Wearable Devices That Detect Illness Before Symptoms Appear: Promise and Evidence

A sore throat or fever may feel like the start of an illness, but the body often changes earlier. Heart rate, sleep, temperature, and breathing patterns can shift before a person notices symptoms. That is why researchers are studying whether everyday wearables can act as early warning systems.

The promise is real, but it has limits. Wearable devices are not diagnostic tools. They may help identify unusual patterns that suggest the body is under stress, including possible infection.

Small changes in daily biometrics may appear before symptoms feel obvious.

What wearables can detect before symptoms appear

Most wearable devices for consumers cannot directly detect the presence of a virus or bacteria. However, they can indirectly indicate the presence of a virus

by measuring changes in physiological signs that are often associated with the body’s response to pathogens.

Some of these physiological indicators that can be measured by smartwatches or fitness bands are as follows:

• Physiological indicator

  
  

• Resting heart rate

  
  

• Heart rate variability

  
  

• Skin temperature

  
  

• Breathing rate

  
  

• Hours of sleep

  
  

• Daily physical activity level

The most important point is that it is not the value of a certain parameter that indicates a virus, but rather the deviation from your personal norm. For example, a resting heart rate of 72 beats per minute cannot indicate anything on its own. However, if a person’s resting heart rate normally averages 65 bpm, then the 72 may be a sign of illness.

Personal baselines matter more than single readings.

What the research shows

Research suggests that information picked up by wearable technology can help predict the onset or imminent onset of certain illnesses. In 2017, scientists used wearable sensors in conjunction with information from smartphones to track patterns of health and sickness. Changes in heart rate, temperature, activity, and other measures were often associated with changes in health status including instances of inflammation and infection.

During the COVID-19 pandemic, research into how wearable technology might identify instances of infection continued with promising results. Scientists found that changes in the data recorded by smart watches and similar devices could help predict a positive test for the virus, as well as instances of sickness unrelated to COVID-19. These patterns were also sometimes seen before symptoms appeared and in instances where people were infected but not symptomatic, while other times the information from wearables was used to confirm self-reported symptoms. The findings were not conclusive, but they suggest that while a watch cannot tell you whether you have COVID-19, the flu, or another infection, the technology has potential to identify risk factors for illness that could help people take earlier precautions like getting tested and limiting interactions as needed.

Wearable alerts can be useful when they are interpreted in context.

Why early illness detection is difficult

The same signals that might indicate an infection at one point might be impacted by numerous other factors. Lack of sleep, alcohol consumption, stress, traveling, physical activity, dehydration, and medication can affect the readings of a wearable device. Such issues can produce two types of positive outcomes:

False alarms

when no infection occurs, but the implantable device mistakes it for a sick season

missed detections

when the implantable device fails to catch illness despite symptoms.

Other issues are connected to variations in technology, individual differences, ethical concerns, and accessibility in detecting diseases with wearables:

Different wearables tend to have different algorithms and sensors, health data is private and has to be handled with care, and not everyone is comfortable being able to use a particular technological tool.

Therefore, wearables should facilitate decision-making rather than replace human judgment.

Several suggestions emerged from the conversation about how wearables might fit into the daily routines of ordinary medical workers. The primary value scenario is detecting a deviation from the norm, which facilitates early medical intervention or even self-isolation to avoid further complications. A wearable device is supposed to make individuals more cautious about their health, which might result in additional measures being taken to ensure well-being, such as staying away from crowds or checking out symptoms with a physician if the situation requires it. Moreover, clinicians will be more informed if their patients are able to provide them with a comprehensive view of their wellbeing rather than just a few figures or a single data point. For instance, a week of elevated resting heart rates and sleep deprivation could be a better indicator of a potential infection.

Consistent use helps wearables learn what normal looks like.

Wearables show strong promise as early warning tools, especially when they track changes from a personal baseline. The evidence is encouraging, but the safest interpretation is cautious: they can raise a flag, not make a diagnosis.

This article is for informational purposes only and should not replace medical advice, testing, or care from a qualified health professional.

References

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Quer, G., Radin, J. M., Gadaleta, M., Baca-Motes, K., Ariniello, L., Ramos, E., Kheterpal, V., Topol, E. J., & Steinhubl, S. R. (2021). Wearable sensor data and self-reported symptoms for COVID-19 detection. Nature Medicine, 27(1), 73–77. https://doi.org/10.1038/s41591-020-1123-x