Confounding and confounders.
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Causality↗
Biomedical subjects
R McNamee
Publications and source records attributed to R McNamee.
Does exposure to landfill waste harm the fetus? Perhaps, but more evidence is needed.
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Congenital Abnormalities↗
The use of a screening questionnaire to identify children with likely asthma.
BACKGROUND: The theory that airway remodeling and possible fixed asthma may result from failure to treat asthma airway inflammation highlights the importance of the early identification of patients with likely asthma. AIM: To identify children with likely asthma whose condition is unknown to the medical services. STUDY: Postal questionnaire survey. SETTING: Children in two general practice populations in 1999. METHOD: Parents completed the postal questionnaire surveys. Two validated scoring systems were used to identify children with 'likely asthma': first, three or more positive responses to five key questions; second, three or more positive responses to the same five questions and one more severe symptom (e.g. exercise-induced wheeze). Questionnaire responses were linked to practice records to determine those with a recorded diagnosis of asthma (ever) or of inhaled medication (past 12 months). RESULTS: Using the first scoring system, 22.5% of children were identified as having likely asthma; more than one-third of these (35.1%) had no corroborative evidence recorded in the practice records. With the second system, 15.5% had likely asthma, a quarter of whom had no corroborative evidence. Depending on the scoring system chosen, between 3.5% and 8% of children in these practices had likely asthma but no corroborative evidence in their records. CONCLUSIONS: Children identified using either of these scoring systems would require full clinical assessment to determine their need for medical intervention. These findings have implications for the allocation of health care resources.
Adolescent↗
Stroke risk from multiple risk factors combined with hypertension: a primary care based case-control study in a defined population of northwest England.
PURPOSE: To examine how hypertension interacts with other known risk factors in affecting the risk of stroke in a primary care based setting. METHODS: Cases were patients with first-ever stroke identified from the community-based stroke register in 1994-95 in northwest England. Two controls per case were randomly selected from the same primary care site and matched by age and sex. Information on predefined risk factors was extracted from medical records. RESULTS: 267 cases and 534 controls were included. Adjusted odds ratio (OR) for stroke from hypertension was 2.6 (95% confidence interval: 1.7-3.9). In hypertensives who were current smokers, risk of stroke was increased 6 fold as compared to non-smokers without hypertension. Hypertensives who had a preexisting history of myocardial infarction or obesity or diabetes had 3 fold higher risks of stroke. Subjects with hypertension and with a history of transient ischemic attack or atrial fibrillation had > or = 8 fold excess risk of stroke. Among them, the risk was greater in those with poorly controlled or untreated hypertension and in those with well or moderately controlled as compared to subjects without both risk factors. There appeared to be a steady increase in risk of stroke according to the number of risk factors present, particularly in hypertensive subjects. CONCLUSIONS: Stroke risks in hypertensives associated with combinations of other risk factors appeared to follow an additive model. Subjects with multiple risk factors should be targeted in order to reduce the overall risk for stroke.
Aged↗
Oestrogen and women's heart disease: ESPRIT-UK.
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Aged↗
Assessment of a simple scoring system applied to a screening questionnaire of asthma in children aged 5-15 yrs.
The aim of the present study was to validate a simple scoring system using a parent-completed screening questionnaire to identify children aged 5-15 yrs who may have asthma. A stratified random sample of 157 children of 1,808 whose parents had answered a postal respiratory questionnaire underwent detailed clinical evaluation. The results were reviewed by three independent paediatricians whose opinions were combined to reach, for each child, decisions regarding three standards: 1) "possible asthma" defined as >50% likelihood of having asthma; 2) "possible asthma" defined as meriting a clinical trial of asthma medication; and 3) "probable asthma" defined as >90% likelihood of having asthma. The combined decisions were compared to three sets of questionnaire scores, in order to determine the positive predictive value, sensitivity and specificity of each set in identifying children with probable/possible asthma. The three sets of chosen questionnaire scores all had positive predictive values of 79-96% for predicting possible asthma, using either the combined expert opinion ">50% likelihood of asthma" or that of "warrants a trial of treatment" as the definition. This suggests that a low proportion of false positives would be obtained were this scoring system to be used for a screening programme. The combined decision >90% chance of asthma could be used as a means of estimating prevalence of asthma in the survey. When used for this, the prevalence of asthma in the surveyed population was 18.8% (95% confidence interval 13.1-26.3). In conclusion, the present scoring system, based on a simple respiratory questionnaire, provides a valid method of identifying children likely to have asthma, and who, if unknown to the medical services, would benefit from clinical review.
Adolescent↗
A matrix of kappa-type coefficients to assess the reliability of nominal scales.
To investigate the reliability of nominal scales, Kraemer proposed a measurement model from which kappa coefficients could be derived. More recently she suggested a matrix of coefficients as a comprehensive summary of reliability, contrasting this with use of a single summary kappa statistic. The main diagonal of the matrix consists of binary kappa coefficients for each category which measure the reliability of each category relative to all others, while the off-diagonal elements are correlation coefficients for pairs of categories. The off-diagonal elements were suggested as measures of confusion between categories. Schouten also suggested coefficients to assess confusion between pairs of categories, which might be used as alternative off-diagonal elements in a summary matrix. The two types of off-diagonal element will be compared. It will be shown that Schouten's coefficients can be expressed in terms of the parameters of Kraemer's measurement model and that they are more easily interpreted as measures of confusion. First, the maximum value for Schouten's coefficient is one. Secondly, for any pair of categories, Schouten's coefficient equals the proportionate reduction in the probability of classifying a subject in one category of the pair having previously classified them in the other. Thirdly, where the coefficient for a pair of categories is less than the summary kappa statistic, it will be shown that combining these two categories will increase the value of the summary kappa statistic. The methods of analysis are applied to data from a study of the reliability of psychiatric diagnosis and used to identify pairs of classifications between which there is substantial confusion.
Humans↗
The application of various protic acids in the extraction of (1-->3)-beta-D-glucan from Saccharomyces cerevisiae.
Glucans are (1-->3)-beta-linked glucose polymers which have immune-stimulating capability. The extraction of water-insoluble (1-->3)-beta-D-glucan form Saccharomyces cerevisiae employs hydrochloric acid. Hydrochloric acid is difficult to employ in the large-scale pharmaceutical extraction of glucans due to its corrosive nature and toxicity. To address these concerns, we determined whether acetic, formic or phosphoric acid can be substituted for hydrochloric acid in the process for the isolation of (1-->3)-beta-D-glucan. The resulting microparticulate glucans were employed as the starting material for the production of (1-->3)-beta-D-glucan phosphate. 13C NMR analysis of the glucan phosphates derived from the acetic, formic or phosphoric acid-extracted microparticulate glucan show excellent correspondence to hydrochloric acid extracted glucan and laminarin, a (1-->3)-beta-D-glucan standard, indicating that the primary structure is not altered by the acid used for extraction. Glucan phosphate prepared from hydrochloric acid had a Mw of 7.2 x 10(4) g/mol, rmsz of 17.7 nm, of 1.50 and (eta) of 49.0 mL/g. Glucan phosphate prepared from acetic acid had a primary polymer peak with a Mw of 1.4 x 10(6) g/mol, rmsz of 23.6 nm, I of 1.93 and (eta) of 62.4 mL/g. Glucan phosphate prepared from formic acid had a main polymer peak with a Mw of 1.2 x 10(6) g/mol, rmsz 27.1 nm, I of 1.56 and (eta) of 89.0 mL/g. Glucan phosphate prepared from phosphoric acid had a primary polymer peak with a Mw of 6.6 x 10(5) g/mol, rmsz of 32.3 nm, I of 2.70 and (eta) of 91.3 mL/g. These data indicate that the molecular mass, size, polydispersity and intrinsic viscosity of the glucan phosphate obtained is influenced by the pKa of protic acid employed to extract the microparticulate glucan. However, the primary structure and side-chain branching are not substantially altered regardless of the acid employed.
Acetic Acid↗
Case-control study of stroke and the quality of hypertension control in north west England.
OBJECTIVE: To examine the risk of stroke in relation to quality of hypertension control in routine general practice across an entire health district. DESIGN: Population based matched case-control study. SETTING: East Lancashire Health District with a participating population of 388,821 aged < or = 80. SUBJECTS: Cases were patients under 80 with their first stroke identified from a population based stroke register between 1 July 1994 and 30 June 1995. For each case two controls matched with the case for age and sex were selected from the same practice register. Hypertension was defined as systolic blood pressure > or = 160 mm Hg or diastolic blood pressure > or = 95 mm Hg, or both, on at least two occasions within any three month period or any history of treatment with antihypertensive drugs. MAIN OUTCOME MEASURES: Prevalence of hypertension and quality of control of hypertension assessed by using the mean blood pressure recorded before stroke) and odds ratios of stroke (derived from conditional logistic regression). RESULTS: Records of 267 cases and 534 controls were examined; 61% and 42% of these subjects respectively were hypertensive. Compared with non-hypertensive subjects hypertensive patients receiving treatment whose average pre-event systolic blood pressure was controlled to < 140 mm Hg had an adjusted odds ratio for stroke of 1.3 (95% confidence interval 0.6 to 2.7). Those fairly well controlled (140-149 mm Hg), moderately controlled (150-159 mm Hg), or poorly controlled (> or = 160 mm Hg) or untreated had progressively raised odds ratios of 1.6, 2.2, 3.2, and 3.5 respectively. Results for diastolic pressure were similar; both were independent of initial pressures before treatment. Around 21% of strokes were thus attributable to inadequate control with treatment, or 46 first events yearly per 100,000 population aged 40-79. CONCLUSIONS: Risk of stroke was clearly related to quality of control of blood pressure with treatment. In routine practice consistent control of blood pressure to below 150/90 mm Hg seems to be required for optimal stroke prevention.
Adult↗
Injuries after falls at work in the United Kingdom and Sweden with special reference to fractures in women over 45.
OBJECTIVES: To describe the relation with age of risk of reported injury after a fall among women at work in two countries, the United Kingdom and Sweden, with particular emphasis on fractures, and to interpret these data. METHODS: Rates of accidents compiled under the national reporting regulations of each country during a two year period were described by age, sex, cause (fall on the level, fall from a height, other), and occurrence of fracture, with emphasis on the relative risk (RR) in workers aged 45 years and over compared with those aged under 45. For fractures (major fractures only in the United Kingdom) among women, RRs were calculated for all occupations, with the three digit occupational classification schemes of each country. Summary RRs for older versus younger women, directly standardised for occupation, were derived. RESULTS: Among women, RRs for injury after a fall on the level and fall from a height were 2.77 and 1.77 respectively in Sweden and 2.28 and 1.54 in the United Kingdom. When restricted to fractures, the RRs became 4.75 and 3.66 respectively in Sweden and 3.35 and 1.97 in the United Kingdom. Standardisation for occupation gave RRs for fractures of 4.87 and 3.75 in Sweden and 3.43 and 2.16 in the United Kingdom. Almost all occupational groups with enough fractures for analysis showed an excess of fractures related to falls among older women. A different age pattern was seen for all injuries or fracture after other types of accidents and for all types of accident in men. CONCLUSION: It is argued that, for fractures at least, the results for women are unlikely to be due to reporting bias and unlikely to be explained by a greater exposure to workplace hazards among older women. Whether there is an increased risk of falling, as distinct from sustaining a fracture, is not clear. The generality of the increased risk suggest that efforts should be made to minimise hazards in all occupational sectors, particularly those using many women.
Accidental Falls↗
Shiftwork and mortality from ischaemic heart disease.
OBJECTIVES: To investigate the relation between shift work and death from ischaemic heart disease (IHD). METHODS: A nested case-control approach was used. The cohort comprised male manual workers who joined an industrial company aged 50 years or under between 1 January 1950 and 31 December 1992 and worked there for at least one month. Cases were 467 cohort members who died during the same period aged 75 years or under, with ischaemic heart disease (IHD) (international classification of diseases (ICD) 410-414) coded from the death certificate. For each case a control worker was chosen, who joined the company at the same age and in the same period but who survived the case. Work status (shift work or day work) was assigned to cases for their entire employment and to controls for that part of their employment which preceded the matching case's death. The main source of information was historical personnel records containing pay codes which differed for day work and shift work. Information on weight, height, blood pressure, and smoking from a pre-employment medical was available. RESULTS: Two thirds of subjects had been employed for at least one month as shift workers and there was evidence that they had slightly better health at recruitment than day workers. The odds ratio for shift workers during the period starting 10 years after shift work began, and after adjustment for height, body mass index, blood pressure, smoking, duration of employment, and job status (skilled or unskilled) was 0.90 (90% confidence interval (90% CI): 0.68-1.21). There was no relation between risk of IHD death, and duration of shift work, but there was evidence of a reduced risk when actively employed as a shift worker, together with an increased risk in the first five years after leaving shift work to do day work. CONCLUSIONS: Shift work did not increase the risk of death from ischaemic heart disease in this study. Those workers with poorer cardiovascular health may be under represented in groups with longer shift work experience because of health related selection out of shift work.
Adult↗
Preliminary analysis of proportional mortality in a cohort of British pottery workers exposed to crystalline silica.
A cohort of 7020 male pottery workers born in 1916-1945 was identified from all employees in dust-exposed trades, subject to medical surveillance by the Benefits Agency Medical Service of the Department of Social Security in Stoke-on-Trent in the United Kingdom. All but 256 (3.6%) were traced, 1016 (15.0%) had died by 30 June 1992, and death certificates were obtained for 940 (92.5%) of the fatalities - 122 from respiratory cancer. After the exclusion of any recorded asbestos exposure, the proportional mortality ratio (PMR) for lung cancer was 1.22 when calculated against national rates (P < 0.02), but the PMR against local rates was 1.04. Logistic regression analyses based on 75 nested case-referent pairs for which the required information was available showed that lung cancer mortality was dominated by smoking and significantly affected by past asbestos exposure. However, for 47 pairs in which both the case and referent had a history of smoking, there was also significant evidence that the risk was related to duration of silica dust exposure in pottery work but not to radiological score.
Ceramics↗
Occupational exposure to hydrocarbons and chronic pancreatitis: a case-referent study.
OBJECTIVES: To investigate the hypothesis that hydrocarbon exposure is a risk factor for chronic pancreatitis. METHODS: 102 cases of chronic pancreatitis and 204 age and sex matched referents were interviewed about their occupational histories, alcohol and cigarette consumption, and diet. Exposure to hydrocarbons was inferred from interview responses by four assessors who were blind to disease state, and these data were then summarised by a cumulative hydrocarbon exposure (CHE) score. RESULTS: After adjustment for alcohol, cigarettes, dietary antioxidants, and social class, odds ratios for low CHE scores were 1.20 (90% CI: 0.62-2.35) and 2.67 (90% CI: 1.22-5.87) for high scores. A test for trend with level of exposure among only those who had exposure scores > 0 gave p = 0.09. Analysis by type of hydrocarbon was limited to four exposures for each of which there were at least 20 exposed patients. The adjusted OR for paint solvents (any level) was 0.96 (90% CI: 0.48-1.93); for diesel exhaust fumes OR = 2.66 (90% CI: 1.05-6.73); for petrochemicals OR = 1.82 (90% CI: 0.80-4.11); and for chlorinated solvents OR = 1.49 (90% CI: 0.58-3.81). CONCLUSIONS: These results support the original hypothesis. Further studies are needed to confirm or refute the findings here and to clarify the types of hydrocarbon involved.
Adult↗
Effect of changes in maternal smoking habits in early pregnancy on infant birthweight.
BACKGROUND: The inverse relationship between maternal smoking and infant birthweight is well documented. AIM: The aim of the present study was to examine whether a change in maternal cigarette consumption in early pregnancy affects the infant's birthweight. METHOD: A total of 5980 women who presented to their general practitioners between 1976 and 1979 with an unplanned pregnancy and the babies resulting from these pregnancies were included in the study. Women were divided into four categories: non-smokers, smokers, quitters and reducers. RESULTS: In terms of mean infant birthweight, the non-smokers had a clear benefit over the smokers whose babies were 153 g lighter (P < 0.001), and over the quitters whose infants were 39 g lighter. There was also an advantage in stopping smoking: the smokers had babies whose mean birthweight was 120 g less than that of the quitters (P < 0.001). There was no demonstrable benefit from reducing cigarette consumption without entirely stopping. CONCLUSION: These findings may have important implications for where best to target health education.
Attitude to Health↗
The effect of induced abortion on subsequent fertility.
OBJECTIVE: To investigate the effect of induced abortion on subsequent fertility. DESIGN: 1. Prospective cohort study of women who had an unplanned pregnancy at recruitment. 2. Retrospective study of women who had a planned pregnancy at recruitment. SETTING: Joint Royal College of General Practitioners/Royal College of Obstetricians and Gynaecologists study based in general practice in England, Scotland and Wales, between 1976 and 1987. SUBJECTS: 1. Prospective study: Four hundred and thirty-three women with a recruitment unplanned pregnancy ending in induced abortion (abortion group) and 1035 women with a recruitment unplanned pregnancy which ended naturally (nonabortion group). All subsequently had a planned pregnancy, or were known to be trying to conceive at some point during the follow-up. 2. Retrospective study: Nine thousand two hundred and ninety-nine women who presented at recruitment with a planned pregnancy. MAIN OUTCOME MEASURE: The women's estimated length of planning time, expressed as a fertility rate ratio. RESULTS: Induced abortion was not related to future fertility. In the prospective study, the fertility rate ratio (FRR) of the abortion group relative to the nonabortion group was 0.94 (95% CI 0.83 to 1.07, P = 0.37). This result was supported by the retrospective study, which again showed no important difference between the two groups. CONCLUSION: Induced abortion does not appear to have an important effect on future fertility.
Abortion, Induced↗
The effect of induced abortion on subsequent pregnancy outcome.
OBJECTIVE: To investigate the effect of induced abortion on the outcome of the next pregnancy. DESIGN: Long-term prospective controlled cohort study. SETTING: Joint Royal College of General Practitioners/Royal College of Obstetricians and Gynaecologists study based in general practice in England, Scotland and Wales. SUBJECTS: 1311 women whose recruitment pregnancy had ended in induced abortion (the abortion group) and 2131 women whose recruitment pregnancy had a natural conclusion (the non-abortion group). MAIN OUTCOME MEASURES: Non-viable outcome (spontaneous or missed miscarriage, ectopic pregnancy or stillbirth), birthweight, length of gestation. RESULTS: Induced abortion was not materially associated with any of the three measures of adverse outcome. Compared with the non-abortion group the relative risk of a non-viable outcome in the abortion group was 1.01 (95% CI 0.81 to 1.27). In the abortion group birthweight was an average 23 g lighter (95% CI -76 g to + 30 g) and length of gestation an average 0.9 days shorter (95% CI -2.2 days to + 0.4 days) than in the non-abortion group. Women who had their abortions in NHS premises had an increased risk of a non-viable outcome (RR 2.55, 95% CI 1.31 to 4.94) and had babies with significantly lower mean birthweight (-119 g, 95% CI -233 g to +5 g) compared with those who obtained their operations in the private sector. Women whose abortion had been carried out by a consultant had the lowest risk of non-viable outcome. Although these differences remained after adjustment for a number of important variables, it is possible that factors not measured in the present study, such as economic status and occupation, played a contributory role. CONCLUSION: Overall, induced abortion was not associated with any important effect on the three measures of adverse outcome in the subsequent pregnancy.
Abortion, Induced↗
Outcome of retrospective cohort studies and study size: a publication bias?
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Attitude↗
Effect of enhanced macrophage function on early wound healing.
Although the macrophage is important to wound healing, research has focused on its relationship to fibroblast and collagen synthesis. This study was designed to assess effects of enhanced macrophage function on early wound healing, before established collagen synthesis. Sprague-Dawley rats had dorsal incisions after one of three treatment regimens: (1) saline solution, 0.5 ml administered intravenously, (2) intravenous glucan, a macrophage stimulant, 20 mg; (3) topical glucan, 20 mg. Intravenous therapy was administered 24 hours before and after incision. Breaking strength was significantly increased (p less than 0.01) by both intravenous glucan (49.8 +/- 5.5 gm) and topical glucan (59.7 +/- 5.6 gm) on the fourth day after incision, compared with controls (22.0 +/- 2.6 gm). Similar results occurred on the seventh day after incision. Although formalin fixation significantly enhanced breaking strength in fresh control wounds (22.0 +/- 2.6 vs 39.5 +/- 2.2 gm), no increase occurred in wounds treated with intravenous glucan (49.8 +/- 5.0 vs 55.3 +/- 6.4 gm), indicating maximal cross-linking of collagen. Collagen synthesis, reflected by tritiated proline uptake, was no different in control versus glucan groups. Supernatants from control or glucan-activated macrophages were injected intraperitoneally or applied topically in the rat model. Activated supernatant, both intraperitoneal and topical, resulted in increased breaking strength on the fourth day after incision. Formalin fixation did not increase breaking strength in the activated supernatant groups. We conclude that enhanced macrophage function increases early wound breaking strength. This effect appears unrelated to collagen synthesis but may be related to increased cross-linking of collagen. Similar effects are seen with activated macrophage secretory products administered intraperitoneally or topically.
Administration, Topical↗