Lack of Sleep, Fatigue and Attention Disorders; How Can We Tell Them Apart?

Sleep consists of cycles that include different stages, among them NREM sleep and REM sleep.

During deep NREM sleep, also called slow-wave sleep, processes important for stabilizing memories and organizing information acquired during the day take place. During REM sleep, characterized by distinctive brain activity and vivid dreams, processes related to memory processing, learning and emotional experience occur.

Both types of sleep contribute to brain functioning, and no single stage is solely responsible for memory or emotional regulation.

During the day, the brain takes in enormous amounts of information, but not every detail is retained in long-term memory. During sleep, memory consolidation processes take place, in which neural representations of learned information are strengthened, changed and integrated into existing knowledge. Research points to an important role for communication between the hippocampus, which is involved in forming new memories, and areas of the cerebral cortex. Therefore, good-quality sleep after learning may improve the ability to remember and use information later.

During sleep, physiological processes occur that help maintain the functioning of the nervous system. One of these involves clearing metabolic waste products from brain tissue, partly through the movement of fluids in a system called the glymphatic system. Research, mainly in animals, indicates a connection between sleep and the activity of this system. However, the extent of its activity and the precise mechanisms in humans are still being studied.

In addition, sleep participates in regulating the activity of neural connections and maintaining a balance between processes of arousal and recovery.

Sleep deprivation particularly affects functions that require sustained alertness, cognitive control and decision-making. When a person is tired, their ability to maintain attention over time decreases, reaction time may lengthen and the risk of errors increases. The ability to inhibit responses and consider alternatives may also be impaired. During significant tiredness, brief moments of reduced alertness may occur, sometimes called microsleeps, in which the brain struggles to maintain continuous attention. From the outside, the result may look like distractibility or impulsivity, even though the main cause is lack of sleep.

Sleep also affects how the brain processes and regulates emotional responses.

Research suggests that sleep deprivation may affect the activity of the amygdala, which is involved in identifying and responding to emotionally significant stimuli, and its communication with prefrontal areas that participate in emotional control. As a result, a tired person may be more sensitive to frustration, react intensely to everyday situations and struggle to recover from an unpleasant experience. In children, tiredness may instead manifest as irritability, restlessness and outbursts, rather than necessarily as a desire to sleep.

The connection between ADHD and sleep difficulties is complex.

Some people with ADHD experience difficulty falling asleep, delayed bedtimes, irregular sleep schedules or a feeling of alertness specifically in the evening. Sometimes there is also a tendency toward a later biological clock, which affects the ability to fall asleep and wake up at conventional times. Conversely, lack of sleep can worsen existing attention symptoms and impair everyday functioning. It is also important to examine possible effects of medication, sleep habits and co-occurring sleep disorders.

One way to understand the source of the difficulty is to examine the relationship between sleep patterns and functioning.

When concentration difficulties occur mainly after a period of insufficient sleep and improve with regular sleep, this may indicate that sleep deprivation contributes significantly. By contrast, ADHD is a neurodevelopmental disorder, so a professional evaluation looks for evidence of a pattern of difficulties that began in childhood and cannot be explained by tiredness alone. However, improvement following sleep does not rule out ADHD, because the two conditions may coexist.

Sleep needs vary according to age, health status and individual differences. The commonly accepted recommendations for sleep duration per day are:

• Children aged 6–12: approximately 9–12 hours.
• Teenagers aged 13–17: approximately 8–10 hours.
• Adults aged 18–64: usually 7–9 hours.

Sleep duration is not the only measure. Sleep continuity, quality and regularity of bedtimes and waking times also affect functioning.

When concentration difficulties are accompanied by persistent tiredness, daytime sleepiness, significant snoring, frequent awakenings or chronic difficulty falling asleep, it is important to consider a sleep assessment. Sometimes it is necessary to rule out disorders such as sleep apnea, disturbances in the timing of the biological clock or other medical conditions.

As part of an ADHD evaluation, information about sleep quality and habits is an important part of the clinical picture. A MOXO test may provide data about attention performance, but it cannot determine whether the difficulties are caused by lack of sleep.

The brain does not stop working when we fall asleep. It continues to process information, consolidate memories, regulate neural processes and support emotional and cognitive functioning. Good-quality sleep does not guarantee that there will be no attention difficulties, but it creates essential conditions for learning, concentration and optimal functioning.

Sometimes, before trying to improve concentration through more effort, it is worth checking whether the brain is receiving the basic conditions it needs to function.