Biomedical subjects
R R Neutra
Publications and source records attributed to R R Neutra.
Characteristics of hazardous material spills from reporting systems in California.
Data on hazardous material releases that occurred between January 1, 1982 and September 30, 1983 in California were obtained from the California Highway Patrol (CHP) and the US Department of Transportation (DOT). The majority of incidents involved highway transport of hazardous materials, although some information was available on air, rail, and stationary facility releases. Vehicle accidents and failure of or damage to the container were the most frequent causes of releases. Proportionately more hazardous materials incidents occurred in early summer than at other times of the year, during weekdays, and daytime hours. The largest proportions of incidents involved the chemical categories of corrosives and fuels. Reported exposures and injuries to response personnel and other people at the scene were relatively few; no fatalities were reported. Few incidents were reported in both data sources, suggesting that the examination of only one data source would yield a gross underestimate of the total number of hazardous materials incidents in California. The lack of available denominator data limits the interpretation of the findings.
Epidemiology for and with a distrustful community.
The epidemiology of diseases associated with chemical waste disposal sites has often been delayed for years after the affected community became aware of the exposure. Frequently, this has resulted in an aroused neighborhood community that is distrustful of those public agencies and officials responsible for protecting their health. It is thus important that positive steps be taken to alleviate the antagonism and to involve the community in an active and constructive role in the epidemiology study. This paper presents a case history of such an incident and highlights some of the lessons learned. The first steps were to involve and inform the community. A citizen and industry advisory committee was formed to participate in the work, publish a newsletter, and conduct regular community meetings. The newsletter and the community meetings were used to identify problems and to explain them; to describe uncertainties of a scientific as well as of political or financial nature; to involve community leaders, including those distrustful; to conduct an epidemiologic census and a neighborhood environmental exposure survey. The end results were a defusing of the antagonism toward authorities, complete acceptance by the community of the merit of the report, a higher quality of report than might otherwise have been possible, and the freedom to move toward alleviating the problems of the disposal site.
Investigation of a cluster of anencephaly and spina bifida.
Environmental factors remain undefined as possible causes of spina bifida and anencephaly. The authors noted a fivefold increased incidence for 1979-1980 in the Antioch-Pittsburg , California area, prompting a case-control study. They studied nine case and 27 control mothers as well as eight case and 17 control fathers to evaluate factors including residence, occupation, drug use, illnesses, and pesticide or chemical exposure. Except for fathers' smoking (p less than 0.05), no exposure was associated with neural tube defects.
The description and initial evaluation of an intensive live-in program in risk reduction.
Drawing upon the epidemiological, clinical, and behavioral studies suggesting the importance and feasibility of multidisciplinary efforts to reduce levels of risk variables for cardiovascular and other chronic diseases, a short-term live-in intervention program was developed. The program includes efforts to reduce smoking, weight, blood lipids, blood pressure, and stress through improving habits of exercise, nutrition, weight management, and stress control delivered to individuals with varying levels of health risk based on measurable biochemical and physiological variables and medical history. Major changes occurred during the 24-day program in 459 individuals enrolled in the program: 68% of smokers ceased, average cholesterol fell from 240 to 200 mg%, ideal body weight fell from 134 to 129% (82 to 79 kg), systolic blood pressure (BP) fell from 131 to 119 mm Hg, diastolic BP fell from 81 to 73 mm Hg. and reported feelings of general well-being increased. Greater changes were observed in the high-risk groups. Follow-up results at 1 year (48% of patients reporting) for those defined as high risk were a net decrease of 22 mg% in cholesterol, 7 mm Hg in systolic BP, 6 mm Hg in diastolic BP, and 6.8% of ideal body weight; 45% of those smoking at admission were still not smoking at 1 year (32% reporting). For those at lower risk there was a general return of risk levels toward baseline values.
The relationship between electronic fetal monitoring and Apgar score.
A study was made of the relationship between electronic fetal heart monitoring and the Apgar score in 14,350 babies delivered between 1970 and 1975 at Beth Israel Hospital, Boston. Simple comparison of Apgar scores in monitored and unmonitored babies showed no difference at 5 minutes. When we controlled for gestational age and other potential confounders, a different pattern emerged. In a group of obviously high-risk pregnancies, monitored babies had a more favorable distribution of 5-minute Apgar scores (3.8% instead of 7.2% with a score below 6, P = 0.020). This group contained the 7.4% of all babies who were greater than or equal to 36 weeks of gestational age at highest risk (with problems such as hydramnios, multiple pregnancy, placental complication, or malpresentation). A similar trend for babies less than 36 weeks' gestational age with the same obstetric complications did not achieve statistical significance. There was no evidence for benefit in the other risk categories.
An attempt at measuring the impact of sanitation and economics on health: a reanalysis of the Colombian National Health Survey.
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The case-control method in medical care evaluation.
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Identification of the noncompliant hypertensive patient.
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Techniques for characterizing a series of blood pressure measurements over time.
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Effect of fetal monitoring on cesarean section rates.
Electronic fetal monitoring (EFM) and cesarean sections (CS) have been studied in 14,484 patients delivered between 1970 and 1975. The primary CS rate for those monitored was 107/1000, and for the unmonitored was 57/1000. Multivariate analysis of these data shows that most of the increase in CS rate associated with monitoring is attributable to inherent differences between monitored and unmonitored patients. Furthermore, the association between monitoring and CSs was not homogeneous among sub-groups. Cesarean sections were relatively less frequent in monitored nulliparas with malpresentation and more frequent in otherwise normal monitored multiparas. These opposing effects tended to balance each other. During the study period the primary CS rate rose from 4.3 to 11.2%. This increase was strong in unmonitored patients and was primarily due to operations undertaken for fetopelvic disproportion. We cannot therefore attribute much of the increasing CS rate at our hospital to fetal monitoring.
Determinants of dropout rate among hypertensive patients in an urban clinic.
Noncompliance with follow-up is a serious problem in the management of hypertension. A retrospective cohort study examined dropout rates and their determinants among 249 randomly selected outpatients with essential hypertension from the medical clinic of an urban teaching hospital. Data were abstracted from hospital records and a subset of dropouts was interviewed. A lifetable analysis revealed that patients who were initiating therapy or who had been under therapy for less than six months had a 50% chance of remaining in care two years later, while 70% of patients who had been under therapy for more than six months at entry were still in care after this period. Patients who were less severely ill by several indicators were the most likely to drop out. It is hypothesized that the low perceived severity of illness, coupled with the costs and inconvenience of care and the lack of physician enthusiasm for the treatment of mild hypertension leads to non-compliance with follow-up.
Effect of fetal monitoring on neonatal death rates.
We analyzed data from 15,846 live-born infants to assess the effect of electronic fetal monitoring on neonatal death rates. The crude neonatal death rate was 1.7 times higher in unmonitored infants than in those monitored. Adjusting for inherent risk and changes in mortality rates and monitoring rates during the years of the study lowered the relative risk to 1.4 (95 per cent confidence interval, 0.85 to 2.45). The estimated yield from monitoring decreased as the inherent risk of the baby declined. Thus, in the highest-risk group 109 lives might be saved for every thousand babies monitored. In the lowest risk group (babies at term with no risk factors) the neonatal death rate is around one per thousand. The absolute benefit for this large group could therefore not exceed one life saved for every thousand babies monitored.
Estimating exposure-specific disease rates from case-control studies using Bayes' theorem.
The methods used for selecting subjects yield three types of case-control studies: 1) incident cases are compared to non-cases chosen to be representative of the exposure distribution among the person-years which produced the cases. In this type of study the exposure-odds ratio equals the incidence density ratio; 2) incident cases are compared to residual non-cases at the end of the risk period (exposure-odds ratio = cumulative incidence-odds ratio); 3) prevalent cases are compared to non-cases (exposure-odds ratio = prevalence odds ratio). In study type 1 the equivalence of odds ratio to rate ratio requires no "rare disease assumption;" this permits estimation of exposure-specific illness rates when the overall rate is known. In study types 2 and 3 the exposure-odds ratio equals the corresponding rate ratios only when exposure-specific rates are low. Nonetheless, exposure-specific rates can be calculated without making any rare disease assumption using Bayes' theorem and information on the overall disease rate. A method for obtaining approximate confidence limits around the exposure-specific rates is presented.
Impact of patient perceptions on compliance with treatment for hypertension.
Patient noncompliance with medical regimens is a major obstacle in achieving hypertension control. In this study the relationships between patients' perceptions of health, disease and medical treatment and compliance were examined in personal interviews with 142 patients under treatment for hypertension. Compliance was measured in terms of blood pressure control, self-reported medication-taking, and appointment keeping. A multivariate log linear technique was used to control confounding. Blood pressure control was found to be associated with the perceived effficacy of the antihypertensive regimen, having medications prescribed for other chronic conditions, a high level of anxiety when hypertension was first diagnosed, the impact of hypertension and its treatment on lifestyle, and a higher educational level. For self-reported medication-taking, the perceived severity of hypertension, having medications prescribed for other chronic conditions and older age were predictive. Blood pressure control and self-reported medication-taking were highly correlated with each other(p = .02). Older age and being employed were the only variables that contributed independently to improved appointment keeping behavior. From these findings, it might be expected that emphasis on the effectiveness of treatment and on the potential threat posed by hypertension would motivate improved blood pressure control.
Appendicitis: decreasing normal removals without increasing perforations.
There is wide interhospital variation in the removal rates of histologically normal appendices, and variation also in appendectomy rates among countries and among hospital catchment areas. Decision theory suggests that better patient workup and careful observation of doubtful cases result in improved discrimination between appendicitis patients and those with nonspecific abdominal pain. By improving the data base and weighing evidence with care, a surgeon can reduce his false-positives without risk of increasing his perforation rate. In some cases it may even be possible to reduce the false-positives while simultaneously reducing perforations. In a survey of New England hospitals there was no inevitable inverse relationship between normal removal rates and perforation rates. Two examples of improvement in performance are cited from the literature.
The four county study of childhood cancer: clusters in context.
Observations of childhood 'cancer clusters' in small communities in central California prompted us to examine the distribution of childhood cancer in communities throughout the region to see if the overall cancer rate or the distribution of 'cancer clusters' was unusual for agricultural towns where pesticide exposure might be elevated. The distribution of rates was evaluated using a variety of methods: comparison of rates to the regional average, evaluation of the empirical observed versus expected Poisson distribution of events, and multivariate modelling using Poisson regression. These analyses suggest that there were no previously undiscovered communities with excess rates, although the index community which prompted the initial investigation does stand out as unusual. We discuss the impact of a range of forces of morbidity on the likelihood of 'cancer clusters' and the distributions of observed and expected numbers of cancers in a population of locales.
Drinking water source and reproductive outcomes in Sprague-Dawley rats.
As part of our work on the influence of water source on reproductive outcome, Sprague-Dawley rats were randomized to tap water, bottled water, or deionized water treatment groups, utilizing 160 animals per treatment; animals received the water prior to and during pregnancy. Rats were shipped in four batches (A-D). Batch effects were seen for several reproductive parameters. Because the tap water supply was interrupted by an earthquake resulting in an unbalanced design, primary analyses utilized only batches C and D, which included most of the tap water-treated rats. A treatment effect with respect to resorption frequency was seen that was marginally significant using a fixed-effects analysis of variance (P = 0.053), but not when batch was entered as a random effect (P = 0.36). The data were modeled by logistic regression, controlling for batch, litter size, and batch-treatment interaction. The odds ratio comparing tap to bottled water was 1.8 (95% CI 1.0 to 3.3, P = 0.05), which was similar to the epidemiologic result that prompted this study. The magnitude of this association varied by batch, and the difference in resorption frequency was within the range of variation seen for control animals. Although these findings do not justify public health action at this time, further investigation is warranted.