Title Page
Abstract
Contents
Chapter 1. Introduction 11
1.1. Study background 11
1.2. Purpose of study 16
1.3. Definition of terms 17
1) Cognitive frailty 17
2) Long-term care initiation 18
Chapter 2. Literature Review 21
2.1. Long-term care system in Korea 21
2.2. Evolving concept of cognitive frailty 25
2.3. Factors associated with long-term care initiation 30
Chapter 3. Methods 35
3.1. Study design 35
3.2. Study data 37
3.3. Study participants 41
3.4. Analytic framework 44
3.5. Study variables 46
1) Dependent variable 46
2) Independent variable 48
3) Covariates 50
3.6. Statistical analysis 53
3.7. Ethical considerations 55
Chapter 4. Results 56
4.1. Baseline characteristics of participants 56
4.2. Difference in characteristics based on frailty status 58
4.3. Incidence rate of long-term care initiation 61
4.4. Effect of cognitive frailty on long-term care initiation 63
1) Kaplan-Meier survival curve estimates 63
2) Assessing the proportional hazard assumption 66
3) Stratified Cox model estimates 69
4.5. Sub-group analysis 71
1) Effect of cognitive frailty on long-term care initiation stratified by depressive mood 71
2) Effect of cognitive frailty on long-term care initiation stratified by sex 74
3) Effect of cognitive frailty on in-home and facility long-term care initiation 79
Chapter 5. Discussion 85
5.1. Effect of cognitive frailty on long-term care initiation 85
1) Cognitive frailty was a significant predictor of long-term care initiation in community-dwelling older adults. 85
2) In depressed older adults, the effect of cognitive frailty on long-term care initiation was increased. 89
3) The effect of cognitive impairment and physical frailty on long-term care initiation varied between men and women. 91
4) Cognitive frailty was a more important predictor of in-home long-term care initiation when considering the type of long-term care benefit. 92
5.2. Implications for nursing practice and policy 94
1) Primary target of preventive nursing care to delay long-term care initiation 95
2) Tailored multimodal programs to delay long-term care initiation 97
3) Advanced digital information systems integrating national health information to identify at-risk population 100
5.3. Limitations 102
Chapter 6. Conclusions 104
References 105
Appendices 120
Appendix 1. Information includes in National Health Insurance Service-Senior Cohort database version 1.0 120
Appendix 2. Disease codes and definition of dementia (Korean Classification of Disease 7th edition) 122
Appendix 3. IRB approval letter 123
Appendix 4. Kaplan-Meier survival function by frailty status 124
Appendix 5. Goodness-of-fit test results for the Cox proportional hazard model stratified by gender 126
Appendix 6. Goodness-of-fit test results for the Cox PH model stratified by type of long-term care benefits 128
국문초록 130
Table 1. Study variables and measurements 52
Table 2. Baseline characteristics of study population (N=39,137) 57
Table 3. Difference in baseline characteristics by frailty status (N=39,137) 59
Table 4. Time at risk, event, and incidence rate 62
Table 5. Log-rank test for equality of survivor functions 65
Table 6. Evaluation of the proportional hazard assumption using goodness-of-fit test 67
Table 7. Effect of cognitive frailty on long-term care initiation 70
Table 8. Effect of cognitive frailty on long-term care initiation stratified by depressive mood 72
Table 9. Effect of cognitive frailty on long-term care initiation stratified by sex 76
Table 10. Incidence rate, hazard ratio, and 95% confidence interval of in-home and facility long-term care initiation 81
Figure 1. Long-term care grading system in Korea 23
Figure 2. Different trajectories of cognitive function 27
Figure 3. Study design with the National Health Insurance Service-Senior Cohort database 35
Figure 4. Construction of the study dataset 40
Figure 5. Target population, accessible population, and study population 41
Figure 6. Flow chart of selecting study participants 43
Figure 7. Analytic framework of the study 45
Figure 8. Kaplan-Meier survival curves by frailty status 64
Figure 9. Evaluation of the proportional hazard assumption using log-log plots for the variable of depressive mood 68
Figure 10. Cumulative hazard of long-term care initiation according to frailty status stratified by depressive mood 73
Figure 11. Cumulative hazard of long-term care initiation according to frailty status stratified by sex 78
Figure 12. Cumulative hazard of long-term care initiation according to frailty status by type of long-term care benefits 84