Clinical Trial Details
— Status: Completed
Administrative data
| NCT number |
NCT00005204 |
| Other study ID # |
1083 |
| Secondary ID |
R01HL038897 |
| Status |
Completed |
| Phase |
N/A
|
| First received |
May 25, 2000 |
| Last updated |
March 15, 2016 |
| Start date |
August 1987 |
| Est. completion date |
July 1989 |
Study information
| Verified date |
November 2001 |
| Source |
National Heart, Lung, and Blood Institute (NHLBI) |
| Contact |
n/a |
| Is FDA regulated |
No |
| Health authority |
United States: Federal Government |
| Study type |
Observational
|
Clinical Trial Summary
To determine if hypertensives and normotensives of similar ages had, on average, different
ratios of 24-hour to overnight excretion of sodium, potassium, and water. Also, to determine
the number of 24-hour collections needed to characterize individuals with respect to the
ratios of 24-hour to overnight excretion and to determine if the ratios of 24-hour to
overnight excretion vary by age and other factors related to blood pressure.
Description:
BACKGROUND:
For decades excess sodium intake has been implicated in the etiopathogenesis of high blood
pressure. Data from epidemiological, clinical, and animal experimental studies all suggest a
direct casual association between excess salt intake and hypertension. Several investigators
suggest that hypertension is the result of an inability of the kidney to excrete salt and
water normally. It is hypothesized that the development of chronic blood pressure elevation
results from the kidney's need to increase urine volume and sodium excretion -- in the
presence of habitual high sodium intake -- in order to maintain homeostasis of the
extracellular fluid volume.
Diurnal variations in excretion of sodium, chloride, potassium and water have been observed
in several studies. Water and electrolyte excretion in normal individuals generally reaches
a maximum sometime around midday with a minimum toward the end of the sleep period. These
studies suggest that the daytime excretion rate exceeds the nighttime rate by 50 to 100
percent. Overnight urine collections have been used in many studies since they are easier to
obtain, but they do not provide a direct estimate of the actual intake of sodium or
potassium. In order to estimate actual intake, overnight values must be corrected to 24-hour
values, that is, by multiplying the overnight values by previously determined ratios of
24-hour to overnight excretions. Preliminary studies by this group of investigators in
hypertensives were the first which computed 24-hour to overnight ratios for excretion of
sodium, potassium and creatinine in a definite way. This study in hypertensives showed a
reversal of the diurnal cycle of sodium excretion. What is not clear in this study and
others is whether the reversal is associated with hypertension or reflects decreased renal
function with age or whether deterioration of renal function is due to the kidney
readjusting its output of salt and water to maintain homeostasis in the face of both an
excess sodium intake and a highly variable day to day intake. In addition, it may be that an
abnormal diurnal pattern of sodium excretion may indicate that one is at risk of development
of hypertension.
DESIGN NARRATIVE:
Each participant provided three 24-hour urine collections, divided into daytime and
overnight specimens for the assessment of sodium, potassium, creatinine, and water
excretion. Four blood pressure measurements were made. Height and weight were measured.
Information was collected on demographic variables, alcohol intake, history and treatment of
blood pressure, medication use, family history of high blood pressure, cigarette use, and
changes in dietary habits. Analysis of variance was the primary method of data analysis.
The study completion date listed in this record was obtained from the "End Date" entered in
the Protocol Registration and Results System (PRS) record.
