Profiles and predictors of healthcare utilization: using a cluster-analytic approach to identify typical users across conventional, allied and complementary medicine, and self-care

Introduction The identification of typologies of health care users and their specific characteristics can be performed using cluster analysis. This statistical approach aggregates similar users based on their common health-related behavior. This study aims to examine health care utilization patterns using cluster analysis; and the associations of health care user types with sociodemographic, health-related and health-system related factors. Methods Cross-sectional data from the 2012 National Health Interview Survey were used. Health care utilization was measured by consultations with a variety of medical, allied and complementary health practitioners or the use of several interventions (exercise, diet, supplementation etc.) within the past 12 months (used vs. not used). A model-based clustering approach based on finite normal mixture modelling, and several indices of cluster fit were determined. Health care utilization within the cluster was analyzed descriptively, and independent predictors of belonging to the respective clusters were analyzed using logistic regression models including sociodemographic, health- and health insurance-related factors. Results Nine distinct health care user types were identified, ranging from nearly non-use of health care modalities to over-utilization of medical, allied and complementary health care. Several sociodemographic and health-related characteristics were predictive of belonging to the respective health care user types, including age, gender, health status, education, income, ethnicity, and health care coverage. Conclusions Cluster analysis can be used to identify typical health care utilization patterns based on empirical data; and those typologies are related to a variety of sociodemographic and health-related characteristics. These findings on individual differences regarding health care access and utilization can inform future health care research and policy regarding how to improve accessibility of different medical approaches.

Variable selection for skew-normal mixture of joint location and scale models

Although there are many papers on variable selection methods based on mean model in the finite mixture of regression models, little work has been done on how to select significant explanatory variables in the modeling of the variance parameter. In this paper, we propose and study a novel class of models: a skew-normal mixture of joint location and scale models to analyze the heteroscedastic skew-normal data coming from a heterogeneous population. The problem of variable selection for the proposed models is considered. In particular, a modified Expectation-Maximization(EM) algorithm for estimating the model parameters is developed. The consistency and the oracle property of the penalized estimators is established. Simulation studies are conducted to investigate the finite sample performance of the proposed methodologies. An example is illustrated by the proposed methodologies.

A Penalized Matrix Normal Mixture Model for Clustering Matrix Data

Along with advances in technology, matrix data, such as medical/industrial images, have emerged in many practical fields. These data usually have high dimensions and are not easy to cluster due to their intrinsic correlated structure among rows and columns. Most approaches convert matrix data to multi dimensional vectors and apply conventional clustering methods to them, and thus, suffer from an extreme high-dimensionality problem as well as a lack of interpretability of the correlated structure among row/column variables. Recently, a regularized model was proposed for clustering matrix-valued data by imposing a sparsity structure for the mean signal of each cluster. We extend their approach by regularizing further on the covariance to cope better with the curse of dimensionality for large size images. A penalized matrix normal mixture model with lasso-type penalty terms in both mean and covariance matrices is proposed, and then an expectation maximization algorithm is developed to estimate the parameters. The proposed method has the competence of both parsimonious modeling and reflecting the proper conditional correlation structure. The estimators are consistent, and their limiting distributions are derived. We applied the proposed method to simulated data as well as real datasets and measured its clustering performance with the clustering accuracy (ACC) and the adjusted rand index (ARI). The experiment results show that the proposed method performed better with higher ACC and ARI than those of conventional methods.

Paclitaxel - Combined Curcumin - Loaded PLA-TPGS - Based Nanoparticles Induce Apoptosis and Inhibit the Growth of Breast Cancer Cells and Multicellular Tumor Spheroids

Paclitaxel and curcumin have been reported as anti-cancer drugs. Here we presented a novel combination of paclitaxel and curcumin-loaded PLA-TPGS (PTX-Cur/PLA-TPGS) nanoparticles prepared by a modified solvent extraction/evaporation technique. These nanoparticles were well distributed and stable in water. This combination of paclitaxel and curcumin gave a higher efficiency of both drugs in cytotoxicity; induced apoptosis; and effect on cell cycles of KPL4 cell line in compare with the use of paclitaxel or curcumin alone or even a normal mixture of these two drugs. Furthermore, PTX-Cur/PLA-TPGS nanoparticles exhibited a powerful ability in preventing MCF7 spheroids growth. Interestingly, curcumin also functioned as both a drug and a label. Base on the autofluorescence of curcumin, the absorption of PTX-Cur/PLA-TPGS nanoparticles into MCF7 spheroids could be followed and calculated. These results suggested that the nanoparticle-drug combination may provide a promising multifunctional delivery system for anti-cancer drugs.

Penalized Maximum Likelihood Estimator for Finite Skew-Laplace-Normal Mixtures

Skew-Laplace-Normal Mixture models is a more flexible framework than the normal mixture models for heterogeneous data with asymmetric behaviors. But it’s likelihood function have some bad math properties, such as the unboundedness of likelihood function and the divergency of skewness parameter, it often mislead statistic inference. In this paper, we given a penalizing the likelihood function method to deal with these problem simultaneously, and we given the detail of proof on parameter have strongly consistency. We also give a modified penalized EM-type algorithms to compute penalized estimators.

Nonparametric Bayesian Learning of Infinite Multivariate Generalized Normal Mixture Models and Its Applications

This paper addresses the problem of data vectors modeling, classification and recognition using infinite mixture models, which have been shown to be an effective alternative to finite mixtures in terms of selecting the optimal number of clusters. In this work, we propose a novel approach for localized features modelling using an infinite mixture model based on multivariate generalized Normal distributions (inMGNM). The statistical mixture is learned via a nonparametric MCMC-based Bayesian approach in order to avoid the crucial problem of model over-fitting and to allow uncertainty in the number of mixture components. Robust descriptors are derived from encoding features with the Fisher vector method, which considers higher order statistics. These descriptors are combined with a linear support vector machine classifier in order to achieve higher accuracy. The efficiency and merits of the proposed nonparametric Bayesian learning approach, while comparing it to other different methods, are demonstrated via two challenging applications, namely texture classification and human activity categorization.