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The authors note that previous studies have shown a "trough" or low period of human performance in the earlyi morning hours between 2 a.m. and 6 a.m., presumably related to the body's daily rhythm. They also note that various studies have shown this can be partially relieved by measures such as taking naps, exposure to bright light, and taking stimulants such as caffeine.Their question is whether a combination of measures could completely relieve this performance loss. Among the measures just mentioned, caffeine--thought to act by antagonizing the brain hormone adenosine--and bright light--thought to act by suppressing melatonin secretion and increasing body temperature--involve different mechanisms of action which might yield additive effects.
They used as subjects 46 healthy young adult men (ages 18-25) who were studied during 45 1/2 hours of sleep deprivation,monitored in the laboratory where they spent 2 1/2 days. Subjects were low to moderate caffeine users (50-200 mg/day) who were instructed to avoid caffeine and alcohol for 24 hours prior to the study.
Subjects were randomly assigned to one of four conditions: (1) Dim Light (no more than 100 lux) and placebo (no caffeine); (2) Bright Light (2500 lux) and placebo; (3) Dim Light and caffeine (200 mg and (4) Bright Light with caffeine. The caffeine or placebo was administered at 10 p.m. and 2 a.m.
Performance tasks included a variety of tests measuring vigilance, reaction time, memory, calculation. At the beginning of the study subjects practised these tests until they showed no further improvement as a result of practice.Also used were the Maintenance of Wakefulness Test, the Stanford Sleepiness Scale, and spectral analysis of the EEG as measures of sleepiness.
Without reviewing in detail results on each performance task, I will simply refer to the authors' observation that performance become worse from the beginning to the end of each night and from the first night to the second. Caffeine alone enhanced performance for most tasks, while Bright Light enhanced performance for certain tasks, and the combined Bright Light-Caffeine treatment yielded the most powerful performance enhancing effect, actually preventing the performance drop usual during the early-morning hours. On the Maintenance of Wakefulness Test, caffeine yielded higher alertness than placebo, more markedly so on the second night than the first.The alerting effects of caffeine (given at 2 a.m.) carried over to testing the next morning at 9:15 a.m. There was a trend to a similar effect of Bright Light. The Stanford sleepiness scale showed reduction of subjective sleepiness with both caffeine and Bright Light. However, no consistent patterns of EEG arousal were observed for any of the treatments.
Generally, the authors noted that Caffeine alone had stronger effects than Bright Light alone, but the combination yielded still stronger effects than either measure by itself. Whereas some researchers have reported an exhaustion of the caffeine effect on the second night of sleep deprivation, this study showed that it was maintained and even improved the second night, perhaps because of the particular timing of caffeine administration in this study--the 10 p.m. dose, occurring earlier than in other studies, came just before the usual onset of melatonin secretion and near the usual time of body temperature peak. They noted that other research suggests higher doses of caffeine may be necessary to counteract longer intervals of sleep deprivation than they studied. They also noted that the effects of Bright Light, presumably mediated via suppression of melatonin and reduction of the usual nighttime fall of body temperature, appears to be limited to the nighttime hours, whereas caffeine exerts its effects throughout the 24-hour day. Some think that, with extended use at high doses, caffeine may not only lose its effectiveness but even have countertherapeutic effects, perhaps by adding to sleep disruption; but I am not aware of this hypothesis being well founded in data. Few heavy caffeine users among sleep apneics complain of inability to sleep. Even if caffeine has lost much of its efficacy for them, it may still play a role at peak levels when they are timed to help the patient through tasks demanding high levels of attention--such as a group meeting at work, or a long drive. This study doesn't begin to address these issues, aside from its clear-cut demonstration of beneficial effects of caffeine in countering the negative effects of sleep deprivation on alertness and performance over a two-day interval. However, it does set the stage for longer-term studies in patient groups. Such mundane measures as coffee used by almost everyone to improve alertness have received much less study than medically sanctioned treatments such as CPAP and prescription stimulants, but may play an important role nonetheless.
The therapeutic potential of Bright Light is well known in the field of seasonal affective disorders, meaning mostly winter depressions, but it may be little known in the context of other sleep disorders except for those that involve mechanisms like phase delay or phase advance of the sleep-wake cycle. The limitation of its effects to the dark hours of the day puts a significant limitation on its usefulness for those who suffer mainly excessive daytime sleepiness from their sleep apnea. However, it may be of value to them in certain specific situations. The onset of melatonin secretion, associated with drowsiness prior to nighttime sleep, may vary considerably in timing from one individual to another. Ordinarily the early evening hours represent a period of enhanced alertness in the daily cycle, in sleep apneics as well as normals. However, some sleep apneics who may find themselves getting drowsy again too early in the evening, say 8 or 9 p.m., might find the use of bright (that is, very bright) light as they attempt to continue working, by delaying onset of melatonin secretion. Furthermore, many sleep apneics have difficulty getting up in the morning, especially if their work requires early rising. While they may well turn on the light at their bedside, the light resulting is far from the kind of bright light described as therapeutic in this study. For these people, it might be helpful to enhance the bedside lighting, as with a couple of strong spotlights attached to the wall by the bed, perhaps timing them to the alarm. For those who are capable of it, a similar or even greater degree of light exposure can be achieved simply by taking a short early-morning walk (after one's coffee).
Doctors should become more aware, with other patients as well as sleep apneics, that there is a strong wish in many people to experience some degree of control over their own symptoms, not just by taking medication or using a medical apparatus, but by taking measures that are freely available to them and offer some sense of autonomy, like taking "vitamins" as some over-the-counter substances are labelled which are not vitamins at all but quite active chemicals (like melatonin). It is highly desirable for controlled medical research to encompass these "self-help" measures which are so important to many patients, rather than limiting studies mostly to treatments which are exclusively "medical" and under the primary control of professionals.
The authors of this paper studied normal young men, and their application of their findings appears directed towards helping people who must adapt to episodic shift work at night, using Bright Light and Caffeine to keep their performance up. There is no reference made to sleep apnea.
However, I thought this article of potential interest to sleep apneics for several reasons. First of all, use of caffeine--while widespread in the general population--seems especially high among people with sleep disorders causing excessive daytime sleepiness, for obvious reasons. In fact, prescription stimulants are also used in their treatment, though more often for narcolepsy than for sleep apneics, where the use of caffeine probably represents an unwitting self-treatment long before the disease is diagnosed. Given its common use in very high doses in sleep apneics, the role of caffeine deserves closer examination at such dosage over extended periods of time. It seems clear enough that some tolerance develops, leading to their high doses, and that physical dependence can ensue, leading to withdrawal symptoms such as headaches when caffeine is abruptly discontinued.
The therapeutic potential of Bright Light is well known in the field of seasonal affective disorders, meaning mostly winter depressions, but it may be little known in the context of other sleep disorders except for those that involve mechanisms like phase delay or phase advance of the sleep-wake cycle. The limitation of its effects to the dark hours of the day puts a significant limitation on its usefulness for those who suffer mainly excessive daytime sleepiness from their sleep apnea. However, it may be of value to them in certain specific situations. The onset of melatonin secretion, associated with drowsiness prior to nighttime sleep, may vary considerably in timing from one individual to another. Ordinarily the early evening hours represent a period of enhanced alertness in the daily cycle, in sleep apneics as well as normals. However, some sleep apneics who may find themselves getting drowsy again too early in the evening, say 8 or 9 p.m., might find the use of bright (that is, very bright) light as they attempt to continue working, by delaying onset of melatonin secretion. Furthermore, many sleep apneics have difficulty getting up in the morning, especially if their work requires early rising. While they may well turn on the light at their bedside, the light resulting is far from the kind of bright light described as therapeutic in this study. For these people, it might be helpful to enhance the bedside lighting, as with a couple of strong spotlights attached to the wall by the bed, perhaps timing them to the alarm. For those who are capable of it, a similar or even greater degree of light exposure can be achieved simply by taking a short early-morning walk (after one's coffee).
Doctors should become more aware, with other patients as well as sleep apneics, that there is a strong wish in many people to experience some degree of control over their own symptoms, not just by taking medication or using a medical apparatus, but by taking measures that are freely available to them and offer some sense of autonomy, like taking "vitamins" as some over-the-counter substances are labelled which are not vitamins at all but quite active chemicals (like melatonin). It is highly desirable for controlled medical research to encompass these "self-help" measures which are so important to many patients, rather than limiting studies mostly to treatments which are exclusively "medical" and under the primary control of professionals.
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