Cognitive abilities predict death during the next 15 years in older Japanese adults.

Aim: The longitudinal relationship between cognitive abilities and subsequent death was investigated among community-dwelling older Japanese adults.

Methods: Participants (n = 1060; age range 60-79 years) comprised the first-wave participants of the National Institute for Longevity Sciences-Longitudinal Study of Aging. Participants' cognitive abilities were measured at baseline using the Japanese Wechsler Adult Intelligence Scale-Revised Short Form, which includes the following tests: Information (general knowledge), Similarities (logical abstract thinking), Picture Completion (visual perception and long-term visual memory) and Digit Symbol (information processing speed). By each cognitive test score, participants were classified into three groups: the high-level group (≥ the mean + 1SD), the low-level group (≤ the mean - 1SD) and the middle-level group. Data on death and moving during the subsequent 15 years were collected and analyzed using the multiple Cox proportional hazard model adjusted for physical and psychosocial covariates.

Results: During the follow-up period, 308 participants (29.06%) had died and 93 participants (8.77%) had moved. In the Similarities test, adjusted hazard ratios (HR) of the low-level group to the high-level group were significant (HR 1.49, 95% CI 1.02-2.17, P = 0.038). Furthermore, in the Digit symbol test, the adjusted HR of the low-level group to the high-level group was significant (HR 1.62, 95% CI 1.03-2.58, P = 0.038). Significant adjusted HR were not observed for the Information or Picture Completion tests.

Conclusions: It is suggested that a lower level of logical abstract thinking and slower information processing speed are associated with shorter survival among older Japanese adults. Geriatr Gerontol Int 2017; 17: 1654-1660.