BACKGROUND:  Close to 10 million Americans suffer from osteoporosis, a disease of the bones.  Bones are living tissues that are constantly being absorbed and replaced.  When the creation of new bone does not keep up with the removal of old bone, osteoporosis occurs.  Bones then become very weak and can break even from a minor fall.  About half of all women over 50 and one in four men will break a bone due to osteoporosis.  Some people lose height and become shorter.  It will affect posture and cause a person to hunch or stoop.  This happens when bone in the spine break or collapse.  Twenty percent of seniors who break a hip die within one year from problems related to the broken bone or from surgery to repair it.  People who do survive require long-term nursing home care.  Osteoporosis is responsible for millions of fractures and billions in costs.  Experts predict that by 2025, $25.3 billion will be spent each year. (Source: www.nof.org).

 

NEW RESEARCH:  While there are so many Americans affected by osteoporosis, the causes of it remain a mystery.  New research is being conducted to address osteoporosis in a unique way.  Postmenopausal women and aging men are not the only ones who have to worry about bone loss.  Studies have found that on average, an astronaut will lose one to two percent of bone mass each month in space.  Researchers believe that by solving the problem of why bone loss occurs in space, important clues will be revealed about what causes osteoporosis on Earth. 

 

Astronauts usually experience bone loss in the lower halves of their bodies (lumbar vertebrae and legs).  Also they experience a rise in calcium levels in the blood, which increases the risk of kidney stones.  The suspected cause of bone loss in space is weightlessness.  The pull of gravity 350 km above Earth’s surface is 90 percent as strong as it is on the ground.  As a result, the acceleration they feel is as little as 0.0001% of the gravitational acceleration on Earth’s surface.  Their bones no longer have to fight against Earth’s gravitational pull.  Therefore, they experience less mechanical strain to the skeletal system. Scientists believe reduced stress on bones may be responsible for the progressive bone loss in long-term residents of space, mimicking what happens to those that are confined to beds due to illness or old age.

 

In prolonged weightlessness, bone mass decreases due to the lack of stress on the bones that slows the formation of new bone.  Fewer bone-building cells, along with a constant level of bone-destroying activity, results in a net loss of bone mass.  Why weightlessness inhibits the development of osteoblasts is currently being studied at Vanderbilt University. A chemical in the development of osteoblast cells from precursor cells is an enzyme called "creatine kinase-B." Scientists are trying to figure out which molecules in the body regulate the activity of this enzyme and how those chemicals are affected by low gravity, hoping that this knowledge will point to a way to boost osteoblast formation in space.  Another study at the Medical College of Georgia is investigating a possible connection between eating and bone destruction.  Ingesting food causes level of a certain hormone to increase in the blood stream.  This hormone can stimulate production of insulin after a meal, triggering cells to absorb glucose from the blood.  Bone cells are sensitive to this hormone.  Researchers have found that when this hormone attaches to "receptor" molecules on bone cells, osteoclast (bone destroying) activity goes down and osteoblast (bone creating) activity goes up.  Whether hormones like this can be given to astronauts as a supplement to prevent bone degradation is unknown to scientists so far.  Another study led by Dr. Douglas Chang at the University of California, San Diego has found that the discs in astronauts are becoming weaker, faster.  In zero gravity, they grow an average of two inches when their spines straighten out, resulting in more disc herniation’s.  NASA research has already made some headway in their research.  For example, their research led to the development of a fast and inexpensive tool to measure the extent of osteoporosis by analyzing the stiffness of bones.  (Source: www.science.nasa.gov).

 

Dr. Douglas Chang, Associate Clinical Professor of Orthopedic Surgery, Chief of Physical Medicine and Rehabilitation at UC San Diego, talks about back pain and space.

Is most all back pain due to compression and is just the opposite?

Dr. Chang: We don’t really know the exact cause of back pain. There are a few things that go wrong that we know. The spine is composed of little blocks of bone and there are little cushions in between those blocks that gives us flexibility. One thing we do know is that those cushions tend to squash down and push out and they can sit on some of the nerves that control the legs and cause a lot pain. We also know that little bone spurs develop in the back and that can be significantly painful. Bone spurs are almost like a little bit of sandpaper or grit in our spines that can be really, really abrasive and irritating. It’s almost like the calcium deposits that sort of develop on our plumbing over the decades. So there’s that, there’s muscle pain and spasms, there’s a few different things and it’s a little mysterious what the exact cause of back pain is.

What are three to five things people could do for their spine every day?

Dr. Chang: I think the most important thing is having an exercise program, a core conditioning program and it doesn’t have to be much.  I mean maybe fifteen minutes, twenty minutes a day of sit ups and maybe some back extension exercises. I have a web site where I worked with a physical therapist and showed a few simple exercises to do. Doing something like that over time, and making sure that the muscles of the stomach and the back holding everything in place are strong, I think is the number one thing that people can do.

How many patients do you see with lower back pain every day?

Dr. Chang:  Uh, I think about twenty.

Is it a nonstop revolving door here with people?

Dr. Chang: I don’t feel that way about them. There are a lot of people with back pain and we’re booked out for months to have people come and see us. It’s really a common problem and I enjoy seeing all the patients and helping them.

You are doing something special. Your lab is basically space, correct?

Dr. Chang: I’m working with a physiologist, Dr. Alan Hargens, and we’re looking at the effects of space on the human body. One project I’m really passionate about is the effect of space and weightlessness on our spines.

Are a lot of astronauts coming back and having back pain problems?

Dr. Chang: Up to eighty five percent have significant back pain to the point it’s affecting their activities of daily living and their mission up in space. When they come back down, they have an increased incidence of disc herniation. Much higher than you’d expect for a comparable age matched population of retired jet pilots and military men.

Why is that?

Dr. Chang: We don’t know and that’s the exact reason why we’re trying to look in to this. We think that in space without the effects of gravity and daily cyclic loading that the soft tissues of the spine are being harmed. Just like we hear about osteoporosis and how it’s real important to do weight bearing exercise and daily loading of our bones, we’re finding that the same situation applies to the soft tissues and the muscles, the discs of our bodies and particularly the spine.

So it’s a certain amount of time. Do you have to be on the space station for six months or can it be like a two week mission?

Dr. Chang:  All of the above. I mean it’s just recently where people have spent a considerable amount of time up in space. We’ve gone back to the log books and for all the different space flights, regardless of time they do seem to have some increased incidents of back pain and disc herniations.