The science of sleep III: Why does it matter?

Research Summary
Pascal Wallisch
Baby Sleep Study Co-Investigator

Sleep is underrated, probably because you are not conscious when it happens. In previous installments of this series, we discussed how the brain regulates sleep-wake cycles, and what you can do to help the brain do so in a modern world that is flooded by short-wavelength light, even at night. Here, we will explain why it you should care – apart from avoiding the subjective discomfort associated with disrupted sleep and wake cycles. In brief, it matters. A lot. Specifically for the long-term health of brain, body and mind of all involved. As a general rule of thumb, there is not a single mental function that is not improved by getting adequate sleep and having well regulated sleep-wake cycles. That is a problem because there is ample evidence that our sleep cycles have never been more disrupted than now – even the average sleep duration has dropped by well over an hour since the introduction of artificial lighting. This matters. There is nothing light about light.

How specifically? Let us count the ways:

  1. Adequate sleep is critical for learning new material. There is no question that lack of sleep impairs memory function.
  2. Without sufficient sleep, creativity and problem solving take a big hit, particularly for tasks that depend on insight.
  3. The ability for self-control really suffers. In other words, you are much more likely to give in to impulses. A successful life in modern society is all about constant and daily impulse control. Lack of sleep makes this much harder.
  4. On a related note, wise decision-making crucially relies on adequate sleep. Some of the most disastrous judgments in recent memory, including Chernobyl and the Exxon Valdez disaster have their root cause in disrupted sleep cycles.
  5. There is ample evidence that disruption of the sleep-wake cycle directly disrupts emotional well-being and leads to depression.
  6. Paying attention – vigilance – is severely impaired by lack of sleep.
  7. Lack of sleep is implicated in hundreds-of-thousands of traffic and work-place accidents each year, in the US alone.
  8. There is increasing evidence that one of the primary functions of sleep is to dispose of toxic waste-materials that accumulate in nerve cells during the day. If these housekeeping functions are not performed, dementia might ultimately ensue.
  9. The effects of sleep disruption are not restricted to brain and mind. The release of a large number of hormones is tied to the sleep/wake cycle. For instance, growth hormone is released during deep sleep. Not getting enough deep sleep could therefore stunt growth in children. In adults, diabetes has been linked to sleep disruption (the association likely goes both ways). Even bone mineral density is weakend by lack of sleep - suggesting, that really all bodily systems are adversely affected by poor sleep quality.
  10. Similarly, there is now compelling evidence that lack of sleep is associated with obesity – and for the same reason. The release of feeding and satiety hormones like Leptin and Ghrelin is tied to the sleep/wake cycle as well.

Importantly, these effects are physiological in nature and increasingly well understood on the level of the brain (it looks like individual neurons are “sleeping” in an unsynchronized fashion, if not getting adequate rest). This means that even if you do what most people do – using stimulants (caffeine is the most popular) to get up in the morning and perhaps downers (alcohol is the most popular) to wind down at night, these measures are no substitute for sleep. Perhaps they will allow you to get through the day, but none of the deleterious effects mentioned above are alleviated by it and if anything, stimulants will make the problem worse in the long term; caffeine has a relatively long biological half-life whereas alcohol is constantly – but rather slowly – eliminated from the body, taking either of them too close to sleep can disrupt sleep-cycles throughout the night. The only sustainable solution is to tackle this problem at the source and restore natural sleep-wake cycles in order to foster restorative sleep.