By now, we’re all used to hearing sleep is important for overall wellness. Oftentimes, quality sleep is linked to deep sleep, but sleep latency is just as important. According to the Sleep Foundation, sleep latency is defined by how long it takes a person to fall asleep. Falling asleep between 20 to 30 minutes is considered too long and may be a sign of insomnia (via Verywell Health). Alternatively, if you’re asleep once your head hits the pillow, the culprit may be a sleep disorder or excessive sleepiness (via Verywell Health).
Different factors affect how fast you doze off during the night. Alcohol, chronic pain, certain medications, napping, and age can all impact sleep latency (per Sleep Foundation). However, the biggest factor responsible for sleepiness is the neurotransmitter adenosine, points out Verywell Health. This is because adenosine influences the sleep and wake centers of the brain by encouraging arousal during wakefulness (via Journal of Neurochemistry). When levels are high, it encourages arousal (which is during wakefulness), but when the adenosine levels decrease, it promotes sleepiness.
Excessive sleepiness is problematic. It can be a signal you’re lacking proper sleep due to waking up often throughout the night. Additionally, it’s linked to other major health conditions like sleep deprivation, sleep apnea, and narcolepsy (via Verywell Health).
How does falling asleep quickly affect your sleep cycle and health?
Each night, your body goes through a series of sleep cycles — four, to be exact. It takes 90 to 120 minutes for your body to move through all stages of sleep (via Sleep Foundation). Stages one through three are considered non-rapid eye movement (NREM) sleep and are where you spend the majority of your sleep cycle (via Sleep Foundation). Stage four — rapid eye movement (REM) sleep — usually takes about 90 minutes to reach and lasts about ten minutes. However, it gradually increases throughout the night with each cycle (per WebMD).
When you fall asleep too quickly or too slowly, it may take you longer to reach stage four sleep, according to the Sleep Foundation. This affects how rested you feel and can prohibit you from getting quality REM sleep. Not getting enough sleep on multiple nights can even create a sleep debt, which can negatively affect cognitive and physical health (per Sleep Foundation).
One way to measure sleep latency is to monitor the sleep cycle from wakefulness to sleep. According to Healthline, there are two tests that measure this: the multiple sleep latency test (MSLT), also known as a nap study, and a polysomnography (PSG), an overnight sleep study. Talk to your doctor if you’re experiencing excessive tiredness.
