mobile phone and computer graphic

A new app for chronic fatigue assesses the severity of symptoms based on heart rate variability.

Myalgic encephalomyelitis, also called chronic fatigue syndrome (ME/CFS), is a long-lasting illness with symptoms of extreme fatigue, which is not helped by resting. Additional symptoms include unrefreshing sleep, poor focus and attention, slow processing of information, and intermittent pain (1).

Chronic fatigue is thought to affect 836,000 to 2.5 million Americans (2), but because of the difficulty in diagnosing the illness, the statistics could be underreported. This difficulty in diagnosing can also increase patients’ symptoms and distress (3). Young adults between 20 and 40 most commonly suffer from chronic fatigue, and women are twice as likely to have the illness (5).

The number of cases is expected to double by 2030 as a side effect of long-haul COVID-19 (6). The symptoms of chronic fatigue and long-haul COVID-19 are similar, and more research is expected to determine whether there is a direct relationship between the two (7).

Doctors usually diagnose chronic fatigue through brain imaging techniques, such as magnetic resonance imaging (MRI), magnetoencephalogram (MEG), positron emission tomography (PET), or microRNA expression (3). Unfortunately, these methods are expensive to perform.

Researchers have looked for other ways to diagnose the condition that are less expensive and are non-invasive. One such method is through heart rate variability (HRV). Heart rate variability is the changes in the time between heartbeats (4). Healthy heart rate variability is complex which allows the body to react to rapidly changing environments.

Heart rate variability and chronic fatigue

Studies have shown that people with chronic fatigue have differences in heart rate variability when compared to healthy people. Doctors have used this to help to assess the severity of chronic fatigue symptoms. Heart rate variability is also an easy and affordable test to perform. Its simplicity lends itself for use as an app for chronic fatigue.

Testing an app for detecting chronic fatigue

Because chronic fatigue is more common in women, fewer studies have been performed that include men, and no studies have been performed which assess the difference in heart rate variability between men and women.

Researchers from Vall d’Hebron, the Universitat Autònoma de Barcelona (UAB) and the Universitat Politècnica de Catalunya BarcelonaTech (UPC) have recently performed a study which assesses the use of an app for chronic fatigue to explore heart rate variability in men and whether it is associated with chronic fatigue. Also, the study looked for differences in heart rate variability and symptoms experienced by men and women. The results were published in the journal Sensors.

The study included 77 chronic fatigue patients (32 men and 45 women) and 44 people without chronic fatigue. Initially, the patients completed five questionnaires that assessed physical symptoms, fatigue impact, severity of autonomic function symptoms, sleep quality index, and anxiety and depression.

Next, the patients wore a cardiac chest band that measured heart rate data and sent it via Bluetooth to the app for chronic fatigue to analyze. Measurements were taken in three five-minute sessions taken between one to three weeks apart.

Heart rate variability can be used to detect chronic fatigue

After statistically analyzing the data, the researchers were able to determine that the heart rate variability data collected from the app for chronic fatigue could be used to predict how severe the chronic fatigue symptoms were. While the data was especially clear for women, the men’s’ data was not as clear, although there was greater cardiac variability (3).

While the questionnaire data and heart rate variability data did not consistently suggest any specific relationship that could be used to diagnose chronic fatigue, researchers were able to determine that high fatigue or high gastrointestinal dysfunction was associated with lower heart rate variability (3) in men.

In a press release study author Dr. Rosa M. Escorihuela reported about the results, “We demonstrated that the use of the app would be especially useful for the monitoring of women suffering from this syndrome, which clearly have a lower variability of heart rate compared to healthy women.”


  1. What Is ME/CFS? – American ME and CFS Society. American Myalgic Encephalomyelitis and Chronic Fatigue Syndrome Society. Accessed July 5, 2021.
  2. Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) | CDC. Published December 30, 2020. Accessed July 5, 2021.
  3. Capdevila L, Castro-Marrero J, Alegre J, Ramos-Castro J, Escorihuela RM. Analysis of Gender Differences in HRV of Patients with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Using Mobile-Health Technology. Sensors. 2021;21(11):3746. doi:10.3390/s21113746
  4. Shaffer F, Ginsberg JP. An Overview of Heart Rate Variability Metrics and Norms. Frontiers in Public Health. 2017;5. doi:10.3389/fpubh.2017.00258
  5. Myalgic encephalomyelitis/chronic fatigue syndrome | Genetic and Rare Diseases Information Center (GARD) – an NCATS Program. Accessed July 5, 2021.
  6. An app to help assess the severity of symptoms in chronic fatigue syndrome. EurekAlert! Published July 1, 2021. Accessed July 5, 2021.
  7. Wong TL, Weitzer DJ. Long COVID and Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS)—A Systemic Review and Comparison of Clinical Presentation and Symptomatology. Medicina. 2021;57(5):418. doi:10.3390/medicina57050418
  8. Image by janjf93 from Pixabay 
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