Effect of infection control measures on the frequency of diarrheal episodes in child care: a randomized, controlled trial.

Background: Diarrheal infections are common in children who attend child care, and preventing transmission of disease in this setting depends on actions by child care staff. We set out to discover whether transmission of gastrointestinal infections in child care could be reduced by improved infection control procedures.

Methods: We performed a cluster randomized, controlled trial of an infection control intervention conducted in child care centers for 1 city in Australia.

Effect of infection control measures on the frequency of upper respiratory infection in child care: a randomized, controlled trial.

Background: Acute upper respiratory infections are common in children who attend child care, and preventing transmission of disease in this setting depends on actions by child care staff. We set out to discover whether transmission of respiratory infections in child care could be reduced by improved infection control procedures.

Methods: We performed a cluster, randomized, controlled trial of an infection control intervention conducted in child care centers in 1 city in Australia.

ML and REML estimation in survival analysis with time dependent correlated frailty.

In the study of multiple failure times for the same subjects, for example, recurrent infections for patients with a given disease, there are often subject effects, that is, subjects have different risks that cannot be explained by known covariates. Standard methods, which ignore subject effects, lead to overestimation of precision. The frailty model for subject effects is better, but can be insufficient, because it assumes that subject effects are constant over time.

Threshold models in a methadone programme evaluation.

The degree of non-compliance with a methadone programme is such that a zero is often recorded as the response variable. Such outcome variables cannot be transformed to normality in order to investigate a regression relationship between the response variable and various risk or treatment variables. The presence of a random effect as well in this regression causes added difficulty in the analysis.

Trends in the prevalence of trachoma, South Australia, 1976 to 1990.

The eye health of rural Aboriginal Australians is known to be poor. Over the past 20 years, Aboriginal communities in remote parts of Australia have had increasing access to eye health services through the National Trachoma and Eye Health Program (NTEHP). Using published and unpublished data, we examined trends in the prevalence of inflammatory trachoma in the Anangu Pitjantjatjara of South Australia.

Sequential continuity of care by general practitioners: which patients change doctor?

Objective: To identify individual and social characteristics of patients making sequential visits to a different rather than the same general practitioner (GP).

Method: Data for this study were extracted from the "Record Linkage Pilot Study" of the National Centre for Epidemiology and Population Health, which linked information from personal interviews with Health Insurance Commission and National Heart Foundation Risk Factor Survey data. Each sequence of visits (any two consecutive visits) made by each participant to the same or a different GP from January 1991 to December 1992 was treated as an event.

Loglinear models using capture-recapture methods to estimate the size of a measles epidemic.

Cases of measles reported separately by doctors, hospitals, laboratories, and others are treated as separate captures and releases of the population of children aged up to 10 years who have been infected by measles in a recent epidemic. Loglinear models are used to assess the adequacy of fit of various models for capture-recapture and the size of the epidemic in different age groups is estimated.

Survival analysis and prognosis for dementia patients.

How long a dementia patient is cared for in the home before admission to a nursing home depends on the state of the patient and the state of the caregiver. Using 5-year follow-up data, the times until entry to nursing home and until death are modeled using a Cox survival model in which patient and caregiver variables at entry to study as well as changes in these variables over the following 12 months are the regression variables. Treatment variables quantify the effects of a caregiver training program.

Time until institutionalization and death in patients with dementia. Role of caregiver training and risk factors.

Objective: To determine which variables best predict prognosis--time to nursing home admission (NHA) and death--in patients with dementia.

Design: Survival analysis employing the Cox proportional hazards model with the use of risk variables pertaining to dementia severity and its rate of progression and caregiver functioning.

Setting: Patients and their caregivers participating in a controlled intervention study of training for caregivers in home management of dementia.

REML estimation for survival models with frailty.

A method of estimation for generalised mixed models is applied to the estimation of regression parameters in proportional hazards models for failure times when there are repeated observations of failure on each subject. The subject effect is incorporated into the model as a random frailty term. Best linear unbiased predictors are used as an initial step in the computation of maximum likelihood and residual maximum likelihood estimates.

Variance components for discordances.

Tests for biotyping isolates give a result that is classified as either positive or negative, indicative of growth or nongrowth of bacteria. The reproducibility of such tests is measured by the number of discordances in replicates of the same measurement. In this analysis the probability distribution of the number of discordances is estimated for each of several tests in the presence of possible random between-laboratory effects as well as random laboratory-test interactions, which are also estimated.

Percutaneous aortic valvuloplasty.

Objective: To determine the short-term and long-term results of percutaneous aortic valvuloplasty.

Design: A retrospective follow-up study.

Setting: The Cardiac Catheterisation Laboratory and Cardiovascular Medicine Unit of a teaching hospital.

Regression with frailty in survival analysis.

In studies of survival, the hazard function for each individual may depend on observed risk variables but usually not all such variables are known or measurable. This unknown factor of the hazard function is usually termed the individual heterogeneity or frailty. When survival is time to the occurrence of a particular type of event and more than one such time may be obtained for each individual, frailty is a common factor among such recurrence times.

A model for the analysis of growth data from designed experiments.

A model for growth data from designed experiments is presented which extends the stochastic differential equation of Sandland and McGilchrist (1979, Biometrics 35, 255-272). Residual maximum likelihood (REML) is used to estimate the parameters of the model. The model is easily extended to incomplete data and is shown to overcome some of the practical difficulties encountered with the profile model.

A Markov transition model in the analysis of the immune response.

A method for the analysis of repeated measures of immune response is given. Typically the reactions of response to stimulus do not occur at the same time for all experimental units so that regression models are inappropriate for this type of data. Instead Markov transition models are suggested and procedures given for testing differences among response patterns.

Environmental Factors Influencing Numbers of Rhizobium leguminosarum biovar trifolii and Its Bacteriophages in Two Field Soils.

Fluctuations in numbers of Rhizobium leguminosarum biovar trifolii and its bacteriophages in two fields with different soil types were followed during a 17-month period in 1981 and 1982. Mean levels of both phage and rhizobia varied significantly (P < 0.05) on different occasions, with rhizobial levels varying from 1.

Smoking: a major predictor of left ventricular function after occlusion of the left anterior descending coronary artery.

The major predictors of left ventricular function after coronary artery occlusion were assessed in 108 consecutive patients who had complete occlusion of the left anterior descending artery as the only important lesion demonstrated at angiography between June 1978 and June 1983. A scoring system was used to identify regional damage on left ventriculograms. Forty two patients were classified as having good left ventricular function and 66 as having varying degrees of impairment.

Estimation of cumulative illness using cross-sectional data.

Using cross-sectional data, a general method is given for assessing cumulative illness due to a particular disease. An application is given to estimating cumulative illness due to otitis media in Australian aborigines and contrasting these results to the non-aboriginal population.

The inheritance of serum cholesterol: adjustment of observed cholesterol levels for age, sex and body weight using inverse-polynomial regression.

Adjustment of observed serum cholesterol levels for biological and environmental variables is an essential step in studying the mode of inheritance of serum cholesterol. Body weight, measured as weight/height2, is found to be an important variable not previously taken into account in regression equations. A method is given for adjusting cholesterol levels for age, sex and body weight, thus obtaining residuals which represent the deviations of cholesterol levels from the mean of the general population for each category of these three factors.

Estimation of environmental and genetic components of quantitative traits with application to serum cholesterol levels.

A mixed model of environmental, polygenic, and major locus effects is developed, allowing for environmental correlations between first-degree relatives and spouses. Maximum-likelihood techniques are used to determine the relative contributions of each of these effects to a quantitative trait. Inclusion of a nuclear family in the sample is assumed to depend on the value of the quantitative trait of one member of the family, so conditional distributions are used.

The effects of body weight on serum cholesterol, serum triglycerides, serum urate and systolic blood pressure.

The effects of body weight and age on serum cholesterol, serum triglycerides, serum urate and systolic blood pressure were examined in 600 male and 400 female blood donors aged 20 to 49 years. In the men significant correlations with body mass index were found for all four variables in each decade. In the women below 40 only the correlation with blood pressure was significant.

The synergistic effect of weight loss and changes in dietary lipids on the serum cholesterol of obese men with hypercholesterolaemia: implications for prevention of coronary heart disease.

The hypolipidaemic effect of a low-fat, low-cholesterol diet, alone and in combination with weight reduction, has been evaluated in two groups of obese men with hypercholesterolaemia. In 41 men who lost 10.3 kg over 11 months and maintained their lower weight for 23.