The effect of calcium supplementation on blood pressure in non-pregnant women with previous pre-eclampsia: A randomized placebo-controlled study
Bibliographic record
Abstract
Low dietary calcium is associated with the hypertensive disorders of pregnancy, and evidence suggests that the risks associated with pre-eclampsia are reduced by calcium supplementation. In the general (non-pregnant) population, low dietary calcium intake is associated with hypertension with inconsistent evidence that calcium supplementation may reduce blood pressure. Women with pre-eclampsia are also at risk of hypertension later in life. An exploratory sub-study among early participants enrolled in the WHO long-term calcium supplementation in women at high risk of pre-eclampsia (CAP) study reported a trend to more blood pressure reduction with calcium in non-pregnant women with previous severe as opposed to non-severe pre-eclampsia. The current study reports the effects of low-dose calcium supplementation in non-pregnant women in the complete trial cohort. The CAP Study was a multi-country randomized, double-blind placebo-controlled clinical trial to test the hypothesis that calcium deficiency may play a role in the genesis of pre-eclampsia in early pregnancy. From 2011 to 2016, non-pregnant women who had pre-eclampsia or eclampsia in their most recent pregnancy were randomized to receive either 500 mg/day elemental calcium or placebo. In this sub-study we compared the change in blood pressure from baseline to the 12-week visit between participants receiving calcium versus placebo for those not pregnant at the 12-week visit. Of 1355 women randomized, 810 attended a 12-week visit without being pregnant, of whom 791 had blood pressure measurements available for both baseline and 12-week visits. There was a greater reduction in blood pressure in the calcium group compared with the placebo group for systolic pressure (difference 3.1 mmHg, 95% CI 0.8 to 5.4) and mean arterial pressure (MAP) (difference 2.0 mmHg, 95% CI 0.1 to 3.8). The difference in diastolic blood pressure reduction (1.4 mmHg, 95% CI −0.5 to 3.3) was not statistically significant (p = 0.140). For women with previous pre-eclampsia with severe features (n = 447), there was significantly greater reduction in blood pressure in the calcium than the placebo group (difference for systolic 4.0, 95% CI 0.7 to 7.3; diastolic 3.0, 95% CI 0.5 to 5.5 and mean arterial pressure 3.3, 95% CI 0.8 to 5.9 mmHg). For women with previous pre-eclampsia without severe features (n = 344), there were no significant differences between calcium and placebo groups. ANOVA analysis found no statistically significant interaction between previous pre-eclampsia severity and treatment, for systolic (p = 0.372), diastolic (p = 0.063) or mean blood pressure (p = 0.103). Low-dose calcium supplementation significantly reduced systolic and mean arterial pressure in non-pregnant women with previous pre-eclampsia. We did not confirm a greater calcium effect in women with previous pre-eclampsia with severe versus non-severe features. The effect of low-dose calcium is of importance since even modest blood pressure reductions at a population level may have important benefits in terms of reduced major complications of hypertension. This study adds to the mounting evidence of health benefits which could be achieved for populations with low dietary calcium through strategies to increase calcium intake, particularly among women at high risk due to previous pre-eclampsia. The trial was registered with the Pan-African Clinical Trials Registry, registration number PACTR201105000267371 (https://pactr.samrc.ac.za/TrialDisplay.aspx?TrialID=267).
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.003 | 0.005 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.005 | 0.003 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.003 | 0.002 |
| Insufficient payload (model declined to judge) | 0.007 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".