrenaline positively correlated with age in blacks. This relationship was not found in whites in whom 20% of young hypertensive subjects (less than 45 years) had significantly raised plasma noradrenaline. Plasma renin activity was again significantly lower in blacks. In white hypertensives plasma noradrenaline and renin activity were significantly correlated. 5. There may be racial differences in the pathogenesis of essential hypertension.

Black People↗