Larry A. Law
The amount of total sleep during early childhood can vary from 11 to 14 hours a day. Six-month old babies have a 50/50 ratio between Non-Rapid Eye Movement (NREM) and REM sleep. Five-year old children have a 70/30 ratio between NREM and REM sleep. Late teens have an 80/20 ratio between NREM and REM. The increasing dominance of NREM sleep reflects the changes going on in the brain. While fetus and newborn babies are creating neural pathways, toddlers are pruning and eliminating the pathways not being used. This fine-tuning ensures an efficient, well-connected brain and explains the difference in the amount of NREM and REM sleep cycles. (For more explanation on exactly what NREM and REM sleep cycles are see my previous article here.)
As children grow into adulthood the optimal amount of sleep changes to 7-9 hours a night. While there are those who pride themselves on needing less sleep each night (4 or 5 hours), they may find themselves hurt in the long run. Alzheimer’s may be what catches up to them. Ronald Reagan and Margaret Thatcher are two famous examples.
When we as adults are in our mid to late 40s, age may strip away 60 to 70% of the deep sleep we enjoyed as a teenager. By age 70, we may lose 80 to 90% of youthful sleep. In addition, sleep becomes interrupted due to more bathroom visits at night, sleep apnea, snoring disruptions, brain degeneration resulting in dementia, and medication interference. The elderly will feel tired more often during the day and feel they need to go to bed earlier at night because they aren't sleeping very well. For these reasons and more, I believe we need to take care of our nutrition, develop good eating habits, exercise, and sustain our emotional wellbeing. This will vastly increase the probability we will age well. We do not need to plan on becoming the typical old person! We can be proactive and grow gracefully into our golden years. For more on what can be done, see my book here.