Heart rate variability (HRV) in ADHD

Heart rate variability (HRV) is also known as heart rate variability.

The heart regulates blood pressure through small fluctuations in pulse rate. The better the heart can regulate blood pressure by slightly lengthening or shortening the time between two beats, the better the blood pressure is balanced. This balancing ability of the heart is measured as HRV.
HRV can be measured using various parameters such as rMSSD, HFA, HF, LFA, LF/HF ratio, SD and TP.
In the non-medical field, simple HRV measurement is possible using sports trackers.

HRV is a stress marker. HRV is reduced in ADHD.¹²³
Methylphenidate improves HRV in persons with ADHD, but it does not reach the level of non-affected people.

• 1. Heart rate variability (HRV)
  • 1.1. RMSSD
  • 1.2. HFA
  • 1.3. HF
  • 1.4. LFA
  • 1.5. LF / HF ratio
  • 1.6. SD
  • 1.7. TP
• 2. HRV measurement with sports tracker
  • 2.1. Garmin vivosmart 3 to 5
  • 2.2. Apple Watch
  • 2.3. Polar H10 chest strap with V800 sports watch
• 3. HRV influence through medication

1. Heart rate variability (HRV)¶

It is certain that the heart’s ability to adapt to small fluctuations in blood pressure, measured as heart rate variability, is a highly significant marker for stress. The higher the heart rate variability (HRV), the lower the stress level. Many thousands of years ago, Chinese doctors already knew that patients whose heart beats like clockwork in an absolutely constant rhythm, i.e. who have a very low to non-existent HRV, are seriously ill.

HRV is the standard measuring instrument for the activity of the parasympathetic nervous system, which is part of the autonomic nervous system.⁴

ADHD is characterized by reduced heart rate variability (HRV), which indicates a reduced stress regulation capacity of the autonomic (vegetative) nervous system ^{5 6 7 8 9 10 11 12 1 13 141}

Heart rate variability can be measured using various parameters.

1.1. RMSSD¶

rMSSD: Root Mean Square of successive differences between inter-beat intervals

• No differences between people with ADHD and those without, even when tested separately by gender, age or ADHD subtype.¹⁵ One small study found reduced rMSSD scores.¹⁶
• Low values correlate with¹⁵
  • Fears
  • Oppositional behavior
  • Social problems

1.2. HFA¶

The HFA is the absolute high frequency power.
HFA maps the parasympathetic (= vagal) tone.

• With regard to HFA, the results are unclear in relation to ADHD.
  One large study found no differences between people with ADHD and those without, even when tested separately by gender, age, or ADHD subtype.¹⁵ One small study found decreased HFA scores.¹⁶ Another study found increased scores in boys with inattention and oppositional defiant behavior (ODD).¹⁷
• Low values correlate with¹⁵
  • Fears
  • Oppositional behavior
  • Social problems

1.3. HF¶

In one study, the normalized high-frequency band of heart rate variability was referred to as HF and described as representing the parasympathetic nervous system. This study found a 20% reduction in HF in boys with ADHD compared to those not affected.¹⁸

1.4. LFA¶

The LFA is the absolute low frequency power.
LFA maps both sympathetic and parasympathetic tone, but in practice represents the sympathetic tone.

• Low values correlate with boys¹⁷
  • Inattention
  • Hyperactivity/impulsivity
  • Oppositional Deficit Disorder (ODD)

1.5. LF / HF ratio¶

LF / HF: Ratio of low frequency power to high frequency power

LF / HF ratio means sympathovagalance. An increase / high values of the LF / HF ratio mean sympathetic dominance, a decrease / low values of the LF / HF ratio mean parasympathetic dominance.

• In ADHD, the LF / HF ratio is higher in both resting and sustained attention states, especially in male children¹⁵¹⁶
• Low values correlate with boys¹⁷
  • Inattention
  • Hyperactivity/impulsivity
  • Oppositional Deficit Disorder (ODD)
• Higher LF / HF ratio during sustained attention correlates with poorer attention performance in people with ADHD and non-affected persons¹⁵

1.6. SD¶

SD: Square of the interval differences

One small study found decreased SD levels in children with ADHD.¹⁶

1.7. TP¶

TP: Total power of HRV

A small study found decreased TP levels in children with ADHD.¹⁶

In children, emotional dysregulation is associated with heart rate variability.¹⁹

2. HRV measurement with sports tracker¶

HRV can now be measured and evaluated using a simple sports watch (fitness tracker).

2.1. Garmin vivosmart 3 to 5¶

The Garmin vivosmart 3 or the successor models vivosmart 4 and vivosmart 5 (be careful, there are some other models that sound similar but do not have HRV measurement) is a standard sports watch that measures the usual data such as heart rate, calorie consumption, sleep, movement, etc. It also measures heart rate variability and provides a granular picture of HRV progression throughout the day. However, as a function rarely found in such fitness tracker sports watches, it also measures heart rate variability and provides a granular picture of HRV progression throughout the day. Long-term evaluations are available via the Garmin app. The cost of this device is between €80 and €140. However, the device only shows an overall HRV value, which is not specified in more detail.

According to this assessment, the evaluations are nevertheless meaningful enough to be able to analyze parameters influencing HRV. For example, it is clearly recognizable when sleep has not entered the recovery range, e.g. due to alcohol consumption.

The clear daily evaluation enables a rough biofeedback utilization. It becomes clear which stressors influence the HRV value. The development of the HRV value shows, for example, whether sleep allows sufficient recovery or whether certain situations lead to particular stress levels. Smoking, for example, directly worsens the HRV value.

Long-term measurement over weeks or months provides insights into which circumstances reduce the stress level and which increase it.

2.2. Apple Watch¶

Although the Apple Watch offers HRV measurement, this is far less detailed than that of the Garmin vivosmart. In addition, we are not aware of any app that displays the values in a meaningful way. In our opinion, the Apple Watch is not particularly useful even for non-medical analyses.

2.3. Polar H10 chest strap with V800 sports watch¶

A more precise option that can also be used for medical analyses (although not approved as a medical device for this purpose) is to measure heartbeats using a chest strap. A combination of an H10 chest strap and a V800 tracking watch (both from Polar), which together cost around €300 (as of May 2018), make it possible to read out the raw heartbeat data over 24 hours. The results can then be analyzed by companies such as Autonom Health. As of May 2018, a single evaluation costs €50 and enables an analysis of the parasympathetic nervous system and (to a slightly limited extent) the sympathetic nervous system. Specific evaluation analyses are provided that are understandable for the person with ADHD.

To date, no evaluations or data analyses are available in relation to ADHD.

3. HRV influence through medication¶

Methylphenidate improves heart rate variability and control of the autonomic nervous system in people with ADHD.⁶²⁰

A compilation of the influence of medication on heart rate variability can be found at www.hrv24.de,²¹²² , although the information on methylphenidate is contradictory. As a result, methylphenidate is likely to increase (improve) the HVR, although the value of non-affected persons is not reached.