a previously reported 30% risk of MI w calcium supp extends to people who are also taking vit D
often taken in combination: Calcium and vitamin D, for bone health
causes a roughly 20% increased risk of both MI and stroke
new study is published online April 19, 2011 in BMJ
Dr Mark Bolland (University of Auckland, New Zealand)
WHI study showed no CV risk with calcium, vitamin D
LAST STUDY WAS CONFUSING
previous meta-analysis highly controversial
looked only at patients taking calcium alone compared with placebo
or people taking calcium and vitamin D compared with people taking vitamin D alone
was at odds with a Women's Health Initiative (WHI) study that showed no adverse CV effects w these supps
confounder: in WHI women already taking ca&vitD were told not to stop even if randomized to placebo, 54% already taking calcium, 47% taking vitamin D at the time of randomization, patient group "contaminated"
Dr Ian Reid (University of Auckland), senior author on the new BMJ study
requested pt level data in order to correct for the confounder
17 000 women not taking supps but put on them-->statistically sig incr in risk of "clinical MI"
(hazard ratio 1.22; p=0.05)
and clinical MI and stroke (hazard ratio 1.16; p=0.05)
women already taking supplements at baseline, no such spike in events was seen
WHI ADDED TO META-ANALYSIS
this data added in as well as two other studies not included in previous meta-analysis n=12,000
new n= almost 30,000
use of calcium or calcium plus vitamin D significantly increased both risk of MI and composite of MI/stroke
at both patient-level data and trial-level data
risk of stroke was significantly increased in the patient-level data
small levels of supplemental calcium create "abrupt" increases in blood calcium levels within hours
one criticism of group's earlier work: CV events occurring too swiftly to be related to calcified plaques
stroke events mbdt longer-term process of calcium accruing in the vessel walls
MI spikes may reflect more acute response to blood ca levels, plt fx change, coag change, EC activity change
NUMBER NEEDED TO HARM
CV effects of Ca are "modest"
25%-30% for MI and 15%-20% for stroke
1000 on Ca+ only-->6 more MI's or strokes and 3 less fractures
NNTH = 178 for cv consequence, 302 for prevention of fracture
*docs should look at other options for bone health
getting Ca+ from diet doesn't seem to have same risk
other studies showing that use of calcium and vitamin D on top of bisphosphonates for osteoporosis have in the past been "reassuring" on CV safety
Bolland MJ, Grey A, Avenell A, et al. Calcium supplements with or without vitamin D and risk of cardiovascular events: reanalysis of the Women's Health
Initiative limited access dataset and meta-analysis. BMJ 2011; DOI: doi:10.1136/bmj.d2040. Available at: http://www.bmj.com.
Bolland MJ, Avenell A, Baron JA, et al. Effect of calcium supplements on risk of myocardial infarction and cardiovascular events: Meta-analysis. BMJ 2010; 341:c3691.
Abrahamsen B, Sahota O. Do calcium plus vitamin D supplements increase cardiovascular risk? BMJ 2011; doi10.1136/bmj.d2080. Available at: http://www.bmj.com.