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Biomedical subjects

P Elliott

Publications and source records attributed to P Elliott.

At least 19 recordsLinked to original sources
PubMed1998

Estimating the incidence rate ratio in cross-sectional studies using a simple alternative to logistic regression.

PURPOSE: Logistic regression is often used for the analysis of cross-sectional studies, and prevalence odds and odds ratios are obtained. Other methods have been proposed for estimating prevalence ratios. An alternative regression method is also available for estimating rate ratios. Its application to cross-sectional studies is discussed. METHODS: When dealing with chronic conditions, it is possible to model binomial data using the complementary log-log link function log(-log(1-pi)), where pi is the prevalence, an option available on many statistical software packages. In effect, these are models for the disease incidence rate lambda, which is assumed to be constant over the underlying follow-up period t. This approach is based on the well-known relationship 1-pi-exp(-lambda t). The cumulative effect of age on prevalence (effectively "time of follow up") can be accounted for in the model, by specifying it as an offset. RESULTS: The regression coefficients associated with the covariates included in the model estimate rate ratios, rather than odds or prevalence ratios. The method is applied to the analysis of the prevalence of respiratory symptoms in 4395 children aged 7-9 years who are residents of Huddersfield (northern England), surveyed in the framework of the SAVIAH (Small Area Variations of Air Quality and Health) study. CONCLUSIONS: By considering saturated models including only sex as a covariate, direct comparison of crude and fitted parameters (odds, prevalence, and rate ratios) shows that, for short follow-up periods, the complementary log-log model is a valid alternative to logistic regression. More complex models including other covariates are also discussed.

Air Pollution↗
PubMed1998

Dietary magnesium intake and blood pressure: a qualitative overview of the observational studies.

Published reports of 30 separate sets of analyses from 29 observational studies relating dietary intake of magnesium to blood pressure (BP) were identified through a comprehensive search using MEDLINE and BIDS-EMBASE. Three studies were prospective, 24 cross-sectional (25 reports), of which four also contained a longitudinal component, and two were obtained from baseline data in a trial. Various dietary methodologies were used: 24-h dietary recall (n = 12), food-frequency questionnaire (8), food record (7), and duplicate diet (2). Twelve reports compared magnesium intake or BP level between subgroups. Seven showed a negative association between magnesium intake and BP level, and five reported no association. From 18 of the 30 sets of analyses either a regression estimate or a Pearson correlation coefficient was reported. Many reports also allowed identification of subgroups by sex, age and race. Ninety population samples and subgroups could thus be identified from the 30 reports. All 11 Pearson-r correlation coefficients reported for systolic BP (SBP) (three significant, P < 0.05) and 10 (out of 12) Pearson-r correlation coefficients reported for diastolic BP (DBP) (four significant) were negative. Seven reports (13 subgroups for SBP, 11 subgroups for DBP) gave partial regression coefficients after adjustment; 10 (seven significant) and eight (six significant) were negative for SBP and DBP, respectively. For 13 subgroups in five papers, Pearson-r correlation coefficients were reported after adjustment for confounding factors. Eight (out of 13) showed a negative relationship for SBP and DBP. This review points to a negative association between dietary magnesium intake and BP. A systematic quantitative overview is needed to reconcile the inconsistencies of the results of individual studies and to quantify the size of such relationship.

Adolescent↗
PubMed1998

Perinatal mortality in an English health region: geographical distribution and association with socio-economic factors.

Although the international and regional variability of perinatal mortality rates have been widely studied, less is known about the variability at the small-area level. The geographical distribution of perinatal mortality in the former North-West Thames Health Region, England, during 1981-90, and its association with small-area socio-economic factors, as measured by the Carstairs index of deprivation, were studied. Recently developed methods of analysis, including use of Bayesian statistics, were applied to obtain descriptive results and maps, and for fitting regression models that allowed for the presence of unmeasured risk factors. Significant heterogeneity (P < 0.001) of perinatal mortality across census wards and districts was found. The 5% of wards with the highest mortality experienced a risk more than 1.7 times that of the 5% with lowest mortality. Significant, positive association between deprivation and perinatal mortality was also found. Assuming causality, social differentials at the small-area level accounted for between 1.3% and 14.1% of all perinatal deaths, depending on which level of the Carstairs index was selected as reference. Although a proportion of such variability might be explained by social characteristics, a better understanding of the nature of the association is necessary.

England↗
PubMed1998

Assessment of the reproducibility of clinical coding in routinely collected hospital activity data: a study in two hospitals.

BACKGROUND: The aim of the study was to assess the reproducibility of clinical coding in two National Health Service hospitals within North West Thames region. METHODS: A retrospective audit was carried out, of clinical coding in hospital episode statistics, involving comparison of the codes assigned by local staff with those assigned by members of an external team unaware of the locally assigned codes. Where local and external coders disagreed, the records were reviewed for a third time by a further independent coder. The subjects were a random sample of 1607 non-maternity, non-psychiatric admissions occurring between 1991 and 1993, stratified for year and type of disease (asthma, diabetes, appendicitis, fractured femur and 'general'--a random selection of any diagnoses). The main outcome measures were the levels of exact agreement between local and external teams over codes for main diagnosis and procedure, and the level of approximate agreement (over the first three characters of the ICD-9 code for diagnosis and the letter and first two digits of the OPCS-4 code for procedure). For disagreements, the outcome measure was the level of agreement between the 'third' coder and the local and external coders. RESULTS: For the main diagnosis in the 'general' group at hospital A, internal and external coders agreed exactly in 43 per cent of the admissions examined and agreed 'approximately' in 55 per cent (kappa = 0.54). For hospital B the corresponding figures were 60 per cent and 72 per cent (kappa = 0.72). Approximate agreement was higher for the specific diseases considered, particularly for asthma (A: 86 per cent; B: 91 per cent) and fractured femur (A: 84 per cent; B: 89 per cent). For the main procedure at hospital A, there was exact agreement for 58 per cent and approximate agreement for 70 per cent (kappa = 0.66). For hospital B, the corresponding figures were 76 per cent and 83 per cent (kappa = 0.80). In cases of disagreement over the first three digits of the ICD-9 code for main diagnosis, the third coder disagreed with both local and external coders in 53 per cent at hospital A and 38 per cent at hospital B. Agreement was slightly better for discharges in 1992-1993 than in 1991-1992. CONCLUSIONS: The full clinical codes in NHS hospital episode statistics (HES) data should be treated with caution. The first three characters of ICD-9 codes for diagnoses and the OPCS-4 codes for procedures were more reliable. For some specific conditions such as asthma and fractured femur, reliability of the first three characters is much higher (for example, 86 per cent and 91 per cent for asthma in the two hospitals), but for the full codes can be worse. Secondary diagnoses or comorbidities may be significantly undercoded. A higher level of agreement in 1992-1993 than in 1991-1992 suggests that coding may be improving.

Abstracting and Indexing↗
PubMed1998

Synaptic activity, induced rhythmic discharge patterns, and receptor subtypes in enriched primary cultures of embryonic rat motoneurones.

Long-term cultures of ventral horn neurones from embryonic rat spinal cord were established, after enrichment using density gradient centrifugation, to give a high proportion of cells (> 82%) with motoneurone characteristics. Neurones were grown on spinal cord glial monolayers for 4-83 days and investigated using whole-cell patch clamp. Synaptic activity interrupted by periods of quiescence increased in frequency with culture age and was suppressed by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and strychnine. However, strychnine (10 microM) or bicuculline (10-30 microM) or removal of Mg2+ alone induced patterned rhythmic bursting. Glutamate (3-300 microM), alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA, 0.3-30 microM), and kainate (1-300 microM) evoked inward currents, as did N-methyl-D-aspartic acid (NMDA, 100 microM) in the absence of Mg2+ and presence of glycine (3-10 microM). Inward currents carried by Cl- were elicited by glycine (10-300 microM) and GABA (1-300 microM), while adenosine (1-10 microM) and cyclopentyladenosine (10 nM-1 microM) evoked a K(+)-dependent hyperpolarization. 5-HT, GABAB, purine A, and metabotropic glutamate receptors modulated synaptic excitation of presumed motoneurones. The results suggest that long-term cultures, containing more than 82% developing motoneurones, are able to generate rhythmic bursting; they respond to many of the neurotransmitters that are likely to be released onto motoneurones developing in vivo.

Adenosine↗
PubMed1997

Cancer incidence near radio and television transmitters in Great Britain. I. Sutton Coldfield transmitter.

A small area study of cancer incidence in 1974-1986 was carried out to investigate an unconfirmed report of a "cluster" of leukemias and lymphomas near the Sutton Coldfield television (TV) and frequency modulation (FM) radio transmitter in the West Midlands, England. The study used a national database of postcoded cancer registrations, and population and socioeconomic data from the 1981 census. Selected cancers were hematopoietic and lymphatic, brain, skin, eye, male breast, female breast, lung, colorectal, stomach, prostate, and bladder. Expected numbers of cancers in small areas were calculated by indirect standardization, with stratification for a small area socioeconomic index. The study area was defined as a 10 km radius circle around the transmitter, within which 10 bands of increasing distance from the transmitter were defined as a basis for testing for a decline in risk with distance, and an inner area was arbitrarily defined for descriptive purposes as a 2 km radius circle. The risk of adult leukemia within 2 km was 1.83 (95% confidence interval 1.22-2.74), and there was a significant decline in risk with distance from the transmitter (p = 0.001). These findings appeared to be consistent over the periods 1974-1980, 1981-1986, and were probably largely independent of the initially reported cluster, which appeared to concern mainly a later period. In the context of variability of leukemia risk across census wards in the West Midlands as a whole, the Sutton Coldfield findings were unusual. A significant decline in risk with distance was also found for skin cancer, possibly related to residual socioeconomic confounding, and for bladder cancer. Study of other radio and TV transmitters in Great Britain is required to put the present results in wider context. No causal implications can be made from a single cluster investigation of this kind.

Adolescent↗
PubMed1997

Cancer incidence near radio and television transmitters in Great Britain. II. All high power transmitters.

A small area study of cancer incidence, 1974-1986, near 20 high power television (TV) and frequency modulation (FM) radio transmitters in Great Britain was carried out to place in context the findings of an earlier study around the Sutton Coldfield transmitter. The national database of postcoded cancer registrations was used with population and socioeconomic data from the 1981 census. Cancers examined were adult leukemias, skin melanoma, and bladder cancer, following the findings in the earlier study of significant declines in risk of these cancers with distance from the Sutton Coldfield transmitter. Childhood leukemia and brain cancer were also examined. Statistical analysis was performed for all transmitters combined, four overlapping groups of transmitters defined by their transmission characteristics, and for all transmitters separately. There were 3,305 adult leukemia cases from 0-10 km (observed/expected (O/E) ratio = 1.03, 95% confidence interval (CI) 1.00-1.07). A decline in risk of adult leukemia was found for all transmitters combined (p = 0.05), two of the transmitter groups, and three of the single transmitters; for all transmitters combined, observed excess risk was no more than 15% at any distance up to 10 km, and there was no observed excess within 2 km of transmitters (O/E ratio = 0.97, 95% CI 0.78-1.21). For childhood leukemia and brain cancer, and adult skin melanoma and bladder cancer, results were not indicative of a decline in risk with distance from transmitters. The magnitude and pattern of risk found in the Sutton Coldfield study did not appear to be replicated. The authors conclude that the results at most give no more than very weak support to the Sutton Coldfield findings.

Adolescent↗
PubMed1997

High-dose-rate brachytherapy in the management of high-grade intraepithelial neoplasia of the vagina.

The majority of women with high-grade intraepithelial neoplasia (VAIN 3) are over 60 years of age and have a history of premalignant or malignant disease of the cervix. Although the natural history of VAIN is not well defined, high-grade lesions are premalignant. Ablative treatment with laser or 5-fluorouracil cream is commonly unsatisfactory. Several series have reported a low rate of recurrence and complications if VAIN 3 is treated with low-dose-rate brachytherapy. This retrospective review reports the outcome of 14 patients treated with high-dose-rate brachytherapy, with a dose of 34 to 45 Gy in 4.5- to 8.5-Gy fractions. Treatment was well tolerated with no severe early or late toxicity observed. At a median follow-up of 46 months 1 patient progressed to invasive carcinoma of the vagina; in another patient VAIN 3 persisted.

Adult↗
PubMed1997

Small-area study of the incidence of neoplasms of the brain and central nervous system among adults in the West Midlands region, 1974-86. Small Area Health Statistics Unit.

This small-area study of incidence of cancers of the brain and central nervous system found evidence of trend (P = 0.02) of cancer risk with deprivation (8% higher risk in affluent areas), but no significant association with urban-rural status. Results were not indicative of a strong geographically determined risk at small-area level.

Adolescent↗
PubMed1997

Vitamin C and blood pressure--an overview.

BACKGROUND: Laboratory and some epidemiological studies suggest that antioxidants, such as vitamin C, are protective for cardiovascular disease. This protective effect may be mediated through blood pressure (BP). This is the first systematic review of epidemiological studies of vitamin C and BP. METHOD: Published cross-sectional studies, prospective studies and trials in humans were identified that examined the association between vitamin C intake or plasma vitamin C levels and BP. Relevant references were located by MEDLINE search 1966-1996, EMBASE search 1980-1996, by searching personal bibliographies, books and reviews and from citations in located articles. RESULTS: Cross-sectional data were available from 18 populations. Ten of 14 reported an inverse association between plasma vitamin C and BP and three of four reported an inverse association with vitamin C intake. The two non-randomised and four randomised controlled trials were all small. Of the randomised trials one reported a significant decrease in BP, one a non-significant decrease and two were uninterpretable. CONCLUSIONS: We found a consistent cross-sectional association between higher vitamin C intake or status and lower BP, though no study controlled adequately for confounding by other dietary factors. Further cross-sectional studies are required to establish whether an independent association exists. If this is shown to be the case larger and longer term trials will be needed to confirm the association is causal. Potentially the impact on cardiovascular disease of a modest change in mean population vitamin C intake is large.

Ascorbic Acid↗
PubMed1997

Urinary biochemical markers of dietary intake in the INTERSALT study.

The INTERSALT Study, an international, collaborative, cross-sectional investigation of the relation between blood pressure and dietary and other factors, used quality-controlled, standardized procedures and assessment of multiple possible confounding factors to study 10,079 men and women in 52 population-based samples in 32 countries. In this study 24-h urinary excretion data were used as biochemical markers of intakes of sodium, potassium, and protein, with repeat examinations done in a randomly selected 8% of participants to asses reliability and correct for regression-dilution bias. INTERSALT showed that high salt intake, low potassium intake, excess alcohol consumption, and energy imbalance resulting in overweight are critically involved in the origins of the high blood pressure prevalent among a majority of adult populations. The findings also show that obtaining accurate estimates of associations between dietary intake and blood pressure requires large population-based samples, high-quality dietary information, control for multiple confounding variables, and modern multivariate methods of data analyses, including correction of observed associations for within-person variation in intake.

Adult↗
PubMed1997

Who are the 'low energy reporters' in the dietary and nutritional survey of British adults?

BACKGROUND: Underreportin in dietary surveys is a potential source of bias in studies of diet and disease. The aim of this study was to identify characteristics of men and women participants in the Dietary and Nutritional Survey of British Adults (DNSBA) who stated that they were neither slimming nor ill, and who reported an average energy intake over a 7-day period below 1.2 times estimated basal metabolic rate (BMR), termed here 'low energy reporters' (LER). METHODS: In all, 2197 men and women aged 16-64 years participated in the DNSBA. Dietary intake was assessed using the 7-day weighed intake method. Their BMR was estimated using predictive equations based upon age, sex and body weight. RESULTS: Compared with non-LER, LER had higher mean ratios of urinary urea nitrogen to dietary nitrogen and urinary potassium to dietary potassium, indicating that, as a group, LER were underreporting at least for protein and potassium intakes. Overall LER were overrepresented among the manual social classes, smokers, and self-reported non-alcohol drinkers, and were on average heavier than non-LER. There was indication of differential reporting of foods and differences in macronutrient and micronutrient densities between LER and non-LER. CONCLUSION: These results suggest that LER may be overrepresented within specific population subgroups and that underreporting bias may not be food and nutrient neutral. This has implications for the design and interpretation of studies of diet and disease.

Adolescent↗
PubMed1997

Syncope and ventricular arrhythmias in hypertrophic cardiomyopathy are not related to the derangement of coronary microvascular function.

UNLABELLED: Non-sustained ventricular tachycardia on Holter and syncope have been considered risk factors for sudden death in hypertrophic cardiomyopathy. AIMS: In these patients the coronary vasodilator reserve is impaired despite normal coronaries, so we evaluated the correlation between the severity of coronary vasodilator reserve impairment and the occurrence of syncope and non-sustained ventricular tachycardia. METHODS AND RESULTS: Eighty-four patients with hypertrophic cardiomyopathy (62 males, age 43 +/- 12 years) had a two-dimensional echocardiographic study and a 48-h Holter. Myocardial blood flow was measured by positron emission tomography, at baseline and after dipyridamole, and the coronary vasodilator reserve was computed as dipyridamole myocardial blood flow/baseline myocardial blood flow. In 27 patients, subendocardial and subepicardial myocardial blood flow was measured in the septum and the subendocardial/subepicardial ratio was computed. Twenty of 84 patients had at least one syncopal episode, and 26 had at least one run of non-sustained ventricular tachycardia on Holter. Baseline and dipyridamole myocardial blood flow, coronary vasodilator reserve, and baseline and dipyridamole subendocardial/subepicardial myocardial blood flow ratio were similar in patients with and without syncope and with and without non-sustained ventricular tachycardia on Holter. However, patients with non-sustained ventricular tachycardia had larger left ventricular end-diastolic (47 +/- 6 vs 44 +/- 5 mm, P < 0.05) and end-systolic diameters (30 +/- 6 vs 27 +/- 4 mm, P < 0.05). CONCLUSIONS: (1) Coronary vasodilation is not more severely impaired in patients with hypertrophic cardiomyopathy and syncope or non-sustained ventricular tachycardia. (2) The left ventricle is more dilated in hypertrophic cardiomyopathy with non-sustained ventricular tachycardia.

Adult↗
PubMed1997

Ecological and individual predictors of birthweight in a northern Finland birth cohort 1986.

This multilevel study of spatial variability in, and determinants of, birthweight was conducted using individual and ecological data in a geographically defined prospective birth cohort for 1986 in northern Finland. The study area comprises three large areas defined by latitude: Northern Lapland (NL), Southern Lapland (SL) and Oulu province (OP), comprising 74 localities with a total study population of 9216 singleton births. The mean birthweight was 3482 g for NL, 3537 g for SL and 3587 g for OP (NL vs. OP and SL vs. OP: P < 0.05). The crude rate for stillbirths was highest in NL. The women in the northernmost area were socially less privileged and the localities less prosperous compared with those in the southernmost area. Significant spatial clustering of mean birthweights was found (P = 0.0016), with highest birthweight in the south-western part of the study area. A variable expressing the wealth of each locality, the financial capacity category (FCC), had its lowest mean value in NL, with a range of one to six for the localities studied here. A multilevel multiple regression model showed that, after allowing for sex, gestational age, mother's age, height and hypertensive disorders, parity, body mass index, previous low birthweight child and smoking as individual determinants of birthweight, part of the residual variation could be explained by the locality wealth parameter. Using the multilevel model, the differences in mean birthweight across the three latitude areas persisted but were reduced (difference OP vs. NL reduced from 105 g to 86.5 g). The relationship between birthweight and FCC was inverse U-shaped with the highest mean birthweight estimated for localities occurring in the middle of the range (FCC = 3). The wealthiest urban localities (FCC = 6) and the most deprived localities (FCC = 1) both had a predicted birthweight about 60 g below the maximum at FCC = 3, if all other factors were held constant. This result, taken together with the spatial clustering of birthweights, suggests that there may be important social and environmental determinants of birthweight that have yet to be identified.

Adult↗
PubMed1997

Trends in stroke mortality in Greater London and south east England--evidence for a cohort effect?

OBJECTIVE AND SETTING: To examine time trends in stroke mortality in Greater London compared with the surrounding South East Region of England. DESIGN: Age-cohort analysis based on routine mortality data. SUBJECTS: Resident population aged 45 years or more. MAIN OUTCOME MEASURE: Age specific stroke mortality rates, 1951-92. MAIN RESULTS: In 1951, stroke mortality was lower in Greater London than the surrounding South East Region in all age bands over 45. It has been declining in both areas but the rate of decline has been significantly slower in Greater London (p < 0.0001). The differences in rates of decline were such that stroke mortality is now higher in Greater London for people under 75. The crossover of age specific stroke mortality rates occurred at different periods in different age bands and is consistent with a cohort effect, with similar rates in Greater London and the surrounding south east for men and women born around 1916-21. This cohort effect does not appear to be consistent with past maternal and neonatal mortality rates in these areas, nor, within the limitations of the data, with the ethnic composition of cohorts. CONCLUSIONS: There seems to be a cohort effect on stroke mortality which is not explained by past maternal and neonatal mortality. If the decline in stroke mortality continues at its current rate, the Health of the Nation stroke target is unlikely to be achieved in Greater London.

Age Distribution↗
PubMed1997

Socioeconomic deprivation, ethnicity, and stroke mortality in Greater London and south east England.

OBJECTIVE AND SETTING: To examine geographical variation in stroke mortality in Greater London compared with the surrounding South East Region of England. DESIGN: Cross sectional, ecological analysis based on electoral wards. SUBJECTS: Resident population aged 45 years or more. MAIN OUTCOME MEASURE: Age specific stroke mortality rates in five age bands, 1986-92. MAIN OUTCOME MEASURE: Age specific stroke mortality rates in five age bands, 1986-92. MAIN RESULTS: In the 45-54 years age band, stroke mortality rate ratios (95% confidence intervals) relative to the surrounding south east were 2.09 (1.81, 2.4) for Inner London and 1.31 (1.15, 1.5) for Outer London for men and 1.64 (1.4, 1.93) and 1.13 (0.98, 1.31) respectively for women. This gradient diminished and reversed with increasing age. In the 85+ age band, rate ratios were 0.82 (0.76, 0.89) for Inner London and 0.89 (0.84, 0.94) for Outer London for men and 0.8 (0.75, 0.85) and 0.88 (0.84, 0.92) respectively for women. Carstairs deprivation index and the percentages of Afro-Caribbean men and women and Irish born men were significantly and positively correlated with stroke mortality at the ward level. The Carstairs effect diminished with increasing age. Adjustment for these variables diminished or abolished the higher stroke mortality risks in London for younger people but had little effect on the lower risks for older Londoners. CONCLUSIONS: Higher rates of stroke mortality among middle aged adults in Greater London, compared with the surrounding South East Region, are associated with socioeconomic deprivation and ethnicity. These factors do not explain the relatively lower stroke mortality among older Londoners.

Black or African American↗
PubMed1997

Angiosarcoma of the liver in Great Britain in proximity to vinyl chloride sites.

OBJECTIVES: To study the incidence of angiosarcoma of the liver in England and Wales 1979-86 and Scotland 1975-87. To investigate whether any non-occupational neighbourhood cases occurred near a vinyl chloride site. METHODS: This is a geographical study of incident cases among the general population of Great Britain. Diagnosis of angiosarcoma of the liver was based mainly on the national cancer registry, the world register of cases among vinyl chloride workers, and the register of cases (including histological review) maintained by the Health and Safety Executive. Proximity (< 10 km) of residence to a vinyl chloride site was based on postcode of address at the time of diagnosis. RESULTS: 55 cases were ascribed to angiosarcoma of the liver in England and Wales with a further six cases in Scotland (annual incidence in Great Britain from all sources of around 1.4 cases per 10 million population). There were two cases with documented exposure to Thorotrast, and 10 cases among vinyl chloride workers. There were no vinyl chloride sites in Scotland. Among the 25 cases in England and Wales with histological diagnosis after review by a panel of pathologists, only 15 were confirmed as angiosarcoma, and one of the two Scottish cases after histological review was also confirmed. Overall, 11 cases ascribed to angiosarcoma were resident within 10 km of a vinyl chloride site; nine were vinyl chloride workers, one further case on histological review was not considered to have been correctly diagnosed as angiosarcoma, and the remaining case, confirmed as angiosarcoma, was employed at a vinyl chloride factory during the late 1950s, although not as a vinyl chloride worker. CONCLUSION: The incidence of angiosarcoma of the liver in Great Britain remains extremely rare. The one confirmed case in a non-vinyl chloride worker within 10 km of a site must nevertheless be presumed to have been exposed to vinyl chloride in the workplace. In the period of study, there were no confirmed non-occupationally exposed cases of angiosarcoma among residents living near a vinyl chloride site in Great Britain.

Adult↗