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Biomedical subjects

R A Kronmal

Publications and source records attributed to R A Kronmal.

At least 91 records · Page 5Linked to original sources
PubMed1983

The effect of assuming independence in applying Bayes' theorem to risk estimation and classification in diagnosis.

The effect of assuming independence in the use of Bayes' Theorem for classification and estimation of risk is examined. Analytic results are provided for two specific multivariate normal models and for a model involving binary variables. Monte Carlo results are presented for the former. In these specific cases and an example from medical research, the (false) independence assumption results in classification error rates comparable or better than rates obtained by using the correct model. For a number of covariance structures selected, the a posteriori distribution becomes more U-shaped as the number of variables increases, thus biasing the estimate of risk toward zero or one.

Bayes Theorem↗
PubMed1983

Epidemiology of rotaviruses in a cohort of 45 Guatamalan Mayan Indian children observed from birth to the age of three years.

A cohort of 45 children was observed from birth to three years of age in their natural ecosystem to determine patterns of infection, morbidity, and growth. Data from enzyme-linked immunosorbent assay analysis for rotavirus of 5,891 extracts (kept frozen since 1964-1969) of weekly fecal specimens were compared against growth, morbidity, and specimen data files, permitting a retrospective description of the epidemiology of rotavirus infection in the cohort. Rotavirus infections were uncommon in the first months of life in intensively breast-fed infants. Infection increased with age to reach a maximal rate in the six- to 18-month age period. While there was a high incidence of diarrhea in the cohort, rotavirus was associated with only 10% of such episodes. The incidence of rotavirus infection was 1.2 episodes per child-year, and the incidence of rotavirus-associated diarrhea was 0.8 episodes per child-year. Serious outbreaks of rotavirus generally occurred from September through December, with as many as one-half of the children becoming infected. Repeated rotavirus infection was a common phenomenon.

Aging↗
PubMed1983

Coronary arteriography and coronary artery bypass surgery: morbidity and mortality in patients ages 65 years or older. A report from the Coronary Artery Surgery Study.

Of 2144 patients age 65 years or older entered into the registry of the Coronary Artery Surgery Study (CASS) who had coronary arteriography, 1086 underwent isolated coronary artery bypass grafting. Complications of angiography included death in four patients and nonfatal myocardial infarction in 17. Eight patients suffered neurologic complications, which were transient in five. The perioperative mortality was 5.2% (57 of 1086), which is significantly greater than the perioperative mortality of 1.9% (151 of 7827) in patients younger than 65 years entered in CASS (p less than 0.001). There was a trend toward an increased mortality rate with age; it was 4.6% (37 of 803) in patients age 65-69 years, 6.6% (16 of 241) in those 70-74 years and 9.5% (four of 42) in those 75 years or older. The duration of hospital stay after operation was significantly longer for the patients 65 years or older than for the patients younger than 65 (13.3 vs 11.4 days; p less than 0.001). Stepwise linear discriminant analysis identified five variables predictive of perioperative mortality: presence of 70% or more stenosis of the left main coronary artery and a left-dominant circulation, left ventricular end-diastolic pressure, a history of current cigarette smoking, pulmonary rales on auscultation, and presence of one or more associated medical diseases. A second linear discriminant analysis, incorporating 7658 CASS patients who underwent isolated coronary artery bypass surgery irrespective of age, examined whether age 65 years or older was an independent predictor of perioperative mortality. The variables selected, in order of significance, were congestive cardiac failure score, left main coronary artery stenosis and a left-dominant circulation, age 65 years or older, left ventricular wall motion score, sex and history of unstable angina pectoris. In patients 65 years or older, the mortality from coronary arteriography is low, whereas mortality from coronary artery bypass surgery is greater than that in CASS patients younger than 65 years.

Aged↗
PubMed1983

Natural history of rotavirus infection in the children of Santa María Cauqué.

A prospective observation of 45 cohort children from birth to three years of age permitted the collection of 5689 weekly stool specimens, along with frequent morbidity, dietary and growth data. Specimens tested by the ELISA showed that all children became infected with rotaviruses during the first three years of life, many repeatedly. The overall rotavirus incidence was 10.6 per 100 child-months (or 1.3 infections per child per year). Rotaviruses exhibited a high pathogenic potential estimated in 65%, but only about 10% of all diarrheas appeared associated with them. Rotaviruses occurred throughout the year but clustering was evident in August through December, with epidemics of greater severity in particular months of certain years. During outbreaks, from a third to one half of all children became infected with rotaviruses in a given month. This and the frequent association of rotaviruses with other enteric agents (34%) suggest that fecal-oral transmission is the main source of infection, a net result of the prevailing low socioeconomic level in the village setting.

Age Factors↗
PubMed1982

C2: a data base management system developed for the Coronary Artery Surgery Study (CASS) and other clinical studies.

For the Coronary Artery Surgery Study (CASS), large variable amounts of data on different form-types are collected on many different patients. In this paper, we describe C2, a "state-of-the-art" command-oriented data base system developed in response to the needs of maintaining a large complex data base and performing subsequent analyses on a large number of studies. C2 provides a friendly, interactive interface with the researcher as well as a powerful method for data extraction, data transformation, and the merging of files from the CASS data base.

Clinical Trials as Topic↗
PubMed1982

Excess weight among children with phenylketonuria.

Children with phenylketonuria (PKU) participating in the PKU Collaborative Study were found to be overweight on average by age 4, particularly the girls. A search was made for factors that were most highly associated with a child's overweight status at age 4, in order to help understand the etiology of the problem, as well as to help predict who would be at highest risk of becoming overweight by 4 years. For the analyses, the PKU children who were above the 93rd percentile of weight for their height and sex at age 4 were classified as overweight, and this group was compared to the normal weight PKU children. Among scores of variables measured on the 151 children during their first 2 years of life, overweight (excess weight for height) at 24 months was the best predictor of overweight status at 4 years. Other probable risk factors of being overweight at 4 years were lower socioeconomic status (for both sexes) and overweight parents and large stature (for the girls only). Factors that were not significantly related to overweight status included the level of restriction of the diet therapy for PKU, energy intake during the first 4 years of life, and the diet composition (protein/energy ratio).

Body Height↗
PubMed1982

[Correlation of the coronary heart disease risk factors and coronary angiographic data].

The findings for 14 risk variables were correlated with the results of coronary angiography in 8807 patients enrolled in the multicenter Coronary Artery Surgery Study. Discriminant function analysis revealed that age, sex, cigarette smoking and level of blood cholesterol best distinguished between the groups with (6688 patients) and without (2119 patients) coronary artery disease (CAD). The relative risk for CAD in patients with the combination of cigarette smoking and an elevated cholesterol level was high in women 55 years old or younger and in men 35 years old or younger. Few women 45 years old or younger (7 out of 97) had CAD when neither of these risk factors were present. Despite these correlations, only limited gains accrued from the use of discriminant function analysis in correctly allocating patients into disease and nondisease groups. Extent and severity of disease in 15298 patients with CAD were significantly (p less than 0.001) but modestly correlated with age, sex, blood cholesterol level and history of diabetes or hypertension. No positive correlation occurred between the arteriographic measures of disease and the cigarette smoking history. Thus, factors influencing the presence of disease may differ from those influencing its extent and severity.

Adult↗
PubMed1980

Risk factors and angiographic coronary artery disease: a report from the coronary artery surgery study (CASS).

The findings for 14 risk variables were correlated with the results of coronary arteriography in 8807 patients registered in the interinstitutional Coronary Artery Surgery Study (CASS). Discriminant-function analysis revealed that age, sex, cigarette smoking and the level of blood cholesterol best distinguished between the groups with (6688 patients) and without (2119 patients) coronary artery disease. A family history of coronary artery disease and the presence of hypertension or diabetes were of addition, but less, discriminating value. The relative risk for coronary artery disease in patients with the combination of cigarette smoking and an elevated cholesterol level was high (> 4) in females age 55 years or younger and in males age 35 years or younger. Few females age 45 years or younger (seven of 97) had coronary artery disease when both of these risk factors were absent. In spite of these correlations, only limited gains accrued from the use of discriminant-function analysis in correctly allocating patients into disease and nondisease groups. This indicates that, while certain factors are significantly correlated with coronary arteriographic findings, their value for predicting the presence of coronary artery disease is limited.

Adult↗
PubMed1979

Physical growth in phenylketonuria: II. Growth of treated children in the PKU collaborative study from birth to 4 years of age.

Height, weight, and head circumference data up to age 4 years are reported for 124 children with phenylketonuria (PKU) who had been started on diet management before 4 months (121 days) of age and who were participating in the Collaborative Study of Children Treated for Phenylketonuria. Growth measurements of both the children and their parents corresponded with national and international standards. The growth of children with PKU was compared also with that of a group of normal children in the United States in whom corresponding longitudinal growth data had been obtained at the Fels Research Institute (FRI). Statistically significant differences betweeen the groups were not noted at any age. However, when these groups were compared on coefficients using curve fitting, a trend toward a greater increase in weight as they became older, noted in both sexes in the PKU study group, was significantly higher (P less than .005) in the PKU study girls compared with the FRI sample. Height growth was identical in both groups, and comparison with family data showed that the children with PKU grew as expected for their genetic endowment.

Body Height↗
PubMed1976

Breast-feeding, weaning and the diarrhoeal syndrome in a Guatemalan Indian village.

Prospective studies in Mayan Indian children living in their natural setting were carried out from 1964 through 1974; observations began at birth and extended at least throughout the first three years of life. Adequate growth and survival were characteristic of exclusively breast-fed infants in the first months of life. Despite the high rate of infection, children exhibited a considerable resistance to intestinal protozoa, enterobacteriaceae and enteric viruses. Resistance against colonic invaders is attributed to the bifidus flora, and that against agents acting in the small bowel, to specific antibodies present in colostrum and milk. Diarrhoeal disease was least in this period and increased with weaning to reach maximum peaks at the time of weaning. The protracted weaning consisted of progressive administration of foods of low biological value given under deficient sanitary conditions. The nutrient value of the diet as a function of the child's weight was adequate in protein but in most cases it was markedly deficient in calories. Infectious diseases, particularly diarrhoea, were found associated with pronounced reductions in the already deficient calorie intake. Infection and infectious disease were common particularly during the first 6 to 18 months of life. Weight loss was a frequent finding during and after episodes of disease. The consequence of the malnutrition-infection interaction is a marked stunting of growth, clearly evident from examination of the growth curves of village children. Nutrient intake did not correlate with growth velocity. By contrast, the duration of breast-feeding was strongly associated with growth in the linear segment of the curve, while in the period of faster growth the correlation was inverse. On the other hand, morbidity was inversely correlated with calorie and protein intake and this was more obvious in the second than in the first year of life. The data indicate that infection is one of the leading factors associated with reduced calorie (and protein) intakes during the critical period of onset of malnutrition and mortality in childhood. By preventing infection, particularly diarrhoea, the food intake, nutrition and growth of children could be significantly improved.

Breast Feeding↗
PubMed1976

Antenatal events and postnatal growth and survival of children in a rural Guatemalan village.

The biological features of all pregnant women and newborn infants in a typical rural village of Guatemala have been studied form 1964 to the present; 458 pregnancied have been analysed. The mothers averaged 143.1 cm in height 52.9 kg in weight and 9 mm in triceps skinfold. The diet of most was adequate in percentage protein but inadequate in iron and other nutrients. Infection was common, two or more episodes occurring in 40 per cent of pregnancies. The newborn population had a birthweight averaging 2533 g and length 45.6 cm. Thirty-four per cent were less than 2501 g at 37 weeks gestation or over; seven per cent were pre-term. The infants' growth was followed till age six years. Survival correlated strongly with birth weight and gestational age. Pre-term infants showed the poorest survival in neonatal and postneonatal infancy; but the survivors thrived therafter. The term-small-for-gestational age infants had poor survival in infancy and during the second and third years. Term infants with adequate weight-for-gestational age had the best survival rate. Postnatal physical growth correlated with birth weight and gestational age but pre-term adequate-for-gestational age infants showed a rate of growth as good as that of term infants.

Adolescent↗