Association of trajectories of cognitive function with cause‐specific mortality and medical and long‐term care costs

Aim Cognitive decline increases mortality risk through dementia‐related pathways and might be associated with increased healthcare costs. Using up to 12 years of repeated measures data, we identified trajectories in cognitive function among community‐dwelling older Japanese adults. We then examined whether these trajectories were associated with all‐cause and cause‐specific mortality, and differences in healthcare costs. Methods A total of 1736 adults aged ≥65 years who were free of disabling dementia completed annual assessments during 2002–2014. Cognitive function was assessed with the Mini‐Mental State Examination. The average number of follow‐up assessments was 3.9, and the total number of observations was 6824 during the follow‐up period. Results We identified five trajectory patterns in cognitive function (high, second, third, fourth, and low) during the 12‐year follow‐up period. The low (2.0%) and fourth (2.2%) trajectory groups had higher hazard ratios for cardiovascular disease mortality, and hazard ratios for other cause mortality were significantly higher for the third (16.8%) and second (38.8%) trajectory groups than for the high trajectory group (40.3%). Until 5 years of follow up, participants in the two lower‐trajectory groups had higher mean combined monthly medical and long‐term care costs. After 8 years of follow up, mean costs were highest for the third trajectory. Conclusions The risk of death from cardiovascular disease was higher in the two lower‐trajectory groups in cognitive function, and they showed higher healthcare costs during the first 5 years of follow up. After 8 years of follow up, the third trajectory had the highest healthcare costs, perhaps because of hospitalizations attributable to gradual cognitive decline. Geriatr Gerontol Int 2019; 19: 1236–1242.