Practical Method for Salt Intake Follow-Up in Hypertensive Patients

Obese and hypertensive (HT) patients should restrict salt intake. In excessive salt intake, ouabain-like compounds inhibit Na/K-ATPase (Na⁺ pump), which increases intracellular Na⁺ and Ca²⁺. Ca²⁺ has a vasotonic effect on arteries and an inotropic effect on the heart and may cause cortical opacities in the lens. To our knowledge, there is still no practical method for salt intake follow-up. This study tested whether salt intake follow-up can be performed with the help of opacity tracking. In total, 400 HT patients (age 30-69 years) with cortical lens opacities were included in the study. Changes in opacities based on biomicroscopic examination at baseline and after 3 months were recorded digitally with the help of imaging software. Salt intake at 1 and 3 months was evaluated with a 24-hr urine Na assay. Changes in opacities were compared among group 1 (∼50% salt reduction), group 2 (∼10% salt reduction), and group 3 (∼15% salt increase). Age and changes in small opacity diameter (SOD) and large opacity diameter (LOD) were the most important determinants of the 50% salt reduction in the third month. For changes in LOD, the sensitivity was 88.5% [confidence interval (95% CI) 85.2-91.7] and specificity was 95.5% (95% CI 93.1-98.7) for predicting a 50% salt restriction during the 3-month period. For SOD, the values were 85% (95% CI 82.5-87) and 95% (95% CI 92.3-97.5), respectively. Opacity changes are a practical method for predicting a 50% reduction in salt intake over a 3-month period in 30- to 59-year-old HT patients.