It would have to be an individual thing, there are no hard and fast rules or answers. One person can look old because of exposure to the sun but may be very healthy due to the vitamin D content in sun light.

Some people are predisposed to cancer due to genetics.

I have MS but besides for that I’m healthy: Ideal weight, good BP, good cholesterol. But I feel like dying sometimes.

I think the answer to your question would be relative to specific individuals. It has to be taken by a case by case situation.

If you ask a Middle School student if their parents are old they are are likely to say, “Yes.”
If you ask a senior citizen if a 40 year old is old they’ll most likely say, “No”.

I spoke with a young girl several weeks ago, and she told me if she had to wear “depends underwear” she would kill herself. After many woman give birth they have to wear protective undergarments due to weakness of their bladders.
The young girl I spoke with may change her mind in the face of the reality of the situation. Again, I give you this example to show how certain things are relative to your age and experience.

Old age isn’t determined so much by years, but rather by factors such as frame of mind, health, mentality, etc.

Illness can certainly make a person look older than they are, as can too much sun over the years, illness, smoking, alcohol usage, stress, and addictions. Additionally, how a person eats and whether or not he/she exercises has a lot to do with it.
The genes can play a part in it as well.

One must keep their minds and bodies active for the sake of their physical and mental health.

It depends on their physiological condition.

some look old at 40 some look young at 80

i think the health of the person consititutes them as elderly.
i know 80 year olds that i wouldnt consider to be “old”. (as in their health and their energy levels.)

I think for human that makes him old is that because of health problem it doesn’t depend in how old you are.

you are as old as you feel

like 85-90 years