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Phil B.FontanarosaMD, Deputy EditorIndividualAuthorStephen J.LurieMD, PhD, Fishbein FellowIndividualAuthor
To the Editor: The large, prospective cohort
study by Dr He and colleagues1 is the first
to document the presence of a positive and independent relationship between
dietary sodium intake and CVD, especially stroke. We have shown in a retrospective
study2 that patients with essential hypertension
whose sodium sensitivity is high have a strong risk of cardiovascular events,
especially stroke, independent of other risk factors.
We have postulated that sodium sensitivity is caused by either a reduced
ultrafiltration coefficient of glomerulus or enhanced tubule sodium reabsorption.3 In addition, we showed that insulin resistance
and resulting hyperinsulinemia were related to increased tubule sodium reabsorption
and high sodium sensitivity. Obesity, which represents a state of insulin
resistance and hyperinsulinemia, induces sodium-sensitive hypertension. Therefore,
the important findings of He et al1 may
be generalized to the concept that sodium intake is a risk for stroke in subjects
with high sodium sensitivity. In patients with primary aldosteronism who develop
secondary hypertension due to enhanced sodium reabsorption, stroke is the
most common cardiovascular complication.4
We showed that in patients with sodium-sensitive hypertension, regardless
of the cause (whether essential or secondary), sodium restriction made the
circadian blood pressure rhythm less volatile.5
In patients with non–sodium-sensitive hypertension, on the other hand,
blood pressure decreased during the night, independent of the amount of sodium
intake and thus representing the "dipper" pattern of circadian rhythm. Since
nondippers, whose blood pressure fails to decrease during the night, are believed
to be at greater cardiovascular risk, especially for stroke, sodium intake
appears to be a cardiovascular risk only in subjects with high sodium sensitivity.
Sodium sensitivity and circadian blood pressure rhythm may be the link between
sodium intake and CVD.
Kimura G. Sodium Intake as a Risk Factor for Cardiovascular Disease. JAMA. 2000;283(15):1957–1958. doi:10.1001/jama.283.15.1957
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