Bmj2008 ca supplementation

Vascular events in healthy older women
receiving calcium supplementation:
randomised controlled trial
Mark J Bolland, P Alan Barber, Robert N Doughty, Barbara Mason, AnneHorne, Ruth Ames, Gregory D Gamble, Andrew Grey and Ian R Reid BMJ 2008;336;262-266; originally published online 15 Jan 2008; doi:10.1136/bmj.39440.525752.BE Updated information and services can be found at:
http://bmj.com/cgi/content/full/336/7638/262
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Vascular events in healthy older women receiving calciumsupplementation: randomised controlled trial Mark J Bolland, research fellow, P Alan Barber, senior lecturer, Robert N Doughty, associate professor,Barbara Mason, research officer, Anne Horne, research fellow, Ruth Ames, research officer,Gregory D Gamble, research fellow, Andrew Grey, associate professor, Ian R Reid, professor Trial registration Australian Clinical Trials Registry ACTRN Objective To determine the effect of calcium supplementation on myocardial infarction, stroke, and sudden death in healthy postmenopausal women.
Design Randomised, placebo controlled trial.
Evidence suggests that high calcium intakes might Setting Academic medical centre in an urban setting in protect against vascular disease. Calcium supplemen- tation has been shown to increase the ratio of high Participants 1471 postmenopausal women (mean age density lipoprotein cholesterol to low density lipopro- 74): 732 were randomised to calcium supplementation tein cholesterol by almost 20% in healthy postmeno- pausal women.1 Studies in humans and animals suggestthat these effects on cholesterol result from calcium Main outcome measures Adverse cardiovascular events binding to fatty acids and bile acids in the gut, leading to over five years: death, sudden death, myocardial malabsorption of fat,2 3 although direct effects of infarction, angina, other chest pain, stroke, transient calcitropic hormones on adipocytes have also been ischaemic attack, and a composite end point of implicated.45 Cholesterol changes of this order may be myocardial infarction, stroke, or sudden death.
associated with 20%-30% reductions in vascular event Results Myocardial infarction was more commonly rates.67 In addition evidence suggests that calcium reported in the calcium group than in the placebo group supplementation causes reductions in blood pressure,8 (45 events in 31 women v 19 events in 14 women, P=0.01).
although these reductions are small and transient.9 The composite end point of myocardial infarction, stroke, Evidence is also inconsistent that high calcium intakes or sudden death was also more common in the calcium are associated with weight loss.9 These data from group (101 events in 69 women v 54 events in 42 women, interventional studies are supported by observational P=0.008). After adjudication myocardial infarction evidence that calcium intake is inversely associated remained more common in the calcium group (24 events with vascular disease. The Iowa women’s health study, in 21 women v 10 events in 10 women, relative risk 2.12, for example, found a one third reduction in deaths from 95% confidence interval 1.01 to 4.47). For the composite cardiovascular events in women whose calcium intakes end point 61 events were verified in 51 women in the (diet or supplements) were in the highest fourth calcium group and 36 events in 35 women in the placebo compared with those in the lowest fourth.10 The Boston group (relative risk 1.47, 0.97 to 2.23). When unreported nurses health study found that women in the highest events were added from the national database of hospital fifth for calcium intake had an adjusted relative risk of admissions in New Zealand the relative risk of myocardial ischaemic stroke of 0.69 (95% confidence interval 0.50 infarction was 1.49 (0.86 to 2.57) and that of the to 0.95) compared with those in the lowest fifth.11 A composite end point was 1.21 (0.84 to 1.74). The study in the United Kingdom reported a strong inverse respective rate ratios were 1.67 (95% confidence intervals relation between calcium intake and standardised 0.98 to 2.87) and 1.43 (1.01 to 2.04); event rates: placebo mortality ratios for ischaemic heart disease.12 Commu- 16.3/1000 person years, calcium 23.3/1000 person nities with a calcium rich water supply also seem to years. For stroke (including unreported events) the relative have lower risks of cardiovascular events.13 risk was 1.37 (0.83 to 2.28) and the rate ratio was 1.45 Because of the high incidence of vascular disease in postmenopausal women any effects of calcium supple- Conclusion Calcium supplementation in healthy ments on vascular health could be as important in terms postmenopausal women is associated with upward of their effects on morbidity and mortality as their trends in cardiovascular event rates. This potentially effects on bone. Although no randomised controlled detrimental effect should be balanced against the likely trials have been designed primarily to assess the effect of calcium supplementation on vascular event rates or particularly oestrogen. We recently reported a five year study of calcium supplementation in 1471 healthy older women (mean age 74).15 We tested whether the potential vascular benefits from calcium use were evident in the context of a randomised controlled trial.
This study is a secondary analysis of a randomisedcontrolled trial of calcium supplementation in healthy postmenopausal women, primarily designed to assessthe effects of calcium on bone density and fracture Time to first myocardial infarction (months) incidence over five years. The methods have been Kaplan-Meier survival plot showing proportion of healthy described previously.115 Briefly, women were included postmenopausal women assigned to calcium supplementation in the study if they had been postmenopausal for more or to placebo that had a verified myocardial infarction during the than five years, were aged 55 or more, and had a life study. Included are events self reported by participants and expectancy of more than five years. We excluded those from the national database of hospital admissions andreview of death certificates (P women who were receiving treatment for osteoporosis or taking calcium supplements; those with any othermajor ongoing disease including hepatic, renal, orthyroid dysfunction, malignancy, or metabolic bone deaths, secondary analyses of the women’s health disease; and those with serum 25-hydroxyvitamin D initiative study have recently shown no consistent levels less than 25 nmol/l. Participants gave written, effects in a population of average age 62.14 Inter- informed consent to take part in the study.
pretation of the data from this study is hampered by its Women were recruited by advertisement, and by failure to show consistent effects of calcium on bone post using electoral rolls. In total, 2421 women density and fractures, poor adherence to study drugs, responded, of whom 641 were ineligible and 309 and a high rate of use of other vasoactive drugs, Table 1 | Descriptiveandbiochemicalcharacteristicsofhealthy,postmenopausalwomenassignedtocalciumsupplementationortoplacebo. Values are means (standard deviations) unless stated otherwise Glomerular filtration rate* (ml/min/1.73 m2) High density lipoprotein cholesterol (mmol/l)† Low density lipoprotein cholesterol (mmol/l)† Ratio of high density lipoprotein to low density lipoprotein† No (%) with previous ischaemic heart disease No (%) with previous stroke or transient ischaemic attack METS=metabolic equivalent intensity level.
*Estimated as recommended by the Australasian Creatinine Consensus Working Group.18†Lipids were measured in a subset of 223 postmenopausal women (111 assigned to calcium supplementation and 112 assigned to placebo). Bloodsamples were taken fasting.
Participants received either 1 g of elemental calcium diagnostic Q waves on the electrocardiogram, electro- daily as the citrate (Citracal; Mission Pharmacal, San cardiographic changes indicative of ischaemia (ST Antonio, TX) or identical placebo. They were asked to segment elevation or depression), or coronary artery take two tablets (each containing 200 mg elemental intervention. We defined stroke as a sudden focal calcium) before breakfast and three in the evening. We neurological deficit of presumed vascular origin that used a validated food frequency questionnaire to assess persisted for more than 24 hours or that led to death, dietary calcium intake.16 Compliance was assessed by and transient ischaemic attack as a sudden focal tablet counts. The women were followed up every six neurological deficit of presumed vascular origin that persisted for less than 24 hours. Sudden death wasdefined in accordance with the international classifica- tion of diseases, ninth revision (code 798.2) as death At each visit we recorded adverse events. We occurring in less than 24 hours from onset of compared the frequency of events in the two groups: symptoms, not otherwise explained. Data for each death, sudden death, myocardial infarction, angina, event were compiled by a doctor and then adjudicated other chest pain, stroke, and transient ischaemic attack, by a cardiologist (myocardial infarction and sudden and a composite cardiovascular end point consisting of death) or neurologist (transient ischaemic attack or sudden death, myocardial infarction, angina, or chest stroke). All were blinded to the participants’ treatment pain. We wrote a more detailed protocol before the analysis of vascular events, and this added an additionalcomposite end point of myocardial infarction, stroke, or sudden death, as this has become the commonly We used Student’s t test to compare the groups for used end point in such analyses. It also enabled continuous variables and Fisher’s exact test for the adjudication of these events. When a myocardial numbers of women experiencing an event. Results are infarction, stroke, or transient ischaemic attack was presented as relative risks with 95% confidence inter- recorded we reviewed the participant’s medical vals. We used Kaplan-Meier survival analysis to records (completed by the family doctor or hospital).
compare the proportion of women in each group For women who died during the study we obtained the experiencing an event over time, using Prism v 4.03 cause of death from hospital records or death (GraphPad Software, San Diego, CA). We calculated certificates. To identify events that occurred during the person time rates for events using Open-Epi V1.1 the study and were unreported by participants we (www.openepi.com) and compared these using an searched the national database of hospital admissions exact midP statistic. Poisson regression was done using for cardiovascular events (discharge codes 410-414 and the GENMOD procedure of SAS. The number needed 430-438, international classification of diseases, ninth to treat or number needed to harm was calculated as the revision). We also reviewed the hospital records related inverse of the absolute difference in event rates between the groups. The significance level was set at We defined myocardial infarction in accordance P<0.05; all tests were two tailed. Unless specified with the Joint European Society of Cardiology and otherwise statistical analyses were done using the SAS American College of Cardiology Committee criteria software package version 9.1 and were based on for acute, evolving, or recent myocardial infarction.17 Thus we classified an event as a myocardial infarction ifthe typical rise and fall of a biochemical marker for myocardial necrosis occurred with at least one of the Overall 1471 healthy postmenopausal women were following: ischaemic symptoms, development of randomised: 732 to calcium and 739 to placebo. Three Table 2 | Potential vascular events self reported by healthy postmenopausal women assigned to calcium supplementation or toplacebo or reported by family members. Values are numbers of women (numbers of events) unless stated otherwise *Differences between groups in numbers of women with reported events, based on Fisher’s exact test.
Table 3 | Verified vascular events self reported by healthy postmenopausal women assigned to calcium supplementation or toplacebo or reported by family members. Values are numbers of women (numbers of events) unless stated otherwise *Differences between groups in numbers of women with reported events, based on Fisher’s exact test.
hundred and thirty six women in the calcium group and proportion of women with a verified stroke or a 296 women in the placebo group stopped the study verified composite end point showed a similar drug before the five year end point. Baseline char- temporal pattern (P=0.2-0.3 for both analyses, data acteristics were similar between the groups (table 1).
Between baseline and five years significant changes When the analyses in table 4 were restricted to events were found in weight (−0.9 kg), systolic blood pressure occurring in participants with more than 60% com- (10 mm Hg), high density lipoprotein cholesterol levels pliance since the start of the study no sudden deaths (0.19 mmol/l), and low density lipoprotein cholesterol were found. For myocardial infarction, stroke, and levels (−0.76 mmol/l); these did not differ between the myocardial infarction or stroke, event rates were little groups. The flow chart of study participants has been changed in the placebo group from those for the cohort presented previously.15 Overall, 90% of participants shown in table 4 (6.6, 11.6, and 18.2), but event rates had complete follow-up. Among those still taking the tended to be higher in the compliant members of the study drugs at five years, tablet compliance was 85% in calcium group (15.5, 22.6, and 38.1). This was reflected both groups in each six month period. When in the respective rate ratios (2.4, 0.8 to 8.5, P=0.14; 2.0, participants who discontinued the study drugs were 0.8 to 5.1, P=0.14; and 2.1, 1.1 to 4.4, P=0.03).
included, compliance over the study was 58% in the Poisson regression analysis was used to determine placebo group and 55% in the calcium group (P=0.13).
whether the effect of treatment on number of events per Table 2 shows the numbers of women with possible participant was independent of age and glomerular cardiovascular events that were self reported or filtration rate (above or below median for each); history reported by family members. Although no difference of ischaemic heart disease, stroke, hypertension, was found between groups in the number of women dyslipidaemia, and diabetes; and compliance with the with any cardiovascular event (angina, chest pain, study drug. The P values for the effect of treatment myocardial infarction, or sudden death), a statistically allocation were not significantly attenuated by adjust- significant increase was found in the number of women ment for any of these potential confounders (table 5), who had a myocardial infarction (P=0.01). Similar but previous ischaemic heart disease and high com- trends were found in the calcium group compared with pliance were identified as independent risk factors.
the placebo group for stroke, transient ischaemic No differences were found between groups in the attack, and sudden death. The composite end point of number of women who had a verified ST segment myocardial infarction, stroke, or sudden death was elevation myocardial infarction or a verified non-ST higher in the calcium group (P=0.008).
segment elevation myocardial infarction, or in the Table 3 shows the number of women with cardio- number of women in whom the diagnosis of myo- vascular events that were self reported or reported by cardial infarction was made by an elevated troponin family members and were confirmed by the adjudica- level in the context of a recent operation or other tion process. A statistically significant increase was important medical illness. Also, no differences were found in myocardial infarction in the calcium group, found between groups in the number of women with but there was not a significant increase in stroke or the different clinical categories of stroke (partial anterior circulation infarct, total anterior circulation infarct, Table 4 shows adjudicated data, including events not lacunar infarct, or posterior circulation infarct).19 reported by participants. A statistically significant The number of women needed to treat for five years increase in the number of women with any of the end to cause one myocardial infarction was 44, to cause one points in the calcium group was no longer found. When stroke was 56, and to cause one cardiovascular event the data were expressed as event rates, however, the was 29. By comparison the number needed to treat to rate ratios for both myocardial infarction and the prevent one symptomatic fracture was 50.
composite end point were of borderline significance.
When these data for myocardial infarction were plotted over time the groups began to diverge at about Evidence that calcium might decrease the incidence of 24 months, and thereafter continued to separate vascular events in healthy postmenopausal women is (figure), although statistical significance was not lacking, despite this study also showing a sustained achieved (P=0.14). Time course analyses of the improvement in the ratio of high density lipoprotein cholesterol to low density lipoprotein cholesterol.1 In controlled trial of a substantial dose of a highly fact the present data suggest the opposite, showing bioavailable calcium supplement and has already significant increases in the rates of adjudicated vascular shown unequivocal effects of this regimen on bone events reported by the women allocated to calcium turnover and bone density. This was something the supplementation. This effect was more noticeable in women’s health initiative did not achieve, possibly those with high compliance with the study drug and because of the low bioavailability of the supplement seems to be progressive during the 30 to 60 months of used by that study, the lower compliance with drug the study, consistent with an initial latent period during taking, or the competing effects of the use of oestrogen which vascular damage occurs before event rates increase. That calcium supplementation might haveadverse effects on vascular disease incidence is of concern because the morbidity and mortality that Some of the largest studies of calcium supplementation would follow from even a small adverse effect on do not mention vascular events,20-22 although the vascular event rates is such that the beneficial effects of randomised evaluation of calcium or vitamin D study calcium supplementation on bone loss would be did report a trend to higher death rates in those rapidly counterbalanced, as shown by the calculations allocated to calcium (18.5%) than to placebo (16.3%).22 of numbers needed to treat and harm in this study.
The findings in a study by Prince et al of 1460 Because of the potential importance of this finding postmenopausal women (mean age 75) randomised we searched for relevant events that had not been to calcium carbonate or placebo over five years were reported by participants. A national database for similar to our own.23 Few details of vascular events are hospital admissions in New Zealand made this given in that publication, but the hazard ratio for the possible, although it is not normal practice to assess diagnosis of incident ischemic heart disease was 1.12 adverse events in clinical trials in this way. This process (95% confidence interval 0.77 to 1.64). Thus the trend is resulted in some attenuation of the calcium effect, in the same direction as in the present study although although the rate ratios for myocardial infarction and non-significant. These confidence intervals do, how- for the composite end point (myocardial infarction, ever, embrace the relative risk found in the present stroke, or sudden death) still had borderline signifi- cance (P value about 0.05). Thus the present study does A much larger randomised controlled trial of the not unequivocally show an adverse cardiovascular effect of calcium carbonate and vitamin D supplemen- effect of calcium but suggests that this matter needs to tation has recently been published by the women’s be considered carefully before calcium supplementa- health initiative investigators.14 This study of 36 000 women, followed over seven years, showed no overalleffect of the supplements on cardiovascular event rates, with a hazard ratio for myocardial infarction or The present study has several limitations, principally its coronary heart disease death of 1.04 (95% confidence small size for a study with cardiovascular end points.
interval 0.92 to 1.18). When the composite end point of The cohort comprised elderly (10% aged more than 80 myocardial infarction, coronary heart disease death, at baseline) and white participants, so the findings are coronary artery bypass graft, or percutaneous coronary not necessarily generalisable to other ages and racial intervention was used, however, the hazard ratio groups. Its strengths are that it is a randomised approached significance (1.08, 0.99 to 1.19). The Table 4 | Verified vascular events self reported by healthy postmenopausal women assigned to calcium supplementation or toplacebo, reported by familymembers, and from the national databaseof hospital admissions in New Zealand.* Valuesare numbersof women (numbers of events) unless stated otherwise *Includes events not self reported by participants but found through the national database of hospital admissions and review of death certificates.
†Differences in numbers of women with verified events, based on Fisher’s exact test.
‡Differences in event rates between groups, based on Fisher’s exact test.
participants in that study differed in several respects the study by Prince et al, or the women’s health from those in the present study: they were younger initiative. Taken together these four studies raise major (mean age 62), heavier (mean body mass index 29), had concerns about the cardiovascular safety of calcium higher calcium intakes (mean 1150 mg/day), were supplementation, particularly with respect to myo- taking vitamin D with the calcium, and 50% were cardial infarction in older postmenopausal women.
taking hormone replacement therapy. Hazard ratiosfor vascular events in the supplemented group tended to be higher in older women and the interaction with The finding of an adverse trend in vascular events with body mass index was significant such that women with calcium supplementation is not necessarily surprising, lower values had a higher cardiovascular risk asso- since calcium supplements acutely elevate serum ciated with the use of calcium and vitamin D. Thus the calcium levels24 possibly accelerating vascular calcifi- hazard ratio for myocardial infarction for women with cation, which is predictive of vascular event rates.25 a body mass index less than 25 was 1.16 and for death High calcium intakes have also been associated with from coronary heart disease for women with a body brain lesions on magnetic resonance imaging scans26 mass index of 25-30 was 1.18, findings similar to those and with vascular calcification27-30 and mortality3132 in in the present study (relative risk of myocardialinfarction, stroke or sudden death, 1.21) in which the patients who receive dialysis. Data from patients mean body mass index was 26.5. Also, in the women requiring dialysis may be relevant to the present health initiative the trend was towards an adverse effect study population because of the age of our participants of calcium supplementation in those with baseline and the associated reduced renal function. The trend to calcium intakes of less than 800 mg/day (hazard ratio more frequent cardiac events in the calcium group does 1.12). If calcium supplementation does contribute to not seem to be secondary to changes in lipids or other vascular adverse events, then the use of a less risk factors, since calcium supplementation was asso- bioavailable supplement in that study may have ciated with beneficial trends in levels of high density reduced the size of any adverse effect, as may the lipoprotein cholesterol and low density lipoprotein poor compliance. The use of oestrogen by half the cholesterol in the present study,1 and these were participants and the administration of vitamin D with sustained until four years’ follow-up, although the calcium might have also obscured any vascular effects differences between groups attenuated in the final year of the calcium supplementation. Thus the results of the (data not shown). Similar beneficial trends in choles- present trial are not incompatible with those of the terol fractions were also shown in the women’s health randomised evaluation of calcium or vitamin D study, Table 5 | Poisson regression models of effects of calcium supplementation or placebo and other variables on composite end point(myocardial infarction, stroke, or sudden death) in healthy postmenopausal women Shepherd J, Cobbe SM, Ford I, Isles CG, Lorimer AR, MacFarlane PW, et al. Prevention of coronary heart disease with pravastatin in menwith hypercholesterolemia. West of Scotland Coronary Prevention Calcium supplementation produces changes in serum lipids Study Group. N Engl J Med 1995;333:1301-7.
that might impact favourably on the incidence of Griffith LE, Guyatt GH, Cook RJ, Bucher HC, Cook DJ. The influence of dietary and nondietary calcium supplementation on blood pressure—an updated metaanalysis of randomized controlled trials. Am J Although observational data support this idea, evidence Reid IR, Horne A, Mason B, Ames R, Bava U, Gamble GD. Effects ofcalcium supplementation on body weight and blood pressure in normal older women: a randomized controlled trial. J Clin EndocrinolMetab 2005;90:3824-9.
Healthy older women randomised to calcium 10 Bostick RM, Kushi LH, Wu Y, Meyer KA, Sellers TA, Folsom AR. Relation of calcium, vitamin D, and dairy food intake to ischemic heart disease supplementation showed increased rates of myocardial mortality among postmenopausal women. Am J Epidemiol 11 Iso H, Stampfer MJ, Manson JE, Rexrode K, Hennekens CH, Colditz GA, This effect could outweigh any benefits on bone from et al. Prospective study of calcium, potassium, and magnesium intake and risk of stroke in women. Stroke 1999;30:1772-9.
12 Knox EG. Ischaemic-heart-disease mortality and dietary intake of 13 Dawson EB, Frey MJ, Moore TD, McGanity WJ. Relationship of metal metabolism to vascular disease mortality rates in Texas. Am J Clin The data on vascular events from a secondary, 14 Hsia J, Heiss G, Ren H, Allison M, Dolan NC, Greenland P, et al.
preplanned analysis of the Auckland calcium study Calcium/vitamin D supplementation and cardiovascular events.
are not conclusive but suggest that high calcium intakes might have an adverse effect on vascular health. The 15 Reid IR, Mason B, Horne A, Ames R, Reid HE, Bava U, et al. Randomized controlled trial of calcium in healthy older women. Am J Med similarities between these findings and those from the dialysis literature suggest that this might be a particular 16 Angus RM, Sambrook PN, Pocock NA, Eisman JA. A simple method for concern in those with poor renal function, particularly assessing calcium intake in Caucasian women. J Am Diet Assoc1989;89:209-14.
elderly people. The subgroup analyses available within 17 Alpert JS, Thygesen K, Antman E, Bassand JP. Myocardial infarction the women’s health initiative would be consistent with redefined—a consensus document of the Joint European Society of this hypothesis. The present data do not permit Cardiology/American College of Cardiology Committee for theredefinition of myocardial infarction. J Am Coll Cardiol definitive conclusions to be reached in this regard but do flag cardiac health as an area of concern in relation to 18 Mathew TH, Australasian Creatinine Consensus Working Group.
calcium use and mandate that this is assessed carefully Chronic kidney disease and automatic reporting of estimatedglomerular filatration rate: a position statement. Med J Aust in future studies of calcium supplementation. In the meantime this potentially detrimental effect should be 19 Bamford J, Sandercock P, Dennis M, Burn J, Warlow C. Classification and natural history of clinically identifiable subtypes of cerebral balanced against the likely benefits of calcium on bone,33 particularly in elderly women.
20 Chapuy MC, Arlot ME, Delmas PD, Meunier PJ. Effect of calcium and cholecalciferol treatment for three years on hip fractures in elderly Contributors: PAB and RD adjudicated the cases. MJB, BM, AH, and RA collected the data. MJB, GDG, and IRR analysed the data. IRR conceived the 21 Chapuy MC, Pamphile R, Paris E, Kempf C, Schlichting M, Arnaud S, study. He is guarantor for the paper. All authors designed the study and et al. Combined calcium and vitamin D-3 supplementation in elderly women: confirmation of reversal of secondary hyperparathyroidism Funding: This study was supported by the Health Research Council of New and hip fracture risk: the Decalyos II study. Osteoporos Int Zealand. Mission Pharmacal supplied the calcium citrate tablets and 22 Grant AM, Anderson FH, Avenell A, Campbell MK, Cooper C, Competing interests: IRR has received research support from and acted as Donaldson C, et al. Oral vitamin D3 and calcium for secondary a consultant for Fonterra and Mission Pharmacal.
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