A recent study from Brazil has found that even people who had mild cases of COVID-19—and were never hospitalized—can experience lingering effects on their heart function.
These effects may increase the risk of future heart problems and suggest the need for rehabilitation, even in younger adults. The study was led by researchers at the Federal University of São Carlos (UFSCar) and published in Scientific Reports.
The researchers examined 130 volunteers who had tested positive for COVID-19 and compared them to a control group of people who had never been infected. The participants were tested at different stages after infection—some within six weeks, others between two to six months, and some between seven to twelve months.
One of the key measurements used in the study was heart rate variability (HRV), which is the natural variation in time between heartbeats. HRV is a well-known indicator of cardiovascular health.
A higher HRV is generally a good sign—it shows the heart can adjust well to stress, physical activity, and changes in the environment. A lower HRV, on the other hand, means the heart is less adaptable and more vulnerable to stress and disease.
The study found that people who had COVID-19 had significantly lower HRV compared to those who had never been infected. This was especially true in the early weeks after infection. While there was some improvement over time, their HRV still didn’t return to the same level as the control group—even up to a year later.
“These results show that COVID-19, even in its mild form, can disrupt the balance of the autonomic nervous system,” explained Dr. Audrey Borghi Silva, who led the research. This part of the nervous system controls automatic functions in the body, like heart rate, blood pressure, and digestion.
The autonomic nervous system has two main branches:
- The sympathetic system, which prepares the body for action and raises the heart rate (the “fight or flight” response),
- The parasympathetic system, which helps the body rest and recover by slowing the heart rate (the “rest and digest” response).
Normally, the heart is regulated by a balance between these two systems. But in people who had COVID-19, the sympathetic system became more dominant, and the calming parasympathetic system was less active. This imbalance can put extra strain on the heart and may raise the risk of future heart issues.
Lead author Aldair Darlan Santos-de-Araújo noted that this imbalance was found even in young and middle-aged people who had not needed hospital care for COVID-19.
Many participants were around 40 years old, and some already had risk factors like obesity, high cholesterol, diabetes, or high blood pressure. COVID-19 appeared to worsen the cardiovascular stress in these individuals.
The researchers also looked at symptoms that people experienced. Those who were closer to the time of infection were more likely to have symptoms like fatigue (50%), headache (56%), loss of taste (53%), anxiety (62%), shortness of breath (dyspnea), cough (47%), and runny nose (50%). This group also had a higher number of unvaccinated individuals (44%).
Importantly, the study found that while heart function did slowly improve over time, it never returned to pre-infection levels during the 12-month follow-up period. This suggests that the heart and nervous system may take much longer to recover, or may need help to return to full health.
Review and Analysis
This study adds to a growing body of research showing that even mild COVID-19 infections can leave lasting impacts on the heart and nervous system. It also highlights an issue that might be going unnoticed in many people—especially younger adults who may have recovered quickly from their initial symptoms and assume they are fully healthy.
By focusing on heart rate variability, the researchers used a subtle but powerful marker of cardiovascular and nervous system health. A lower HRV doesn’t usually cause symptoms right away, but over time, it can be a warning sign for more serious heart problems.
Another important takeaway is that recovery from COVID-19 isn’t always complete, even after months. The heart and nervous system may still be struggling to find balance, and this could explain symptoms like fatigue, anxiety, and difficulty exercising—commonly reported in long COVID cases.
The researchers recommend that rehabilitation programs should be considered, even for people who had mild COVID-19. Light exercise, stress reduction, and breathing techniques may help restore the balance between the sympathetic and parasympathetic systems.
In short, the study suggests that recovery from COVID-19 doesn’t end when the fever or cough fades. Paying attention to heart health—even months after a mild infection—could help prevent future complications.
If you care about heart health, please read studies that yogurt may help lower the death risks in heart disease, and coconut sugar could help reduce artery stiffness.
For more information about health, please see recent studies that Vitamin D deficiency can increase heart disease risk, and results showing vitamin B6 linked to lower death risk in heart disease.
The research findings can be found in Scientific Reports.
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