title: Discovering subpopulation structure with latent class mixed models.
abstract: The linear mixed model is a well-known method for incorporating heterogeneity (for example, subject-to-subject variation) into a statistical analysis for continuous responses. However heterogeneity cannot always be fully captured by the usual assumptions of normally distributed random effects. Latent class mixed models offer a way of incorporating additional heterogeneity which can be used to uncover distinct subpopulations, to incorporate correlated non-normally distributed outcomes and to classify individuals. The methodology is motivated with examples in health care studies and a detailed illustration is drawn from the Nutritional Prevention of Cancer trials. Latent class models are used with longitudinal data on prostate specific antigen (PSA) as well as incidence of prostate cancer. The models are extended to accommodate prostate cancer as a survival endpoint; this is compared to treating it as a binary endpoint. Four subpopulations are identified which differ both with regard to their PSA trajectories and their incidence rates of prostate cancer.
authors.affiliation: Division of Biostatistics, University of California, San Francisco, USA. chuck@biostat.ucsf.edu
authors.forename: C E
authors.initials: CE
authors.lastname: McCulloch
authors.forename: H
authors.initials: H
authors.lastname: Lin
authors.forename: E H
authors.initials: EH
authors.lastname: Slate
authors.forename: B W
authors.initials: BW
authors.lastname: Turnbull
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000428:Alcohol Drinking; D001416:Back Pain / Q000628:therapy; D003953:Diagnosis-Related Groups / Q000191:economics; D005133:Eye Movements / Q000502:physiology; D006801:Humans; D007349:Insurance, Health, Reimbursement / Q000191:economics; D016014:Linear Models; D008137:Longitudinal Studies; D008297:Male; D008954:Models, Biological; D010818:Practice Patterns, Physicians'; D017430:Prostate-Specific Antigen / Q000097:blood; D011471:Prostatic Neoplasms / Q000097:blood / Q000178:diet therapy / Q000517:prevention & control*; D012559:Schizophrenia / Q000473:pathology; D012643:Selenium / Q000494:pharmacology; D016019:Survival Analysis
chemical_list: D017430:Prostate-Specific Antigen; D012643:Selenium