Sal DiMarco Jr. for The New York Times
The upward trajectory of youth starts falling for most people after 40. In a file photo, a Macungie, Pa., middle school nurse, Linda Duffy, measures a student.
Relax. You’ve been through this before.
Back when you were a baby baby boomer, your doctor probably laid you down every few months and measured your height.
Then came the big day: you toddled into the doctor’s office on your own two feet and instead of lying down to be measured, you stood up. And the odds are that when the doctor jotted down your height, it seemed to suggest that you had shrunk since the last visit.
The truth, of course, was that you weren’t really shrinking. When you were measured standing up, gravity compressed your spine. In follow-up visits, you quickly made up for lost ground, your height milestones rising on the doctor’s chart much as they may have in pencil markings on a kitchen wall.
Decades later, pretty much the same thing is probably happening to you right now, with two minor differences: you actually are shrinking. And you are not likely to get that height back.
Starting at about age 40, people tend to lose about four-tenths of an inch of height every decade, said Dr. David B. Reuben, chief of geriatrics at the David Geffen School of Medicine at U.C.L.A. Some of the height loss occurs as part of the normal aging process, and some because of disease. Our old friend gravity, bane of the first vertical height measurement, also plays a role. “It’s a Newton thing,” said Dr. Reuben, a past president of the American Geriatrics Society.
As we age, the disks between the vertebrae of the spine, sometimes described as gel-like cushions, dry out and become thinner, with the result that the spine becomes compressed. The bone loss known as osteoporosis can also contribute. People who have the condition may sustain small compression fractures in the spine, often without their knowledge. “The best way to think about those is if you step on a soda can and the soda can just kind of crumples,” Dr. Reuben said.
The fractures can lead to excessive curving of the spine, which can be seen in many people as they age. When it is very pronounced, it is considered hyperkyphosis, sometimes known as dowager’s hump. Hyperkyphosis, however, can occur even in the absence of fractures, often as a result of a loss of muscle tone, especially in core muscles like the abdominals. Even the flattening of the arches of the feet that comes with time can contribute to a loss of height.
There is not much to be done about many of these changes, but people who exercise, strengthening their core, may retain or gain height through better posture. And some research, while not definitive, has offered promising evidence that yoga may even help reverse the curving of the spine. If the yoga is begun at an earlier age, it may be possible to prevent the condition altogether, though more research would need to be done to establish this.
Making sure to get enough calcium and vitamin D can help, Dr. Reuben said, and there are medications used to prevent the fractures caused by osteoporosis.
Of course, if sit-ups or downward dogs are not your style, there are two simple tricks to being taller. Check your height in the morning, when it is at its maximum. Or ask your doctor to measure you lying down.
Questions about aging? E-mail boomerwhy@nytimes.com
