When sick, many individuals notice a change in their heart rate. This often leads to questions about why the heart beats faster. The heart’s rhythm is influenced by numerous factors, including the body’s state of health.
Physiological Basis of Heart Rate Increase
Illness often increases heart rate. When fighting infection or inflammation, the immune system becomes highly active. This triggers the release of chemicals like inflammatory cytokines, which directly influence heart function and signal increased blood flow.
The autonomic nervous system, specifically its sympathetic branch, plays a significant part. Sickness acts as a stressor, activating the “fight-or-flight” response and releasing hormones like adrenaline and norepinephrine. These hormones stimulate the heart, causing it to beat faster to meet the body’s heightened demands. This increased cardiac output ensures oxygen and nutrients are delivered more rapidly to tissues and organs combating illness.
Illness often increases the body’s metabolic rate, expending more energy on immune processes. This heightened metabolism requires additional oxygen, prompting the heart to pump more blood. Accelerating the heart rate facilitates the transport of immune cells and removal of metabolic waste products.
How Different Illnesses Affect Heart Rate
Common illnesses influence heart rate through distinct mechanisms. Fever, a frequent symptom of infection, directly elevates heart rate. For every 1.8°F (1°C) increase in body temperature, heart rate can rise by approximately 10 beats per minute. This occurs as the heart works harder to circulate blood and regulate body temperature.
Dehydration, common during sickness, also increases heart rate. When the body loses fluids, blood volume decreases, making the blood thicker. The heart must pump faster to circulate this reduced and more viscous blood effectively, ensuring organs receive sufficient oxygen and nutrients. Electrolyte imbalances, accompanying dehydration, may also disrupt electrical signals that regulate heart rhythm, contributing to a racing heart rate.
Infections activate a systemic inflammatory response that accelerates heart rate. The immune system releases white blood cells and inflammatory markers, which can cause blood vessels to expand. This signals the brain to increase heart rate and blood flow to inflamed areas, aiding in immune cell delivery to combat pathogens. Stress from fighting an illness can also trigger stress hormones, further contributing to a faster heart rate.
Recognizing Concerning Heart Rate Changes
An elevated heart rate is a common and normal response to illness, but it is important to recognize when these changes become a cause for concern. For most healthy adults, a normal resting heart rate ranges between 60 and 100 beats per minute. During sickness, a temporary increase beyond this range is expected as the body works to recover. For example, a normal heart rate of 70 BPM might rise to around 95 BPM when sick.
However, certain signs indicate an elevated heart rate may signify a more serious issue requiring medical attention. If heart rate remains consistently above 100 beats per minute at rest, it warrants evaluation. Symptoms prompting immediate medical consultation include chest pain, shortness of breath, dizziness, fainting, lightheadedness, or irregular heartbeats like fluttering or pounding.
These symptoms, combined with a persistently high heart rate, could indicate underlying conditions such as arrhythmias, severe dehydration, or other complications needing professional assessment. Monitoring these changes and seeking timely medical advice helps differentiate a normal physiological response from a potentially serious health problem.