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Biomedical subjects

B Armstrong

Publications and source records attributed to B Armstrong.

At least 55 records · Page 3Linked to original sources
PubMed1998

Mortality in people taking selegiline: observational study.

OBJECTIVE: To evaluate mortality among patients with Parkinson's disease receiving different treatment. DESIGN: Cohort study based on computerised medical records. SETTING: UK General Practice Research Database. SUBJECTS: 12 621 patients aged between 35 and 90 years who had received a prescription for an antiparkinsonian drug, whether or not a diagnosis of Parkinson's disease had been recorded. Patients prescribed an antipsychotic drug before or at the same time as their first antiparkinsonian drug or before age 35 were excluded to avoid including drug-induced Parkinsonism. MAIN OUTCOME MEASURE: Death from any cause. RESULTS: 1720 deaths occurred during 14 000 person-years of observation. There was a non-significant 11% (95% confidence interval 0% to 23%) increase in the risk of death associated with taking selegiline either alone or in combination with levodopa. The death rate was higher among younger patients (aged under 80 years) and those with a recorded diagnosis of Parkinson's disease taking selegiline alone. CONCLUSIONS: The results are compatible with a small excess mortality in people taking selegiline and suggest a larger excess in patients under 80 years of age and those with a confirmed diagnosis of Parkinson's disease taking selegiline without levodopa.

Adult↗
PubMed1998

Evaluation of linked cancer registry and hospital records of breast cancer.

BACKGROUND: Information on the treatment of women with breast cancer in Australia is generally available only from special surveys. Analysis of routinely collected datasets may be more timely and cost effective, if the data are sufficiently accurate and complete. OBJECTIVE: To evaluate the accuracy and completeness of data on treatment in linked records of breast cancer from two routinely collected datasets. METHODS: The NSW Department of Health linked NSW Central Cancer Registry (CCR) records for 2,636 women diagnosed with breast cancer in NSW in 1992 to all hospital admission records in the NSW In-patient Statistics Collection (ISC) from January 1991 to June 1994. We queried the original paper records of subsets of women to identify missing or miscoded information and cases not notified to the CCR. We also compared the treatment data with data collected independently from the medical records of 19% of the women. RESULTS: ISC records linked to 89% of the CCR records. The CCR had identified 94.9% of women with breast cancer treated as hospital in-patients and 83% of these women had surgical treatment recorded in the ISC. The linked dataset under-estimated the percentage of women having breast-conserving therapy (-4%) and slightly over-estimated the percentage having mastectomy (+1%). We estimated that 42% of women treated surgically for breast cancer had actually had breast-conserving surgery, compared with 39% in the original dataset. There was no evident bias by age or by urban or rural residence in the under-recording of breast conservation. There was 94% agreement on the type of surgery between the linked dataset and the independent dataset.

Adult↗
PubMed1997

Transhepatic access to the atrioventricular ring for delivery of radiofrequency energy.

INTRODUCTION: Transcatheter radiofrequency ablation is an effective, safe treatment of arrhythmias in children. However, despite technical advances, patients with obstructed venous access to the heart have not been candidates for this treatment. METHODS AND RESULTS: Two children (8.2 and 10.9 kg) with complex congenital heart disease, supraventricular tachycardia, and obstructed venous access underwent successful radiofrequency ablation of either a right (one patient) or left (one patient) accessory pathway using the transhepatic route to the heart. CONCLUSION: This experience underscores the usefulness of the transhepatic approach in small patients, in patients with limited venous access, and in patients with complex congenital heart disease.

Arterial Occlusive Diseases↗
PubMed1997

Lung cancer in relation to employment in the electrical utility industry and exposure to magnetic fields.

OBJECTIVES: A recent study found that lung cancer may be associated with exposures encountered in the electrical utility industry. To further evaluate this possibility, data were collected and analysed from five large electrical utility companies in the United States. METHODS: A cohort of 138905 male workers employed between 1950 and 1986 was followed up for mortality to the end of 1988, with 20733 deaths identified of which 1692 were due to lung cancer. Mortality from lung cancer was examined in relation to the duration of employment in specific jobs thought to have high exposure to 60 Hz magnetic fields and to an index of cumulative exposure to magnetic fields based on personal measurements. Exposure to pulsed electromagnetic fields (PEMFs) as estimated from another study was also considered. Poisson regression generated rate ratios for categories of exposure based on comparisons within the cohort adjusted for age, calendar year, race, socioeconomic status, work status, and estimated exposure to asbestos. RESULTS: Mortality rose modestly with duration of work as an electrician or power plant operator reaching rate ratios of 1.4 with > or = 20 years in those jobs but not with duration of work as a lineman or a combination of jobs thought to have high exposures to 60 Hz magnetic fields or PEMFs. Cumulative indices of exposure to 60 Hz magnetic fields and PEMFs were both associated with rate ratios of 1.2-1.3 in the highest intervals. CONCLUSIONS: These data suggest that lung cancer is not strongly associated with duration of employment in specific jobs associated with high potential exposure to 60 Hz magnetic fields or to PEMFs. Small associations of lung cancer with indices of both 60 Hz magnetic fields and PEMFs leave open the possibility that larger associations have been diluted through exposure misclassification. Refined exposure assessment, especially to PEMFs, would be required to evaluate that possibility.

Cohort Studies↗
PubMed1997

Carpal tunnel syndrome: what is attributable to work? The Montreal study.

OBJECTIVE: To estimate the fraction of carpal tunnel syndrome (CTS) that is attributable to work in the total adult population of the island of Montreal. METHODS: The population consisted of 1.1 million people 20-64 years of age, with 73.2% of men and 60.6% of women employed. The rates of first surgery for CTS were compared between occupational groups and the total adult population with the standardised incidence ratio (SIR) method. Rates of surgery for the island of Montreal were obtained from the provincial data base of payments. The occupational history was obtained from telephone interviews of a sample of surgical cases. The attributable fractions in exposed people were calculated with odds ratios (ORs) obtained from logistic regressions with non-manual workers as the control group. RESULTS: The surgical incidence of CTS was 0.9/1000 adults. SIRs for all manual workers were 1.9 (95% confidence interval (95% CI) 1.4-2.5) in men and 1.8 (95% CI 1.4-2.2) in women, and the fractions attributable to work were 76% (95% CI 47-88) and 55% (95% CI 33-69), respectively. Seven occupational groups were identified as having excess risk of surgical CTS, with fractions attributable to occupation ranging from 75% to 99%. CONCLUSION: Among manual workers on the island of Montreal, 55% of surgical CTS in women and 76% in men was attributable to work. Increased risk of surgical CTS was found in seven occupational groups.

Adult↗
PubMed1996

Characteristics of users and nonusers of health clinics in inner-city junior high schools.

PURPOSE: To compare the demographic, behavioral, psychosocial, and academic characteristics of users versus nonusers of inner-city junior high school-based health clinics. METHODS: Students who used (n = 1344) and did not use (n = 2394) the health clinics based in four junior high schools in an economically disadvantaged, medically underserved New York City school district were compared on their responses to a health risk survey administered at the end of the 1991/92 academic year. RESULTS: Compared to students who did not use the clinics, students who used the clinics were more likely to have had unprotected sexual intercourse, to have had suicide intentions or attempts, to be suspended from school for fighting, to be exposed to violence and the illicit drug culture, to hold beliefs favoring involvement in sexual intercourse and suicidality, and to have failed subjects in school. CONCLUSIONS: Users of these junior high school-based health clinics are engaging in behaviors and hold beliefs that place them at risk for serious adverse health outcomes. School-based clinics have the potential to provide early intervention for these high risk adolescents.

Adolescent↗
PubMed1996

Use of the His/RVA electrode catheter in children.

Comprehensive electrophysiologic study with radiofrequency ablation requires a number of intracardiac catheters. To reduce the number of catheters placed in children, the authors evaluated a series of customized catheters that combined the functions of two catheters. The customized 6F catheter contains eight electrodes placed in pairs at 4, 5, 6, 7, or 8 cm from the tip for recording the His electrogram and at the tip for right ventricular pacing. The amplitude of the bundle of His potential recorded through the His right ventricular apex (RVA) catheter (n = 63) and the ventricular pacing threshold (in mA) (n = 48) were measured and compared to the maximal bundle of His potential recorded with a 6F hexapolar catheter in 24 and 13 other patients, respectively. The relationship between the distance from the distal electrode pair at the tip and the third electrode from the tip (the His/RVA distance) and patient size was analyzed in 42 patients. Following the initial study in the 90 patients, the selection of the optimal His/RVA catheter for 19 patients was determined by examining the regression plots derived from the first group of 90 patients. The measured His/RVA distance was then determined by noting the His/RVA distance of the catheter used. Regression analysis was then used to evaluate the fit between the predicted His/RVA distance based on weight, height, or body surface area (BSA) and the observed His/RVA distance. The maximal bundle of His electrogram measured in the two groups using the His/RVA catheter was compared. To evaluate catheter stability during the study, the amplitude of the maximal His potential was measured in the 19 patients at the onset, midpoint, and end of the study. The maximal His potential recorded through the octapolar catheter (0.21 mV) was significantly (P < .04) greater than that recorded through the hexapolar catheter (0.10 mV). The mean ventricular threshold measured through the octapolar catheter (0.44 mA) was significantly (P < .001) less than that measured through the hexapolar catheter (1.13 mA). There was a significant (P < .0001) correlation between BSA, weight, and height and the His/RVA distance. There was no significant difference in the mean maximal amplitude of the His potential (0.21 +/- 0.31 mV vs 0.15 +/- 0.12 mV) recorded through the His/RVA catheter between the two groups. The His/RVA distance estimated by weight, when plotted against the measured distance, demonstrated a good correlation (r = .84) between the expected His/RVA distance based on the subject's weight and that actually observed. In 18 of 19 subjects, the first catheter based on the patient's weight (in kilograms) predicted the appropriate and only catheter used. There was no significant difference in the mean maximal bundle of His electrogram recorded at the beginning of the study (0.15 +/- 0.12 mV), midway into the study (0.15 +/- 0.11 mV), and at the end (0.13 +/- 0.13 mV); however, there was extensive variation within individuals and over time. These data support the recording of a stable, high-quality bundle of His electrogram and RVA pacing through a single catheter system and, hence, have important, practical implications for invasive electrophysiologic studies in children.

Adolescent↗
PubMed1996

The development, reliability, and validity of a risk factor screening survey for urban minority junior high school students.

PURPOSE: To develop and evaluate a risk factor screening survey as a mechanism to identify inner-city junior high school students who may benefit from medical or mental health services available in school-based clinics. METHODS: A 36-item health risk factor screening survey was developed and administered to 3,787 predominantly Hispanic students from four schools in an economically disadvantaged, medically underserved New York City school district. Students who indicated that they were experiencing one of five major risk factors (suicidality, sexual activity, parental or guardian substance use, personal substance use, or having run away) were scheduled to visit the clinic for services, and to have their survey responses validated by clinic interview. RESULTS: The development of the screening tool resulted in a short, easy to read and understand survey instrument that was feasible to administer within a classroom setting. The reliability of the instrument was excellent, and the results of the validity study indicated that it was successful in identifying students who did not need clinic services. The screening tool produced mixed results in identifying those truly in need through single item identification (e.g., produced a moderate number of "false positives"), although combining items on the screening tool produced much higher positive predictive values. CONCLUSIONS: This screening tool can be used to effectively focus limited clinical resources on those in need. Outreach surveys of this type should be considered as a valuable component of a school-based clinic service delivery strategy.

Adolescent↗
PubMed1996

Inorganic particles in the lungs of five aluminum smelter workers with pleuro-pulmonary cancer.

This paper reports on the inorganic particles in the lungs of four workers who died from lung cancer and one who died from mesothelioma. All five workers were involved in different operations and activities in aluminum reduction plants. Retained fibrous and nonfibrous particles were evaluated by transmission electron microscopy and energy dispersive spectroscopy after lung digestion. Asbestos fibers, fragments of silicates, and metal-rich nonfibrous particles of chromium-cobalt and aluminum were detected. Conclusions drawn from the evaluation of the particles retained in the lungs of only five workers must be cautious. However, these results are consistent with the hypothesis that carcinogenic polycyclic aromatic hydrocarbons may not be the only contaminants that could explain excess mortality from malignant lung neoplasm in aluminum smelter workers.

Adult↗
PubMed1996

Compensating lung cancer patients occupationally exposed to coal tar pitch volatiles.

OBJECTIVES: To investigate the process of deciding on compensation claims by lung cancer patients exposed occupationally to coal tar pitch volatiles. METHODS: For each case of lung cancer the probability that it was caused (probability of causation (PC)) by coal tar pitch volatiles was expressed as an increasing function of cumulative exposure to benzo-a-pyrene-years. This was assessed from several exposure-response models fitted to data from a large epidemiological study of aluminum production workers. For some models, PC depended also on the smoking habit of the cancer patient. RESULTS: Estimation of relative risk by exposure group indicated that over 50% of lung cancers were attributable to coal tar pitch volatiles (PC > 50%) at exposures above 100 micrograms/m3-years benzo(a)pyrene. A linear relative risk model indicated that 50% PC was first achieved at 342.2 micrograms/m3-years benzo(a)pyrene, or 190.1 micrograms/m3-years benzo(a)pyrene according to the upper 95% confidence limit for risk increment. Corresponding figures for a power curve model were 210.3 and 45.9. With these five figures as compensation criteria compensation would have resulted in 31.4%, 2.7%, 19.2%, 15.7%, and 39.2% of cancers studied, compared with an estimated total proportion of cancers studied attributable to coal tar pitch volatiles of 15%-26%. If risks due to coal tar pitch volatiles and smoking multiply, PC does not depend on the amount smoked. If the two risks are additive, however, PC depends on the amount smoked according to a formula, with the figures mentioned applying to an average smoking history (24.4 pack-years). CONCLUSION: Because of its simplicity and because it falls within the range of criteria based on several more sophisticated approaches, we prefer the criterion of 100 micrograms/m3-years, based on the relative risks by exposure group. However, the compensation board of the Canadian province of Quebec, on consideration of these alternatives, has proposed as a criterion that the upper 95% confidence limit of PC for the patient be at least 50%, assuming an additive relative risk model and allowing for their smoking habit.

Aluminum↗
PubMed1996

Carrying and using weapons: A survey of minority junior high school students in New York City.

To explore weapon carrying among young, inner-city adolescents, a survey was administered in fall 1993 to 2005 predominately Hispanic students (mean age = 12.8 years) in three New York City junior high schools. The survey revealed that 21% of students reported personally carrying a weapon; guns and knives were the weapons most commonly carried. Most of those who carried guns reported that they bought them. Forty-two percent indicated that they had a family member or close friend who had been shot. Boys and older students were more likely to report carrying weapons. Preventive efforts may need to begin before or on entry into junior high school rather than high school.

Adolescent↗