Modulating Heart Rate Oscillation Affects Plasma Amyloid Beta and Tau Levels in Younger and Older Adults

Listen or Download Podcast Version:

Citation

Min J, Rouanet J, Martini AC, Nashiro K, Yoo HJ, Porat S, Cho C, Wan J, Cole SW, Head E, Nation DA, Thayer JF, Mather M. Modulating heart rate oscillation affects plasma amyloid beta and tau levels in younger and older adults. Sci Rep. 2023 Mar 9;13(1):3967. doi: 10.1038/s41598-023-30167-0. PMID: 36894565; PMCID: PMC9998394.

Sharable

Note: You can share anything you want from these 411s—the more sharing the better. But this is my attempt to condense the findings into a bite-sized wisdom nugget:

This is the first study to show that a behavioral intervention may reduce the risk of Alzheimer’s.  They found that slow breathing reduces levels of amyloid-beta, a key Alzheimer’s biomarker, in younger and older adults, suggesting that it may reduce the risk of Alzheimer’s and promote healthy brain aging.

4 Fundamentals

 

1. Essential Background Material

 

  • One reason that rates of Alzheimer’s disease might increase with age is that, in general, the activity of the sympathetic nervous system increases with age.  In contrast, the activity of the parasympathetic branch decreases as we age.

  • This age-related nervous system dysfunction may impact Alzheimer’s by modulating how peptides and proteins are produced and removed in the body and brain.

  • Specifically, amyloid-b (AB) peptides and tau proteins, both of which are critical in Alzheimer’s risk, may increase as sympathetic nervous system activity increases.

  • Therefore, the authors reasonably hypothesized that activities that increase parasympathetic activity might reduce AB and tau concentrations, thus reducing Alzheimer’s risk.

  • Because slow breathing is a noninvasive way to stimulate the parasympathetic nervous system, they hypothesized that it could potentially reduce AB and tau levels.

 

2. What Did this Research Do?

 

There were 108 participants in this study, subdivided into older (N=54; an average age of about 66) and younger (N=54; an average age of about 23) groups to separately test the effects of the breathing exercise on Ab and tau levels in these different populations.

 

The participants were randomly separated into two groups.  One group used HRV biofeedback to maximize heart rate oscillations using slow breathing (which I’ll call the “breathing group”).  This group performed a standard one-day HRV biofeedback procedure, testing breathing rates from ~4.5 – 6.5 breaths a minute.  Whichever rate maximized their HRV was considered their resonant frequency, and they were told to breathe at this rate for the duration of the study.  They used an equal inhale-to-exhale ratio.

 

The other group (I’ll call them the “non-breathing group”) minimized HRV through various methods, such as listening to music or visualization of different scenes.

 

During the 4 week study period, both groups did 20-40 minutes of daily practice with a heart rate monitor clipped to their ear while watching a screen (in my opinion, this is an essential part of the upcoming results).

 

The primary measurements here are AB40, AB42, pTau-181, and tTau, as they appear to be most relevant to determining the risk of Alzheimer’s.

 

However, this was part of a larger, longer-lasting study.  So, in addition to Ab and tau, there were also cognitive tests, blood tests, emotional tests, MRI scans, and the participants were told to wear a Whoop strap for the duration of the experiment to monitor sleep.

 

 

3 & 4. What Were the Major Findings and Why Do They Matter?

 

(Because this paper is outside our usual scope, I’m testing out combining these two sections to make it easier to understand.  The major result will be bolded, and the “Why It Matters” will come immediately after.)

 

The breathing group significantly lowered both AB40 and AB42 peptides. In contrast, they significantly increased in the non-breathing group. These findings held true when analyzed separately for younger and older adults.

 

  • This is the first study to show that a behavioral intervention can lower AB peptides.  Because these peptides are a significant risk factor for Alzheimer’s disease, this provides evidence that slow breathing could help reduce the risk of Alzheimer’s while also promoting healthy AB levels throughout adulthood.  This is groundbreaking.

 

There were no significant changes in tTau or pTau-181.  Ratios of the different measurements (AB42/AB40 and pTau-181/tTau) did change for the different age groups, but altogether, there were no conclusive findings.

 

  • These ratios are important for determining if slow breathing reduces the production of AB and tau or increases the clearance of these critical markers.  From their discussion, it seems that slow breathing has the potential to do both (reduce production and increase clearance).  But, from a mechanistic standpoint, this is something future research will have to examine more thoroughly.

 

There were no significant changes in “negative affect” (negative emotions and moods) for either group.

 

  • This was a surprising yet glossed-over finding of the study.  Shouldn’t slow breathing help them feel more relaxed, leading to better emotional health?  To understand this unexpected finding, I think looking at the study protocol is crucial.  Participants were asked to use an ear clip and stare at a computer screen the whole time.  Additionally, they were wearing Whoop straps, and the younger adults took saliva samples every morning.  If anything, the entire process probably stressed them more than it relaxed them.  Thus, these findings on emotional health don’t surprise me, but this is just my speculation.

 

 

 

1 Big Takeaway

 

Slow breathing reduces levels of AB, a key biomarker of Alzheimer’s risk, in younger and older adults, suggesting that it may reduce the risk of Alzheimer’s and promote healthy brain aging.

 

 

 

1 Practical Application

 

Practice slow breathing at a comfortable rate between 4.5-6.5 breaths a minute for 20 minutes daily to potentially reduce your risk of Alzheimer’s and promote healthy brain aging. 

 

In this study, they used an equal inhale-to-exhale ratio.  However, using a slightly longer exhalation would likely be ok too (if that’s what you prefer) because some research suggests this approach leads to greater activation of the parasympathetic nervous system.