Why do Fevers get Worse at Night?

The illness goes bump in the night may not be just a patient's imagination. Doctors have sensed for centuries that many diseases actually do get worse at night and science has begun to confirm this impression.

Fevers are often worse at night. The same is often said about asthma, arthritis and the flu. And although heart attacks commonly occur in the morning, researchers believe they are frequently triggered by night-time happenings in the body. There is a field of study in biology devoted to understanding how the time of day affects our health called chronobiology.

The symptoms of fever are abnormally high body temperature, shivering and sweating, headache, muscle ache, loss of appetite, and general fatigue. In some cases, children under 5 may suffer seizures during high fever spikes alarming for parents, but not usually life-threatening. 

It’s important to remember that fever itself is not a disease. In fact, it’s the exact opposite a sign that the body’s immune system is fighting off a bacterial or viral infection although it can be a cause for serious concern. Like if an infant less than two months of age is running a fever greater than 100.4 degrees Fahrenheit, or if anyone with a compromised immune system spikes a fever.

There are some fairly obvious explanations for fever symptoms to be magnified during the evening hours.  Just like our sleep schedules, our immune system also has a rest pattern of its own when it is more active and when it is not. Our immunity defends the body differs from day to night. Hence, doctors generally don’t rule out fever before 24-48 hours even if you are feeling completely fine during the day.

During the day, our immune cells protect us but as night approaches, immune cells get less active and do some inflammatory action, by deliberately increasing the body temperature in hopes of killing the bacteria. This phenomenon is called ‘temporary fever’, which fight infections.

It's the body’s defence mechanism ensuring that the entire immune defence force is prepared to put up a fight during the morning since it is the time when most productive things happen. 

There’ is one other element that we don’t quite fully understand, but it seems to be important. We know that two key hormones cortisol and adrenaline are suppressed when we sleep. From extensive studies on asthma management, we have learned that when the level of these hormones is reduced at night, it’s harder for asthmatics to breathe. Researchers believe this restriction also exacerbates fever symptoms at night. 

When you or your family members have a troubling fever, trust your instincts if you think something is wrong, then call your paediatrician or family doctor for advice.