Rheumatology: 15. Osteoporosis Review John P
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Clinical basics Rheumatology: 15. Osteoporosis Review John P. Wade Synthèse The case Mrs. C is an otherwise healthy, 58-year-old woman who consults her primary Dr. Wade is with the Division care physician after experiencing the acute onset of severe low thoracic pain. of Rheumatology, University She reports having lifted her heavy grandson the previous day. X-ray films of of British Columbia, and the thoracic spine show a 50% compression fracture of the T11 vertebra. She Vancouver General Hospital, has always had a reasonable intake of calcium and maintains an active Vancouver, BC. lifestyle. She reached menopause at the age of 48 years, but she did not choose hormone replacement therapy because she was concerned that it This article has been peer reviewed. might be associated with breast cancer. She continues to smoke 1 pack of cig- arettes a day (despite counselling from her physician) and drinks alcohol so- CMAJ 2001;165(1):45-50 cially. She has no family history of osteoporosis or cardiac disease. Mrs. C This series has been reviewed had a hysterectomy 10 years ago for reasons that are unclear. She is accom- and endorsed by the Canadian panied by her only daughter, a nurse, who is anxious that the appropriate Rheumatology Association. tests be carried out and that treatment be started immediately. The Arthritis Society salutes CMAJ steoporosis is a common clinical problem that has been well reviewed.1–3 for its extensive series of articles The lifetime risk of an osteoporotic fracture is 1 in 4 among women and on arthritis. The Society believes 1 in 8 among men. Changing demographics will lead to a significantly in- that this kind of information is O crucial to educating physicians creased risk as the population ages and to staggering health care costs in Canada and the United States.4–8 The ability to diagnose osteoporosis 10–20 years before about this devastating disease. clinically identifiable fractures occur has given the primary care physician the lead- ing role in the prevention and treatment of this condition. The primary care physi- Series Editor: Dr. John M. Esdaile, cian can encourage the patient to make lifestyle changes and can provide other Professor and Head, Division of Rheumatology, University of British medical interventions early on, before there is irreversible bone loss or before clini- Columbia, and Scientific Director, cally identifiable fractures occur. Identifying common risk factors (Table 1) can in- Arthritis Research Centre of crease the likelihood of an early diagnosis of osteoporosis. Canada, Vancouver, BC. Diagnosing osteoporosis Osteoporosis may be suspected because of the presence of risk factors but is con- firmed by the following: first, a history of fracture and a subsequent determination of low bone mineral density (BMD), second, low BMD without an earlier fracture and, third, blood tests to exclude other types of metabolic bone disease. Estimating fracture risk using BMD studies Although bone quality is normal in osteoporosis, the quantity of bone is re- duced. The net balance between the formation of bone (a function of osteoblasts) and its resorption (a function of osteoclasts) determines whether the amount of bone increases or decreases over time. Bone mass, which is determined by the net effect of these 2 processes, increases from birth until the third decade of life, when it begins to decline in both men and women. A more rapid decline occurs in women during their early postmenopausal years.1 Currently, BMD is the best independent risk factor for fractures.4,5 BMD can be partly quantified by histomorphometric analysis of bone biopsy specimens, but this di- rect means of analysis is expensive and not useful in clinical settings. The widespread use of simple noninvasive bone densitometry has resulted in significant improvement in the early detection of osteoporosis. Dual-energy x-ray absorptiometry (DEXA) is a pre- cise way of measuring BMD. The radiation risk of DEXA is extremely low (10% of the radiation of a chest radiograph). Assessment of BMD using radiographs of the hand and CMAJ • JULY 10, 2001; 165 (1) 45 © 2001 Canadian Medical Association or its licensors Wade ultrasound attenuation are methods that are less expensive BMD between 1 and 2.5 standard deviations (SDs) below the than DEXA and might be used to screen patients, but their peak value is defined as osteopenia. A density that is more than clinical role, and whether these methods will replace DEXA, 2.5 SDs below the peak value confirms the diagnosis of osteo- remains uncertain. Heel ultrasound can be used as a screening porosis; severe osteoporosis includes the presence of a clinical test for osteoporosis, but up to 10% of patients will have false fracture. It is important to recognize that the WHO classifica- “normal” results, in spite of having significant osteoporosis. tion was primarily designed to assign patients to categories for Because degenerative changes in the lumbar spine or clinical trials. In clinical practice, this strict criterion is less use- calcification of the aorta may result in false elevations of ful, because the physician often wishes to initiate treatment for BMD in elderly patients, it is more reasonable to assess the a patient before the presence of osteoporosis is confirmed. BMD of the proximal femur. In younger individuals, how- ever, measurement of the BMD of the lumbar spine is Treatment more accurate and preferable. Studies of cost-effectiveness need to be carried out to determine whether a single site or Dietary calcium and vitamin D 2 sites should be measured. A BMD measurement is useful if it will alter the clinical Dietary calcium intake or calcium supplements should decision-making process. Determination of BMD in be recommended for all women and men, both young and women at menopause provides the primary care physician old. Clinical studies have shown that calcium can reduce and the patient with useful information about whether bone loss by up to 0.5% per year compared with placebo. treatment is needed. In addition, most clinical trials of osteoporosis treatments Once a baseline level of BMD is obtained, the physician use calcium and vitamin D in the placebo control group, must decide whether future BMD tests will be helpful. The and such studies often show no bone loss or even slight im- Osteoporosis Society of Canada recommends a follow-up provement in BMD over 3 years.9 measurement of BMD in 2–3 years, but this recommendation Common calcium supplements include calcium carbonate can be tailored to the individual patient. A repeated test will and calcium citrate. Calcium carbonate is an effective and in- provide reassurance that treatment has been effective. Local expensive form of calcium supplement that is readily available guidelines may limit the frequency of repeated BMD testing. (e.g., 1 Tums tablet contains 200 mg calcium compared with 300 mg in a 250-mL glass of skim milk or whole milk). Pa- In the future tients with previous renal calculi should avoid excess calcium supplements and should consider calcium citrate if necessary. Markers of bone formation and resorption might be useful Studies have revealed decreased levels of vitamin D in in addition to BMD measurement in determining response to elderly people, providing a further reason to suggest that treatment. Current clinical urinary markers are not accurate, patients take vitamin D (800 IU/d). but if sensitive serum markers become clinically available in A European study that considered levels of calcium and the next few years, these will need to be evaluated. vitamin D in elderly nursing-home patients found that pro- viding calcium citrate (1200 mg calcium) and vitamin D Defining osteoporosis (800 IU) daily resulted in a reduction in hip fractures of up to 50%.10 These studies have resulted in the recommenda- The World Health Organization (WHO) categorizes bone tion that all patients should have a good dietary calcium in- loss as osteopenia, osteoporosis or severe osteoporosis.7 Cur- take and should take vitamin D supplements (Table 2). rent BMD is compared with a patient’s theoretical peak BMD. Lifestyle factors Table 1: Important risk factors for bone fractures and osteoporosis Women who smoke should be encouraged to stop. Smoking results in earlier menopause and significant bone • Advanced age loss in women. In addition, postmenopausal women who are • Female sex smokers benefit less from oral conjugated estrogens in terms • Being white or of Asian origin of maintaining BMD.11 If estrogen is required, smokers • Thin build might be candidates for oral or transdermal estradiol. • Premature menopause Heavy alcohol intake is another significant risk factor for • Family history of osteoporosis osteoporosis. In men, this is one of the most common rea- • Low dietary intake of calcium sons for the development of osteoporosis and bone frac- • Smoking tures. To minimize the adverse effect on bones, alcohol • Heavy alcohol intake should be limited to 1–2 drinks daily. • Endocrine problems (gonadal failure, hyperthyroidism Weight-bearing activity reduces bone loss and improves and hyperparathyroidism) bone strength.12 People who exercise regularly have greater • Corticosteroid use muscle bulk and are less likely to fall, resulting in a de- 46 JAMC • 10 JUILL. 2001; 165 (1) Osteoporosis creased number of fractures of the proximal femur and the of postmenopausal osteoporosis (Table 3). Transdermal es- upper extremities. Weight-bearing exercises include walk- trogen is effective in treating bone loss but may be less ben- ing, dancing, climbing stairs and performing a low-impact eficial than oral estrogens regarding lipid metabolism. exercise program. Using small ankle or wrist weights can Although ERT treatment to alleviate menopausal symp- further augment BMD in weight-bearing exercise regimes. toms can be tapered off over months or a few years,17 long- Patients should be encouraged to walk briskly for 1 hour, 3 term treatment is required to inhibit bone loss.