Circadian Rhythms — Another Of Nature's Wonders
January 2, 2018 at 4:56 p.m.
By Max [email protected]
This sparked my interest, and I began to investigate other effects the "biological clock" or "circadian rhythms" have on our well-being. (I will use the terms interchangeably.)
Scientists are increasingly finding new ways circadian rhythms affect us. For example, circadian rhythms can influence hormone release, eating habits, digestion, body temperature, sleep and even the sense of smell. Disruption in circadian rhythms can lead to the increased incidence of many diseases, including metabolic disease and cancer.
My experience and knowledge about the subject was limited to jet lag, a recognized sleep disorder I suffered from traveling to the west coast or to Europe, and more recently, chronotherapeutics, a topic of interest to prescribers, pharmacists and patients.
According to the National Institutes of Health, circadian rhythms are physical, mental and behavior changes that follow a daily cycle. They respond primarily to light and darkness in an organism's environment, and they are found in most living things. Circadian rhythms can be thought of as part of a biological clock, an innate timing device composed of specific proteins that interact with cells throughout the body. The possession of some form of clock permits organisms to optimize physiology and behavior in advance of the varied demands of the day/night cycle. Such internally generated daily rhythms are given the name circadian rhythms from the Latin circa (about) and dies (day).
Jet lag is a recognized sleep disorder that results from crossing time zones too rapidly for the circadian rhythms to keep pace. They are normally synchronized to the solar light-dark cycle and promote alertness during the day and sleep at night. Unfortunately, the clock is slow to reset, so that after time zones have been crossed, the signals for sleep and wakefulness do not match the local light-dark and social schedules. The incidence of jet lag disorder is unknown, but it presumably affects a large proportion of the more than 30 million travelers who embark from the United States each year for destinations that necessitate flights across five or more time zones.
For most people, it is more difficult to travel east than west because the internal factors of the biological clock are typically longer than 24 hours and it is easier to lengthen the day than to shorten it. Tolerance to the effects of jet lag appear to decrease with increasing age. Symptoms of jet lag include insomnia and daytime sleepiness, diminished physical performance (travel fatigue), cognitive (the ability to think) impairment and gastrointestinal disturbances. Travel fatigue can be reversed within a day or two with adequate diet, rest and sleep, but other symptoms persist until the circadian rhythm is realigned.
Disturbances in circadian rhythms can also occur when workers change shifts and are associated with blindness. Night workers can have almost continuous jet lag symptoms, potentially leading to insomnia, heart disease, obesity and diabetes. Melatonin, a natural hormone that plays a role in sleep, may help these conditions, but there is a lack of long-term studies to prove safety for extended use.
Chronotherapeutics or chronotherapy is a relatively recent addition to pharmacy practice based on circadian rhythms. Researchers have found that giving some drugs at specific times can improve effectiveness and reduce side effects. One study, for example, found that higher levels of anti-flu antibodies are produced when vaccinations are given in the morning. Cholesterol-lowering drugs are most effective when taken at bedtime, and the Food and Drug Administration recommends administering them at night.
Chronotherapy is particularly useful when considering the time for administering drugs used to treat cancer. Timing their regimen can significantly affect their toxicity and effectiveness. One example is the drug cisplatin. It has been found that giving the drug at the time of day when the patient's urinary output is highest reduces the effect on the kidneys.
Cancer is not the only disease likely to be affected by the biological clock. Clinical trials have shown antihistamines are most effective when taken at night or early in the morning. Other studies established that inhaling corticosteroids at bedtime is most effective in combating allergy symptoms. Certain drugs used for high blood pressure should also be taken at night rather than in the morning. Ask your pharmacist for advice.
Of course, synchronizing medications to the biological clock is easier said than done, as not everyone's rhythms are the same.
One thing is certain: Any clinical study for a drug should consider the time it is given.
Max Sherman is a medical writer and pharmacist retired from the medical device industry. He has taught college courses on regulatory and compliance issues at Ivy Tech, Grace College and Butler University. Sherman has an unquenchable thirst for knowledge on all levels. Eclectic Science, the title of his column, touches on famed doctors and scientists, human senses, aging, various diseases, and little-known facts about many species, including their contributions to scientific research. He can be reached by email at [email protected].
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This sparked my interest, and I began to investigate other effects the "biological clock" or "circadian rhythms" have on our well-being. (I will use the terms interchangeably.)
Scientists are increasingly finding new ways circadian rhythms affect us. For example, circadian rhythms can influence hormone release, eating habits, digestion, body temperature, sleep and even the sense of smell. Disruption in circadian rhythms can lead to the increased incidence of many diseases, including metabolic disease and cancer.
My experience and knowledge about the subject was limited to jet lag, a recognized sleep disorder I suffered from traveling to the west coast or to Europe, and more recently, chronotherapeutics, a topic of interest to prescribers, pharmacists and patients.
According to the National Institutes of Health, circadian rhythms are physical, mental and behavior changes that follow a daily cycle. They respond primarily to light and darkness in an organism's environment, and they are found in most living things. Circadian rhythms can be thought of as part of a biological clock, an innate timing device composed of specific proteins that interact with cells throughout the body. The possession of some form of clock permits organisms to optimize physiology and behavior in advance of the varied demands of the day/night cycle. Such internally generated daily rhythms are given the name circadian rhythms from the Latin circa (about) and dies (day).
Jet lag is a recognized sleep disorder that results from crossing time zones too rapidly for the circadian rhythms to keep pace. They are normally synchronized to the solar light-dark cycle and promote alertness during the day and sleep at night. Unfortunately, the clock is slow to reset, so that after time zones have been crossed, the signals for sleep and wakefulness do not match the local light-dark and social schedules. The incidence of jet lag disorder is unknown, but it presumably affects a large proportion of the more than 30 million travelers who embark from the United States each year for destinations that necessitate flights across five or more time zones.
For most people, it is more difficult to travel east than west because the internal factors of the biological clock are typically longer than 24 hours and it is easier to lengthen the day than to shorten it. Tolerance to the effects of jet lag appear to decrease with increasing age. Symptoms of jet lag include insomnia and daytime sleepiness, diminished physical performance (travel fatigue), cognitive (the ability to think) impairment and gastrointestinal disturbances. Travel fatigue can be reversed within a day or two with adequate diet, rest and sleep, but other symptoms persist until the circadian rhythm is realigned.
Disturbances in circadian rhythms can also occur when workers change shifts and are associated with blindness. Night workers can have almost continuous jet lag symptoms, potentially leading to insomnia, heart disease, obesity and diabetes. Melatonin, a natural hormone that plays a role in sleep, may help these conditions, but there is a lack of long-term studies to prove safety for extended use.
Chronotherapeutics or chronotherapy is a relatively recent addition to pharmacy practice based on circadian rhythms. Researchers have found that giving some drugs at specific times can improve effectiveness and reduce side effects. One study, for example, found that higher levels of anti-flu antibodies are produced when vaccinations are given in the morning. Cholesterol-lowering drugs are most effective when taken at bedtime, and the Food and Drug Administration recommends administering them at night.
Chronotherapy is particularly useful when considering the time for administering drugs used to treat cancer. Timing their regimen can significantly affect their toxicity and effectiveness. One example is the drug cisplatin. It has been found that giving the drug at the time of day when the patient's urinary output is highest reduces the effect on the kidneys.
Cancer is not the only disease likely to be affected by the biological clock. Clinical trials have shown antihistamines are most effective when taken at night or early in the morning. Other studies established that inhaling corticosteroids at bedtime is most effective in combating allergy symptoms. Certain drugs used for high blood pressure should also be taken at night rather than in the morning. Ask your pharmacist for advice.
Of course, synchronizing medications to the biological clock is easier said than done, as not everyone's rhythms are the same.
One thing is certain: Any clinical study for a drug should consider the time it is given.
Max Sherman is a medical writer and pharmacist retired from the medical device industry. He has taught college courses on regulatory and compliance issues at Ivy Tech, Grace College and Butler University. Sherman has an unquenchable thirst for knowledge on all levels. Eclectic Science, the title of his column, touches on famed doctors and scientists, human senses, aging, various diseases, and little-known facts about many species, including their contributions to scientific research. He can be reached by email at [email protected].
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