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Biomedical subjects

J A Hanley

Publications and source records attributed to J A Hanley.

At least 55 records · Page 3Linked to original sources
PubMed1994

The relationship of urgent hospital admissions for respiratory illnesses to photochemical air pollution levels in Montreal.

The relationship between the number of daily urgent hospital admissions for respiratory illnesses (31 hospitals) and ambient air pollution in Montreal, Canada, was investigated for warm periods between 1984 and 1988. Air pollutants included 1-hr and 8-hr maximum ozone, estimated particulate matter < or = 10 microns in aerometric diameter (PM10), and estimated sulfate (SO4(2-) fraction of PM10. Regression analyses controlled for seasonal and day-of-week trends, autocorrelation, temperature, and relative humidity. For July and August periods, there was a statistically significant (P < 0.01) univariate relationship of all respiratory admissions to 8-hr maximum ozone, which became nonsignificant when coregressed with temperature. Levels of ozone which never exceeded the U.S. National Ambient Air Quality Standard (NAAQS) of 120 ppb and high intercorrelations between ozone, particulates, and temperature may explain this finding. Asthma admissions in the May-October periods increased by 2.7% over mean levels for each 12 micrograms/m3 increase in PM10 levels 3 days prior to the admission day (95% confidence interval, 0.7 to 4.8%). In the July and August periods, hospital admissions for respiratory illnesses excluding asthma were 9.6% higher (95% confidence interval, 0.5 to 18.7%) when estimated SO4(2-) had exceeded 8.1 micrograms/m3 4 days prior to the admission day compared to days when SO4(2-) was at or below this level. There were no significant (P < 0.05) associations of a reference group of nonrespiratory admissions to air pollution after controlling for weather. The above results were found despite levels of PM10 which never exceeded the NAAQS of 150 micrograms/m3. The associations found are relevant to public health, since hospital admissions are expected to be accompanied by considerably more frequent occurrences of less serious outcomes. The present findings suggest that particulate air pollution during photochemically active periods is related to respiratory morbidity in Montreal.

Air Pollutants↗
PubMed1994

Estimation of unmeasured particulate air pollution data for an epidemiological study of daily respiratory morbidity.

The standard approach to government-mandated aerometric monitoring of airborne particulates across North America is to sample every sixth day year round. However, such data are inadequate for epidemiological studies which aim to examine daily time series relationships of particulate air pollution to respiratory health responses. The aim of the present study was to estimate missing daily particulate matter < or = 2.5 and < or = 10 microns in aerometric diameter (PM2.5 and PM10) and sulfate (SO4(2-) to a degree sufficiently accurate and reliable to allow the use of these estimates, along with the measured data, in an investigation of the relationship of air pollution to respiratory hospital admissions in Montreal during the 1980s. Prediction equations were developed for May through October periods using available daily levels of predictor variables which included: relative humidity-corrected light extinction coefficient (bext) derived from airport visual range sightings, coefficient of haze (COH), SO2, NOx, CO, O3, wind speed, wind direction, barometric pressure (BP), temperature, relative humidity, and total precipitation. Three fourths of the available gravimetric particulate data were used to develop prediction models, while the remaining fourth was used to test the reliability of the model (holdout data). All final models explained over 70% of the variability in the particulate air pollutants and were reliable when tested against the holdout data. The strongest (P < 0.001) and most consistent predictors were bext, COH, and O3 measured on the same day as the particulate, and BP lagged 1 day in the past. Other selected variables were same day NOx, BP, and minimum temperature. Although the present approach to the estimation of missing particulate air pollution may increase the level of exposure misclassification, it does allow for the use of existing network databases in epidemiological studies of daily air pollution health effects even though particulate data is only measured on certain days.

Air Pollutants↗
PubMed1994

Projecting the lifetime risk of cancer from exposure to diagnostic ionizing radiation for adolescent idiopathic scoliosis.

Adolescent idiopathic scoliosis (AIS) is a disorder characterized by lateral curvature of the spine and is the most prevalent orthopedic disorder in this age group. The diagnosis and management of AIS requires multiple full-spinal radiographs, leading to potentially high doses of ionizing radiation. The purpose of this study was to estimate in a cohort of subjects with AIS the organ-specific doses of x-ray radiation from spinal radiographs and to calculate the lifetime number of cancers attributable to these exposures. The cohort consisted of AIS patients referred from 1960 to 1979 to a large pediatric hospital in Montreal, Quebec. Organ-specific x-ray doses were estimated using a Monte Carlo procedure that accounted for the radiant energy of the x-ray beam. Cumulative doses for each subject were obtained by summing the estimated doses over all radiographs. These estimates of dose and published estimates of risk from the U.S. National Academy of Sciences Fifth Committee on the Biological Effects of Ionizing Radiation were then incorporated into a life table procedure to project the excess lifetime risk of cancer. About 85% of the 2,181 subjects in the cohort were first referred for scoliosis between the ages of 11 and 17 y. The mean number of radiographs over an average 3-y follow-up period was 12. Organs receiving the highest mean cumulative doses (about 0.03 Gy) were the thyroid gland and the female breast. About 10 excess incident cancer cases (out of a total of 399 projected) and about four excess deaths (out of a total of 247 projected) were estimated to occur over the lifetime of the 1,847 women in the cohort. This is equivalent to an excess lifetime risk of about 1 to 2% (12-25/1,000) among women. Although doses today from spinal radiographs are considerably lower than two decades ago, doses and risks can be further reduced through the use of the posteroanterior view in place of the more traditional anteroposterior view.

Adolescent↗
PubMed1993

Terminal digit preference, random error, and bias in routine clinical measurement of blood pressure.

We examined the presence, magnitude, and consequences of systematic and random errors caused by terminal digit preference in the measurement of highest systolic blood pressure during prenatal visits in 28,841 non-referred pregnant women who delivered between 1 January 1982 and 31 March 1990. In the overall distribution of terminal digit readings, 78% were read to 0, 15% to even digits other than 0, 5% to 5, and only 2% to odd digits other than 5. This preference for 0's was consistent across the entire distribution of blood pressure and for a variety of maternal characteristics. The relative frequency of the cutoff value of 140 mmHg (i.e. the percentage of readings on 140 mmHg) within the range containing the value (i.e. 138-142 mmHg) was similar to the relative frequency of other multiples of 0. This was true whether the comparison was made in the overall study sample, or in a pre-selected low-risk subgroup or high-risk subgroup, indicating no systematic bias. On the other hand, a strong tendency to read blood pressure values to the nearest 0 had a marked effect on the classification of hypertension. Changing the definition of hypertension from > or = 140 mmHg to > 140 mmHg produced a reduction in prevalence of hypertension from 25.9 to 13.3% in the overall study sample, from 15.4 to 6.3% in the low-risk subgroup, and from 43.3 to 25.3% in the high-risk subgroup. Epidemiologic studies that compare prevalences of hypertension in different populations based on routine clinical measurement of blood pressure and a single cutoff point should assess the consequences of terminal digit preference in defining hypertension.(ABSTRACT TRUNCATED AT 250 WORDS)

Bias↗
PubMed1992

The psychological and physical health of family members caring for an elderly person with dementia.

Most elderly persons with dementia are cared for at home, usually by the spouse or an adult child. The objective of the present study was to determine whether there is an excess of psychological and physical health problems among family caregivers (CGs) of elderly persons with dementia. Data were obtained by interview from close family members of dementia patients (CGs), and from a comparison group made up of close family members of patients undergoing cataract surgery (non-caregivers, NCGs). CGs had significantly higher levels of depression and physical symptoms than NCGs. The association between caregiving and the health variables was stronger among subjects who were the patient's spouse than among those who were the patient's child. Furthermore, greater behavioral disturbance in the demented patient was associated with higher levels of morbidity in the CG. The results suggest that CGs might benefit from careful monitoring of their health status, and from greater access to specialized support services.

Aged↗
PubMed1992

Mantel-Haenszel techniques and logistic regression: always examine one's data first and don't overlook the simpler techniques.

The authors point out that, in addition to logistic regression, there are other, simpler techniques available for making an adjusted estimate of association between an outcome and a risk factor. Also, the consequence of mismodelling with regression, i.e. of missing the real relationship between an outcome and a risk factor, is illustrated with an example. The need to 'examine one's data' prior to performing multivariable techniques is emphasised.

Epidemiologic Methods↗
PubMed1991

Sampling events in space and time: a case study of burn injuries.

We describe the sampling plan used to estimate the number of burn injuries seen at emergency departments of hospitals in New England. We present the rationale for each of the options considered and the implications of each. The chosen plan included all 256 hospitals, but used a different systematic one-day-in-ten sample for each of ten subgroupings of the hospitals. The findings suggest that over 47,000 injuries or almost 400 per 100,000 population were seen at New England Emergency Departments in a 1-year period. This incidence is 60 per cent higher than pre-project estimates would have suggested. From the variability of the data in the sample, we calculate that our estimate is probably no more than 3 per cent under or over the 'correct' rate that would have been obtained by a full non-sampling approach, costing almost 10 times as much. Additional support for our strong belief in the accuracy of the sample-based estimate is provided by the fact that if we had used the same sampling approach to estimate the number of hospitalized burn injuries, our estimate would have been in error by only 124 or 4 per cent from the total 3276 obtained by 100 per cent sampling of hospitalization records.

Burns↗
PubMed1991

Twin pregnancy: the impact of the Higgins Nutrition Intervention Program on maternal and neonatal outcomes.

Perinatal outcomes were compared between 354 twins treated with the Higgins Nutrition Intervention Program and 686 untreated twins. After differing distributions of key confounding variables were adjusted for, the twins in the intervention group weighed an average of 80 g more (P less than 0.06) than the nonintervention twins; their low-birth-weight rate was 25% lower (P less than 0.05) and their very-low-birth-weight rate was almost 50% lower (P less than 0.05). Although the rate of preterm delivery was 30% lower in the intervention group (P less than 0.05), the rates of intrauterine growth retardation were similar in the two groups. Fetal mortality was slightly higher (14 vs 12 per 1000, NS), but early neonatal mortality was fivefold lower (3 vs 19 per 1000, P less than 0.06) in the intervention group. Maternal morbidity was significantly lower (P less than 0.05) in the intervention group. There was a trend towards lower infant morbidity in the intervention group. These results suggest that nutritional intervention can significantly improve twin-pregnancy outcome.

Birth Weight↗
PubMed1990

Rural physician survey.

In August 1989, the Physician Manpower Training Commission conducted a survey in an effort to learn what factors influence the recruitment and retention of physicians in rural Oklahoma communities. The results of the survey are summarized in this article.

Humans↗
PubMed1989

Signal detection in digital chest-phantom images acquired with an image intensifier.

Signal detection performance was evaluated on the basis of ROC analysis using both digital and conventional images of a humanoid chest phantom. Simulated focal (coin) lesions were the target pathology. Digital images were acquired using a 57-cm image intensifier, digitized to 1024 x 1024 x 10 bits, and compared, in both video and laser-printed film formats, with conventional 14 x 17-inch chest films. Signal detection using digital video and laser printed images, of the same image polarity as conventional images, was found not to differ significantly from that achieved using conventional images, despite the smaller size of the digital images.

Humans↗
PubMed1989

Predicting mortality based on body composition analysis.

The role of the Nae/Ke ratio (the ratio of exchangeable sodium to exchangeable potassium) was examined as a nutritional marker in surgical patients in relation to anthropometrical and biochemical indexes by its ability to identify patients at risk for mortality after hospitalization. In 73 patients with sepsis and malnutrition (Training Group, Madrid) the following were determined: percentage of recent weight loss, triceps skin fold, midarm muscle circumference, serum albumin, serum transferrin, delayed hypersensitivity skin test response, total lymphocytes, and Nae/Ke ratio by multiple isotope dilution. The predictive power of Nae/Ke ratio was so strong (F = 105.1; p less than 0.00001) that it displaced anthropometric, biochemical, and immunologic variables from the linear equation derived from stepwise discriminant analysis using hospital mortality as the dependent variable. A theoretical curve of expected deaths was developed, based on an equation obtained by logistic regression analysis: Pr/death/ = 1/(1 + e[11.8-5.2 Nae/Ke]). Pre- and post-test probabilities on that curve allowed us to determine two cut-off values, Nae/Ke ratios of 1.5 and 2.5, which were markers for nonrisk and mortality, respectively. The model was tested in a heterogeneous data base of surgical patients (n = 417) in another hospital (Validation Group, Montreal). For patients exhibiting an abnormal Nae/Ke ratio (greater than 1.2) and a greater than 10% of probability of death, 54 deaths were expected and 53 observed (X2 = 1.8 NS). Two tests confirmed the basic agreement between the model and its performance, a G statistic of -0.704 and the area beneath the "receiver-operating-characteristic" (ROC) curve (Az = 0.904 + 0.0516 for the Madrid group vs. Az = 0.915 + 0.0349 for the Montreal group, NS). It was concluded from this analysis that, compared with the usual anthropometric measurements, the Nae/Ke ratio, if available, is the best method for identifying malnourished patients at risk of dying.

Adolescent↗
PubMed1989

Receiver operating characteristic (ROC) methodology: the state of the art.

Receiver operating characteristic (ROC) methodology has been increasingly used in medical applications in the last 10 years. The text by Swets and Pickett has popularized the technique and the journal Medical Decision Making (1981--) provides a forum for further methodologic issues. In this article, I will (1) describe the nature of the data generated by ROC studies; (2) evaluate the choices of summary indices of performance (accuracy); (3) outline the data-analytic techniques used, and how to incorporate data from multiple observers and multiple "readings"; (4) review proposed alternatives to the commonly used binormal ROC model; and (5) discuss issues, such as verification bias, and challenges, such as multicenter comparative imaging studies and the difficulty of obtaining "truth data", which need to be addressed when adapting ROC methods to medical contexts.

ROC Curve↗
PubMed1988

Environmental exposure to tobacco smoke and lung function in young adults.

The relationship between lung function and environmental exposure to tobacco smoke (passive smoking) was studied in 293 nonsmoking young men and women, 15 to 35 yr of age. A self-administered mailed questionnaire was used to assess the lifetime environmental exposure to cigarette smoke at home and at work for each subject. Lung function information used here had been gathered in the course of a previous study of the determinants of lung function in early adulthood. In men, maximal midexpiratory flow rate (FEF25-75) decreased in relation to an index of cumulative lifetime environmental exposure to tobacco smoke at home, after taking into account the effects of cumulative exposure at work as well as age, height, body size, respiratory pressures, and cooking fuels used at home. The components of this exposure index most closely related to the reduction in FEF25-75 were maternal smoking habits and exposure to second-hand smoke during childhood. In women, the diffusing capacity of the lung (DLCO) decreased in relation to cumulative exposure to tobacco smoke at work, after accounting for the effects of cumulative lifetime exposure at home and the other factors mentioned above. These findings contribute to the gathering evidence that environmental exposure to tobacco smoke is harmful to respiratory health, and suggest that the effects are not insignificant. For instance, the FEF25-75 of a young man 20 yr of age who had never smoked and always lived at home would be 800 ml less if both his parents smoked than if they did not.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1987

Computer modelling of measurement error in longitudinal lung function data.

The effect of measurement error on the accuracy of results in two epidemiological study designs involving longitudinal lung function data was assessed using computer modelling. Five realistic data sets (cohorts) were created, each of 400 subjects, half of whom were exposed to an agent whose effects approximated in magnitude that of cigarette smoking. In each cohort, FEV1 decline was modelled after 6, 4 and 2 years of observation with and without error in the measurement of level of FEV1. For each length of observation the effect of exposure on decline was estimated using a follow-up design comparing the FEV1 decline between exposure groups, and a case-control design comparing risk of exposure in subjects in the top 20th percentile of FEV1 decline (cases) to exposure in those in the bottom 20th percentile (controls). For both study designs an exposure effect at p less than or equal to 0.01 could only be consistently detected after 6 years of observation.

Computer Simulation↗