Speculation: Does Chronic and Severe Unhealthy Sleep in Childhood Cause Brain Damage?
When a growing child does not receive enough vitamin D, the result is soft bones (rickets). Vitamin D deficiency causes bone disease that might be severe and cause persistent deformities, especially bowing of the legs. Sleep deficiency impairs brain health (Blog Posts 1–5 and 38). When a growing child does not receive enough quality sleep, might this be severe enough to produce brain damage, either reversible or persistent? The answer is not known. Please do not worry if now and then your child gets a little short on sleep but is well rested most of the time. But I would worry if sleep problems are persistent and severe. In the extreme, long-term experimental sleep deprivation in laboratory animals has been shown to permanently damage the brain and even cause death.
Here are some opinions that suggest this topic should be taken seriously by parents:
- Why do we need to sleep? Recent research by Dr. Giulio Tononi tells us that the purpose of sleep is to weaken or prune the unimportant noise coming into our brain so that important signals remain stronger. Think of pruning a tree: You selectively remove targeted branches to promote healthy growth. Here’s an example of what pruning might look like in our brain. You are practicing a musical instrument and you hit the wrong note. The wrong note does not fit well with previous, older memories of hitting the right note, and sleep erases the memory of hitting the wrong note, leaving behind a stronger memory of hitting the right notes. During sleep, the brain is refreshed by eliminating memories of insignificant events, but memories of more important or salient items will be preserved. A 2019 study, led by Professor Shuntaro Izawa, supports this idea that during sleep, pruning or active forgetting is vital for “helping the brain forget new information that is not important.” This culling of information allows more memory resources to be available to us the next day. Dr. Izawa’s research shows that only during REM sleep, certain nerve cells started firing the electrical signals necessary to effectively remove unimportant memories. In adults, experimental sleep restriction primarily leads to deficits in REM sleep, so maybe the brain gets cluttered with unimportant memories, making it hard for us to focus on the present.
This theory, in Dr. Tononi’s words, “predicts that sleep is especially important in childhood and adolescence, times of concentrated learning. In youth, connections between nerve cells are formed, strengthened, and pruned at an explosive rate never approached in adulthood. One can only wonder what happens when sleep is disrupted or insufficient during critical periods in development. Might the deficit corrupt the proper refinement of neural circuits? In that case, the effect of sleep loss would not merely be occasional forgetfulness or misjudgment but a lasting change in the way the brain is wired [emphasis added].” Support for this idea comes from animal studies. “Consequences of extremely stressful early-life events leave permanent changes in the brain . This molecular ‘scar’ may act as a predisposing factor in development of psychopathologies later in life. Sleep, particularly REM sleep, appears to be the most sensitive behavioral indicator of the early-life events in adulthood [Emphasis added].” Sleep quality, not just sleep duration, is important (Blog Post 15).
- Professor Sadeh performed objective sleep measures on children at age 12 months. Children who had lower quality sleep at 12 months were more likely to have compromised regulation of attention and behavioral problems at 3-4 years of age, even though there was no significant contemporary association between sleep and attention regulation or behavior problems at age 3-4 years of age. Professor Sadeh raised the tentative possibility that “it could be argued that sleep disruptions at an early age interfere with vulnerable brain maturational processes that later result in compromised regulatory capabilities and our findings suggest that the impact of sleep deficits at critical stages of early brain maturation could potentially lead to long-term consequences [Emphasis added].
- In toddlers, at 30–36 months, Dr. Rebecca Berger experimentally eliminated a single nap. She noted that when only one nap is eliminated, “acute sleep restriction causes dampened positive emotion displays when positive responses are expected (solvable puzzle), as well as increased negative emotion under challenging conditions (unsolvable puzzle). Sleepy children may view and respond to the world differently than children who are well-rested: they may not be able to take full advantage of positive experiences and may not be as able to manage challenges. A lack of sleep in contexts that rely on young children’s mastery of new information (e.g., preschool) may have significant and potentially dire long-term consequences [Emphasis added].”
- Sleeping well appears to enhance brain maturation. In a study by Dr. Salome Kurth, connections between the right and left sides of the brain increased as much as 20 percent over a single night’s sleep in a group of children 2–5 years old. Connections strengthened as the children aged. “Sleep is a key environmental contributor to brain optimization processes and plays a crucial role in brain maturation,” Dr. Kurth concluded. “In critical phases of development (walking, talking, problem solving), the maturation of skills not only require cortical activity during waking but also a subsequent period of sleep. There are strong indications that sleep and brain maturation are closely related. I believe inadequate sleep in childhood may affect the maturation of the brain related to the emergence of development or mood disorders [Emphasis added].”
(To be continued.)