I always thought the shrinking process didn’t didn’t start until you were some ancient age like 75 or 80. I guess gravity starts pulling you down early because I’m a mere 45 years old and unless the inch marks on my tape measure are wrong, I’ve shrunk 1/4" since I was in high school. How about the rest of you?
I just saw that poster when I was in the pharmacy today! It says shrinkage is NOT a normal part of aging, although 1/4" is nothing to worry about anyway - you can do that much with a haircut. Any major stooping or shrinkage is quite likely to be caused by osteoporosis, according to the poster. It recommends folic acid; I recommend not worrying about it for 1/4". I’m sure somebody who knows more than I will be along soon.
My shrinkage was noticeable as soon as I got out of the pool.
[Elaine]Shrinkage? As in laundry?[/Elaine] 
Osteoporosis is certainly the main contributor to “shrinking” in older age, especially for women. Posture is also related; the “widow’s hump” (spinal curvature) is also a contributing factor in percieved loss of height. It’s not that your spine has shortened, just that it is not in a (relatively) straight line anymore.
Also somewhat related (and not sex-linked) is gradual deterioration of the spinal disks. The disks are (in youth) filled with a gelly-like material. Evidently this deteriorates or dries out somewhat with age, and the reduced volume between vertebrae makes you shorter.
<brainfart> Sorry, that should e “Jelly-like” </brainfart> :smack:
A few possible explainations for the 1/4 inch difference :
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inaccurate measurement. Perhaps when you measured yourself in high school you added 1/8 inch, and today you subtracted 1/8 inch.
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You measured your height in high school wearing shoes. Today you measured your height barefoot. Or thick and thin soles on your shoes.
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Time of day. First thing in the morning, when you have been lying down for 8 hours, you are at maximun height. At the end of the day, when you have been vertical for 16 hours, gravity has compressed you a little. You are slightly shorter at the end of the day than the start.
Posture and flexibility do make a difference. I used to have a rather stooped posture till I started taking yoga classes. Now my measured height is from a quarter-inch to a half-inch taller than it used to be even when I did my best to “stand up straight”.
Your spine compressed over the copurse of the day. That can seriously afect your measured height.
Not somewhat related, but directly on point and the main reason one shrinks with age. Dessication of the nucleus pulposi (the “jelly-like” material) occurs with age, causing narrowing of the intervertebral disc spaces. Since you have over 30 disc spaces, you can see where even a minute shrinking in all the spaces would result in a substantial shrinking; however, the discs usually involved are in the lower lumbar spine, but even if it’s only two or three, you can easily lose over an inch of height, as I have. And this starts to occur at a relatively early age. Very few people do not have some shrinkage by the time they reach 50, IMHO.
In forensic anthropology, I was taught that we basically start decreasing in stature by about age 30 because of spinal decompression, bone loss, etc. In fact, the regression formula for stature (see the section Stature Estimation) takes this into account.
Incidentally, this reminds me of something an experienced forensic anthropologist told me about using driver’s licenses to confirm the identity of a body. You can’t depend on the license’s height for males or the license’s weight for females because men usually lie about how tall they are, and women usually lie about how much they weigh, at least on the driver’s license.
At least this was his experience. I never confirmed it.
It might just be that we put down our correct height when we get the license, at 16 or 17, and then never bother to change it. My license says 6’2", and that was the absolute truth in 1968. I’m about an inch shorter today.
Well, at least where I am, when I renew a license, they ask me for my weight, but never for my height. They assume that it probably doesn’t change - well, at least not significantly.