Biomedical subjects

G J Prescott

Publications and source records attributed to G J Prescott.

10 recordsLinked to original sources

PubMed2005

A Bayesian approach to prospective binary outcome studies with misclassification in a binary risk factor.

Misclassification in a binary exposure variable within an unmatched prospective study may lead to a biased estimate of the disease-exposure relationship. It usually gives falsely small credible intervals because uncertainty in the recorded exposure is not taken into account. When there are several other perfectly measured covariates, interrelationships may introduce further potential for bias. Bayesian methods are proposed for analysing binary outcome studies in which an exposure variable is sometimes misclassified, but its correct values have been validated for a random subsample of the subjects. This Bayesian approach can model relationships between explanatory variables and between exploratory variables and the probabilities of misclassification. Three logistic regressions are used to relate disease to true exposure, misclassified exposure to true exposure and true exposure to other covariates. Credible intervals may be used to make decisions about whether certain parameters are unnecessary and hence whether the model can be reduced in complexity. In the disease-exposure model, for parameters representing coefficients related to perfectly measured covariates, the precision of posterior estimates is only slightly lower than would be found from data with no misclassification. For the risk factor which has misclassification, the estimates of model coefficients obtained are much less biased than those with misclassification ignored.

Bayes Theorem↗

PubMed2003

A cohort study of reproductive risk factors, weight and weight change and the development of diabetes mellitus.

AIMS: Reproductive factors (parity, miscarriages, terminations), oral contraceptive use, hormone replacement therapy, body weight at first pregnancy and weight gain following pregnancy may be associated with a long-term risk of diabetes. The aim of this study is to investigate the independent risks of reproductive factors and body weight for diabetes in later life. METHODS: This is a retrospective cohort study of 1257 parous women who had a first pregnancy between 1951 and 1970. Reproductive history, weight and height were measured at the time of first pregnancy, then assessed by questionnaire in 1997 for all women. A clinical examination and an analysis of blood samples were undertaken for 992 women. The main outcome was incidence of diabetes based on medical history, medication and random glucose measurement. RESULTS: Sixty of the 1257 (4.8%) women developed diabetes. Body mass index at index pregnancy and after 28-48 years follow-up were both significantly associated with risk of diabetes, this increased with greater weight gain. There was a non-significant increased risk of diabetes associated with stillbirths and miscarriages after age and BMI adjustment. CONCLUSIONS: In parous women, higher BMI at index pregnancy, weight gain during follow-up and BMI in later life strongly predict diabetes risk.

Abortion, Induced↗

PubMed2003

Hospitalization in the first year of renal replacement therapy for end-stage renal disease.

BACKGROUND: The requirement for hospitalization of patients on dialysis is likely to be a surrogate marker of age and comorbid diseases. It may also reflect the level of care delivered, and substantially increases the cost of this expensive therapy. AIM: To identify the factors most strongly associated with hospitalization. DESIGN: Prospective population study. METHODS: Data were recorded for all patients starting RRT in Scotland over one year, including the reasons for and duration of, each hospital admission during the first year of RRT. Factors most strongly associated with hospitalization were determined by Poisson regression analysis. RESULTS: Overall, 526 patients were admitted to hospital on 1668 occasions (median 3, IQR 1-4) for 13384 days (median 13, IQR 4-35). Formation of vascular access for haemodialysis (HD) was the most frequent reason for admission, followed by infections. Age, comorbidity, mode of presentation for RRT and primary renal diagnosis were all significantly associated with prolonged hospitalization. Attainment of UK Renal Association standards for urea reduction ratio and serum albumin concentration, and vascular access in the form of arterio-venous fistulae were associated with less hospitalization in patients treated with HD by 90 days. DISCUSSION: Patients in their first year of RRT have a high requirement for in-patient care, 8.6% of patient treatment days being spent in hospital. Vascular access formation, failure and complications account for a large proportion of this. Age and comorbidity prolong the time spent in hospital. As the RRT population continues to increase, with older patients and those with greater comorbidity, in-patient facilities must also expand.

Adolescent↗

PubMed2002

Coincidence of immune-mediated diseases driven by Th1 and Th2 subsets suggests a common aetiology. A population-based study using computerized general practice data.

BACKGROUND: The recent rise in the prevalence of immune-mediated diseases has been attributed to environmental factors such as a lack of microbial challenge, or dietary change, that deviate the overall balance between mutually antagonistic subsets of T helper (Th) cells. OBJECTIVE: An alternative proposal is that recent environmental changes have resulted in an immune system that is more likely to produce both Th1 and Th2 responses against benign antigens. The prediction of this hypothesis, that Th1 and Th2-mediated diseases are not mutually exclusive, and may be positively associated, is tested here in a whole population. METHODS: Data from General Practices participating in the Scottish Continuous Morbidity Recording (CMR) project were used to determine the coincidence of the major Th2-mediated atopic diseases; asthma, eczema and allergic rhinitis, with the Th1-mediated autoimmune conditions; type I diabetes, rheumatoid arthritis and psoriasis. We also identified the prescription rates of inhaled therapy for asthma in patients with Th1-mediated disease. RESULTS: There was a significant increase in the risk of presenting with a Th1-mediated autoimmune condition in patients with a history of allergic disease (standardized prevalence ratio (95% confidence interval) 1.28 (1.18-1.37)). Likewise, the standardized prevalence ratios of presenting with either eczema (1.67 (1.48-1.87)) or allergic rhinitis (1.22 (1.02-1.44)) were significantly increased in subjects with a history of Th1-mediated disease. There was a particularly strong association between current psoriasis and current eczema (standardized prevalence ratio ofpsoriasis in subjects with eczema 2.88, 95% confidence interval (CI) 2.38-3.45). There was also a significant increase in prescriptions for inhaled asthma therapy in patients with Th1 disease. CONCLUSION: It is concluded that Th1- and Th2-mediated diseases are significantly associated in a large General Practice population. This finding supports the proposal that autoimmune and atopic diseases share risk factors that increase the propensity of the immune system to generate both Th1- and Th2-mediated inappropriate responses to non-pathological antigens.

Adolescent↗

PubMed2002

Acute renal failure requiring renal replacement therapy: incidence and outcome.

BACKGROUND: Renal replacement therapy (RRT) for acute renal failure (ARF) may be provided in many settings within the hospital. Such patients require a high level of care and often have a poor prognosis. No prospective studies have accurately defined this population, making the prediction of necessary resources and the planning of services difficult. AIM: To ascertain the incidence, causes and outcomes of acute renal failure requiring renal replacement therapy in Scotland. DESIGN: A prospective observational census of all clinical areas providing renal replacement therapy in three Scottish health boards (Grampian, Highland, Tayside). METHODS: Patients were identified by liaison with each unit providing RRT. Factors precipitating renal failure and reasons for RRT were recorded at the time of initiation. Comorbid disease burden was scored using the Charlson index. Patient status at 90 days was assessed from case-notes, contacting general practitioners where necessary. RESULTS: 375 patients per million population per year received RRT; 203 per million per year for either ARF or acute-on-chronic renal failure. 73.5% of patients receiving RRT for ARF died within 90 days, 23.5% became independent of RRT. The median duration of hospital admission was 19 days. DISCUSSION: The annual incidence of ARF requiring RRT is just over 200 per million population, almost twice that of end-stage renal disease requiring RRT. Such treatment places high demands upon health care resources.

Acute Kidney Injury↗

PubMed2001

Asthma admissions and thunderstorms: a study of pollen, fungal spores, rainfall, and ozone.

Asthma admissions have been reported to increase during thunderstorms. In some cases, this has been attributed to rises in pollen or fungal spore counts occurring alone or in combination with rainfall. We tested the hypothesis that thunderstorms in general are associated with asthma admissions, and investigated the possible roles of pollen, fungal spores, ozone, and other meteorological factors. We obtained data on multiple pollen and fungal spore counts, rainfall, temperature, ambient ozone concentrations, and asthma admissions for 32 dates when lightning strikes were recorded in the Cardiff/Newport area, and 64 matched dates in previous and subsequent years. Poisson regression models were used to investigate associations between admissions and proposed causative environmental factors. The number of asthma admissions was greater on days with thunderstorms than on control days (p<0.001). There were no associations or interactions between admissions and any pollen or fungal spore counts or rainfall. After adjusting for thunderstorms, there was an independent association between increasing ozone concentration, when temperature was included in the model, and increasing admissions (p=0.02). Asthma admissions are increased during thunderstorms. The effect is more marked in warmer weather, and is not explained by increases in grass pollen, total pollen or fungal spore counts, nor by an interaction between these and rainfall. There was an independent, positive association between ozone concentrations and asthma admissions.

Allergens↗

PubMed2000

Continuing medical education by anaesthetists in scotland: activities, motivation and barriers.

A postal questionnaire survey was carried out to determine the activities, motivation and barriers to continuing medical education amongst career grade anaesthetists in Scotland. Four hundred and ten consultants and 49 non-consultant career grade anaesthetists were surveyed with a response rate of 84.5%. All respondents had taken part in some educational activities in the past two years. Over 80% had attended 10 or more departmental meetings and over 90% had attended meetings of a Regional society or National meetings. Less than 50% had attended for clinical experience with a colleague and only 20% had done so in another centre. There were trends of changing educational activity with increasing age. The most common motivation was to keep up to date for current clinical duties with keeping up to date for teaching second, but younger consultants were more likely to undertake continuing medical education activities in case their clinical duties changed. Perceived barriers to continuing medical education were similar for internal and external activities but funding was less of a limitation for those working in district general hospitals. There is scope for encouraging activities such as clinical experience with a colleague and a need to explore in greater detail the perception of barriers to continuing medical education and their influence on participation.

Adult↗

PubMed2000

Can we improve early mortality in patients receiving renal replacement therapy?

BACKGROUND: Approximately one in eight patients with end-stage renal disease (ESRD) die within the first three months of starting renal replacement therapy (RRT). We investigated which factors might improve this early mortality. METHODS: We performed a prospective nationwide study of all patients commencing RRT for ESRD in Scotland over one year. Patients were classified according to how they presented to start RRT, their burden of comorbid diseases, access prepared for dialysis, and duration of care by a nephrologist prior to commencing RRT. Those factors most strongly associated with death within 90 days of commencing treatment were determined by logistic regression analysis. RESULTS: Patients with an acute unexpected element to their presentation for RRT had early mortality rates between 6.0 and 8.9 times greater than those who commenced RRT electively after a period of care from a nephrologist. Patients in high and medium comorbidity risk groups had early mortality rates of 4.7 and 2.2 times greater than those in the low-risk group. Low serum albumin had a significant association with early death. Patients who progressed steadily to ESRD, who had a planned start to dialysis, and who had mature access were 3.6 times more likely to survive beyond three months than those with no access; they were, however, also younger with less comorbidity. CONCLUSIONS: The factors principally associated with early mortality are nonelective presentation for RRT, comorbid illness, and low serum albumin. Patients cared for by a nephrologist before requiring RRT who have mature access have better short-term survival than those without access. They are also younger with less comorbidity. It may be possible to improve short-term survival in this "unplanned" group if referred early to facilitate reducing cardiovascular risk factors and preparation for RRT.

Adolescent↗

PubMed2000

Investigation of factors which might indicate susceptibility to particulate air pollution.

OBJECTIVES: To determine whether previous symptoms or recognized risk factors of cardiovascular ill health, are associated with an increased likelihood of adverse health effects related to particulate air pollution. METHODS: Cardiovascular event rates were studied relative to urban concentrations of particulate air pollution and baseline risk factors. The Edinburgh artery study consisted of a cohort of 1592 subjects aged 55-74 and was followed up to the end of March 1998 for a median of 10 years resulting in about 5 million person-days of observation. Baseline measurements included plasma fibrinogen and blood and plasma viscosity. A nested case-control approach was used to investigate a possible interaction between effects of these selected baseline risk factors and particulate air pollution, on subsequent event rates. RESULTS: During the follow up period there were 343 fatal and non-fatal myocardial infarctions or strokes. Trends in adverse cardiovascular outcomes related to pollution were identified among subjects belonging to the highest baseline quintile of plasma fibrinogen. Evidence for interactions between concentrations of particulate pollution and fibrinogen was not established at conventional levels of significance. CONCLUSIONS: People with high concentrations of plasma fibrinogen might be more susceptible to adverse cardiovascular effects of particulate air pollution, but limitations of power mean that evidence relating to such an interaction is not conclusive. A range of cardiopulmonary risk factors warrant investigation in relation to possible susceptibility to air pollution.

Aged↗

PubMed1998

Urban air pollution and cardiopulmonary ill health: a 14.5 year time series study.

OBJECTIVES: To examine possible associations between daily concentrations of urban air pollutants and hospital emergency admissions and mortality due to cardiac and pulmonary disease. METHODS: A time series study was conducted in the City of Edinburgh, which has a population of about 450,000. Poisson log linear regression models were used to investigate the relation of the daily event rate with daily air pollution concentrations of sulphur dioxide (SO2) and black smoke from 1981 to 1995, and of nitrogen dioxide (NO2), ozone (O3), carbon monoxide (CO), and particulate matter (PM10) from 1992 to 1995. Adjustments were made for seasonal and weekday variation, daily temperature, and wind speed. RESULTS: The most significant findings were positive associations over the period 1981-95 between black smoke as a mean of the previous three days and daily all cause mortality in people aged > or = 65, and respiratory mortality also in this age group (3.9% increase in mortality for a 10 micrograms/m3 increment in black smoke). For hospital emergency admissions between 1992 and 1995 the two most significant findings (p < 0.05) were for cardiovascular admissions of people aged > or = 65 which showed a positive association with PM10 as a mean of the 3 previous days, and a negative association with O3 as a mean of the previous three days. Analyses of outcomes based on linkage with previous cardiorespiratory emergency admissions did not show substantially different results. CONCLUSION: These data suggest that in the City of Edinburgh, after correction for confounders, there was a small but significant association between concentrations of black smoke and respiratory mortality in the older age group, probably attributable to higher pollution levels in the early part of the study period. There were also generally weak and variable associations between day to day changes in concentrations of urban air pollutants at a single central point and emergency hospital admission rates from cardiac and respiratory disease.

Adult↗