Amyloid β42 and Total Tau Levels in Cerebrospinal Fluid Associate with Survival in an 85-Year-Old Population-Based Cohort Followed until Death

BACKGROUND: Dementia of Alzheimer's type (AD) is related to decreased survival. It is not clear whether also biological markers of AD are related to mortality. Low levels of amyloid beta-42 (Aβ42) and high levels of total tau (T-tau) protein in cerebrospinal fluid (CSF) are established biomarkers for AD. OBJECTIVE: Our aim was to investigate whether levels of Aβ42 and T-tau are associated with survival among octogenarians independently of dementia status. METHODS: Sixty-five 85-year-olds underwent lumbar puncture and were followed with repeated neuropsychiatric examinations until death. RESULTS: Lower CSF Aβ42 (p = 0.010) and higher CSF T-tau (p = 0.005) at the age of 85 were associated with lower survival independently of dementia status at baseline and follow-up. Low CSF Aβ42 and high CSF T-tau were also related to baseline dementia at the age of 85 years, and lower CSF Aβ42 with increased dementia incidence during the first 3 years of follow-up. CONCLUSIONS: Biological markers of AD are associated with mortality in octogenarians. The reason for this needs further study. Our findings highlight the importance to consider the competing risk of death when evaluating biological markers of AD in the very old.