Table 2 Relative risk of incident hypertension for the highest compared with the lowest category of calcium intake

From: Dietary calcium intake and hypertension risk: a dose–response meta-analysis of prospective cohort studies

   n RR (95%CI) I2(%), Pheterogeneitya P between b
All studies   8 0.89 (0.86–0.93) 0%, 0.53
Source of intake      
Dietary calcium   7 0.89 (0.86–0.93) 0%, 0.43 0.70
Total calcium (diet + supplement)   1 0.85 (0.63–1.07)
Dietary source of calcium      
Dairy calcium   2 0.87 (0.83–0.92) 0%, 0.54
Nondairy calcium   2 0.92 (0.72–1.11) 78.8%, 0.03
Sex      
Men   1 0.85 (0.76–1.10) 0.38
Women   2 0.87 (0.81–0.92) 0%, 0.70
Both   5 0.92 (0.87–0.97) 0.9%, 0.40
Geographical region      
US   4 0.89 (0.84–0.93) 0%, 0.50 0.17
Europe   3 1.00 (0.88–1.12) 0%, 0.90
Asia   1 0.87 (0.80–0.94)
Dietary assessment method      
FFQ   6 0.88 (0.84–0.92) 0%, 0.85 0.06
Dietary record   1 1.01 (0.88–1.14)
Median intake      
<700 mg/day   2 0.86 (0.80–0.93) 0%, 0.71
≥700 mg/day   4 0.92 (0.85–0.98) 36%, 0.19
Follow-up duration      
<5 years   5 0.92 (0.84–1.00) 0%, 0.47 0.47
≥5 years   3 0.89 (0.85–0.93) 1%, 0.36
Number of cases      
<3000   5 0.95 (0.88–1.02) 0%, 0.78 0.04
>3000   3 0.87 (0.82–0.92) 0%, 0.92
Adjustment for confounders      
Alcohol consumption Yes 7 0.89 (0.86–0.93) 1%, 0.42 0.88
No 1 0.92 (0.63–1.36)
Physical activity Yes 5 0.89 (0.84–0.93) 2%, 0.39 0.48
No 3 0.91 (0.84–0.99) 0%, 0.62
Smoking Yes 4 0.89 (0.84–0.94) 26%, 0.25 0.69
No 4 0.91 (0.84–0.99) 0%, 0.68
Sodium intake Yes 3 0.87 (0.82–0.91) 0%, 0.98 0.09
No 5 0.94 (0.87–1.00) 0%, 0.54
Magnesium intake Yes 3 0.86 (0.80–0.92) 0%, 0.92 0.24
No 5 0.91 (0.86–0.97) 12%, 0.34
Potassium intake Yes 3 0.86 (0.80–0.92) 0%, 0.92 0.24
No 5 0.91 (0.86–0.97) 12%, 0.34
  1. FFQ food frequency questionnaire, RR relative risk
  2. aP-heterogeneity within subgroups with the use of a random-effects model
  3. bP-heterogeneity between subgroups with the use of a fixed-effects model