People sleep nearly one third of their lives and infants sleep significantly more than adults (Franken, Kopp, Landolt, & Luthi, 2009). The function of sleep has hypothesized by different researchers; however, surprisingly there is no general consensus as to what the function and purpose of sleep actually is. It is known that sleep deprivation can have some serious consequences, especially in infants. The reason for this is that growth cycles as well as other developmental and functional processes occur in both the brain and body during sleep (Franken et al., 2009). Since getting adequate sleep is vital in infants it is important to understand their sleeping needs and patterns. In order to understand how to establish safe sleep patterns for children less than 18 months of age is important to understand the stages of sleep, the hypothetical functions of sleep, and the needs of infants regarding sleep at this stage of development.
Stages of Sleep
Normal sleep moving through cycles of rapid eye movement sleep (REM sleep) and non-REM sleep (e.g., slow brain wave sleep). During REM sleep infants will breathe more irregularly, experience twitches in their limbs, display rapid eye movements under closed eyes, and display increased heart rates and blood pressures. The core and limb muscles are actually paralyzed in REM sleep and the twitches or more reflexive (Franken et al., 2009). REM sleep is where most dreaming occurs and brain wave patterns resemble those occurring during wakefulness.
There are four stages of non-REM sleep aptly named stages one through four. Stages three and four are termed "slow-wave sleep" due to the appearance of markedly slower brain waves patterns (delta waves) in these stages. These are considered the deepest stages of sleep. Normally individuals begin at stage one and progress through the four stages to REM sleep and then the cycle repeats (Zepelin, Siegel, & Tobler, 2005).
Hypothetical Functions of Sleep
There is an increased need for sleep in infants observed in many species of mammals and there have been some hypothesized selective advantages regarding this. First, sleep is a reduced period of metabolism in both the brain and body where growth is more likely to occur (Zepelin et al., 2005). Secondly, a sleeping infant is less likely to attract predators and easier to transport across treacherous conditions (Franken et al., 2009). Mammalian infants typically are less well developed than the infants of other species. The cerebral cortex in these infants has not yet developed and there are limited opportunities for learning and interaction in the outside world and this could be another advantage to reduced waking periods (Zepelin et al., 2005).
Some of the above evolutionary explanations for sleep in infants do not appear to provide a sufficient explanation of the relative dominance of REM sleep in human neonates. For example REM sleep in infants under 18 months of age appears to take up about 50% of the total time these infants are asleep, whereas this percentage decreases in by adulthood is about 20% of total sleep time (Siegel, 2000). REM sleep may be involved in the prevention of endogenous activity that prevents altered sensory stimulation forming abnormal neural connections in the visual system (Zepelin et al., 2005), prevent pruning of critical neural connections that are not currently being stimulated (Franken et al., 2009), an important in developing neural connections involved in memory and other functions (Siegel, 2001).
Non-REM sleep appears to restore the body and this is where growth occurs (McNamara et al., 2010). For instance, growth hormones peak during delta sleep, the deepest stage of non-REM sleep. Since many of the restorative and developmental processes occur in non-REM sleep infants also need to get sufficient non-REM sleep.
Sleep Patterns in Infants
Surprisingly, the good number of sources that supply recommendations on how much sleep in the patterns of sleep that should be targeted for infants under 18 months of age did not get their information from empirical evidence but instead from parental reports regarding how much their infant children sleep (So, Adamson, & Horne, 2007). So et al. (2007) reported that infants under 18 months old slept an average of 16-17 hours daily. There is no good reason to think that average sleep times of large numbers of infants can apply to every single child. In addition, cultural variables also affect the total time that infants 18 months or younger sleep. The National Sleep Foundation reported that children in the United States appear to be getting less sleep than in the past prior to So et al.'s finding (National Sleep Foundation, 2004) and similar trends have been observed in other countries (Iglowstein, Jenni, Molinari, & Largo, 2003). This raises the question as to whether infants are getting the correct amount of sleep.
Some Guidelines Establishing Safe Sleep Patterns for Infants
One of the better empirical studies that can be useful to help to establish safe sleep patterns for infants came from Iglowstein et al. (2003) who tracked the sleeping patterns of nearly 500 children from birth to age 16. The researchers found that infants one month of age slept an average of about eight hours each night with over 95% of the babies getting between six and 13.5 hours of sleep at night, whereas the overall average sleep time for these infants was 14 to 15 hours of sleep.
When infants were three months old the average total sleep time remain between 14 and 15 hours; however they spend more time sleeping at night about 10 hours on average. At six months of age the average sleep time began to decline somewhat to about 14.2 hours with the average rate of nighttime sleep jumping to about 11 hours. From six months on the average overall sleep declined to about 13.6 total hours by 18 months of age but the amount of nighttime sleep appeared to remain fairly stable.
As can be observed from Iglowstein et al. (2003) sleep requirements for infants are to be met by daytime naps as well as nighttime sleep. Thus, safe and adequate sleeping patterns for infants include naps during the day time. In this study babies that were one-month-old slept an average of five to six hours in the daytime. There was quite a range of daytime napping with almost all the baby sleeping somewhere between two and nine hours during the day. By three months of age babies average slightly lower than five hours of daytime napping with most of them napping between one and eight hours during the day. By six months of age daytime napping had dropped off sharply to an average of slightly under three and one-half hours with the majority sleeping between 40 minutes and six and a half hours during the day. By the age of one year children slept on average about two and a half hours during the daytime, whereas by 18 months of age this was down to about an average of two hours of daytime napping, whereas nighttime sleep periods remain steady on average at around 11 hours.
From this data it appears that babies will initially require more napping during the daytime and will level off on their nighttime sleeping habits and about six months of age. Thus, a concerned parent should provide plenty of opportunity for child to sleep during the day and follow all the child's natural tendencies to stay up during the day while providing plenty of sleep time in the evening.
Some Special Concerns
Of course these patterns can only be used as guidelines. There are always some special caveats that parents should remember. For instance, cultural variables appear to have some affect on total sleep times for infants. In one study Asian were found to sleep and an average of two hours less than Caucasian babies, whereas in some European cultures infants sleep more than infants in America (Mindell, Sadeh, Kohyama, & How, 2010). This may reflect how different cultures view the need for sensory stimulation in their children. For example, Asian cultures may value more sensory stimulation, whereas Western European cultures may place more value on rest and rejuvenation.
Other factors such as individual differences in children will dictate how often and the pattern of sleeping that the child adopts. A general rule of thumb is to allow the child to sleep as much as they need to and to keep the child's schedule as regular as possible (Quillin & Glenn, 2004). Another factor that affects the sleeping patterns of children is whether or not the child is breast-fed or not. It appears that children that are breast-fed naturally do not sleep as much as children who are reared on formula (Quillin & Glenn, 2004).
Lowering the Risk of Sudden Infant Death Syndrome
Sudden infant death syndrome (SIDS) is characterized by the abrupt death of an infant not predicted by a previous medical history. This sudden and death is still unexplained following a detailed investigation of the scene of the child's death and thorough autopsy. Most often the infant…