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15 March 1997 | Volume 126 Issue 6 | Page 492
The simultaneous publication of two well-done meta-analyses of the effect of calcium supplementation on blood pressure [1, 2] gives insight into how meta-analyses are done. Both meta-analyses seem to have used rigorous methods, yet the number of studies combined (16 compared with 6 for hypertensive patients and 13 compared with 33 for normotensive patients) and the total number of study patients (1231 compared with 2412) were quite different. A brief review of some of the references indicates that the same study [3] was used for normotensive persons in one meta-analysis and for hypertensive patients in another and that different sample sizes were noted for the same [4]. The latter was also used for hypertensive patients in one meta-analysis and for normotensive persons in the other. Although the two meta-analyses have generally similar conclusions about the summary effect on blood pressure, the reported effect on diastolic blood pressure in hypertensive patients was statistically significant in one meta-analysis but not in the other. Fortunately for the reader, it seems that the overall effects are small enough to be dismissed as not useful in everyday clinical practice.
1. Allender PS, Cutler JA, Follmann D, Cappuccio F, Pryer J, Elliott P. Dietary calcium and blood pressure: a meta-analysis of randomized clinical trials. Ann Intern Med. 1996; 124:825-31.
2. Bucher HC, Cook RJ, Guyatt GH, Lang JD, Cook DJ, Hatala R, et al. Effects of dietary calcium supplementation on blood pressure. JAMA. 1996; 275:1016-22.
3. Cappuccio FP, Markandu ND, Singer DR, Smith SJ, Shore AC, MacGregor GA. Does oral calcium supplementation lower high blood pressure? A double blind study. J Hypertens. 1987; 5:67-71.
4. Tanji JL, Lew EY, Wong GY, Treguboff C, Ward JA, Amsterdam EA, et al. Dietary calcium supplementation as a treatment for mild hypertension. J Am Board Fam Pract. 1991; 4:145-50. About Letters
The Editors welcome submissions for possible publication in the Letters section. Authors of letters should:
LETTER
Dietary Calcium and Blood Pressure
TO THE EDITOR:
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Palo Alto Veterans Affairs Health Care System, Palo Alto, CA 94304
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