P4–136: Blood pressure decline in the oldest‐old is related to death, not dementia or Alzheimer's disease pathology

In the oldest-old, blood pressure (BP) is lower in people with dementia. It has been proposed that BP begins to decline a few years before the development of dementia. Here we investigate whether decline in BP is related to the presence or absence of dementia or AD pathology at death. The study included 138 participants who underwent autopsy from the 90+ Study, a population-based epidemiological study of aging and dementia in the oldest-old. Participants were examined in-person every 6 months from 2003 to 2012. Systolic (SBP) and diastolic (DBP) blood pressure measurements were taken at every visit. Dementia diagnoses (DSM-IV) were assigned post-mortem during a consensus conference using all available clinical information including longitudinal neuropsychological testing, neurological exam, medication use, and medical records. Pathological Alzheimer's disease (AD) was defined as an index score > 3, created by adding Braak tangle score (0=I/II, 1=III/IV, 2=V/VI) and CERAD neuritic plaque score (0=none/rare, 1=moderate, 2=frequent). Neuropathological evaluations were done blinded to clinical diagnoses. BP trajectories from baseline to death were compared using random effects models. At death, participants ranged in age from 90 to 108 years, were followed up to 7 years (mean= 2.7 y), 71% were women, and 51% had dementia. SBP declined at a rate of 2.9 mmHg/year. Rates of SBP decline did not differ by dementia status or level of AD neuropathology. SBP for participants without dementia declined 2.8 mmHg/year, whereas participants with dementia declined 3.0 mmHg/year (p=0.81). SBP for participants with low levels of AD pathology declined 2.6 mmHg/year, whereas participants with high levels of AD pathology declined 3.6 mmHg /year (p=0.25). Results were similar for diastolic BP and pulse pressure (SBP-DBP) (Table). SBP and DBP in the oldest-old declines in the years before death but this decline does not depend on dementia status or AD neuropathology. Declines in BP may be part of the dying process rather than a consequence of neurodegenerative disease.