We often say that "older people sleep less, they will habitually get up early." There is some truth to this statement, but it also depends on the situation. Some older people sleep less because of habit, and some older people sleep less because of changes in body functions.
I go back to my hometown almost once every two weeks, and at home I usually don't get up until after eight, but my parents basically get up after six. Not because they're older, but it's a habit. When I was a kid, my parents basically got up around six every day. If it was busy farming time, they would get up even earlier.
For decades, they had developed the habit of getting up early. The biological clock of human beings is such that once a habit is formed, they can still get up at the right time even if they don't have an alarm. When they were young, getting up early was a necessity, but when they were old, getting up early was a habit.
Elderly people sleep less as they get older, which is a physiological response. Ageing people's daily activities become smaller, the body's organs are not so tired, the brain's required rest time also becomes shorter, so most of them will wake up naturally around six o'clock every day. Even if they lie in bed and want to sleep or can't sleep, it's not because of insomnia, but because they've had enough sleep.
Usually, the elderly also need to strengthen their physical exercise as a way to enhance their body's resistance and avoid diseases. There are a lot of elderly people exercising every day on the riverbank to the east of our neighborhood, playing Tai Chi, dancing, and practicing the sword. Every time I pass by to see this group of elderly people's mental outlook are particularly envious, that one of them are like a young man, energetic, full of spirit ah!