Diagnostics For Mixture Regression Models: Applications To Public Health
Funder
National Health and Medical Research Council
Funding Amount
$128,250.00
Summary
In many public health studies, finite mixture regression models are often used to analyse data arising from heterogeneous populations. It is important to assess the stability of parameter estimates and the validity of statistical inferences when the underlying assumptions appear to be violated, but appropriate diagnostics are lacking in the literature. This research aims to develop effective diagnostic methods for assessing the adequacy of mixture regression models and the sensitivity of accompa ....In many public health studies, finite mixture regression models are often used to analyse data arising from heterogeneous populations. It is important to assess the stability of parameter estimates and the validity of statistical inferences when the underlying assumptions appear to be violated, but appropriate diagnostics are lacking in the literature. This research aims to develop effective diagnostic methods for assessing the adequacy of mixture regression models and the sensitivity of accompanying test statistics. The methodology developed will enable health care professionals to focus on substantive issues and to draw accurate and valid conclusions inferred from correlated and over-dispersed outcomes. In the presence of anomalous observations, the influence diagnostics can provide insights into the source of heterogeneity and the apparent over-dispersion, while accommodating the inherent correlation due to the longitudinal study design or nested data structure. Significance of the research lies in its scientific novelty and the breadth of its practical applications. The benefits to public health will accrue both nationally and internationally. For the empirical studies that motivated and are linked to this research, evaluation of health outcomes has significant implications in the prevention and control of recurrent urinary tract infections, hospital strategic planning, and post-stroke care and rehabilitation management. Moreover, appropriate assessment of a physical activity intervention for older adults is pertinent to falls prevention and reduction of musculoskeletal disorders among sedentary seniors.Read moreRead less
Hierarchical Finite Mixture Modelling Of Health Outcomes: A Risk-adjusted Random Effects Approach
Funder
National Health and Medical Research Council
Funding Amount
$117,000.00
Summary
In medical and health studies, finite mixture regression models have been used to analyze data arising from heterogeneous populations. Traditionally, the application of mixture models is mainly concerned with finite normal mixtures. Recent computational advances and methodological developments have enhanced the extension of the method to non-normal finite mixtures, such as the modelling of discrete responses in finite mixture of generalized linear models and overlapping phases of failure time da ....In medical and health studies, finite mixture regression models have been used to analyze data arising from heterogeneous populations. Traditionally, the application of mixture models is mainly concerned with finite normal mixtures. Recent computational advances and methodological developments have enhanced the extension of the method to non-normal finite mixtures, such as the modelling of discrete responses in finite mixture of generalized linear models and overlapping phases of failure time data in the context of survival analysis. However, due to the hierarchical study design or the data collection procedure, the inherent correlation structure and-or clustering effects present may contribute to extra variations and violation of the independence assumption, resulting in spurious associations and misleading inferences based on the finite mixture model. This project aims to present a unified approach to accommodate both heterogeneity and dependency of observations, by incorporating random effects into finite mixture regression models. The new methodology will provide an integrated framework to analyze heterogeneous and correlated health outcomes. Three empirical studies are considered, namely, evaluation of an occupational injury reduction intervention, length of hospital stay modeling, and analysis of survival times of patients after cardiac surgery. The long term benefits to bioscience are accurate and valid conclusions inferred from medical and health studies, as well as the correct identification of high-risk subgroups. For the three application areas of this project, the improved analyses will specifically enable the evaluation of a participatory ergonomics intervention, the assessment of hospital efficiency and factors influencing length of hospitalization, and the determination of effectiveness of treatments prescribed pre- and post- operation, respectively.Read moreRead less
Maintaining And Developing The Health In Men Study
Funder
National Health and Medical Research Council
Funding Amount
$403,014.00
Summary
The aim of this study is to improve our understanding of healthy aging in older men. The outcomes we are interested in include common acute medical problems such as heart attacks or stroke, chronic debitilating problems such as dementia or heart failure and psycho-social challenges of ageing such as depression and isolation. We have been studying a group (4,250) men for nearly a decade. These men have provided us with a large amount of information about their background, life style and health an ....The aim of this study is to improve our understanding of healthy aging in older men. The outcomes we are interested in include common acute medical problems such as heart attacks or stroke, chronic debitilating problems such as dementia or heart failure and psycho-social challenges of ageing such as depression and isolation. We have been studying a group (4,250) men for nearly a decade. These men have provided us with a large amount of information about their background, life style and health and we are now following them to see what predicts the outcomes of interest. This research is important because the proportion of the population aged 75 years and over is expanding rapidly. Although we know a lot about predictors of health and illness in middle age, we know surprisingly little about these things in the elderly. This research aims to answer some of these questions.Read moreRead less
Functional And Structural Imaging Of Auditory Infomation Processing Deficits In Recent-onset And Chronic Schizophrenia
Funder
National Health and Medical Research Council
Funding Amount
$376,000.00
Summary
Abnormalities in the auditory system have long been suspected to be present among people who suffer from schizophrenia and other psychotic disorders, due in part to the high prevalence of auditory hallucinations amongst these patients. Over the last decade, a group of Australian researchers have identified an index of auditory information processing, recorded from scalp electrodes, that is abnormal in patients with schizophrenia, and their biological relatives. The present project will examine t ....Abnormalities in the auditory system have long been suspected to be present among people who suffer from schizophrenia and other psychotic disorders, due in part to the high prevalence of auditory hallucinations amongst these patients. Over the last decade, a group of Australian researchers have identified an index of auditory information processing, recorded from scalp electrodes, that is abnormal in patients with schizophrenia, and their biological relatives. The present project will examine the relationship between these electrophysiological findings, and a new non-invasive technique of functional brain imaging, looking at changes in blood flow, that can identify the specific brain regions that are active during auditory information processing, and link these to the sources of the scalp recorded measures. Both of these functional measures will be examined in relation to the volumes of brain tissue, measured from magnetic resonance imaging scans using new analysis tools, that enable the identification of subtle changes in brain anatomy. By examining patients who have recently developed schizophrenia, those who have suffered from the illness for longer periods of time, and their close relatives, this study will provide the opportunity to identify biological markers of increased vulnerability for the development of schizophrenia.Read moreRead less