Salt, Hypertension, and the Lens

Abstract

Background: Salt is important in the pathogenesis of hypertension (HT). Salt-sensitive hypertension (SSH) accounts for about half of all HT cases. In SSH, sodium/potassium adenosine triphosphatase (Na⁺/K⁺-ATPase) activity is impaired. Impaired Na⁺/K⁺-ATPase activity in the lens epithelium results in cortical opacities in the peripheral equator of the lens. We investigated the sensitivity of cortical lens opacities in detecting SSH.

Methods: The study included 191 SSH and 159 non-SSH, salt-resistant HT (SRH) patients (350 HT patients total), aged 40-80 years. One hundred twenty-four sex- and age-matched patients without a HT diagnosis made up the control group. Daily salt intake of all groups was calculated from 24-hr urinary Na excretion. SSH was diagnosed when the difference in mean arterial blood pressure values obtained during high- and low-Na diets was ≥10%. Non-SSH, SRH was diagnosed when the difference was <10%.Two researchers examined the presence of cortical lens opacities biomicroscopically using the diffuse, direct, Scheimpflug, and retroillumination from fundus methods.

Results: Total lens opacity was predictive of SSH among all cases (P < 0.001), with a sensitivity and specificity of 75.4% [95% confidence interval (CI): 68.6-81.3] and 83.6% (95% CI: 77.0-89.0), respectively. Its positive and negative predictive values were 84.7% (95% CI: 79.4-88.8) and 73.9% (95% CI: 68.6-78.5), respectively.

Conclusions: Lens opacities can be used as a finding that can be easily observed in the detection of SSH and excess salt intake.

Keywords: biomicroscopy; hypertension; lens; salt; salt sensitivity hypertension.