ORIGINAL ARTICLE EPIDEMIOLOGY, CLINICAL PRACTICE AND HEALTH
Associations of aging trajectories for an index of frailty score with mortality and medical and long-term care costs among older Japanese undergoing health checkups Yu Taniguchi,1,2 Akihiko Kitamura,2 Takumi Abe,2,3,4 Gotaro Kojima,5 Tomohiro Shinozaki,6 Satoshi Seino,2 Yuri Yokoyama,2 Yu Nofuji,2 Tomoko Ikeuchi,7 Yutaka Matsuyama,8 Yoshinori Fujiwara2 and Shoji Shinkai2,9 1
Center for Health and Environmental Risk Research, National Institute for Environmental Studies, Ibaraki, Japan 2 Research Team for Social Participation and Community Health, Tokyo Metropolitan Institute of Gerontology, Tokyo, Japan 3 Centre for Urban Transitions, Swinburne University of Technology, Melbourne, Victoria, Australia 4 Japan Society for the Promotion of Science, Tokyo, Japan 5 Videbimus Clinic Research Center, Tokyo, Japan 6 Department of Information and Computer Technology, Tokyo University of Science, Tokyo, Japan 7 Human Care Research Team, Tokyo Metropolitan Institute of Gerontology, Tokyo, Japan 8 Department of Biostatistics, School of Public Health, The University of Tokyo, Tokyo, Japan 9 Kagawa Nutrition University, Saitama, Japan
Aim: Using up to 13 years of repeated-measures data, we identiﬁed aging trajectories for an index in frailty score among older Japanese undergoing health checkups. In addition, we examined whether these trajectories were associated with all-cause and cause-speciﬁc mortality and healthcare costs. Methods: In total, 1698 adults aged ≥65 years completed annual assessments during 2002–2014. During follow-up, the average number of follow-up assessments was 3.9, and the total number of observations was 6373. Frailty was deﬁned by using the following criteria from Fried’s phenotype: slowness, weakness, exhaustion, low physical activity and weight loss. Results: We identiﬁed four aging trajectories for frailty. Speciﬁcally, 6.5%, 47.3%, 30.3% and 16.0% of participants were in the high, second, third and low trajectory groups, respectively. As compared with the low trajectory group, the high trajectory group had greater risks of cardiovascular disease (adjusted hazard ratios of 3.42) and other-cause death (adjusted hazard ratios of 3.04). The high trajectory group had the highest medical costs until late in the eighth decade of life, costs decreased after age 70 years and were lowest at age 90 years (estimated at $116.7); however, medical and long-term care costs greatly increased after age 80 years in the second and third trajectory groups. Conclusions: Higher aging trajectories in frailty score were associated with elevated risks for cardiovascular, other-cause and all-cause death among older Japanese receiving health checkups. Medical and care needs greatly increased for the second and third trajectory groups when their frailty level was progressed in later life. Geriatr Gerontol Int ••; ••: ••–•• Geriatr Gerontol Int 2020; ••: ••–••. Keywords: frailty, long-term care costs, medical costs, mortality, trajectories.
Correspondence Yu Taniguchi, PhD, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan. Email: [email protected]
Received: 18 June 2020 Revised: 16 August 2020 Accepted: 14 September 2020
Introduction Frailty is a geriatric syndrome characterized by decreased physiological reserve and resistance to stressors attributable to accumulated
© 2020 Japan Geriatrics Society
age-related deﬁcits.1 The frailty model differs from the disease model, in which illness or injury leads to disability. The frailty model describes how frailty status is a mediator of incident disability, rather than triggering disease or injury. Accumulated evidence
Y Taniguchi et al. suggests an association of frailty with adverse health outcomes such as disability,2 hospitalization, dementia and premature death.1,3,4 Frailty is a growing public health concern worldwide. A previous meta-analysis reported that frailty prevalence was 1.9%, 3.8%, 10.0%, 20.4% and 35.1% among communitydwelling Japanese adults aged 65–69, 70–74, 75–79, 80–84 and ≥85 years, respectively.5 Previous cross-sectional studies analyzed frailty prevalence by age group in several countries6,7; however, few studies have used repeated-measures data on age-related frailty trajectories among older adults. Using data from up to six assessments over a period 10 years, Rogers et al. identiﬁed aging trajectories in frailty, in relation to baseline physical activity status, among UK older adults.8 Aging trajectory patterns in frailty are unclear, and we know little of how frailty progresses with aging among older populations. An attempt to identify aging trajectories in frailty might identify characteristics of abnormal aging and facilitate a population approach to frailty prevention. Initial frailty status is an independent risk factor for mortality,1,3,4 which suggests that aging trajectories for frailty, as determined by repeated-measured analysis of longitudinal data, might shed considerable light on the risks of adverse health outcomes such as mortality. Nevertheless, to date, no such investigation has been conducted. In addition to examining all-cause mortality risk, the risks of speciﬁc causes of death among older adults should be assessed in relation to frailty trajectory. Japan is a world leader in multiple health metrics, including longevity; however, challenges related to social health insurance and the long-term care insurance (LTCI) system are substantial. Nursing care costs in Japan have been increasing and exceeded 10 trillion yen (about 91 billion US dollars) in 2018, and higher long-term care costs are a crucial issue in Japan. Frailty was reported to be associated with use of healthcare resources such as hospitalization and nursing home placement,2 which increases medical costs. However, the association of frailty status with medical or long-term care costs has not been studied. This prospective study analyzed repeated-measures data on annual frailty status from a 13-year longitudinal study of Kusatsu Town, Japan. The three objectives were to: (i) identify aging trajectories in a frailty index among community-dwelling older Japanese receiving checkups; (ii) determine whether age trajectories in frailty score were associated with all-cause or cause-speciﬁc mortality; and (iii) identify differences in healthcare costs (medical and long-term care costs) between age trajectories.
Methods Participants As part of collaboration with the government of Kusatsu Town, in Gunma Prefecture, Japan, we initiated a longitudinal study of aging and health in 2001. Annual preventive health check-ups were offered to all residents aged ≥40 years. In addition, participants aged ≥70 years (≥65 years after 2006) underwent geriatric assessments during 2002–2014. All older residents were invited to participate in annual check-ups, which were conducted in a similar manner. The study design is described in detail elsewhere.9–11 All participants in health checkup assessments gave their written informed consent, in accordance with conditions approved by the Ethics Committee at Tokyo Metropolitan Institute of Gerontology. To be eligible for the study, individuals had to provide complete annual data for the frailty score index. The data source for the present study was 1698 (of 1747) adults aged ≥65 years living in Kusatsu Town who completed annual frailty assessments at
least once during the period from June 2002 to July 2014. The average number of follow-up assessments was 3.9, and the total number of observations was 6373 during follow-up (Fig. S1).
Frailty assessment Frailty score was derived from an index based on the criteria used in Fried’s phenotype,12 namely: slowness (usual gait speed