Adapted from BMJ 13 Nov 2021 from American Journal of Epidemiology.
Measurements using an Actigraph were taken from 13,000 adults and children in the USA to determine what a “normal” sleep duration was. The amount of sleep taken by individuals can be highly variable, and this can also change due to their age and stage of life and occupation.
For females, the 50th centile, the middle of the sleep range, was 8.3 hours a night, starting from age 6. As a young adult, this reduced to just over 7 hours and stayed constant till there was a small increase at age 65.
For males, the middle of the sleep range was 8.1 hours at age 6 and reduced to 6.5 hours in early adulthood and increased slightly at age 60.
My comment: I’ve always needed a lot more sleep than this. 10 or 11 is better for me and in autumn, just after the clocks change, I can sleep for 14 hours a night if I am not disturbed. I perk up a little bit in the spring and can cope with 9 hours a night. For much of my life, particularly working as a doctor on call and having young children I had a lot less sleep than I really needed. I have seen that sleeping a lot is associated with a higher rate of dementia, but too bad!
In California, a longitudinal study of more than 50,000 women, looked at how environmental influences affected how long it took to get to sleep and how long the sleep lasted.
Shorter sleep duration was associated with exposure to artificial light at night and air pollution. (Associated with cities). Where there was a lot of environmental noise, it took longer to fall asleep.
Contrasting with this, living in areas with more green space led to women falling asleep faster and staying asleep longer.