Survival Models and Data Analysis REGINA C. ELANDT-JOHNSON Department of Biostatistics School of Public Health University of North Carolina at Chapel Hill NORMAN L. JOHNSON Department of Statistics. University of North Carolina at Chapel Hill JOHN WILEY AND SONS, New York • Chichester • Brisbane • Toronto • Singapore Contents PART 1. SURVIVAL MEASUREMENTS AND CONCEPTS 1. SURVIVAL DATA 1.1 1.2 1.3 1.4 1.5 1.6 2. Scope of the Book Sources of Data Types of Variables Exposure to Risk Use of Probability Theory The Collection of Survival Data MEASURES OF MORTALITY AND MORBIDITY, RATIOS, PROPORTIONS, AND MEANS 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 Introduction Ratios and Proportions 2.2.1 Ratios 2.2.2 Proportion Rates of Continuous Processes 2.3.1 Absolute Rate 2.3.2 Relative Rate 2.3.3 Average (Central) Rate Rates for Repetitive Events Crude Birth Rate Mortality Measures Used in Vital Statistics 2.6.1 The Concept of Population Exposed to Risk 2.6.2 Crude Death Rate 2.6.3 Age Specific Death Rates 2.6.4 Cause Specific Mortality Used in Vital Statistics Relationships Between Crude and Age Specific Rates Standardized Mortality Ratio (SMR): Indirect Standardization 3 3 4 5 6 6 7 9 9 10 10 11 12 12 13 14 16 17 18 18 20 21 21 22 22 vil vlll Contents 2.9 Direct Standardization 2.10 Evaluation of Person-Years of Exposed to Risk in Long-Term Studies 2.10.1 'Exact'Dates for Each Individual Available 2.10.2 Only Years of Birth, Entry, and Departure Available 2.11 Prevalence and Incidence of a Disease 2.11.1 Prevalence 2.11.2 Incidence 2.12 Association Between Disease and Risk Factor. Relative Risk and Odds Ratio 2.12.1 Relative Risk 2.12.2 Odds Ratio 3. SURVIVAL DISTRIBUTIONS 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 Introduction Survival Distribution Functions ( Hazard Function (Force of Mortality) Conditional Probabilities of Death (Failure) and Central Rate Truncated Distributions Expectation and Variance of Future Lifetime Median of Future Lifetime Transformations of Random Variables Location-Scale Families of Distributions Some Survival Distributions Some Models of Failure 3.11.1 Series System 3.11.2 Parallel System Probability Integral Transformation Compound Distributions Miscellanea 3.14.1 Interpolation 3.14.2 Method of Statistical Differentials Maximum Likelihood Estimation and Likelihood Ratio Tests 3.15.1 Construction of Likelihood Functions 3.15.2 Maximum Likelihood Estimation 3.15.3 Expected Values, Variances and Covariances -of the MLE's 3.15.4 Assessing Goodness of Fit 25 25 26 29 31 31 32 35 36 37 Contents ™ PART 2. MORTALITY EXPERIENCES AND LIFE TABLES 4. LIFE TABLES: FUNDAMENTALS AND CONSTRUCTION 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10 4.11 4.12 4.13 4.14 4.15 5. Introduction • Life Table: Basic Definition and Notation Force of Mortality. Mathematical Relationships Among Basic Life Table Functions Central Death Rate Interpolation for Life Table Functions Some Approximate Relationships Between nqx and „** 4.6.1 Expected Fraction of the Last n Years of Life 4.6.2 Special Cases 4.6.3 Exponential Approximation Some Approximations to ju.x Concepts of Stationary and Stable Populations 4.8.1 Stationary Population 4.8.2 Stable Population Construction of an Abridged Life Table from Mortality Experience of a Current Population 4.9.1 Evaluation of nMx 4.9.2 Estimation of Jx 4.9.3 Estimation of nqx 4.9.4 Evaluation of the Life Table Functions Some Other Approximations Used in Construction of Abridged Life Tables Construction of a Complete Life Table From an Abridged Life Table Selection Select Life Tables Some Examples Construction of Select Tables COMPLETE MORTALITY DATA, ESTIMATION OF SURVIVAL FUNCTION 5.1 5.2 5.3 Introduction. Cohort Mortality Data Empirical Survival Function Estimation of Survival Function From Grouped Mortality Data 83 83 83 93 95 96 99 100 100 101 101 102 103 103 104 105 106 107 108 110 111 114 115 117 119 128 128 129 133 Contents 5.3.1 5.3.2 5.4 5.5 5.6 5.7 5.8 5.9 5.10 5.11 6. Grouping into Fixed Intervals Grouping Based on Fixed Numbers of Deaths Joint Distribution of the Numbers of Deaths Distribution of Pt Covariance of Pt and Py (i <j) Conditional Distribution of q{ Greenwood's Formula for the (Conditional) Variance of P, Estimation of Curve of Deaths Estimation of Central Death Rate and Force of Mortality in [/,,/,+ 1) Summary of Results INCOMPLETE MORTALITY DATA: FOLLOW-UP STUDIES 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 Basic Concepts and Terminology 6.1.1 Incomplete Data 6.1.2 Truncation and Censoring 6.1.3 Follow-up Studies 6.1.4 Other Kinds of Follow-up 6.1.5 Topics of the Chapter Actuarial Estimator of q{ From Grouped Data 6.2.1 Amount of Person-Time Units. Central Death Rates 6.2.2 Effective Number of Initial Exposed to Risk. Estimation of qt 6.2.3 Estimation of Survival Function Some Maximum Likelihood Estimators of qt 6.3.1 Failure Time Alone Regarded as a Random Variable 6.3.2 Failure Time and Censoring Time Regarded as Random Variables Some Other Estimators of qt 6.4.1 Moment Estimator of qt 6.4.2 Estimator of qi Based on Reduced Sample Comparison of Various Estimators of qt Estimation of Curve of Deaths Product-Limit Method of Estimating the Survival Function From Individual Times at Death Estimation of Survival Function Using the Cumulative Hazard Function 133 135 137 138 138 138 140 141 142 144 150 150 150 150 151 153 153 154 154 156 157 162 163 Contents 7. xl FITTING PARAMETRIC SURVIVAL DISTRIBUTIONS 7.1 7.2 Introduction Some Methods of Fitting Parametric Distribution Functions 7.3 Exploitation of Special Forms of Survival Function 7.4 Fitting Different Distribution Functions over Successive Periods of Time 7.5 Fitting a "Piece-Wise" Parametric Model to a Life Table: An Example 7.6 Mixture Distributions 7.7 Cumulative Hazard Function Plots—Nelson's Method for Ungrouped Data • 7.7.1 Complete Data 7.7.2 Incomplete Data 7.8 Construction of the Likelihood Function for Survival Data: Some Examples 7.9 Minimum Chi-Square and Minimum Modified ChiSquare 7.10 Least Squares Fitting 7.11 Fitting a Gompertz Distribution to Grouped Data: An Example 7.12 Some Tests of Goodness of Fit 7.12.1 Graphical'Test" 7.12.2 Kolmogorov-Smirnov Statistics. Limiting Distribution 7.12.3 Anderson-Darling ^-Statistic 7.12.4 Chi-Square Test for Grouped Data 8. COMPARISON OF MORTALITY EXPERIENCES 8.1 8.2 8.3 8.4 Introduction Comparison of Two Life Tables 8.2.1 Graphical Displays 8.2.2 Conditional Probabilities qx 8.2.3 Conditional Expectations and Median of Future Lifetime Comparison of Mortality Experience with a Population Life Table 8.3.1 Test Based on Median of Future Lifetime 8.3.2 Test Based on Expected Future Lifetime Some Distribution-Free Methods for Ungrouped Data _ 8.4.1 Two Sample Kolmogorov-Smirnov Test 181 181 182 182 185 186 191 196 196 200 200 209 209 211 214 214 215 218 219 225 225 225 226 227 227 228 228 229 231 231 xii Contents 8.4.2 Two Sample Wilcoxon Test for Complete Data 8.4.3 Modified Wilcoxon Tests for Incomplete Data 8.5 Special Problems Arising in Clinical Trials and Progressive Life Testing 8.5.1 Early Decision 8.5.2 Multistage Testing 8.5.3 Testing for Trends in Mortality Patterns 8.5.4 Staggered Entries and Withdrawals 8.6 Censored Kolmogorov-Smirnov (or Tsao-Conover) Test 8.7 Truncated Data. Pearson's Conditional X2 Test 8.7.1 Two Sample Problem . 8.7.2 Extension to k Treatments 8.8 Testing for Consistent Differences in Mortality. Mantel-Haenszel and Logrank Tests 8.8.1 Mantel-Haenszel Test 8.8.2 Logrank Test 8.8.3 Extension to r Experiments (Classes) 8.9 Parametric Methods 8.10 Sequential Methods PART 3. MULTIPLE TYPES OF FAILURE 9. THEORY OF COMPETING CAUSES: PROBABILISTIC APPROACH 9.1 9.2 9.3 9.4 9.5 9.6 Causes of Death: Basic Assumptions Some Basic Problems "Times Due to Die" The Overall and 'Crude' Survival Functions 9.4.1 The Overall Survival Function 9.4.2 The Crude and Net Hazard Rates 9.4.3 The Crude Probability Distribution for Cause ca Case when Xl,...,Xk are Independent Equivalence and Nonidentifiability Theorems in Competing Risks 9.6.1 Equivalent Models of Survival Distribution "Functions 234 236 240 240 241 242 242 243 247 247 249 251 251 258 260 261 261 Contents 9.6.2 9.7 9.8 9.9 10. M U L T I P L E DECREMENT LIFE TABLES 10.1 10.2 10.3 10.4 10.5 10.6 11. Nonidentifiability of the Member of a Parametric Family of Distributions Proportional Hazard Rates Examples Heterogeneous Populations: Mixture of Survival Functions Multiple Decrement Life Tables: Notation Definitions of the M D L T Functions Relationships A m o n g Functions of Multiple Decrement Life Tables Crude Forces of Mortality Construction of Multiple Decrement Life Tables from Population (Cross-Sectional) Mortality Data 10.5.1 Mortality D a t a : Evaluation of naqx a n d ^q^ 10.5.2 Construction of M D L T Some Major Causes of Death: An Example of Constructing the M D L T 280 280 282 288 294 294 295 295 297 298 298 300 301 SINGLE DECREMENT LIFE TABLES ASSOCIATED W I T H MULTIPLE DECREMENT LIFE TABLES: THEIR INTERPRETATION AND MEANING 309 11.1 11.2 309 11.3 12. Elimination, Prevention, a n d Control of a Disease Mortality Pattern from Cause Ca Alone: 'Private' Probabilities of Death 11.2.1 How Might the S D F from Cause Ca Alone be Interpreted 11.2.2 Estimable, Although not Observable, Waiting Time Distributions Estimation of Waiting Time Distribution for Cause Ca: Single Decrement Life Table 310 310 311 312 ESTIMATION AND TESTING HYPOTHESES IN COMPETING RISK ANALYSIS 12.1 Introduction. Experimental D a t a 323 323 Contents 12.2 12.3 12.4 12.5 PART 4. 13. Grouped Data. Nonparametric Estimation 12.2.1 Complete Data 12.2.2 Follow-up Data 12.2.3 Truncated Samples Grouped Data. Fitting Parametric Models 12.3.1 Choice of a Joint Survival Function 12.3.2 Fitting Crude Parametric Distribution to Mortality Data from Each Cause Separately Cohort Mortality Data with Recorded Times at Death or Censoring. Nonparametric Estimation 12.4.1 Complete Data 12.4.2 Incomplete Data Cohort Mortality Data with Recorded Times at Death or Censoring. Parametric Estimation 13.3 13.4 13.5 13.6 13.7 331 332 332 334 335 SOME MORE ADVANCED TOPICS CONCOMITANT VARIABLES IN LIFETIME DISTRIBUTIONS MODELS 13.1 13.2 324 324 326 326 329 329 Concomitant Variables The Role of Concomitant Variables in Planning Clinical Trials General Parametric Model of Hazard Function with Observed Concomitant Variables 13.3.1 Types of Concomitant Variables 13.3.2 General Model 13.3.3 Some Other Expressions for the General Model Additive Models of Hazard Rate Functions Multiplicative Models 13.5.1 Exponential-Type Hazard Functions 13.5.2 Gompertz and Weibull Models with Covariates Estimation in Multiplicative Models 13.6.1 Construction of the Likelihood Function 13.6.2 Multiple Failures Assessment of the Adequacy of a Model: Tests of Goodness of Fit 13.7.1 Cumulative Hazard Plottings 13.7.2 ^.Method of Half-Replicates 345 345 346 346 347 348 Contents 13.8 13.9 13.10 13.11 13.12 13.13 13.14 14. Selection of Concomitant Variables13.8.1 Likelihood Ratio Tests of Composite Hypotheses 12.8.2 Step-Down Procedure 13.8.3 Step-Up Procedure Treatment-Covariate Interaction Logistic Linear Model Time Dependent Concomitant Variables Concomitant Variables Regarded as Random Variables Posterior Distribution of Concomitant Variables Concomitant Variables in Competing Risk Models AGE OF ONSET DISTRIBUTIONS 14.1 14.2 14.3 14.4 14.5 14.6 15. XT Introduction Models of Onset Distributions 14.2.1 Incidence Onset Distribution 14.2.2 Waiting Time Onset Distribution 14.2.3 Life Tables and Onset Distributions Estimation of Incidence Onset Distribution from Cross-Sectional Incidence Data Estimation of Incidence Onset Distribution from Prevalence Data 14.4.1 Estimation of Age Specific Incidence from Prevalence Data: No Differential Mortality 14.4.2 Affected Individuals Are Subject to Differential Mortality Estimation of Waiting Time Onset Distribution from Population Data Estimation of Waiting Time Onset Distribution from Retrospective Data 14.6.1 No Differential Mortality Between Affected and Unaffected 14.6.2 Effects of Differential Mortality MODELS OF AGING AND CHRONIC DISEASES 15.1 15.2 Introduction Aging and Chronic Diseases 15.2.1 Biological Aging 367 368 369 370 372 374 377 379 380 381 392 392 392 393 394 394 395 398 398 399 403 403 404 410 414 414 415 415 xvi Contents 15.3 15.4 15.5 15.6 15.7 15.2.2 Hazard Rate: A Measure of Aging 15.2.3 Models of Chronic Diseases Some Models of Carcinogenesis 15.3.1 A One-Hit Model of Carcinogenesis: Gompertz Distribution 15.3.2 Multi-Hit Models of Carcinogenesis: Parallel Systems and Weibull Distribution Some "Mosaic" Models of a Chronic Disease "Fatal Shock" Models of Failure 15.5.1 A Two Component Series System 15.5.2 Generalization of the "Fatal Shock" Model to n Components Irreversible Markov Processes in Illness-Death Modeling 15.6.1 Basic Concepts 15.6.2 A Two Component Parallel System: Two Distinct States Before Failure 15.6.3 Extension to /--Component Parallel System with r States 15.6.4 A Model of Disease Progression Reversible Models: The Fix-Neyman Model Author index Subject index 415 416 416 416 417 418 420 420 422 423 423 424 426 426 431 433 447
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