PROJECT SUMMARY
The cascade of pathological changes involved in Alzheimer’s disease (AD) starts many years before AD
diagnosis, suggesting that intervening with still-healthy adults will be most successful. According to the
influential amyloid hypothesis, an imbalance between ß-amyloid (¿ß) production and clearance initiates
changes that lead to AD. This hypothesis suggests that early intervention targeting ¿ß levels should be
particularly effective in preventing AD, but the field has yet to test this core prediction of the hypothesis. A
major obstacle is the lack of safe and low-cost interventions that reduce ¿ß. Initial findings (N = 108) from our
recently completed heart rate variability (HRV) biofeedback clinical trial indicate that daily sessions attempting
to increase (via resonance-frequency breathing) vs. decrease (via personalized strategies) heart rate
oscillations have significant opposing outcomes on plasma ¿ß levels. Resonance-frequency breathing reduced
overall plasma ¿ß levels in both younger and older adults, and, among adults aged 55-70, increased
¿ß42/¿ß40 ratios, a biomarker of reduced amyloid deposition in the brain. In this stage II double-blinded
randomized trial, we aim to test hypotheses regarding the mechanisms behind this result as well as cognitive
outcomes in African-American and European-American adults aged 50-70. Participants will complete ten
weeks of daily paced breathing sessions, randomized to either a resonance-frequency breathing or a random-
paced breathing condition. We hypothesize that resonance-frequency breathing reduces plasma biomarkers of
AD risk via two synergistic pathways: 1) afferent vagus nerve activity suppresses noradrenergic activity that
stimulates Aß production; and 2) heart rate oscillations increase cerebrospinal fluid (CSF) flow, increasing
brain clearance of Aß42 in adults in their 50’s and 60’s in whom glymphatic clearance is declining. We will
model how pre/post intervention change in plasma AD biomarkers relates to biomarkers associated with each
of these hypothesized pathways. Compared with European Americans, African Americans have higher AD risk
and higher noradrenergic/sympathetic system activity. They therefore may particularly benefit from resonance-
frequency breathing. Across ethnicities, reduced levels of ¿ß should especially benefit adults in their 50’s and
60’s, in whom amyloid is starting to aggregate in the brain as glymphatic clearance becomes less effective.
The initial aggregative ¿ß form (oligomeric ¿ß) interferes with synaptic plasticity, so we will assess how much
participants in the two conditions improve their performance on cognitive tasks they practice daily for 10
weeks. This innovative project will serve as a foundation for future long-term clinical trials to test the potential
of resonance-frequency breathing to slow cognitive decline and prevent AD by reducing ¿ß.