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For several decades, scientists have been accumulating knowledge about circadian rhythms, the daily ups and downs of our metabolic processes. Only recently, however, have they returned to the time honored concept of chronotherapy to help people get well.
Whether someone has high blood pressure or not, stroke is more likely to occur during the late afternoon or early evening. Strokes, both ischemic (caused by blood clots) and hemorrhagic (caused by bleeding vessels in the brain) are rare at night.
Pulmonary embolism (blood clots in the lungs) and deep vein thrombosis (DVT) are most likely between ten in the morning and one in the afternoon. Death from pulmonary embolism, however, is most likely to occur earlier in the morning, after waking up.
A dripping nose (rhinorrhea) is one of the more troubling symptoms of colds and seasonal allergies. Runny nose is most likely to occur in the evening, and just after you want to go to sleep, and then again in the morning. The nasal "spigot" gets turned off, usually, during the middle of the day. Knowing this tells you that the best time to take an antihistamine, particularly if it is going to make you sleep, is an hour or two before bedtime.
Asthma, chronic brochitis, emphysema, and chronic obstructive pulmonary disease tend to follow a course strangely similar to Traditional Chinese Medicine's "time of the lungs," between three and five in the morning. Four in the morning is prime time for asthma attacks. COPD symptoms tend to be worst between midnight and eight in the morning.
At night, the kidneys produce a hormone called vasopressin. This reduces urine production, so we can sleep undisturbed. When there is an urge to urinate at night, there could be a hormonal disturbance, but there is more likely to be a problem with sleep apnea, which forces more blood flow through the kidneys, resulting in greater urine production, urinary tract infection, or, in men, prostate disease.
The stomach uses acid to digest food. For that reason, stomach acidity is greater when we have not eaten recently, which for most of us is after midnight. If you are prone to gastroesophageal reflux disease symptoms, the most severe acid burns will come at night. GERD tends to come in "daytime" or "nighttime" patterns, depending on the degree to which anatomical features cause the disease. If the fundamental problem is that there is just too much pressure on the stomach, heartburn and GERD will tend to manifest themselves shortly after eating. If the problem is more hormonal in nature, the symptoms will tend to occur at night.
Infections And Fever
Viral infections tend to cause higher fevers in the afternoon, especially between four and eight o'clock. Bacterial infections tend to cause higher fever in the morning, especially between six and ten o'clock.
The stress hormone cortisol is the body's way of relieving the constant inflammation causes by allergies, arthritis, eczema, and psoriasis. When cortisol levels are lower, especially at night, pain, swelling, itching and redness tend to be worse. Medications should be timed to relieve nighttime symptoms.