Investigation into the Difference of Cognitive Decline between the Centenarians and Alzheimer's Disease
Yoshinori Nishimoto1, Takashi Sasaki2, Yukiko Abe2, Mika Konishi3, Daisuke Ito4, Shogyoku Bun3, Yuri Otaki5, Norikazu Hara5, Akinori Miyashita5, Takeshi Ikeuchi5, Yasumichi Arai6
1Department of Neurology, Keio University School of Medicine, 2Center for Supercentenarian Medical Research, Keio University School of Medicine, 3Department of Psychiatry, Keio University School of Medicine, 4Department of Physiology, Keio University School of Medicine, 5Department of Molecular Genetics, Brain Research Institute, Niigata University, 6Nursing and Medical Care, Center for Supercentenarian Medical Research, Keio University
Objective:
To explore the differences between age-related cognitive decline, in which ADL is relatively preserved, and Alzheimer's disease (AD), in which independent living becomes difficult within a few years.
Background:
Japan is one of the countries with the highest population of healthy long-lived individuals in the world. There are more than 90,000 centenarians in Japan, some of whom maintain relatively good cognitive function beyond age of 100. Studies of cognitive function in centenarians are considered important for elucidating the mechanism of resistance to the onset of dementia.
Design/Methods:
Among 1,017 centenarians, we examined the correlation between MMSE and age in 638 subjects with MMSE assessed fully. Various factors, including APOEε4 positivity, were compared between the centenarians (638 subjects) and the AD group (223 subjects) attending the memory clinic. In addition, the MMSE sub-items were examined to find out differences in the pattern of decline in the cognitive function between the centenarian group and the AD group (34 subjects), which were adjusted for the total score of MMSE. The Student’s t-test, chi-square test, and log-rank test of Kaplan-Meier survival curves were used for statistical analyses.
Results:
A negative correlation between MMSE and age was observed even after the age of 100 years. APOEε4, which is highly associated with cognitive dysfunction in general ages, lost effects on the decline in cognitive function after the age of 108. MMSE analysis showed that the scale of the sub-item following 3 step orders was retained in centenarians, while it was reduced in late-phase of AD, being as a specific point of difference. The retention of associative function that transfer spatial cognition to spontaneous actions was a characteristic of centenarians’ cognition.
Conclusions:
Patterns of cognitive impairment in centenarians and Alzheimer's disease are different. This is one of the most critical points in distinguishing age-related cognitive dysfunction from dementia in clinical practice.