Talk to the Veterans Crisis Line now
An official website of the United States government
Search | Search by Center | Search by Source | Keywords in Title
Chen B, Zhou XH. Non-homogeneous Markov process models with informative observations with an application to Alzheimer's disease. Biometrical journal. Biometrische Zeitschrift. 2011 May 1.
Dimensions for VA is a web-based tool available to VA staff that enables detailed searches of published research and research projects. Identifying risk factors for transition rates among normal cognition, mildly cognitive impairment, dementia and death in an Alzheimer''s disease study is very important. It is known that transition rates among these states are strongly time dependent. While Markov process models are often used to describe these disease progressions, the literature mainly focuses on time homogeneous processes, and limited tools are available for dealing with non-homogeneity. Further, patients may choose when they want to visit the clinics, which creates informative observations. In this paper, we develop methods to deal with non-homogeneous Markov processes through time scale transformation when observation times are pre-planned with some observations missing. Maximum likelihood estimation via the EM algorithm is derived for parameter estimation. Simulation studies demonstrate that the proposed method works well under a variety of situations. An application to the Alzheimer''s disease study identifies that there is a significant increase in transition rates as a function of time. Furthermore, our models reveal that the non-ignorable missing mechanism is perhaps reasonable.
