Age affects sleep more than any other natural factor. In REM (rapid eye movement) sleep muscles are paralyzed and dreaming is active. In NREM (non-rapid eye movement) the sleep is supposedly thought-like rather than bizarre and hallucinogenic. The first graph shows the relationship between hours or sleep and age which has very clear negative correlation. On the other hand, the percentage of that sleep being REM sleep has a slightly irregular negative correlation.

National Institutes of Health (US); Biological Sciences Curriculum Study. NIH Curriculum Supplement Series [Internet]. Bethesda (MD): National Institutes of Health (US); 2007. Information about Sleep. Available from: https://www.ncbi.nlm.nih.gov/books/NBK20359/