Sleep: An Introduction
Our body clock is a 24-hour internal clock that informs us when to eat, sleep, and wake up. External factors such as sunlight, darkness, and temperature have an impact on it. When it's dark outside, your eyes give a signal to your brain. Your brain then transmits a signal to your body to release melatonin, the hormone that helps make you sleepy and aids in the process of falling asleep. Melatonin is suppressed when it is light outside.
During the morning hours, Melatonin levels fall, and another hormone called Cortisol is released to help us wake up and be alert. Going to bed and waking up at roughly the same time helps keep the body clock and these hormones regular.
Understanding the Development of Baby Sleep
The body clock, aka circadian rhythm, of a newborn is immature. The circadian rhythm begins to develop gradually around 6 weeks, and the cycling of melatonin and cortisol does not occur until about 3 months of age. As a result, until about 3 months of age, a baby's sleep is erratic, irregular, and lacks a consistent concentration of sleep and waking. A baby will sleep both during the day and at night. They truly are unable to distinguish between the two.
Around 3 months old, when the circadian rhythm develops, a baby's sleep will consolidate more at night, and your baby will spend some more time being awake during the day.
The longer we stay awake, the stronger the desire to sleep becomes. Sleep stress is lowest in the morning after a good night's sleep and peaks at bedtime as it builds up. When we go to sleep for the night, our sleep pressure is reset. This is why some babies find it difficult with early morning wakings, which are much more difficult than bedtime struggles. After a long period of sleep, a baby's sleep pressure is reset, and their need for sleep has been reduced, allowing them to protest.
During the first six months of a baby's life, distinct sleep stages do not yet exist. Instead, they exhibit what are known as active and quiet sleep. The first stage is active sleep, which is equivalent to REM sleep, and a baby, like an adult, can be easily woken from REM sleep. Halfway through the cycle, the baby goes into quiet sleep, which is more difficult for him to wake up from.
Baby Sleep Stages
Stage 1 consists of very light sleep. When a baby first begins to nod off, his or her eyes are heavy and blink in and out. Baby appears to be dozing off.
Stage 2 consists of light sleep. Baby begins to disengage from his surroundings, but he is easily startled.
Stage 3 is deep sleep or slow wave sleep. This is the beginning of deep sleep. Brain waves are slow and are referred to as "delta waves," while faster waves are referred to as "beta waves." If the baby is awakened at this stage, he or she may be confused and groggy.
Stage 4 is the deepest stage of sleep. This is the most restorative and deepest stage of sleep. The heart rate slows, the muscles relax, and the breathing slows. The brain only displays delta waves. It is extremely difficult to rouse a baby from this stage of sleep. Certain hormones are released, which are necessary for the baby's growth and development, as well as muscle growth. The immune system is strengthened, and the bones grow and develop. The body does the majority of its repair and regeneration work in stages 3 and 4. This is also the stage at which older children experience night terrors and bedwetting. Some scientists combine stages 3 and 4 into a single stage.
Stage 5 is REM Sleep. This is the light, active sleep, when dreaming occurs. Energy is provided to the brain and body. Blood flow, breathing, and brain activity increases.
Understanding Baby Sleep Cycles
In between sleep cycles, a baby may have difficulty falling back asleep. When a baby transitions from deep sleep to light sleep, he or she may awaken and have difficulty falling back asleep, especially if the baby does not know how to fall asleep on their own.
This is why it is critical to teach independent sleeping skills. It is not uncommon for a baby who uses props to fall asleep after just one cycle. They may even fall asleep for 2-3 cycles and have trouble with the 4th for example. The reliance on props to fall asleep results in frequent night wakings and/or short naps.
The first REM sleep cycle of the night is the smallest. The night grows longer and longer as it goes on. This indicates that the baby is spending more time in a lighter stage of sleep. This is usually the cause of a baby's early morning wakings and difficulty falling back asleep. It is critical for a baby to learn independent sleep so he or she can return to sleep during the light stages of sleep in the early morning. Because REM, or dream sleep, dominates the latter half of our sleep as adults, this is usually why our dreams are so vivid when we wake up in the morning.
Babies transition in and out of sleep because their sleep cycles are so short. If a baby doesn't know how to transition independently, it can lead to many night wakings and crying out for the parent's help. Also, since babies spend more time in light sleep during the first few months of life, they are easily aroused. If a baby wakes, but knows how to fall back to sleep on their own, they can quickly and easily do this with minimal disruption to their sleep and parent's sleep.
Babies may appear to be sleeping, but they have been in a light sleep state for a long time. It takes about 20 minutes for a baby to fall asleep. Parents are frequently required to rock their baby for at least that amount of time before they can lay them down. A parent may report that they put their baby down to sleep after some rocking or feeding, but the baby immediately wakes up. Other parents report that they rock for 20-30 minutes and that their baby only sleeps for 30-45 minutes (or a sleep cycle).
Neither of these scenarios is ideal. It is best to place the baby down when he or she is awake and aware of his or her surroundings, so that he or she can fall asleep on their own and do the same.
Parents will also report that they lay baby down awake at bedtime, and baby falls asleep just fine, but then use a prop like feeding or rocking for middle of the night wakings. Baby usually falls asleep fine at bedtime because baby is exhausted from poor sleep, or has become dependent on props only for middle of the night wakings. Helping baby fall asleep on their own during the night will be important.
