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Calcium supplements in older women: Compliance is crucial

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A large, five-year placebo-controlled study of calcium supplements in relatively healthy and ambulatory elderly women (>70 years) showed no significant protection against fractures, most likely because of lack of compliance, Australian researchers report in the April 24, 2006 issue of the Archives of Internal Medicine However, an effect was seen in the women who managed to comply (taking more than 80% of their tablets). This prespecified subgroup represents just over half of the trial population- 830 women out of a total of 1460 participants (56.8%).

Calcium supplements are “ineffective as a public-health intervention in preventing clinical fractures in the ambulatory population owing to poor long-term compliance,” the researchers conclude. However, the regimen (calcium carbonate 600 mg twice daily) is effective in individuals who are compliant, they add. In this group, the risk of any clinical osteoporotic fracture was reduced by a factor of 0.34 (fracture incidence in the calcium group was 10.2% vs 15.4% in the placebo group). So where do these latest findings leave doctors treating elderly women? Although calcium supplements are ineffective as a public-health intervention, they should still be recommended to individuals, although patients have to be “supercompliant, otherwise the effect size is too small,” Dr Richard Prince (University of Western Australia, Perth) comments to rheumawire. “Public health and clinical practice are the two faces of healthcare.” Prince says that physicians involved in personal healthcare should recommend that patients over 70 years of age increase their calcium intake by 1.2 g, taken as a 600-mg dose twice a day, and they should do this irrespective of their bone-mineral density (BMD) as measured by dual x-ray absorptiometry (DXA). “If they do so, and the patients carefully follow this advice, then they will have 30% fewer fractures over five years,” he tells rheumawire. This effect is comparable to what has been seen with bisphosphonates. However, he points out that the effect with calcium was seen in a general population and it “applied to all, if they did what they were asked to do,” whereas “the evidence base for bisphosphonates, of course, applies only to patients with osteoporosis (DXA T score <2.5)."The recommendation to take calcium should also include a recommendation to take vitamin-D supplements if the vitamin-D level is low, which is a frequent problem for whites in the northern hemisphere, Prince adds. In the Australian study he headed, most women had vitamin-D levels that were generally above the deficient range; in a small subset tested, only 6.1% were deficient (with levels below 12 ng/mL or <30 nmol/L). This contrasts with data from North America, where studies have found vitamin-D deficiency in a large majority of postmenopausal women, as previously reported by rheumawire.Prince notes that it is also important to advise patients - in the first instance, before considering pharmaceutical therapy - to alter their lifestyle (diet and exercise). "The smart ones do," he adds. Compliance was "quite good" The trial conducted by Prince and colleagues recruited women from the electoral rolls in Western Australia, inviting them by letter to join in the study. It was supported by a grant from the Healthway Health Promotion Foundation of Western Australia and by a project grant from the National Health and Medical Research Council of Australia. After five years, 236 individuals (16.2%) sustained 297 incident osteoporotic fractures. An intention-to-treat analysis showed no effect of calcium on the risk of fracture - there was no difference in the number or type of fractures sustained between placebo- and calcium-treated patients, the researchers report. The lack of a significant effect is "likely due to the lack of compliance with the medication regimen, which in the power calculation before commencement of the study was predicted to be 30% but was in fact 43%," the researchers write. "This is a limitation of the study but reflects the difficulties of implementation of preventive health practice in all such studies." Prince tells rheumawire that the rate of compliance seen in this trial "was quite good for a five-year study." However, he adds: "I was surprised that the size of the treatment effect was so dependent on compliance ... The problem appears to be that the duration of action of dietary calcium on suppressing parathyroid hormone is too short - hence the importance of regular twice-daily dosing for five years."(Source: (1) Prince RL, Devine A, Dhaliwal SS, and Dick IM. Effects of calcium supplementation on clinical fracture and bone structure. Arch Intern Med 2006; 166:869-875:Rheumawire: Joint and Bone: April 2006.)

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Posted On: 4 May, 2006
Modified On: 16 January, 2014

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