Narcolepsy | Why Do I Feel Sleepy All The Time?

Excessive Daytime Sleepiness (EDS) is the primary and most debilitating symptom of narcolepsy. It manifests as a persistent and overwhelming feeling of sleepiness, regardless of the amount of sleep obtained the previous night. Individuals with EDS experience "sleep attacks," which are sudden, irresistible urges to sleep that can occur at any time, often in inappropriate situations such as during a conversation, while eating, or at work. This is not simply feeling tired; it is a profound neurological inability to maintain wakefulness. The underlying cause is a dysfunction in the brain's sleep-wake cycle regulation. Specifically, the brain fails to produce or utilize hypocretin (also known as orexin), a critical neurotransmitter responsible for promoting alertness and stabilizing wakefulness. Without sufficient hypocretin signaling, the boundary between being awake and asleep becomes blurred, allowing elements of sleep, particularly REM sleep, to intrude into waking hours. This results in the constant battle against sleep that defines the daily experience of a person with narcolepsy.

Cataplexy is a sudden and transient episode of muscle weakness or paralysis, triggered by strong emotions. Laughter, excitement, surprise, or even anger can cause an individual to lose muscle control, leading to effects ranging from a slight drooping of the eyelids or slackening of the jaw to a complete collapse of the body. Importantly, the person remains fully conscious and aware during the episode. Cataplexy is the most specific symptom of Type 1 narcolepsy and is directly linked to the loss of hypocretin neurons. It is essentially an intrusion of REM sleep atonia—the natural paralysis that occurs during REM sleep to prevent us from acting out our dreams—into a state of wakefulness. The emotional trigger stimulates the same brain pathways that control muscle tone during REM sleep, causing a sudden loss of voluntary muscle control while the individual is awake.

Hypnagogic hallucinations are vivid, dream-like experiences that occur as an individual is falling asleep, while hypnopompic hallucinations occur upon waking. These are not true dreams but rather dream elements intruding into a state of semi-consciousness. They can be visual, auditory, or tactile and are often bizarre or frightening. Sleep paralysis is the temporary inability to move or speak that occurs when waking up or falling asleep. The mind is awake, but the body remains in a state of atonia (muscle paralysis) characteristic of REM sleep. These two symptoms often occur together and are manifestations of the same underlying issue in narcolepsy: the disorganization of the sleep-wake cycle and the inappropriate intrusion of REM sleep features into wakefulness.

Although individuals with narcolepsy are excessively sleepy during the day, they paradoxically experience fragmented and poor-quality sleep at night. This is known as disrupted nighttime sleep. The same neurological instability that allows sleep to intrude into the day also allows wakefulness to intrude into the night. People with narcolepsy may wake up frequently throughout the night for no apparent reason. This fragmentation prevents them from cycling through the normal, restorative stages of sleep, contributing further to their daytime sleepiness. The brain's inability to maintain a consolidated state of either sleep or wakefulness is the central problem, leading to a 24-hour cycle of sleep-wake disarray.

The primary distinction between Narcolepsy Type 1 (NT1) and Narcolepsy Type 2 (NT2) lies in the presence or absence of cataplexy and the level of the neurotransmitter hypocretin. NT1 is diagnosed when a person experiences both excessive daytime sleepiness and definitive cataplexy. Alternatively, a diagnosis can be made if a person has low levels of hypocretin-1 in their cerebrospinal fluid, as measured by a spinal tap, even without cataplexy. NT1 is known to be an autoimmune disorder where the body's immune system mistakenly attacks and destroys the hypocretin-producing neurons in the hypothalamus. In contrast, Narcolepsy Type 2 is diagnosed when an individual has excessive daytime sleepiness but does not experience cataplexy. Their cerebrospinal fluid hypocretin levels are typically normal. The exact cause of NT2 is less understood, but it represents a disorder of sleep-wake regulation without the specific features of cataplexy and hypocretin deficiency that define NT1.