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Biomedical subjects

E G Knox

Publications and source records attributed to E G Knox.

At least 37 records · Page 2Linked to original sources
PubMed1992

Leukaemia clusters in Great Britain. 2. Geographical concentrations.

STUDY OBJECTIVE: The aim was to test a large set of childhood leukaemia and lymphoma registrations for the presence of short radius spacial clusters. DESIGN: The study was a geographical cluster analysis. SETTING: England, Wales and Scotland. PATIENTS: All registrations for leukaemia and lymphoma between 1966 and 1983 in children aged 0 to 14 years were examined. The records included date and age of registration, sex, diagnosis, and the map reference of the postcode of residence. Of the 9411 registrations, 8888 were suitable for inclusion. MAIN RESULTS: There was a significant excess of case pair addresses separated by < 0.5 km. There was also a significant excess of pairs sharing the same postcode. Both findings were based upon comparison with random pairs of postcodes drawn from the Central Postcode Directory. Examination for clustering at this very short range was based upon a clear prior hypothesis derived from the results of a study of space-time interaction, reported in a companion paper. CONCLUSIONS: It is postulated that the space-time interaction and the geographical concentrations shown here result from a common epidemic process. The epidemiology of this disease is characterised by short range geographical concentrations, with temporal non-homogeneity superimposed. The findings exclude certain artefacts which remained unresolved in the space-time interaction study. The distributions almost certainly reflect biological processes, and the most probable explanation is in terms of an infective process.

Adolescent↗
PubMed1991

Cot deaths in Birmingham.

The spatial and temporal distributions of cot deaths and of infant respiratory deaths in Birmingham between 1964 and 1984 were examined. Respiratory deaths declined and cot deaths increased, and the combined rate showed a downward trend. Seasonal variations were identical in the two groups and in each case were more powerfully related to date of death than to date of birth. Cumulative mortalities were parallel by age, depended crucially upon the quarter of the year in which the child was born, and were identical for the two classes of death. The separation of the temporal trends probably owed more to changes in diagnostic practice than to biological or epidemiological processes. Powerful space-time interactions were detected for both groups and for cross-pairs belonging to different groups. There was a four-yearly oscillation in the combined death rate, of doubtful statistical significance, but synchronous with a similar oscillation reported by other investigators using national data. The four-yearly oscillation was also synchronous with the four-yearly pattern for national isolations of Mycoplasma pneumoniae.

Age Factors↗
PubMed1990

Epidural anaesthesia and long term backache after childbirth.

OBJECTIVE: To examine the relation between epidural anaesthesia and long term backache after childbirth. DESIGN: Data from postal questionnaire on morbidity after childbirth sent to women who had delivered in one maternity hospital between 1978 and 1985 were linked to maternity case notes for each woman. SETTING: Maternity hospital in Birmingham. SUBJECTS: 11,701 Women who had delivered their most recent baby at the maternity hospital during the defined period and who returned their completed questionnaires. MAIN OUTCOME MEASURES AND RESULTS: Of the 1634 women who reported backache, 1132 (69%) had had it for over a year. A significant association was found between backache and epidural anaesthesia (relative risk = 1.8); 903 of 4766 women (18.9%) who had had epidural anaesthesia reported this symptom, compared with 731 of the 6935 women (10.5%) who had not had epidural anaesthesia. This association was consistent in both "normal" and "abnormal" deliveries, the only exception being after an elective caesarean section when no excess backache occurred after epidural anaesthesia. CONCLUSIONS: The relation between backache and epidural anaesthesia is probably causal. It seems to result from a combination of effective analgesia and stressed posture during labour. Further investigations on the mechanisms causing backache after epidural anaesthesia are required.

Anesthesia, Epidural↗
PubMed1988

Evaluation of a proposed breast cancer screening regimen.

The Forrest working group on breast cancer screening recommended routine mammography for women in the United Kingdom at ages 50, 53, 56, 59, 62, and 65. Benefits were costed at about 3000 pounds for each life year recovered, but there was no estimate of the cost of each life saved, and the consequent reduction in mortality from breast cancer in the general population of the United Kingdom was not estimated. The present study addressed both of these issues using an interactive computer modelling process. Long term savings were calculated at 900 deaths a year in England and Wales--that is, about 8% of the total deaths from breast cancer--and 9% of life years currently lost. The cost of each death saved from breast cancer was estimated at 39,000 pounds.

Age Factors↗
PubMed1988

Cancer of the cervix and the papilloma viruses.

Squamous cancer of the cervix depends upon infection by Human Papilloma Virus (HPV), of which there are many strains. Some are more dangerous than others and they appear to compete with each other for "territory". The prospective use of vaccines and antiviral agents for HPV infection could disturb the balance of this ecosystem. This study derives the expressions for the prevalences of the different strains at equilibrium. The important parameters of these expressions are 1) the rate of change of sexual partner, 2) infectiousness on contact, and 3) the rates at which an infectious/immune phase decays to a non-infectious/immune phase, and then towards partial or full susceptibility to re-infection. The responses to changes in these parameters are investigated. Analysis shows that the balance between competing strains is locally and precariously stable; it can survive moderate inter-strain variations of the transmission and decay parameters; but larger differences, whether natural or artificially induced, can result in the rapid elimination of the disadvantaged strain. This might be exploited in a preventive programme. Conversely, if a harmless strain were eliminated, the harmful strains would fill the territorial gap, and the incidence of cervical cancer might increase.

Carcinoma, Squamous Cell↗
PubMed1988

Smoking in pregnancy: effects of stopping at different stages.

Of 4341 pregnant women, 3106 were non-smokers and 1235 were smokers at the start of pregnancy. Eighty-five had stopped smoking before 6 weeks gestation, 119 between 6 and 16 weeks, and 56 stopped after 16 weeks. A further 51 stopped temporarily and 924 smoked throughout pregnancy. The mean birthweight of the groups differed. There were also social and biological differences such as might partly explain birthweight variations so comparisons were repeated after allowing for these factors. Standardized mean birthweights were greater for all groups who stopped than for persistent smokers. Those who stopped before 6 weeks and between 6 and 16 weeks gestation had infants 217 and 213 g, respectively, heavier than the persistent smokers and similar to the non-smokers. Babies born to those who stopped after 16 weeks, or temporarily, were intermediate in weight. Appropriate advice is that stopping any time before 16 weeks is best, but stopping after this is still beneficial.

Adult↗
PubMed1987

Ten-day rule.

Explore the source record for details and available documents.

Child↗
PubMed1987

Evolution of rubella vaccine policy for the UK.

The principles of rubella vaccine strategy are reviewed against the background of the current UK programme of vaccinating female adolescents, and the contrasting North American programme of vaccinating young children of both sexes. The effects of using both systems simultaneously are then considered: in particular the question of supplementing the established UK system with child vaccination. Previous computer-simulation and mathematical models predicted the consequences of this policy change with insufficient precision, so an elaborated model is proposed, developed and described. Its special advantages over the simpler model from which it was developed are that it represents the detailed pattern of subsequent temporal change, and allows for the effects of earlier epidemic patterns, of seasonal variations in transmission rates, of earlier vaccine policies and changing levels of implementation. Predictions for the current UK programme, unchanged in principle but converging upon target uptake rates, are compared with the effects of introducing a supplementary policy of vaccinating children. Benefits accrue from supplementary child-uptakes greater than about 50%, but the cost effectiveness is poor. In the absence of a commitment to rubella eradication, and provisions for making vaccination compulsory, it should probably not be undertaken.

Computer Simulation↗
PubMed1987

Effect of anti-smoking health education on infant size at birth: a randomized controlled trial.

The effects of anti-smoking health education during pregnancy on smoking behaviour and the subsequent infant's size at birth were investigated in a controlled trial. It was found that the planned educational intervention was incompletely carried out and was given more effectively to primigravidae in whom subsequent reduction of smoking was more evident. The effects of educative intervention on size at birth were therefore analysed for first and later pregnancies separately. The differences in birthweight and length between the intervention and control groups were concentrated almost entirely among the first born infants who were 68 g heavier and 0.75 cm longer in the intervention group than the first born infants in the control group.

Anthropometry↗
PubMed1987

Effectiveness of screening for congenital dislocation of the hip.

The incidence of congenital dislocation of the hip (CDH) in Birmingham was measured in the period 1942-52 and again in 1950-54; it is measured now in 1974-83. Despite the introduction of neonatal screening for CDH in November 1966, between the times of the earlier and the present measurements there was no indication that CDH requiring prolonged treatment had declined. The performance of the procedure itself was poor. It detected only a third of genuine cases, and the false positives outnumbered the true positives by 10:1. The incidence of 'definite' cases varied markedly from year to year in a manner suggesting diagnostic idiosyncracies rather than genuine fluctuations. There was no evidence in particular maternity units that high levels of early detection led to low levels of late diagnosis. Indeed, maternity units with the worst results--the highest rates of late diagnosis and of prolonged treatment--had the highest rates of early detection and early treatment. Current theories of natural history, aetiology, and treatment should be reappraised.

Diagnostic Errors↗
PubMed1987

Assay of disaturated phosphatidylcholine in amniotic fluid as a test of fetal lung maturity: experience with 2000 analyses.

We determined concentrations of disaturated phosphatidylcholine (DSPC) in nearly 2000 amniotic fluid samples obtained either transabdominally or as vaginal pools. Here we report our comparison of these DSPC values with the lecithin/sphingomyelin (L/S) ratios for amniotic fluid samples obtained from diabetic and nondiabetic pregnancies and also between transabdominally or vaginally collected samples uncontaminated by blood or meconium. DSPC measurement is at least as good as the L/S ratio in predicting the absence of respiratory distress syndrome. DSPC concentrations were, however, lower in diabetic than in nondiabetic pregnancies, supporting the hypothesis that DSPC synthesis may be impaired in fetuses of diabetic mothers. Visually uncontaminated samples collected transabdominally or vaginally, when grouped according to length of gestation, have similar DSPC values but different L/S ratios. Thus, even in the absence of blood or meconium, DSPC may be a more useful test than the L/S ratio for vaginally pooled samples.

Amniotic Fluid↗
PubMed1986

A transmission model for AIDS.

Mathematical and computer-simulation models of sexually transmitted diseases, which have been used to study gonorrhoea and human papilloma virus transmissions, are applied to the study of AIDS. The problems of adapting the general model to the new problem, within already established principles, are described; and solutions offered. The objective is to predict equilibrium levels for the prevalence and incidence of HTLV-III infection in the U.K. Within the uncertainties of the available information on sexual behaviour in our society, on the risk of transmission and on the natural history of the infection, the model predicts: the infection will be self-sustaining in the heterosexual as in the homosexual population, the equilibrium prevalence of HTLV-III infection may attain 500-800 per 1000 among promiscuous male homosexuals and female prostitutes: 1 to 5 per 1000 among non-promiscuous heterosexual males and females: and 8 to 15 per 1000 overall, these equilibria will be reached in about 10 years among the promiscuous classes, but not for 40 years among the less promiscuous, this implies 20,000 to 40,000 deaths from AIDS per year in the U.K., these estimates will be modified by behaviour changes in the population as a whole, responding to fear of infection and to health-education approaches, but substantial control will depend upon the production of a vaccine and its preferential use in the promiscuous classes.

Acquired Immunodeficiency Syndrome↗
PubMed1986

A model basis for the control of whooping cough.

The problems of controlling and ultimately eradicating pertussis are addressed in the face of the apparent impermanence of vaccine immunity, and the limited protection offered while it lasts. Interactions between partial immunity, reduced infectiousness, responses to a superimposed natural infection, changing mean ages of infection and alternative rates of transmission before the vaccine was introduced, are considered in an integrated manner. Mathematical expressions were developed for these different components, from which a computer program was constructed for predicting the levels of control to be expected from different vaccination strategies. The most important of the parameters determining outcomes are those relating to levels of uptake, the choice of a one-course or two-course policy, and the specification of the vaccine itself. As might be expected, high levels of uptake and a two-course policy are necessary for high levels of control, but they will not necessarily succeed. The detailed specification of the type of protection to be offered by a vaccine is also crucial. The most important necessity is for a vaccine immunity with a low rate of decay; but in the presence of decay (which greatly reduces the feasibility of eradication) it is important that the vaccine should protect against the clinical disease without preventing the child from being infected with the organism, and thus attaining permanent immunity.

Child↗
PubMed1986

Perinatal mortality standards: construction and use of a health care performance indicator.

Perinatal mortality rates are an important index of the performance of perinatal health care services, but comparisons are confounded by variations in the prior risk status of the clienteles of different districts and different maternity units. A method of allowing for these differences has been devised. It is based jointly upon the exclusion of certain classes of birth, and on indirect standardisation for birthweight and a number of modifying factors. The method is described, tested, demonstrated, and proposed for more general use.

Birth Weight↗