Relationship between Total Kihon Checklist Score and Age-Specific Deaths among Late-Stage Older Adults in Otawara City (Aged 75 and Older) over a 15-Year Period.

Introduction: While the Japanese long-term care insurance system supports an ageing society, there are concerns about the shortage of financial resources and labour force. Further, extending healthy life expectancy and narrowing the gap with the average life expectancy are important issues. In this study, we aimed to examine, over a 15-year period, the relationship between the total Kihon Checklist (t-KCL) score and age-specific deaths among late-stage older adults aged 75 and older who were not certified for long-term care insurance.

Methods: The participants were older adults residing in Otawara City, Tochigi Prefecture, who were aged 75 years or older as of 2006. The participants, who were not certified by the long-term care insurance system, were asked to complete the KCL by a community welfare committee member. Based on their t-KCL scores, the participants were classified as robust (0-3 points), pre-frail (4-7 points), and frail (≥8 points). The deaths of those aged 75-89 years who had completed the KCL were investigated. Information on deaths was obtained from local authorities. Statistics were examined for the risk of robust, pre-frail, and frail mortality using a Cox proportional hazards model with age and gender as covariates for the 75-79, 80-84, and 85-89 age groups.

Results: Of the 7,924 participants, 3,423 (75-79 years: 1,990, 80-84 years: 1,059, 85-89 years: 374) were ultimately eligible for the study. Of these, 2,450 (75-79 years: 1,238, 80-84 years: 861, 85-89 years: 351) died over the 15-year study period. Hazard ratios for death in frailty as determined by the t-KCL score were 1.337 (95% confidence interval [CI], 1.162-1.540) for the pre-frail group and 2.012 (95% CI, 1.7756-2.305) for the frail group at 75-79 years, respectively, compared with the robust group; 1.511 (95% CI, 1.271-1.797) at 80-84 years only in the frail group; and 1.567 (95% CI, 1.140-2.154) at 85-89 years, also in the frail group.

Discussion: The relationship between frailty and mortality weakens after age 80. The results suggest that factors other than frailty may have a stronger influence on mortality risk after the age of 80.