Heart Rate Variability and Hair Loss

We know that stress is bad for our hair. High levels of stress (and especially prolonged or chronic stress) can lead to excessive hair loss by shortening our hair’s growth phase and putting the follicle into an extended rest phase.


A woman wearing an Apple Watch carrying a brown leather tote bag.


 Less growing + more resting = thin, sparse hair


But, the idea of “stress” can seem so vague. How do I know if I am stressed enough to expect hair loss?

First, it’s important to stress (see what I did there) that psychological stress is really just one potential source of stress that can contribute to hair loss. For example, under-eating and overtraining is another form of stress that can impact our hair growth.

Second, we can’t think of all stress as being only bad. Stress is an adaptive mechanism that has helped our species to survive millennia; it enables us to react appropriately to threats (flee hungry tigers, dodge the spears of our enemies, quickly put out fires, etc.).

The issue between acute (i.e. short-term) stressors like those examples and the constant, chronic and long-term stressors that many of us find ourselves inundated with today is that we are not adapted to thrive under conditions like these. And this has put many of us in a sort of evolutionary mismatch to our environment.


Are You Stuck In “Fight-or-Flight”?


Let me introduce you to the autonomic nervous system (ANS). The ANS is responsible for many of our functions and goes about it’s work of innervating our bodies without us having to consciously ask it to do so (the word “autonomic” literally means involuntary or unconscious).

The ANS is made up of two distinct branches: the parasympathetic nervous system and the sympathetic nervous system. Maybe you’ve heard these two referred to by their other names: the rest-and-digest branch (parasympathetic) and the fight-or-flight branch (sympathetic).

The parasympathetic nervous system is our relaxation and recovery response.  When it’s in control functions like digestion, detoxification – even creative thinking – are prioritized.

When the sympathetic nervous system is in control your body is preparing your body to react to stress. Hormones like cortisol and adrenaline (epinephrine) start flowing, our heart rate speeds up, our airways expand, our pupils dilate, and on.

When we actually need to fight-or-flight (remember hungry lions, and so on), having the sympathetic nervous system take over and respond to an acute situation is critical. Being faced with an imminent threat that we need to fight-or-flight from would be an inappropriate time for our body to prioritize rest-and-digestion. This is why we can’t think of stress as always bad, because it can sometimes be the appropriate response.

Again, where we run into trouble is when we are faced with a chronic onslaught of stressors that keep our body “stuck” in the sympathetic nervous system, or fight-or-flight branch. This is the state of stress that can be especially damaging to our health and the health of our hair.


Are you stressed? No more than usual…


That’s how a lot of conversations with my clients go. Unfortunately, “no more than usual” tends to still be way more stress than what is optimal. After becoming accustomed to high-levels of continuous stress coming at you from all angles, sometimes this abnormal activation of our sympathetic nervous system can actually start to feel normal.

What we need is a way to actually measure whether we are spending an abnormally high amount of time being stuck in our fight-or-flight (sympathetic) branch – – we know that engaging sympathetic nervous system is sometimes appropriate but that we shouldn’t be spending extended periods of time there.


Heart Rate Variability (HRV)


As a metric, heart rate variability (HRV) can help us to actually quantify how balanced those two branches of our ANS are by measuring the variability of our heart rate.

Fight-or-flight (sympathetic) produces faster heart beats. Rest-and-digest (parasympathetic) is associated with slower heart rates. Being able to move between one and the other, experiencing different heart rates throughout any given day is considered a positive sign of health and resilience. But, being stuck in one mode (usually the sympathetic branch) can be a sign of maladaptation.

In general terms, high heart rate variability is good and low heart rate variability is not so good.


A cup of tea on a stack of magazines next to an Apple Watch


Here are some of the factors that can contribute to high vs low heart rate variability (HRV):

Factors That May Contribute to Low Heart Rate Variability 

  • Chronic Stress
  • Dehydration
  • Alcohol consumption
  • Overtraining
  • Inflammation and infections
  • Blood sugar dysregulation/insulin resistance
  • Poor sleep
  • Circadian rhythm dysregulation
  • Poor nutrition

Factors That May Support High Heart Rate Variability 

  • Low stress levels
  • Balanced activity levels
  • Adequate hydration
  • Quality sleep
  • Good nutrition
  • Balanced circadian rhythm

High heart rate variability is considered a measure of a balanced stress response, resiliency, good recovery, and fitness. In contrast, low heart rate variability may be an indication of chronic stress, overtraining, or illness.

Knowing that your HRV is high or low can give you insight into providing your body what it needs in the moment: Is your body craving rest, relaxation, and nourishment? Or, is it ready to take on challenge?


How To Measure Your Heart Rate Variability


If you know your HRV and can identify some of the factors that may be making it less than optimal, you can start to make changes to your diet and lifestyle to improve this metric and therefor your overall health and well-being.

If you use a wearable fitness device that claims to track HRV, read on to make sure that you’re using it to access the best quality data.

If you’re using HRV to understand how your parasympathetic nervous system (fight-or-flight) is behaving, then the best way to measure your HRV is by wearing a tracking device overnight or taking an HRV measure first thing in the morning. Assessing your HRV at these two times decreases the number of outside factors that can muddy this data since fleeting stimuli (your lunch, that email, this news story, your pet) can have an impact on your heart rate.

Many fitness devices with HRV technology measure your HRV at random times throughout the day (for example, Apple Watch). This is not very high-quality information about your HRV since it hasn’t controlled for those outside influencing factors and isn’t reproducible (a quality that is really important when you’re looking at health data).

If you want to wear a fitness device that will track your HRV overnight my favorite option is the Oura Ring. Bonus, it has a lot of other useful health info that it can track and their accompanying app can help guide you on your overall resilience for that day (as well as specific tweaks you can make to improve this) based on your data.

If you would rather do a once a day morning reading of your HRV, you can use the Apple Watch (here is a blog about the special trick that you need to use to get a morning reading), chest straps (like these ones), or apps like HRV4Training that can use the camera on your phone to make an assessment.

Important Tip: If you do the once a day morning reading option, remember that you are trying to make each day’s reading as consistent as possible. Ideally, you would complete it measurement at the same time every day, while laying down, before you even get out of bed.


Not A One-And-Done Assessment


Whichever option you decide to use, it’s also important that you gather enough HRV data for it to be relevant. It will probably take at least four consecutive days to establish your norm (also called baseline) and you should probably plan on completing an assessment every day (weekdays and weekends) for at least a month before trying to make to many conclusions about what your data is trying to tell you. In general, the longer you track your HRV, the more detailed analysis you can get out of the apps you decide to use.

Using HRV tracking daily can also help you to decide how to tailor your day to your nervous system’s needs, making strategic changes to balance your stress levels.




  1. https://www.ncbi.nlm.nih.gov/pubmed/29486547
  2. https://www.ncbi.nlm.nih.gov/pubmed/21332532
  3. https://www.ncbi.nlm.nih.gov/pubmed/27924215
  4. https://www.ncbi.nlm.nih.gov/pubmed/25726222
  5. https://www.ncbi.nlm.nih.gov/pubmed/10683099
  6. https://www.ncbi.nlm.nih.gov/pubmed/12370569
  7. https://www.ncbi.nlm.nih.gov/pubmed/23847549
  8. https://www.ncbi.nlm.nih.gov/pubmed/23601527
  9. https://www.ncbi.nlm.nih.gov/pubmed/32295262

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