I walked with a cane for a few months last year, and not ONCE did I see kids enjoying themselves so I could wave my cane at them. Not once. Seriously, kids these days.
Most people in the local area have to be to work by 7:00, and families with former farmers would be working by 6:00. Do that for decades and you stilll get up at the crack of dawn, because your body learned to wake up at a certain time.
Another old fart checking in. I go to bed around midnight, wake about 4:30 make a cup of coffee, take it back to bed and promptly fall asleep to wake up again about 7:30.
Microwave the coffee and stand glaring out the window deciding on who to annoy today 
Dunno about old people, but it’s been established that teenagers’ internal clocks tell them to sleep later in the mornings than either children or adults. (Coupla cites here and here.)
That’s because they’re all on my lawn and in my Jell-O tree.
I attribute my early rising to habit. The last 20 some-odd years I worked I was in my office no later than 6:00 each morning, and some mornings as early as 4:00. Of course, I was away from there as early as 2:00 in the afternoon, too, so it worked out well for me on both ends of the day as far as traffic went.
Earlier in my career I worked nights which meant sleeping days. I did that for several years and managed to adapt to that fairly well, too.
Even as a young adult I was never able to go for long stretches without sleep. Once in a while I could go up to 24 hours without sleep, but rarely over that much. On the other hand, the longest I can remember ever sleeping, and that was when I was sick with the flu or something, was right at 24 hours. That was heaven!
But even these days, when my bedtime is anywhere from 10:00 PM to 2:00 AM, depending on what’s on TV worth watching, I usually wake for good by 7:00. However, somehow my system knows when it’s the weekend, even though it’s hard to distinguish from the weekdays as far as my activities go, and I may sleep as late as 8 or 9. That happens maybe once or twice a month.
So, as I said to start with: habit.
This is the most scientific answer to the thread and is likely one strong cause according to animal research. The pineal gland secretes less and less melatonin as you get older causing sleep patterns to change as well. A few years ago, some researchers suggested that reduced melatonin secretion played a role in the aging process itself. I am not sure if that theory is currently in vogue but you can buy melatonin over the counter and it often acts as a powerful sleep aid.
My old man wakes up about eight, I think. And I’m pretty sure he does it only because there’s limited daylight, and he can’t do stuff in his garden in the dark.
BTW… he’s not a grumpy old coot… he’s happy as a clam now that he’s retired and doesn’t have to put up with the BS at his old job, and can spend his time gardening and restoring old model trains, and screwing around on the internet.
As I understand the issue (and I apologize for no cite, but I am at work right now) it is due to human evolution. Teenagers generally stay up late (thus able to watch for danger/predators, adults are more active during the day (thus able to take advantage of the daylight hours), and the elderly generally wake up earlier (theoretically about the same time the teenagers are winding down). This helps keep more constant vigilance for whatever societal unit is subsisting together.
Widely believed, but not really true.
Lastest thinking in sleep research circles says that older folks need just as much sleep as they did in their prime, but their sleep cycles no longer function as they did before (see above cites about melatonin as a possible cause/effect/co-condition).
So they wake up early, can’t drop off back to sleep, and decide to get up. Eventually the fortunate ones get into a mid-day nap pattern to compensate. Others have supper at 2:30 PM and nod off in front of the 6 PM news.
There aren’t that many old people club hopping till 2 in the AM.
I thought they got up and stayed up the minute they woke for fear of going back to sleep and not waking up.
Maybe old people, not forced to adapt their sleep patterns to their jobs anymore, have the luxury of going back to a sleep pattern that was common to man for most of known history: Segmented sleep.
I am happy to say I stand corrected. Maastricht’s explanation fits the bill. Eh, that’s what I get for not taking the time to cite. slaps wrist
“EAT HICKORY!” /seinfeld
Personally I like to get an early start on writing angry letters to the newspaper. Since the newspaper switched from afternoon to morning delivery, I’ve adjusted my sleep schedule accordingly.
Oh I so get that segmented sleep thing. It’s how I live on weekends. Nothing like an afternoon nap to fill you full of zip for a nice long evening.
I’m curious if there are any old people that regularly sleep in late, because I’ve never met one.
That doesn’t work for me. When I wake up from my normal night-time sleep, I usually pop right out of bed and I’m ready to go. If I take an afternoon nap, I wake up from it groggy and incoherent and it takes a couple hours to get moving again. (I’m 40)
The trick is not to nap for a long time. In fact, I’ve found 12 minutes is excellent. I don’t know exactly why, but if you are awakened just after you’ve fallen asleep, it feels as though you’ve slept for hours - as you you wake up refreshed and energized. If you snooze for more than a half-hour, then I think you end up in very deep sleep or something and it’s very hard to wake up well.
Oh, and I’m not old. I’m just a lifelong napper.