Sleepiness can be defined as a form of fatigue in which a person’s likelihood of falling asleep is increased. It’s familiar to everyone, daily, predictable and desirable phenomenon when it occurs right before bedtime. However, it is not uncommon that sleepiness and, more generally, fatigue occur during awake times, which may adversely affect performance and quality of life. In this article, we aim to provide practical guidelines for the evaluation and examination of these patients.
Patients seeking medical attention usually refer to the problem of their alertness as fatigue, which could be more generally characterized as a subjectively experienced unsatisfactory alertness. The concept of fatigue is inconsistent in different languages and also in the scientific literature, which is reflected in the additional difficulty in clinical work. For example, in other studies, patients have often been asked about the occurrence of “compulsive falling asleep,” a phenomenon that is difficult to discern, since the tendency does not have to be manifested (each time).
In practical work, it is good to divide fatigue patients into two main groups: those with no increased risk of falling asleep (often the main problem is insomnia and not drowsiness), and those with an increased likelihood of falling asleep (ie, excessive daytime sleepiness). In the first group, the following are common: increased psychophysiological activation associated with various factors and psychological and psychiatric causes. In the latter group of people suffering from sleepiness, common or otherwise relevant causes are listed in Table A.
Factors that may be associated with an increased likelihood of falling asleep.
- Lack of sleep
- Poor sleep hygiene
- Use of intoxicants
- Irregular sleep or sleep pattern transitions
- Recurrent symptoms that interfere with sleep (eg pain, heartburn, nocturnal or dyspnoea)
- Diseases that affect the general condition
- Many medicines
- Psychiatric disorders
- Many brain diseases
- Recurrent episodes of seizures during sleep (eg epilepsy or some parasomnias)
- Narcolepsy and idiopathic and periodic hypersomnia sleep disorders
- Breathing problems during sleep
Different types of sleepiness: what is normal, what is excessive?
The extreme form of drowsiness can be considered as falling asleep. However, it is not the only clinically relevant manifestation of somnolence. Falling asleep is usually preceded by a subjective feeling of loss of alertness. It may include, for example, difficulty in attentiveness and concentration, and impaired environmental perception, memory and reasoning, and reaction speed. The alertness can fluctuate for a longer period at the border of sleep and being awake, which can result in “microsleep” that can last for only few seconds. There may still be tens of minutes of automation, so that the poorly managed action continues and there will be no memory of the events of that time. An example of this is, for example, a sleepy housewife who finds dirty laundry in the fridge and groceries in the washing machine without ever remembering how they got there. In children, on the other hand, sleepiness can paradoxically manifest itself as overactivity.
After falling asleep, somnolence may appear as an abnormal length or depth of sleep. Typical symptoms of actual hypersomnias (eg, idiopathic hypersomnia) are long and continuous nights sleep. Even in the morning, waking up the patient is difficult and it can take up to hours to reach a more refreshed state.
Also confusional arousals can occur.
It is not easy to set boundaries for normal and excessive or abnormal sleepiness. The ability of people to stay awake and refreshed varies greatly. It is influenced by both individual (eg motivation) and situational factors (eg environmental stimulus). Situations that develop symptoms can be used as guidelines. Mild drowsiness may occur, for example, when watching TV, reading or traveling. Moderate drowsiness may occur at meetings, concerts, or while driving. These situations are not always to be considered abnormal, especially if they occur occasionally and include, for example, sleep deprivation, (heavy) meals, alcohol or a warm environment, or if the symptom occurs in the afternoon. Severe drowsiness may occur while eg. eating, talking, walking. For example, fatigue in a narcolepsy patient has been compared to a condition that results from a healthy person being awake continuously for 48-72 hours.
“I love sleep. My life has the tendency to fall apart when I’m awake, you know?”
How sleepiness is being measured?
The measurement of wakefulness, including sleepiness, begins with the patient’s subjective evaluation, and it is good to use systematic methods. A good overview of the situation is provided by a sleep journal held for at least a week or two. Occasionally used questionnaires look at phenomena related to wakefulness and sleep, among others. frequency of fatigue and falling asleep (“every day or almost every day”, “3-5 days a week”, “1-2 days a week”, “less than once a week”, “less than once a month or never”). The Epworth Sleepiness Scale, which has been in use for about ten years, has proved useful (Table 2). Its correlation with the best-validated objective sleep test for multiple sleep latency test (mslt) is quite good. Sleep delay test is a clinical neurophysiological, polygraphic method for registering alertness that can measure the time taken to fall asleep. Registration is done with the patient lying down in a dark, soundproofed examination room every two hours, 4-5 times during the same day. The key test result is expressed as an average of the occurrence of S1 sleep phases. If the patient does not fall asleep, a sleep delay of 20 minutes is noted.
Although the sleep delay test is the best of the diagnostic measurement methods, there are several limitations to its usefulness. It is laborious process and has limited availability. The test gives you instructions to try to fall asleep, so fatigue mainly reflects the ability to fall asleep, which also varies a lot between people. Some people have a good ability to relax and they can fall asleep exceptionally fast in a in a peaceful environment, but also can remain awake without difficulty unless, for example, sleep deprivation contributes. For these people, the “pathological” result of the sleep delay test cannot be considered significant. On the other hand, for example, pain (such as caffeine withdrawal headaches) or distraction associated with the registration situation (high tension, heat or noise) may significantly change the registration result.
Reliable and useful use of the sleep delay test as an aid in clinical work requires experience in practical implementation, interpretation of the measurement result and its clinical evaluation. Patients should not have any medication or irregularities in sleep patterns that may affect the outcome. According to international recommendations, it would be ideal to do a sleep polysomnography the previous night, so that the length and structure of sleep are known when evaluating the sleep delay test and its reliability. This is not always possible, and often the diagnostic value of an expensive sleep delay test remains questionable.
How to interpret the sleep delay test result?
It is generally accepted that an average sleep delay of less than five minutes is abnormal and a delay of more than ten minutes as normal. There are no general guidelines for interpreting averages between 5 to 10 minute delays, but their importance should be evaluated on a patient-by-patient basis. In one study, the limit for normal sleep delay was set at eight minutes in healthy middle-aged men.
The reverse version of the sleep delay test, the maintenance of wakefulness test (MWT), has also been increasingly used in recent years. In Maintenance of Wakefulness Test (MWT), the patient is in a dimly lit room in a semi-sitting position and is instructed to try to stay awake. Otherwise, it is essentially equivalent to a sleep delay test. Maintenance of Wakefulness Test has even been found to be more useful than the sleep delay test, for example, in measuring drug response and driving ability assessment. The problem with diagnostic use, however, is that this test is not as well validated, the reference values are less well established, and it does not usually detect REM sleep, which is important for narcolepsy diagnosis (although the finding is not very specific).
Summary of excessive sleepiness
The basis for assessing fatigue and somnolence are accurate symptom analysis and thorough examination of the patient’s state of health, habits, and life. It is a good idea to use the type of situation and how frequently the person experiences symptoms as guidelines for assessing excess and abnormality. It is important to consider the possibility of sleep deprivation and to evaluate its contribution to the development of symptoms of fatigue. For one night alone, 1-2 hours of sleep deprivation may have a significant impact on the alertness of the following day. Further examinations should be considered individually. In particular, use of the sleep delay test must be accurate and bear in mind its limitations, especially if the previous night’s sleep is not confirmed by sleep polysomnography.
The question “when sleepiness is excessive” could briefly be answered as referring to the difficulty of maintaining a state of alertness sufficient to function and quality of life in the ordinary work environment after a normal night’s sleep.