What is Osteoporosis and Low Bone Mass (Osteopenia)?
Osteoporosis is a condition of low bone mass, where bones become thin, brittle and weak. Low bone mass (formerly osteopenia) is a less severe condition of low bone mass along the same spectrum, and usually precedes the diagnosis of osteoporosis. Osteoporosis is very common, affecting up to nearly 20% of US women over age 50. Low bone mass is even more prevalent and may affect between 38-50% of US women in this same age group. Risk of osteoporosis and osteopenia increase with age because bone mass typically peaks at age 30, and then women lose ~ 0.5% of their bone mass each year thereafter until menopause. During the first 5-8 years after menopause, women may lose more than 5% of their bone mass each year.
What are Risk Factors for Osteoporosis?
- Personal history of fracture
- Family history of osteoporosis
- Caucasian race
- Low body weight
- Early menopause (especially prior to age 45)
- Lack of exercise
- Long-term low calcium intake
How Can Osteoporosis be Prevented?
Osteoporosis can be prevented with regular, weight-bearing exercise, adequate calcium intake, and limiting alcohol and tobacco use. Weight-bearing exercise, like aerobic fitness and strength training, increases bone mass before menopause , and slows down bone loss after menopause. Adequate calcium and vitamin D intake also slow the rate of bone loss. The National Institutes of Health recommends the following daily calcium intake based on age group and menopausal status:
- Women under age 51: at least 1000 mg of calcium per day
- Premenopausal women ages 51 and older: at least 1200 mg of calcium per day
- Postmenopausal women and all women over age 65: at least 1500 mg of calcium per day
The National Institutes of Health and the Institute of Medicine both recommend the following daily vitamin D intake based on age group:
- Women under age 70: at least 600 IU of vitamin D daily
- Women ages 70 and older: at least 800 IU of vitamin D daily
Good sources of calcium and vitamin D include milk, yogurt, leafy green vegetables, nuts, and calcium-fortified cereals. Calcium supplements can also contribute to total daily calcium intake, but keep in mind that the body can only absorb ~ 500mg of calcium at a time. This means that if you are taking more than 500 mg of calcium in a supplement form, it should be divided into 2 doses.
What are the Screening Recommendations for Osteoporosis?
Screening for osteoporosis is recommended for all post-menopausal women aged 65 years or older, and may be performed as frequently as every 2 years. Screening may also be recommended for women younger than age 65 depending on their personal risk factors. Screening is performed with a Bone Mineral Density (BMD) test, which is performed in our office or at one of the local radiology offices.
The BMD test uses low dose x-rays to measure bone mass in the multiple areas of the body, including the spine, hip and wrist. Combining your BMD test result with important pieces of clinical information like your age, height, weight , tobacco history, and medication use, the Fracture Risk Assessment Tool (FRAX) score can be calculated. FRAX predicts your 10-year probability of a major bone fracture or hip fracture due to osteoporosis. This FRAX score can then be used to guide treatment recommendations. Typically, medical treatment is recommended for patients with a ≥ 20% probability of major bone fracture or a ≥ 3% probability of hip fracture.
How is Osteoporosis Treated?
First line treatment for osteoporosis is typically a class a medications called the bisphosphosphonates, which slow bone breakdown and thereby increase bone density. Common bisphosphonates include alendronate (Fosamax), risedronate (Actonel), and ibandronate (Boniva). Oral bisphosophonates may cause upper gastrointestinal side effects and are not usually used in patients with gastroesophageal reflux disease (GERD) or other abnormalities of the esophagus. Zoledronic acid (Reclast) is another bisphosphonate that is administered intravenously once a year, thereby avoiding the gastrointestinal side effects of the oral agents.
Other medications for the treatment of osteoporosis include selective estrogen receptor modulators (SERMs), like raloxifene, as well as calcitonin, parathyroid hormone and denosumab (Prolia). Denosumab is a monoclonal antibody that works by inhibiting osteoclasts, the cells responsible for breaking down bone. It thereby reduces bone degradation and consequently, the progression of osteoporosis. Prolia is administered as an subcutaneous (under the skin) injection in the office every 6 months.