Osteoporosis - An Overview
Definition
Osteoporosis is defined as "a disease characterized by low bone mass, microarchitectural deterioration of bone tissue, or both, leading to skeletal fragility." Osteopenia is a precursor to osteoporosis.
Epidemiology
- Osteoporosis affects an estimated 30 percent of postmenopausal white and Asian women in the U.S. Rates are lower, though not inconsequential, among other groups: approximately 10 percent of African American women and 13 to 16 percent of Hispanic women age 50 and older have osteoporosis.
- Hip fractures occur in 15 percent of elderly women.
- Only one-third of hip-fracture patients will return to pre-fracture independence.
- As our population ages, the number of hip fractures is expected to triple by 2040.
- Long-term sequelae include fractures of hip, spine, wrist, ribs, etc.; chronic fracture pain; and compression of internal organs from repeated vertebral compression fractures and kyphosis.
- As with post-menopausal women, hypogonadism in men may accelerate bone loss.
- Corticosteroid therapy, severe hyperthyroidism, and hyperparathyroidism can also cause rapid bone loss.
Risk Factors
There are many risk factors for osteoporosis and fractures, but the most important clinical risk factors are:
- Age
- Family history of fracture in first-degree relative (particularly prior to age 80)
- Personal history of fracture after age 40
- Current cigarette smoking
Prevention
Peak bone mass is reached in the late twenties for women, mid-thirties for men. Prevention should start in the teenage years or earlier. The 2010 Institute of Medicine Guidelines recommend the following daily allowances of calcium and vitamin D.
| Age | Recommended Daily Intake |
|---|---|
| Infants 0 to 6 months | 200 mg |
| Infants 6 to 12 months | 260 mg |
| Children 1-3 years old | 700 mg |
| Children 4-8 years old | 1000 mg |
| Children & young adults 9-18 years | 1300 mg |
| Adults 19-50 years | 1000 mg |
| Women and men over 50 years | 1200 mg |
| Age | Recommended Daily Intake |
|---|---|
| Birth to 11 months | 400 IU |
| Ages 1 to 70 years | 600 IU |
| Age 70 and over | 800 IU |
* The Institue of Medicine will be coming out with new recommendations in 2010.
Weight-bearing exercise on sites susceptible to fracture (i.e., walking for hip and spine density, weights for wrists)
Fall prevention is critical.
Screening
A 2011 USPSTF guidelines suggest that BMD be performed on:
- All women 65 and older
- Women 50-64 with a 10 year risk of fracture > or = to 9.3%
- Men 70 year or older or any age if 10 year risk of fracture > or = to 9.3%
The World Health Organization FRAX calculator can be used to calculate this risk the 10-year risk
Older risk-assessment tools have largely been supplanted by FRAX but may be useful where limited risk factor information is available or as a paper-based scoring system. Examples include the following:
- ORAI (Osteoporosis Risk Assessment Instrument)
- SCORE (Simple calculated risk estimation score)
- OST (Osteoporosis Self-assessment Tool
Diagnosis and Follow-up
- Diagnosis is made by T-score on DXA of less than -2.5 OR
- By fragility fracture regardless of T-score (i.e., vertebral compression fracture).
- Site of DXA measurement (hip/spine/wrist) best predicts fracture at that site.
- Best site for overall prediction of fracture risk is the hip.
- DXA should not be repeated more frequently than every 2 to 5 years unless you expect rapid loss, such as with steroid use.
Treatment
- Calcium, vitamin D, and weight-bearing exercise, as above
- In the United States, the National Osteoporosis Foundation and the USPFTF recommends consideration of pharmacologic treatment of postmenopausal women and men aged 50 years and older, based on the following:
- A hip or vertebral (clinical or morphometric) fracture
- T-score ≤-2.5 at the femoral neck or spine after appropriate evaluation to exclude secondary causes
- Low bone mass (T-score between -1.0 and -2.5 at the femoral neck or spine) and either a
- 10-year probability of a hip fracture ≥3% or
- 10-year probability of a major osteoporosis-related fracture ≥20% based on the US-adapted WHO FRAX algorithm
- Clinicians judgment and/or patient preferences may indicate treatment for people with 10-year fracture probabilities above or below these levels
- The choice of pharmacologic therapy should be individualized. Choices include:
- Bisphosphonates, selective estrogen receptor modulators, RANKL inhibitors, teriparatide, calcitonin, estrogen and testosterone.