[EDITORIAL NOTE: I've posted a new story at Blogher.org - Elder Fashion - An Oxymoron.]

In Part 1 of this series we discussed the language of aging which often, in the U.S., is used to marginalize elders. In a small effort to counteract this, the word “old” is used on this blog as a neutral descriptor. It just means a person has lived many years, nothing more.

Today, let’s look at the medical definitions of old.

One of the failings of our culture is to stereotype old people as being all the same. Although the exact divisions fluctuate, the research and medical communities know better, dividing elders into three categories which fall into these general age groups:

• The Young-old: 55 to 74
• The Mid-old: 75 to 84
• The Old-old: 85 and up

Some skip the “mid-old”, including them with the “old-old”, and some place centenarians in a fourth category all their own.

It is important to remember that people are as different at these stages as children are from adolescents, as different as a 35-year-old is from a 60-year-old. Also, individual elders age at dramatically different rates so that sometimes an 80-year-old’s decline can be no more than that of a 60-something. Other times, a 60-year-old can have aged as much as an average 80-year-old.

So while aging is highly individualized, determined by a combination of genetics, nutrition, activity, health and a variety of other, unknown, factors, the changes themselves that occur with getting older are understood. They begin to become evident even before we reach the young-old category and continue throughout late life.

Bones lose calcium. Kidneys become less efficient. Heart muscle becomes stiffer. Gallstones may develop. Skin becomes thinner, drier and less elastic. Focusing the eyes becomes more difficult. For men, the prostate gland enlarges. Hearing can deteriorate and here is an interesting note: men tend to lose the ability to hear high tones; women to lose the ability to hear low tones.

These are normal changes that occur in the body beginning in our 50s. No matter how many face lifts a person has, or Botox injections, or how many miles one runs or weights one lifts, or how careful about nutrition, the body gradually loses some of its capabilities.

Nothing known to medical science will reverse these changes although medical intervention can control the effects of many, which is how lifespan has been increased. And, contrary to much popular belief, mental and physical activity, good nutrition, appropriate medical treatment when necessary, strong social connections and acceptance of one’s age can make the later stages of life as abundant in their way as our younger years have been.

So the medical/physical answer to when is someone old – on average, between 50 and 55.

When is Someone Old? – Part 1: Language