Osteopenia: An Overview

Osteopenia is a condition where the bone density is lower than normal but not so low that it meets the criteria for osteoporosis. The term is derived from the Greek words osteo, meaning bone and penia, meaning poverty. If taken literally, osteopenia means "poor bone".

Osteopenia is a loss of mineral density within bone tissue. It represents part of a continuum with osteoporosis; the two conditions are linked although not everyone with osteopenia will develop osteoporosis.

Osteopenia Diagnosis

 

Normal	BMD greater than 1 sd below the mean of young adults
Osteopenia	BMD between 1-2.5 sd below the mean of young adults
Osteoporosis	BMD more than 2.5 sd below the mean of young adults
Severe or established	BMD more than 2.5 sd below the mean of young adults plus one or more fragility fractures.

 

Table 1 Diagnostic criteria for osteoporosis

Table 1 describes the diagnostic criteria for osteoporosis (3) as developed by the World Health Organisation (WHO) and illustrates where osteopenia fits into the continuum.

Osteopenia is determined based on the findings of bone mineral density (BMD) testing. A special machine called a DXA machine (DXA stands for dual energy x-ray absorptiometry) is used to measure the amount of bone mineral in a certain area. Testing can be performed on your forearm, wrist, hand, hip, spine, or foot. The BMD test is an important tool in the arsenal of osteoporosis doctors, and they are commonly ordered by doctors.

The findings of a BMD test are classified according to comparison with average values of healthy subjects which provides a ‘T-score’. A T-score, between -1.1 and -2.4 identifies osteopenia. The lower the T-score (higher the negative number), the higher the risk for bone fracture.

Symptoms of Osteopenia

Osteopenia has been described as a "silent" condition (4). There are no outward signs or symptoms, although certain risk factors and precursors can be identified.

Risk Factors which may influence loss of BMD

Most cases of osteopenia are seen in post menopausal women, this is due to the influence of estrogen on bone cells (i.e. where estrogen levels are decreased osteoclasts have a prolonged lifespan so more mineral is deorbed than absorbed into the bone). Women also generally have a lower peak BMD. Peak BMD is reached around the age of 30; as we age it steadily decreases. Other risk factors include: a personal or family history, low body weight, a sedentary lifestyle, diet, smoking and other medical conditions.

Individuals who exhibit such risk factors should consider screening for osteopenia/osteoporosis. The National Osteoporosis Foundation (5) lists the following as recommendations for undergoing DXA testing:

• Women: postmenopausal and under age 65 with risk factors for osteoporosis, over 65 whether or not there are risk factors present
• Men: age 50-70 with risk factors for osteoporosis, over age 70 whether or not there are risk factors present
• Anyone over age 50 after a bone break

If a patient gets shorter with age, that often provokes a bone mineral density test. Other reasons your doctor may give you a BMD test:

• Long-term use of certain medications including steroids for breast cancer, prostate cancer, aromatase inhibitors, cortisone, and hormone replacement therapy
• Hyperthyroidism or Hyperparathyroidism
• Frailty syndrome
• Fracture or bone loss in spine
• Chronic back pain that causes the doctor to suspect a fracture

Prevalence of Osteopenia

Because there are no obvious symptoms of osteopenia, it is impossible to accurately predict how many people have this condition as many cases may go unreported. A study in 2007 stated that approximately 33.6 million adults were osteopenic in 2002; it went on to estimate that this figure may rise to 47.5 million by 2020.

Treatment of Osteopenia

Appropriate treatment of osteopenia makes osteoporosis preventable.

Drugs that stop bone re-absorption and hormone replacement therapy have been proven to help for osteoporosis but there is little long term evidence as to their efficacy in osteopenia. The National Osteoporosis Foundation guidelines for post-menopausal women and men aged 50 or older recommend that:

• People with T-scores of -1 and above (normal bone density) do not need to take an osteoporosis medication.
• People with T-scores between -1 and -2.5 (osteopenia) should consider taking an osteoporosis medication when they have certain risk factors.
• All people with T-scores of -2.5 and below (osteoporosis) should consider taking an osteoporosis medication.

A recent development which may assist doctors and patients to decide if osteoporosis medication is necessary is a tool called "Absolute Fracture Risk Assessment" which estimates a person’s chance of breaking a bone over a period of 10 years.

Regardless of whether medication is used, other interventions should be implemented in patients with osteopenia. Ensuring that there is sufficient calcium and vitamin D in the diet, lifestyle modifications such as stopping smoking and getting regular resistance exercise will help to maintain bone mineral density.

Controversy: Disease-mongering?

Some allege that osteopenia is an artifical illness manufactured by the pharmaceutical companies to sell drugs. Here is an NPR story on that. The British Medical Journal published an analysis on this question in 2008. Text here.

References

1. McArdle, WD, Katch, FI and Katch, VL. Exercise physiology - Energy nutrition and human performance. 6th edition. s.l. : Lippincott Williams & Wilkins, 2006.
2. Hormone therapy for the prevention of bone loss in menopausal women with osteopenia. Is it a viable option? Hohenhaus, M H, McGArry, K A and Nananda, F C. 16, 2007, Drugs, Vol. 67, pp. 2311-2321.
3. The role of physiotherpay in the prevention and treatment of osteoporosis. Bennell, K L, Khan, K and McKay, S. 2000, Manual Therapy, Vol. 5, pp. 198-213.
4. An observational study on the adherence to treatment guidelines of osteopenia. Buencamino, M C A, et al. 6, 2009, Journal of womens health, Vol. 18, pp. 873-881.
5. National Osteoporosis Foundation. [Online] http://www.nof.org.
6. Prevelence of low femoral bone density in older US adults from NHANES III. Looker, AC, et al. 1997, J. bone mineral res., Vol. 12, pp. 1761-1786.
7. Primary care use of FRAX (R): Absolute fracture risk assessment in postmenopausal women and older men. Siris, ES, Baim, S and Nattiv, A. 1, 2010, Post Graduate Medicine, Vol. 122, pp. 82-90.
8. Who's affraid of the big bad Wolff: 'Wolff's law' and bone functional adaptation. Ruff, C, Holt, B and Trinkaus, E. 2006, Am. J. Physical anthropology, Vol. 129, pp. 484-498.