J Korean Med Sci.  2013 Apr;28(4):555-563. 10.3346/jkms.2013.28.4.555.

Elevation of Morning Blood Pressure in Sodium Resistant Subjects by High Sodium Diet

• Rhee MY
• Lim CY
• Shin SJ
• Oh SW
• Park YS
• Kim JW
• Park HK
• Kim CI
• Park CY
• Kim SW

• KMID: 1786963
• DOI: http://doi.org/10.3346/jkms.2013.28.4.555

Abstract

The present study evaluated the response of blood pressure (BP) by dietary sodium in sodium resistant (SR) subjects. One hundred one subjects (mean age, 46.0 yr; 31 hypertensives) were admitted and given low sodium-dietary approaches to stop hypertension (DASH) diet (LSD, 100 mM NaCl/day) for 7 days and high sodium-DASH diet (HSD, 300 mM NaCl/day) for the following 7 days. On the last day of each diet, 24 hr ambulatory BP was measured. Morning systolic BP (SBP) and diastolic BP (DBP) were elevated after HSD in all subjects (P < 0.01), but daytime SBP and DBP were not changed (P > 0.05). In hypertensive subjects, morning DBP elevation was greater than daytime DBP elevation (P = 0.036), although both DBPs were significantly elevated after HSD. The augmented elevation of morning DBP in hypertensive subjects was contributed by the absolute elevation of morning DBP (P = 0.032) and relative elevation to daytime DBP (P = 0.005) in sodium resistant (SR) subjects, but not by sodium sensitive subjects. Although there was no absolute elevation, SR subjects with normotension showed a relative elevation of morning SBP compared to daytime SBP change after HSD (P = 0.009). The present study demonstrates an absolute and relative elevation of morning BP in SR subjects by HSD.

Keyword

Sodium; Hypertension; Sodium Resistance

MeSH Terms

Adult
Blood Pressure/*drug effects
Diet, Sodium-Restricted
Humans
Hypertension/*physiopathology
Middle Aged
Sodium, Dietary/*pharmacology
Time Factors
Sodium, Dietary

Figure

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  Fig. 1 Comparison of ambulatory blood pressure after one week of low sodium DASH diet (closed bar) and high sodium DASH diet (open bar). Study population was divided into two groups, subjects with sodium sensitivity (SS) and sodium resistance (SR). Each group was further grouped in hypertensive subjects with sodium sensitivity (SS-HT) and sodium resistance (SR-HT), and normotensive subjects with sodium sensitivity (SS-NT) and sodium resistance (SR-NT). Data are expressed as a mean±SEM. *P < 0.0001; †P < 0.001; ‡P < 0.01; §P < 0.05. P value was derived from paired t-test. D, daytime; N, nighttime; M, morning; SBP, systolic blood pressure; DBP, diastolic blood pressure; MBP, mean blood pressure.

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  Fig. 2 Comparisons of daytime, nighttime and morning blood pressure changes. Data are expressed as a mean±SEM. P value derived from paired t-test of morning BP changes vs daytime BP changes, and nighttime BP changes vs daytime BP changes. △BP, magnitude of blood pressure change calculated by subtracting blood pressure after low sodium diet from that after high sodium diet; NT, normotensive subjects; HT, hypertensive subjects; SS, sodium sensitive subjects; SR, sodium resistant subjects; SS-HT, hypertensive subjects with sodium sensitivity; SS-NT, normotensive subjects with sodium sensitivity; SR-HT, hypertensive subjects with sodium resistance; SR-NT, normotensive subjects with sodium resistance; SBP, systolic blood pressure; DBP, diastolic blood pressure; D, daytime; N, nighttime; M, morning.

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