Depending on the length of duration, fatigue is divided into 3 categories. ‘Acute fatigue’ that is recovered overnight, ‘subacute fatigue’ that lasts around 1 week, ‘chronic fatigue’ that lasts more than 6 months.
When fatigue continues, it is because the body hasn’t rested properly. During night time, parasympathetic nerve activity increases and gets ready for sleep, and if brain fatigue gets accumulated the sympathetic nerves stays activated, making it hard to fall asleep. This is why people suffer from situations like “unable to fall asleep despite being tired”.
if chronic fatigue continues, risk of circulatory diseases like hypertension, angina, cardiac infarction, digestive diseases like stomach and duodenum ulcers increases and immunity decreases, making it easier to get infectious diseases like cold or influenza. Cancer incidence especially increases. Generally, cancer cells are removed by the body’s immune system, but when immunity decrease, an environment favoring cancer cells is generated. Also, chronic brain fatigue has a negative effect on mental health. A person’s normal mental state is maintained by
a balanced secretion of neurotransmitters like dopamine, serotonin, and noradrenaline. When brain fatigue is accumulated, neurotransmitter secretion is disturbed, and the risk of psychical disorders like lethargy or depression increases.
Some people claim that they don’t get tired because they have strong willpower and less stress, but this is never true.
People who address every situation with an optimistic mind seem like they don’t get tired, but this is only because they are in an “excited” state, hence unable to feel tired. Dopamine, which brings pleasure, is released when motivation and sense of accomplishment activate the brain. Dopamine suppresses pain, and when it is released in vast amounts, one cannot feel “tiredness”.
If someone works without resting and is always fully motivated, we must question “hidden fatigue”’
something that the person himself/herself can’t even acknowledge. If one can’t detect tiredness, they are likely to overwork without resting. The reason why cases where a healthy person collapses without any forewarning occur often is because the accumulated hidden tiredness has, so-called, exploded.