for important confounders, including MMSE score at baseline. Approximately half
of participants were classified as having a high MMSE score trajectory—their
cognitive function persisted from age 65 to 80 and then slowly declined until age
90. This trend was similar to that for normal aging as reported previously in a 5-year
longitudinal study (Jacqmin-Gadda, Fabrigoule, Commenges, & Dartigues, 1997).
Cognitive function gradually decreased in the 43% of participants who were classified as having a middle trajectory. Although they remained cognitively intact from
age 65 to 75, cognitive function began to decline after age 80 years, and estimated
MMSE score was lower than 24 from age 85 to 90 years. Furthermore, the 5% of
participants with a low MMSE score trajectory had an estimated MMSE score of
23.4 at age 65 and a more rapid decline until age 90 years. Findings from a previous
analysis of cutoff values for incident certified need for care in the LTCI system
(Taniguchi et al., 2015) suggested that the present low trajectory pattern is useful for
clinical evaluation of elders.
The World Alzheimer Report estimated that the annual global cost of dementia is
$818 billion, 85% of which is related to family and social burdens rather than to
medical care (Livingston et al., 2017). Declining cognitive trajectories might therefore be associated with increased mortality risk and health-care costs, such as
medical and long-term care costs. This prospective study of community-dwelling
older adults used repeated-measures data on cognitive function from the Kusatsu
Longitudinal Study. The three objectives were to identify trajectories over time in
cognitive function among a general population of community-dwelling older Japanese, to determine whether these trajectories were associated with all-cause and
cause-specific mortality, and to examine differences in health-care costs (medical
and long-term care costs) between trajectories.
To be eligible for the study of a general population of community-dwelling older
Japanese, individuals had to be free of disabling dementia at baseline, as assessed by
the LTCI system. The data source for the present study was 1736 adults aged
65 years or older from the Kusatsu Longitudinal Study during the period from
2002 through 2014. The average number of follow-up assessments was 3.9, and
the total number of observations was 6824 during follow-up. Cognitive function was
assessed with the MMSE. The underlying cause of death was coded by using the
International Classification of Diseases, Tenth Edition (ICD-10). The relevant
ICD-10 codes were I00 to I99 for cardiovascular disease (CVD) and C00 to C97
for cancer; all other codes were classified as “other.” Local registries recorded
401 (23.6%) incident deaths among the 1736 participants during the period through
2016. Among the 401 incident deaths, 391 (97.5%) were linked with Japanese
national vital statistics (121 CVD deaths, 100 cancer deaths and 170 other deaths).
The official medical insurance system includes National Health Insurance and health
insurance for older people, and these insurance systems cover almost all medical
treatment and medical provider fees. Payments from insured persons to medical
providers are made on a fee-for-service basis, in which the price of each service is
determined by a uniform national fee schedule. The Japanese LTCI system provides
long-term care services, community-based services, and in-facility services. All
primary insured persons aged 65 years or older are candidates for care. When insured
70
Y. Taniguchi and H. Matsushita
of participants were classified as having a high MMSE score trajectory—their
cognitive function persisted from age 65 to 80 and then slowly declined until age
90. This trend was similar to that for normal aging as reported previously in a 5-year
longitudinal study (Jacqmin-Gadda, Fabrigoule, Commenges, & Dartigues, 1997).
Cognitive function gradually decreased in the 43% of participants who were classified as having a middle trajectory. Although they remained cognitively intact from
age 65 to 75, cognitive function began to decline after age 80 years, and estimated
MMSE score was lower than 24 from age 85 to 90 years. Furthermore, the 5% of
participants with a low MMSE score trajectory had an estimated MMSE score of
23.4 at age 65 and a more rapid decline until age 90 years. Findings from a previous
analysis of cutoff values for incident certified need for care in the LTCI system
(Taniguchi et al., 2015) suggested that the present low trajectory pattern is useful for
clinical evaluation of elders.
The World Alzheimer Report estimated that the annual global cost of dementia is
$818 billion, 85% of which is related to family and social burdens rather than to
medical care (Livingston et al., 2017). Declining cognitive trajectories might therefore be associated with increased mortality risk and health-care costs, such as
medical and long-term care costs. This prospective study of community-dwelling
older adults used repeated-measures data on cognitive function from the Kusatsu
Longitudinal Study. The three objectives were to identify trajectories over time in
cognitive function among a general population of community-dwelling older Japanese, to determine whether these trajectories were associated with all-cause and
cause-specific mortality, and to examine differences in health-care costs (medical
and long-term care costs) between trajectories.
To be eligible for the study of a general population of community-dwelling older
Japanese, individuals had to be free of disabling dementia at baseline, as assessed by
the LTCI system. The data source for the present study was 1736 adults aged
65 years or older from the Kusatsu Longitudinal Study during the period from
2002 through 2014. The average number of follow-up assessments was 3.9, and
the total number of observations was 6824 during follow-up. Cognitive function was
assessed with the MMSE. The underlying cause of death was coded by using the
International Classification of Diseases, Tenth Edition (ICD-10). The relevant
ICD-10 codes were I00 to I99 for cardiovascular disease (CVD) and C00 to C97
for cancer; all other codes were classified as “other.” Local registries recorded
401 (23.6%) incident deaths among the 1736 participants during the period through
2016. Among the 401 incident deaths, 391 (97.5%) were linked with Japanese
national vital statistics (121 CVD deaths, 100 cancer deaths and 170 other deaths).
The official medical insurance system includes National Health Insurance and health
insurance for older people, and these insurance systems cover almost all medical
treatment and medical provider fees. Payments from insured persons to medical
providers are made on a fee-for-service basis, in which the price of each service is
determined by a uniform national fee schedule. The Japanese LTCI system provides
long-term care services, community-based services, and in-facility services. All
primary insured persons aged 65 years or older are candidates for care. When insured
70
Y. Taniguchi and H. Matsushita