How much sleep do I need?
Also known as the sleep homeostatic process
Recommended sleep duration changes with age
You may remember being a child or teenager and needing a lot more sleep than you do now. This is normal across the human life-cycle, with sleep need reducing about an hour for most people 65+ years of age (as shown in the figure above). But more significantly than the change across age, note the variation in sleep need across the 65+ age group (5-9 hours). This shows how important it is for you to understand your unique sleep needs and what is required for you to not feel excessively drowsy during the day.
Do we actually need less sleep when we are older than 65?
You probably noticed that the graph shows 65 year olds needing an hour less sleep. However, there is debate in the sleep literature on whether this is indeed the case. It may instead be that as we get older, due to chronic stress, irregular circadian rhythms, and the body breaking down, it becomes more difficult to produce regenerative sleep. Dr. Gartenberg ascribes to this theory. If we needed 7-9 hours our whole lives as adults, we probably need that much as we are older as well. Getting healthy sleep, and especially deep sleep, simply becomes more difficult as we age.
Sleep Need is also tied to sleep quality
In sleep science, sleep need is referred to as the homeostatic component of sleep. This is the major factor that drives alertness throughout the day. The longer you are awake, the greater your need for sleep. This is due to the buildup of the neurotransmitter adenosine. Caffeine blocks adenosine, and this is why coffees, teas, and sodas keep us awake and alert. But sleep amount alone does not dictate your sleep need. The quality of your sleep also plays a major role. For example, if you get 9 hours of sleep after a night of partying, it might actually be less regenerative after maintaining a healthy circadian rhythm and only getting 7 hours of sleep. The amount of deep sleep, or Slow-Wave-Sleep (SWS), plays a major role in your sleep need as well. The more SWS that you get each night, the more regenerative your sleep and the longer your body will be able to stay alert throughout the day.
I sleep only 5 hours a night and feel fine - what gives?
For 99.9% of the population, sleeping only 5 hours on a regular basis is extremely unhealthy. It results in increased prevalance of almost every chronic health disease. These types of people are known as "short sleepers" and a basic google search can show you how detrimental this is for health and well being. Many people think that they fall into this category, but it is extremely unlikely. Often what happens is these individual are living in a state of hyper-arousal and stress that they get used to. It's like the say, "You don't know water until you've left the fishbowl." Once you start getting a healthy amount of sleep (7-9 hours), you will begin to realize how important it was for not only your physical well being, but your mental health as well.