It can be taken for granted that to be awakened is disturbing. But what about those more frequent cases where there is noise intrusion, yet the sleeper sleeps on. Progress without price? Doctors are not so sure.
Starting about ten years ago, doctors began scientific studies of sleep. They discovered that we sleep in repeated cycles ranging from a shallow level to a deep level. They were even able to detect the all-important dream state, the REM (Rapid Eye Movement). Each level apparently contributes to the restorative function of sleep. For sleep to perform its restorative function, each sleeper must experience the complete sleep cycle, with the requisite number of minutes in each stage.
According to one Swiss medical researcher, Dr. H. R. Richter, "For complete recovery during the night and to guarantee full efficiency at work during the next day one needs six to eight hours of undisturbed sleep with approximately 1 to 1½ hours of dream state."
Without awakening the sleeper, noise stimuli will constrict his blood vessels, change his heart rate and muscular tone.
The effect of noise during sleep can be recorded and analyzed. To find out what noise does to the sleep stages, investigators use the electroencephalogram (EEG) to record the patterns of brain waves during sleep. According to Dr. Richter the EEG is the technique of choice for investigations into the question of whether traffic noise does affect the central nervous system, even when people imagine they have slept well and do not remember the nightly disturbances.
Noise does not have to be anywhere near a deafening 85 decibels to disturb the sleep stages. Even noise of a low intensity produces arousal reactions, and what is significant, prevents the sleeper from reaching the deep sleep stage.
Canadian researchers have sought a correlation between the noise level of a passing vehicle and the extent of arousal. Observations of changes in the brain wave patterns have shown that the deep sleep stage can be cut short by the passing of a single truck. The Canadian National Research Council's studies showed that some subjects may awaken "more than 50 per cent of the time at a peak noise level of the passing truck of 50 decibels...At 70 decibels the most probable reaction is to awaken..." Some sources recommend that interiors of bedrooms not exceed 30 or 35 decibels. The fact that such relatively low noise levels can so profoundly influence the sleeping state takes on great significance when one realizes that transportation modes and air conditioners expose millions of sleeping people to levels of 50 decibels and much higher.
According to Dr. Richter, the number of disturbances during the night may be even more important than the intensity of the noise. He observes that motor vehicles on expressways, which now are almost as busy at night as during the day, can disturb a sleeper at the rate of once every few seconds. He notes that the sleeper does not get used to irregular stimuli of short duration.
Summarizing the work of other investigators, he further states: "Sleep deprivation leads to psychic alterations, as irritability, tiredness, delirious and even paranoic states. Among others West and colleagues have studied the psychosis of sleep deprivation. They even suggest that long-term sleep deprivation may cause irreversible changes in the nervous system. Hartmann recently emphasized that most probably the lack of dreamstate is the main factor for these psychic abnormalities."
Studies have been made of prisoners subjected to "brainwashing." Extreme sleep deprivation created physical sensations such as itching and blurred vision, and mental symptoms ranging from mild memory lapses to hallucinations and actual psychoses. In a paper presented at the 1965 annual meeting of the Association for Research in Nervous and Mental Diseases, Dr. Louis J. West, Director of the Psychiatry Department of the University of Oklahoma, observed that during the Korean War, Air Force prisoners who gave false confessions had been awakened at irregular intervals and allowed to sleep only in snatches.
One reason the full impact of noise on civilian sleep and health has not been thoroughly examined is probably that patients suffering from subclinical sleep deprivation syndromes usually do not relate such vague symptoms as aches and pains, headaches, fatigue, visual disturbances, poor concentration, apathy and depression to disturbed sleep. Neither do these types of symptoms necessarily drive them to the doctor. If they do, unless the doctor is given information with which to understand the patient's sleep environment, he may not relate the symptoms to sleep deprivation, according to Dr. West.
The problem is that since the sleep-deprived individual is generally able to perform standard tasks and otherwise give the appearance of good health, the subtle effects of mild subclinical sleep deprivation syndrome go unnoticed. These include "subtle impairment of creative thinking, of imaginative and original approaches to the challenges of everyday life, of vigorous solutions to complex problems and other manifestations of the highest integrative neuro-biological functions." It would seem that long-term impairment of such abilities would be undetectable on the basis of a single test measurement, yet might be open to detection if performance levels were compared over a long period of time. This is another area in which research is needed.
In considering sleep deprivation, account must be taken of the impact of forcing everybody to wake up at 7:00 A.M., the typical hour for the beginning of legal noise nuisance. Doctors are beginning to find out that, metabolically, there actually are two types of individuals, day people and night people. Since each individual has his own sleep-waking rhythm, to force a "night person" to wake at a fixed hour in the morning is to deprive him of sleep. The forced loss of an hour's sleep in the morning may cause a number of internal physiological reactions that make the victim start his day tense and tired, observed Dr. A. Huwiler at the Baden-Baden meeting. Patients of his who lived near the Zurich airport were being awakened by the early-morning idling of aircraft. Dr. Huwiler acknowledged that there is no scientific proof of the connection between airport noise and patients' symptoms of fatigue, heart and circulatory changes, and the like, but he believes there is a good case for probability. Must we not find out?
Difficulty in falling asleep is associated with tension, resentment, or frustration. Noise may contribute to any or all of these emotional states. Dr. Edward F. Crippen, Deputy Health Commissioner of Detroit assigned to investigate that city's 1967 riots, suggested to the 95th Annual Meeting of the American Public Health AssocIation that part of the tension found in ghettoes may be attributable to interrupted sleep. "The din of the modern city," he said, includes "noises far above levels for optimum sleeping. Result: insomnia and instability."
One side effect of sleep deprivation is the resort to sleeping pills. "The use of, and addiction to sleep-inducing pills," states Dr. Richter, "has become a psychiatric problem of our modern times." Sleeping pills can be a harmful solution. Dr. West, who urges caution in the use of drugs for sleeping, has observed that true sleep must be distinguished from "barbiturate stupor." Some types of sleeping pills in themselves modify the natural sleep stages.
"Of all effects of noise," concluded England's conservative Wilson Committee, "repeated interference with sleep is least to be tolerated because prolonged loss of sleep is known to be injurious to health."