Fantastic, brilliant post. I am fascinated by sleep, and at the age of almost 56, I generally sleep like a baby most nights. I think this could be due to several factors - mainly because I do loads of exercise, simply because I'm obsessive about hillwalking and climbing; secondly because I rarely eat anything with added sugar - I find that if I eat a sugary treat in the evening when I'm very tired, it gives me a "quick fix energy boost", making me alert again, which makes me wonder how much impact a sugary diet has on sleep quality; and thirdly because since I was made redundant from a very stressful job several years ago, I mainly work my own hours and I'm much more relaxed than I used to be, despite not having a steady income :)
Certainly my quality of sleep is massively better now than when I was an anxious, insomniac teenager - so I wonder how much the general population deterioration of sleep quality with age might be due to outside factors such as diet, exercise and anxiety.