Search PubMed⌕ Search

Biomedical subjects

S G Thompson

Publications and source records attributed to S G Thompson.

At least 109 records · Page 6Linked to original sources
PubMed1990

Relation of urinary cotinine concentrations to cigarette smoking and to exposure to other people's smoke.

The relation of urinary cotinine measurements to tobacco consumption in smokers and to exposure to other people's smoke in non-smokers was studied in 49 smokers and 184 reported non-smokers attending a health screening centre. The median urinary cotinine concentration was 1623 ng/ml in the smokers and 6.1 ng/ml in the non-smokers. In smokers the average urinary cotinine concentration increased with reported habitual cigarette consumption; in non-smokers it increased with the reported total seven day duration of exposure to other people's tobacco smoke. Cotinine concentrations were approximately three times higher in non-smokers living with a spouse or partner who was a smoker than in those living with a non-smoker; their reported duration of exposure to tobacco smoke was also three times higher. Non-smoking subjects who were exposed to any tobacco smoke and who lived with a smoker reported 70% of their exposure to be at home (56% for men and 86% for women); the men reported more exposure at work than non-smoking men who lived with a non-smoker. This study confirms the relation of urinary cotinine to stated tobacco smoke exposure in both smokers and non-smokers and further validates the use of information on the smoking habits of the spouse or partner as a measure of tobacco smoke exposure in epidemiological studies of non-smokers.

Adult↗
PubMed1989

The measurement of haemostatic factors in 16 European laboratories: quality assessment for the Multicentre ECAT Angina Pectoris Study. Report from the European Concerted Action on Thrombosis and Disabilities (ECAT).

As part of a European multicentre prospective study involving the measurement of a number of haemostatic factors, a quality assessment (QA) scheme was organized. This paper describes the preparation, design and results of the first QA exercise, involving 16 European laboratories and 10 haemostatic assays. The design allowed the investigation, for each assay, of the variability between duplicates and the variability between days within each centre, and of the agreement between centres. A graphical presentation of each centre's performance in comparison to that of others was adopted, which preserved the confidentiality of each centre's results. The factor VIII clotting activity assay (VIII:C) and the rocket immuno-electrophoresis assays of von Willebrand factor related antigen (vWF R:Ag), antithrombin III, protein C and histidine-rich glycoprotein showed the highest between-duplicate and between-day coefficients of variation (CVs), whereas the clotting assays of activated partial thromboplastin time and fibrinogen had the lowest CVs. CVs for the enzymatic assays using synthetic substrates of antithrombin III, plasminogen and alpha-2-antiplasmin were between these extremes. The between-centre CVs were high for both the VIII:C and vWF R:Ag assays. The QA exercise showed that, in multicentre studies involving the measurement of haemostatic factors, it is feasible to undertake analysis locally at each centre.

Angina Pectoris↗
PubMed1989

Serum cholesterol and subsequent risk of cancer: results from the BUPA study.

In the BUPA study, a prospective study of 22,000 men attending a screening centre in London, the mean serum cholesterol level of the 267 men who developed cancer was 6.66 mmol l-1, not significantly different from the mean level of 6.72 mmol l-1 among the 525 unaffected controls matched for age, smoking history and the calendar quarter of their attendance at the screening centre. There was, however, a significant difference in serum cholesterol levels among men who were diagnosed as having cancer less than 2 years after the date of blood collection (6.49 mmol l-1 for the 116 cancer subjects and 6.78 mmol l-1 for the 224 controls (P = 0.02)) but not in men who developed cancer 2-11 years after blood collection (6.79 mmol l-1 for the 151 cancer subjects and 6.68 mmol l-1 for the 301 controls). The observation that the association between low serum cholesterol and cancer was confined to men in whom a diagnosis of cancer was made within 2 years after the date of blood collection suggests that the low serum cholesterol is a metabolic consequence rather than a precursor of the cancer. Our results, which are consistent with the majority of other published studies, indicate that a low serum cholesterol is not a cause of cancer.

Adult↗
PubMed1989

Risk factors for stroke and myocardial infarction in women in the United Kingdom as assessed in general practice: a case-control study.

Data available in the United Kingdom through the Medical Research Council's General Practice Research Framework were recorded in a study of 603 women aged 45-69 with confirmed diagnoses of stroke or myocardial infarction, each matched by age with two controls. Current cigarette smoking and a family history of myocardial infarction were both strongly associated with the risk of stroke and myocardial infarction, with relative risks of 2.47 (95% confidence interval 1.89 to 3.23) and 1.93 (95% confidence interval 1.52 to 2.44) respectively. The relative risks associated with past smoking decreased according to the length of time since stopping smoking. A family history of stroke was not significantly related to the risk of stroke or myocardial infarction. Single women had a lower risk of stroke and myocardial infarction than married women (relative risk 0.49), but parity, past use of oral contraceptives, and menopausal state were not significantly related to the risk of stroke and myocardial infarction in this study. Other characteristics that were identified as risk factors either for subsequent stroke or for myocardial infarction included not only hypertension, diabetes, and past histories of stroke and myocardial infarction, but also past histories of gynaecological cancer and of venous thrombosis. The association with venous thrombosis may indicate the importance of the haemostatic system in a common pathogenesis of venous thrombosis and myocardial infarction.

Aged↗
PubMed1989

The use of hormonal replacement therapy and the risk of stroke and myocardial infarction in women.

STUDY OBJECTIVE: To determine whether there is an association between the use of hormonal replacement therapy (HRT) and the risk of stroke and myocardial infarction (MI). DESIGN: A case-control study of women with stroke or MI was undertaken. SETTING: The cases were notified from 83 general practices to the coordinating centre at Northwick Park Hospital, where the diagnoses were independently confirmed. SUBJECTS: The cases, 603 white women aged 45-69, were each matched to two controls for age and general practitioner. Of the controls, 79% were the first eligible, 15% the second eligible and 6% were obtained at the third or more attempt. MEASUREMENTS AND MAIN RESULTS: A research nurse completed a questionnaire for each case and both controls, which included information obtained from the medical notes on the prescriptions of HRT. An independent quality control check on the selection of controls and on the abstraction of information from the medical notes was made. More than one HRT prescription had been given to 109 cases (18%) and 174 controls (14%), showing a weak association between the risk of stroke and MI and the past use of HRT (relative risk [RR] 1.36, 95% confidence interval [CI] 1.01-1.81). There was a stronger association with preparations contained progestogen alone (RR 1.90, 95% CI 1.11-3.25). On average, HRT had been used 9 years before recruitment to the study and for 15 months. However, the observed gradients of risk according to the duration of HRT use and time since HRT use do not support a causal interpretation. Also, the estimated relative risks were reduced when allowance was made for other cardiovascular risk factors. CONCLUSIONS: There is no evidence that the use of HRT as recently prescribed in the UK constitutes a major cardiovascular risk or benefit.

Aged↗
PubMed1988

Serum beta-carotene and subsequent risk of cancer: results from the BUPA Study.

In the BUPA Study, a prospective study of 22,000 men attending a screening centre in London, serum samples were collected and stored. The concentration of beta-carotene was measured in the stored serum samples from 271 men who were subsequently notified as having cancer and from 533 unaffected controls, matched for age, smoking history and duration of storage of the serum samples. The mean beta-carotene level of the cancer subjects was significantly lower than that of their matched controls (198 and 221 micrograms l-1 respectively, P = 0.007). The difference was apparent in subjects from whom blood was collected several years before the diagnosis of the cancer, indicating that the low beta-carotene levels in the cancer subjects were unlikely to have been simply a consequence of pre-clinical disease. Men in the top two quintiles of serum beta-carotene had only about 60% of the risk of developing cancer compared with men in the bottom quintile. The study was not large enough to be able to indicate with confidence the sites of cancer for which the inverse association between serum beta-carotene and risk of cancer applied, though the association was strongest for lung cancer. The association may be due to beta-carotene affecting the risk directly or it may reflect an indirect association of cancer risk with some other component of vegetables or with a nonvegetable component of diet that is itself related to vegetable consumption.

Adult↗
PubMed1988

Lack of association between haemostatic variables and the presence or the extent of coronary atherosclerosis.

Blood samples were taken for haemostatic analysis from 225 patients with angina pectoris who were admitted to hospital for coronary angiography. beta thromboglobulin, platelet factor 3, platelet factor 4, factor VII:C, factor VIII:C, von Willebrand factor antigen, activated partial thromboplastin time, fibrinogen, antithrombin III, protein C:Ag, plasminogen, and antiplasmin were measured before angiography. Patients who had had a myocardial infarction in the two months before the investigation were excluded from the study. Multiple linear regression analysis showed that none of the haemostatic variables contributed independently to the prediction of an angiographic score that indicated the extent of coronary atherosclerosis. History of myocardial infarction, male sex, worsening of angina pectoris, serum triglycerides, and ejection fraction were independently associated with the angiographic score. There were some significant correlations between haemostatic variables and conventional risk factors for coronary heart disease. Thus data obtained from haemostatic analyses of peripheral venous blood do not permit the presence or the extent of atherosclerosis in coronary arteries to be predicted.

Adult↗
PubMed1987

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 was 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.

Analysis of Variance↗
PubMed1987

Serum vitamin E and subsequent risk of cancer.

In a prospective study of about 22,000 men attending a screening centre, serum samples were collected and stored. The concentration of vitamin E (alpha-tocopherol) was measured in the stored serum samples from 271 men subsequently notified as having cancer and from 533 unaffected controls, matched for age, smoking history and duration of storage of the serum samples. The mean vitamin E level of the cancer subjects was not significantly different from that of their matched controls. The mean level in the cancer subjects who were diagnosed as having cancer before the elapse of one year from the date of blood collection was, however, significantly lower than the mean concentration of their matched controls (10.0 and 11.5 mgl-1 respectively, P = 0.003). For subjects whose cancers were diagnosed one or more years after blood collection the difference was not statistically significant either for all cancers or for cancers of six sites considered separately, viz. lung, colon and rectum, stomach, bladder, central nervous system and skin. The most likely explanation for these results is that the low vitamin E levels observed in these subjects were a metabolic consequence, rather than a precursor, of the cancer. This would explain, at least in part, the overall inverse association between serum vitamin E and risk of cancer observed in the published epidemiological studies on serum vitamin E and cancer.

Adult↗
PubMed1987

The relationship between smoking and the response to anti-hypertensive treatment in mild hypertensives in the Medical Research Council's trial of treatment.

The antihypertensive efficacy of propranolol in the treatment of mild hypertension was significantly impaired in cigarette smokers, whereas that of bendrofluazide was not affected by smoking habit. This diminished efficacy of propranolol in smokers may be one of several possible factors operating to reduce its primary preventive action against strokes, and possibly against coronary events.

Adult↗
PubMed1987

Estimating a woman's risk of having a pregnancy associated with Down's syndrome using her age and serum alpha-fetoprotein level.

The risk of an individual woman having a pregnancy associated with Down's syndrome was estimated from her age and her serum alpha-fetoprotein (AFP) level at 14-20 weeks gestation. The estimates were made using published data on the risk of Down's syndrome in relation to maternal age from 4528 affected and over 5 million unaffected pregnancies, and on the risk in relation to serum AFP from 68 affected and 36,645 unaffected pregnancies. Separate estimates were derived for AFP levels using gestational age based on the time since the first day of the last menstrual period and on an ultrasound biparietal diameter measurement. In each case this was done with and without adjusting AFP levels to take account of maternal weight. The same sources of data were also used to construct six Down's syndrome screening policies, each combining information on maternal age and serum AFP. For example with one policy the detection rate would be 28% and would involve selecting 2.8% of unaffected pregnancies for amniocentesis; using age alone the same detection rate could only be achieved by selecting 4.3% of unaffected pregnancies for amniocentesis--an increase of 50%. In general, screening for Down's syndrome using both maternal age and serum AFP is more efficient than either alone.

Age Factors↗
PubMed1987

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.

Climacteric↗
PubMed1986

Does breathing other people's tobacco smoke cause lung cancer?

The available epidemiological studies of lung cancer and exposure to other people's tobacco smoke, in which exposure was assessed by whether or not a person classified as a non-smoker lived with a smoker, were identified and the results combined. There were 10 case-control studies and three prospective studies. Overall, there was a highly significant 35% increase in the risk of lung cancer among non-smokers living with smokers compared with non-smokers living with non-smokers (relative risk 1.35, 95% confidence interval 1.19 to 1.54). Part of this increase was almost certainly caused by the misclassification of some smokers as non-smokers. As smokers, who are more likely to get lung cancer than non-smokers, tend to live with smokers this misclassification probably exaggerated the estimated increase in risk. Adjustment for this error reduced the estimate to 30% (relative risk 1.30), but as people who live with non-smokers may still be exposed to other people's smoke this estimate was revised again to allow for the fact that a truly unexposed reference group was not used. The increase in risk among non-smokers living with smokers compared with a completely unexposed group was thus estimated as 53% (relative risk of 1.53). This analysis, and the fact that non-smokers breathe environmental tobacco smoke, which contains carcinogens, into their lungs and that the generally accepted view is that there is no safe threshold for the effect of carcinogens, leads to the conclusion that breathing other people's tobacco smoke is a cause of lung cancer. About a third of the cases of lung cancer in non-smokers who live with smokers, and about a quarter of the cases in non-smokers in general, may be attributed to such exposure.

Female↗
PubMed1986

Haemostatic function and ischaemic heart disease: principal results of the Northwick Park Heart Study.

The Northwick Park Heart Study (NPHS) has investigated the thrombotic component of ischaemic heart disease (IHD) by the inclusion of measures of haemostatic function. Among 1511 white men aged between 40 and 64 at the time of recruitment, 109 subsequently experienced first major events of IHD. High levels of factor VII coagulant activity and of plasma fibrinogen were associated with increased risk, especially for events occurring within 5 years of recruitment. These associations seemed to be stronger than for cholesterol, elevations of one standard deviation in factor VII activity, fibrinogen, and cholesterol being associated with increases in the risk of an episode of IHD within 5 years of 62%, 84%, and 43% respectively. Multiple regression analyses indicated independent associations between each of the clotting factor measures and IHD but not between the blood cholesterol level and IHD incidence. The risk of IHD in those with high fibrinogen levels was greater in younger than in older men. Much of the association between smoking and IHD may be mediated through the plasma fibrinogen level. The biochemical disturbance leading to IHD may lie at least as much in the coagulation system as in the metabolism of cholesterol.

Adult↗
PubMed1986

An international and interregional comparison of haemostatic variables in the study of ischaemic heart disease. Report of a working group.

Levels of haemostatic variables that may be involved in thrombogenesis have been compared in groups of men of similar mean age in communities at very low (Gambia), high (England and Czechoslovakia) or very high (Scotland and Finland) risk of ischaemic heart disease (IHD). There was a consistent gradient of higher factor VII levels with higher IHD risk and also suggestive gradients in the case of two other vitamin K dependent factors, factors II and X. Mean platelet counts were lower and mean fibrinolytic activity was greater in Gambian men than in European men. There was a suggestive though not entirely consistent association between mean fibrinogen levels and IHD risk in the groups from IHD-endemic countries. The results as a whole, and particularly those on factor VII, strengthen the case for the increasingly detailed epidemiological as well as laboratory investigation of the role of the haemostatic system in thrombogenesis and IHD.

Adult↗
PubMed1986

An association between the factor VII coagulant activity and thrombin activity induced by surface/cold exposure of normal human plasma.

To test whether factor VII activation correlated with the generation of thrombin activity when plasma was exposed to a glass surface and reduced temperature, an association was sought between the changes in factor VII clotting activity (VIIc) and fibrinopeptide A concentration (an index of thrombin activity) in platelet-poor citrated plasma from 42 healthy adults. The Spearman rank correlation (rs) between responses was 0.82 (P less than 0.001). The VIIc assay response to surface/cold exposure was unaffected when thrombin was suppressed by hirudin. An assay for factor VII activity based upon its activation of tritiated factor X revealed an association between the increase in fibrinopeptide A concentration and reduction in functional factor VII concentration during activation of a subset of 22 plasma samples (rs = -0.62; P = 0.003). This loss of functional factor VII was probably due to conversion of active factor VII to its non-functional end-product by factor Xa. The results suggest that VIIc is an index of flux within the coagulation system and support the hypothesis that a high VIIc is an indicator of a hypercoagulable state.

Adult↗
PubMed1986

Comparison of an ELISA with a RIA method for serum alpha-fetoprotein determination in screening for fetal neural tube defects.

An enzyme-linked immunosorbent assay (ELISA) was evaluated for serum alpha-fetoprotein determination in the antenatal screening for fetal open neural tube defects. The ELISA was used concurrently with an existing radioimmunoassay (RIA) method until serum specimens from 5000 pregnant women, between 15 and 20 weeks gestation, had been tested. The accuracy of the ELISA was similar to that of the RIA; the median AFP values by gestational week obtained with the ELISA were, on average, 2 KIU/L higher than the corresponding RIA values; the 10th and 90th percentiles, in terms of multiples of the median (MoM), were very similar. The precision of the two methods was also similar. The ELISA method yielded 1.8% results from unaffected pregnancies above 2.5 MoM compared with 1.4% by RIA, a small but statistically significant difference (P = 0.03). Both methods detected the same affected pregnancies identified during this period; five open neural tube defects, three with exomphalos and three intra-uterine deaths. The ELISA method was simple, required about one quarter less operator time than the RIA and enabled results to be generated in one day rather than the two days required by RIA. The ELISA method is a suitable alternative to RIA for routine use in screening for fetal neural tube defects.

Enzyme-Linked Immunosorbent Assay↗