Osteoporosis: The Silent Disease by Numbers

Image credit by  PublicDomainPictures  from  Pixabay

Image credit by PublicDomainPictures from Pixabay

The most common symptom of osteoporosis is….No symptom! As this silent disease progresses, you may not have any indication that the strength of your skeleton is diminishing, putting you at risk of a serious and debilitating bone fracture. In fact, a fracture could be the first symptom that you have osteoporosis.

The best screening we have for bone strength at this time measures bone mineral density (BMD) using a DEXA scan (Dual-energy X-ray absorptiometry), where two x-ray beams are aimed at the bones.  When the soft tissue absorption is subtracted, the bone’s mineral density can be determined from the absorption of each beam by bone. The level of exposure to radiation is about 50 times lower than of that of a mammogram. It is a brief, noninvasive test covered by Medicare after age 65.  For younger women past menopause, a scan may be appropriate depending on their risk factors for osteoporosis.

The most popular risk assessment tool is called FRAX, which estimates your risk of having an osteoporosis-related fracture in the next ten years. It involves a list of about a dozen factors, including age, gender, weight, height, previous fracture, parental fracture history, smoking, alcohol consumption and use of steroids. If your FRAX assessment indicates a risk of fracture, then you are encouraged to get a DEXA scan to determine your level of bone mineral density (BMD).

Bone Density Readings: What the Numbers Mean

A BMD test measures your bone mineral density and compares it to that of an established norm or standard to give you a score. Although no bone density test is 100-percent accurate, the BMD test is an important predictor of whether a person will have a fracture in the future. The readings are generally taken on one side of the body (right or left) at three sites - the wrist, hip and spine.

T-Score vs. Z-Score

There is no universal form for reporting the results of a DEXA scan. The reports vary widely in appearance depending on where the test was done. Women often bring me their report asking how to interpret the measurements, which look like a series of hieroglyphics.

Generally, you see two different scores, the T-score which compares your bones to those of a young, healthy adult, and the Z-score, comparing you to age-matched peers.  The T-score is the definitive one since it shows the degree of bone loss with age, a normal process since we all lose bone mass and strength as we get older; however, we do not all develop osteoporosis.  Differences between your BMD and that of the healthy young adult norm are measured in units called standard deviations (SDs). The more standard deviations below 0, indicated as negative numbers, the lower your BMD and the higher your risk of fracture.

World Health Organization (WHO) definitions based on bone density levels:

Normal             BMD within 1 SD (+1 or -1) of the young adult mean

Low Bone Mass (Osteopenia)    BMD between 1 and 2.5 SD (-1 to -2.5) of the young adult mean

Osteoporosis    BMD of 2.5 SD (-2.5) or more below the young adult mean 

An Example:  Here is the summary of one report.

EXAM:  DX DEXA AXIAL   Date of Exam: 07/23/2018

HISTORY:  Evaluation of bone density. Female. Postmenopausal.

TECHNIQUE:  The study was performed on a Hologic densitometer.

FINDINGS:
Lumbar spine L1-L4 T-score: -1.8. Z-score: 0.5.
Left femoral neck T-score: -2.4. Z-score: -0.4.
Left total hip T-score: -1.9. Z-score: -0.2.
No gross hip structural abnormality. No gross lumbar spine structural abnormality.

COMPARISON: Comparison is made to prior DXA examination from 7/13//2016.
Lumbar spine:  Statistically significant increase (+6.0%) in bone mineral density.
Total left hip:  No statistically significant change in bone mineral density.

FRACTURE RISK:

In this patient, the FRAX ten-year probability of fracture is:
Major osteoporotic (humerus, forearm, spine, or hip): 14%
Hip fracture: 3.8%

The 10-year risk estimate in this patient was calculated from the patient’s reported age, sex, weight, height, ethnicity, and femoral neck BMD.

IMPRESSION: According to the WHO classification, the patient has osteopenia (low bone mass).

Joan Pagano Kitchen Sink Leg Lifts

This woman brought me her results, asking how to interpret them. Her doctor had simply marked the 6% improvement in her lumbar spine and said all “is as it should be.” From my perspective, I saw something more worrisome: The left femoral neck, which is the fragile shaft of the femur (thigh) bone, has a T-score of -2.4, classified as osteopenic. However, it is bordering on osteoporosis, and a hip fracture is the most debilitating and life-changing fracture of all. 

As an exercise professional, I would recommend specific weight-bearing exercises like squats, uphill walking and stair climbing, as well as standing straight-leg lifts which you can do at your kitchen sink.

How Exercise Can Help

After age 40, the goals of exercise are to maintain bone mass, offset or reduce bone loss and improve balance and coordination to prevent falls.  Exercise should maximize the load to the bones with a progressive (i.e. gradual intensification) program of weight bearing aerobic exercise, weightlifting and balance training. Since loading the bones is site-specific, target the skeleton from all angles with focus on the sites that are vulnerable to fracture - the wrist, spine and hip. If you've already been diagnosed with osteoporosis, avoid jarring the spine and other vulnerable joints.

Of course, this information should not take the place of guidance from your own physician or other medical professional.  Always consult with your doctor before beginning an exercise program or becoming much more physically active.

For more detailed information about finding the appropriate level of intensity for exercise relative to your level of bone density, please read my blog, Which Exercise is Best for Osteoporosis?

© Copyright – Joan L. Pagano.  All Rights Reserved Worldwide.

Joan Pagano serves on the National Osteoporosis Foundation Ambassador Leadership Council. For expert guidance on strength training techniques, step by step photos depicting how to perform the exercises and a selection of well-rounded workouts please check out Joan’s book Strength Training Exercises for Women at http://bit.ly/JPFSTEW