Abstract Body: Background: To examine the associations between salt intake and hypertensive disorders of pregnancy among women with and without calcium supplementation.
Methods: Researchers used questionnaires to collect dietary information including calcium and multivitamin supplement use, and condiments such as salt and soy sauce consumption were obtained through weighing. Salt consumption was estimated based on salt and soy sauce during cooking. Hypertensive disorders of pregnancy were ascertained through the clinical records. Logistic regression models were used to estimate odds ratios (ORs) and 95% CIs. Interactions were assessed by adding interaction terms between calcium supplement use and salt intake levels in the models.
Results: The analysis included 4192 pregnant women with complete follow-up data until delivery, and there were 109 cases of hypertensive disorders of pregnancy. Among women without calcium supplements at baseline, higher daily salt intake (≥5.0 g) was significantly associated with an 86% increased risk of hypertensive disorders compared to those with intake <5.0 g (95% CI 1.07-3.24, P=0.029). This association was not found in those taking calcium supplements (OR 0.66, 95% CI 0.34-1.28, P=0.218). Interaction analysis showed significant heterogeneity in the association between salt intake and hypertensive disorders of pregnancy based on calcium supplement use (P for interaction=0.019). Similar results were observed when the low-calcium group was redefined based on multivitamin supplements and dietary calcium intake. Joint analysis showed that compared to those taking calcium supplements with salt intake <5.0 g/day, the ORs for hypertensive disorders of pregnancy among those taking calcium supplements with salt intake ≥5.0 g/day were 0.64 (95% CI 0.34-1.22, P=0.177) and 0.49 (95% CI 0.26-0.93, P=0.030) for non-users with salt intake <5.0 g/day. For non-users of calcium supplements with salt intake ≥5.0 g/day, the OR was 0.90 (95% CI 0.50-1.61, P=0.719). These results were consistent across subgroup and sensitivity analyses.
Conclusions: Our study revealed that in the participants without calcium supplements, higher salt intake was associated with a higher risk of hypertensive disorders of pregnancy, while this association was not observed in the people taking calcium supplements. These findings suggest that the balance between sodium and calcium intake may be an important factor influencing the development of hypertensive disorders of pregnancy.