Dolphins are known to only sleep with half of their brain at a time (unihemispheric slow-wave sleep). This is because if they were to sleep properly and become fully unconscious they would drown, get killed by a predator, or freeze in the ocean. Click for more dolphin-sleep info.
Cats are also known for their weird sleeping habits or ‘cat naps’. A common myth is that despite always seeming to be asleep, cats are usually only partially asleep, where their brain hasn’t quite shut off and they have not yet reached the REM phase of sleep (the phase where dreaming occurs). This is why the cheeky felines always seem to be half listening in to your conversation.
Aging and sleep in humans:
As people age their sleep worsens. Falling asleep becomes more difficult and there are so many factors that could prevent one from staying asleep. It is this aging process that potentially leads to the common misconception: Elderly people need less sleep.
I myself believed this, I made the connection that young babies need a lot of sleep because they are growing both physically and mentally (obviously a very demanding task). This made sense that then as you grew older you wouldn’t necessarily require as much sleep because growing slows down. Conventional bedtimes also supported my theory. If I go to bed at 8pm now instead of last year when it was 7.30, this is because now I am 12 years old, and no longer a puny 11 year old. Further supporting my theory was the fact that my parents slept late, say around midnight, but struggled in the mornings to get up, and then my grandad would seemingly never sleep, apart from falling asleep in front of the television very late at night, but he always woke up early with ease. Leading me to the logical conclusion that my parents NEEDED more sleep but had to get up early for work so didn’t get enough sleep, while my grandad just needed less sleep.
It was later in life that I found out about the weird sleep behaviours of two animals; cats and dolphins, adding bonus logic on top of my previous logic: As you age, you become more like a cat or a dolphin, you don’t require the same level of sleep as a typical human, therefore you are becoming another animal…
Logical? Somewhat, perhaps I lost the logic by introducing the animals to my theory.
True? No, not really.
Investigating my theory further:
So … I was right with the theory that young people need more sleep (check out the image below). The reasons behind this are as suspected, physical and mental development are still happening. Research on sleep in postnatal rat pups is able to indicate the importance of sleep in early development stages, even in humans (because many mammals develop in similar ways).
A 1986 study did just this, they prevented newly born rat pups from achieving REM sleep, this is the phase of sleep that dreaming occurs in, it was given the name due to the amount of eye movement that occurs beneath the eyelids, limbs will also often twitch in this phase. Reducing the pups amount of REM sleep when they were young induced hyperactivity, hyperanxiety, attentional distractibility, sleep disturbances, reduced sexual performance and reduced cerebral cortical size when they became adults.
Another more recent study (2014) found that the twitching that occurs during REM sleep allows for neural and motorsensory development, that is, whenever a twitch occurs it creates and develops pathways in the brain that allow for improved functioning at a later date.
My theories about my parents needing more sleep than my grandad also seem to make sense according to the visual below. But my theories about becoming animal-like?
Now I know humans are not growing up and suddenly turning into animals, my theory more points towards the possibility that as people age their sleep cycle changes in a way that makes their sleep more like the way other animals sleep.
According to the National Sleep Foundation (a foundation started in 1990 by a group of leaders in sleep medicine) dedicated to improving health and well-being through sleep education and advocacy, people’s sleeping patterns do change as they age. This is usually to do with the individual and it mostly occurs due to external factors.
Circadian Rhythms (daily rhythms of your body functions) change; what used to be a usual bedtime becomes too late, but because they still need the same amount of sleep they find themselves waking up that much earlier.
As people age they also take longer to fall asleep, they spend more time in the light phases of sleep and they are more likely to suffer with sleep disruptive symptoms, such as weakened bladder, sleep apnea, or even just their bad hip or knee that won’t stop throbbing.
To combat the bad sleep at night, elderly people often need to nap during the day. Instead of the sleeping pattern that they learnt as they grew older, they have to revert back to when they were younger.
Comparing sleep patterns:
As you can see in the above pictures, ‘normal adults’ (without sleep disorders) do not have sleep patterns at all similar to cats or dolphins, however you can see that elderly people have relatively broken sleep with REM phases only occasionally, a lot like the REAL cat sleep cycle. Elderly people do not have similar sleeping patterns to dolphins because both hemispheres of their brain will sleep at the same time, whereas the dolphin only allows one side to sleep at once.
SOOOOOooooo…. my logic sort of prevails, as we age our sleep becomes more like that of an animal, the domesticated cat! … Perhaps a topic for your next biology report.