Good sleep is dependent upon a delicate balance of nervous system chemicals called neurotransmitters. When biological and environmental disturbances cause imbalances in these neurotransmitters, sleep issues occur. As the National Institute of Neurological Disorders and Stroke explains, the human brain progresses through many stages of sleep during the night. The first of these stages is called stage 1 or light sleep. During a typical night, the brain will revert through the stages and reach the light sleep stage several times. However, several internal and external factors can disrupt the sleep cycle and cause an individual to spend too much time in the light sleep stage.
In an attempt to protect humans from physical harm during their sleep, the brain evolved to prevent a complete shutdown of the senses during stressful situations. If a person feels threatened, the brain will remain alert. Anxiety serves as a defense mechanism by keeping the brain prepared to address sudden, external threats.
Though modern humans may experience few physical threats, they do experience other forms of anxiety that affect the brain in the same way. When the brain perceive a threat, whether real or imagined, the neurotransmitters that tell the brain to remain alert override the neurotransmitters that would allow the brain to relax in less stressful conditions. As a result, anxious thoughts may prevent the brain from progressing normally through the sleep stages.
Movement and sound
An active pet in the bedroom, a restless partner, or the sound of a police siren will alert the senses to activity and remind the sleeping brain that the person may be in danger. Though the alert brain will recognize a pet or a distant siren as harmless, the sleeping brain is less logical. The disturbance may cause the brain to revert to stage 1 sleep regardless of the source of the distraction.
When the human eye is exposed to sunlight, the optic nerve sends a signal to the pineal gland in the brain to decrease the production of a hormone called melatonin. As the level of melatonin decreases, alertness increases. Artificial light is known to inhibit melatonin production in the same way. Regarding one sleep study, WebMD states, “Exposure to room light during the usual hours of sleep suppressed melatonin levels by more than 50%.”
Age also significantly affects levels of melatonin production. According to WebMD, older adults naturally produce less melatonin. Therefore, older adults tend to sleep more lightly.
Having children to protect often triggers alertness in the human brain. From an evolutionary perspective, the human brain would naturally be more alert when offspring need protection. Many parents of young children will instinctively sleep lightly in case of physical threats. Also, because infants need assistance many times a night, the brain may have difficulty shutting down because of the conscious awareness that a sleep disturbance is approaching.
Remedies for the light sleeper
The light sleeper can take steps to correct many of the external and internal factors affecting sleep quality. White noise, isolation, and stress reduction techniques may help alleviate the effects of environmental sleep disturbances. However, if these measures do not improve sleep quality, the light sleeper should discuss the condition with a doctor or other sleep professional.