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Letters
April 19, 2000

Sodium Intake as a Risk Factor for Cardiovascular Disease

Author Affiliations
 

Phil B.FontanarosaMD, Deputy EditorIndividualAuthorStephen J.LurieMD, PhD, Fishbein FellowIndividualAuthor

JAMA. 2000;283(15):1957-1958. doi:10.1001/jama.283.15.1957

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.

References
1.
He  JOgden  LGVupputuri  SBazzano  LALoria  CWhelton  PK Dietary sodium intake and subsequent risk of cardiovascular disease in overweight adults.  JAMA. 1999;282:2027-2034.Google Scholar
2.
Morimoto  AUzu  TFujii  T  et al.  Sodium sensitivity and cardiovascular events in patients with essential hypertension.  Lancet. 1997;350:1734-1737.Google Scholar
3.
Kimura  GBrenner  BM The renal basis for salt sensitivity in hypertension. In: Laragh JH, Brenner BM, eds. Hypertension: Pathophysiology, Diagnosis and Management. New York, NY: Raven Press; 1995:1569-1588.
4.
Nishimura  MUzu  TFujii  T  et al.  Cardiovascular complications in patients with primary aldosteronism.  Am J Kidney Dis. 1999;33:261-266.Google Scholar
5.
Uzu  TIshikawa  KFujii  TNakamura  SInenaga  TKimura  G Sodium restriction shifts circadian rhythm of blood pressure from nondipper to dipper in essential hypertension.  Circulation. 1997;96:1859-1862.Google Scholar
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