A study examines the relationship between urine sodium excretion and systolic blood pressure in a large cohort of patients from several countries. The following results are reported for change in systolic blood pressure for every 1-g increase in urine sodium excretion: Which of the following best describes the study results?
A)High sodium excretion causes susceptibility to hypertension
B)In non-hypertensive individuals, there is no association between systolic blood pressure and increase in sodium excretion
C)The slope of association is steeper for patients with hypertension than those without hypertension
D)Younger individuals (age

Question

A study examines the relationship between urine sodium excretion and systolic blood pressure in a large cohort of patients from several countries.  The following results are reported for change in systolic blood pressure for every 1-g increase in urine sodium excretion: Which of the following best describes the study results?
A)High sodium excretion causes susceptibility to hypertension
B)In non-hypertensive individuals, there is no association between  systolic blood pressure and increase in sodium excretion
C)The slope of association is steeper for patients with hypertension than those without hypertension
D)Younger individuals (age <45) are more susceptible to the effect of sodium on blood pressure
E)Younger individuals (age <45) have higher sodium excretion

Quizplus · Accepted Answer

Explanation: This study examined the association between change in systolic blood pressure and urine sodium excretion in 98,029 patients. As part of the study, the interactions with different variables (eg, hypertensive state, age) were analyzed. As the values reported in the table represent changes in systolic blood pressure (for every 1-g increase in urinary sodium excretion), the null value for the corresponding confidence intervals (CIs) is 0 (as 0 would represent no change in systolic blood pressure). There was a statistically significant association between hypertensive state and change in systolic blood pressure for every 1-g increase in urine sodium excretion (P-value for interaction <0.001). Patients with hypertension had an average increase of 2.37 mm Hg in systolic blood pressure for every 1-g increase in urine sodium excretion. The corresponding 95% CI does not include the null value; therefore, that increase was statistically significant. Patients without hypertension also had a statistically significant increase, but the average increase was 1.38 mm Hg. The CIs for the 2 groups (no hypertension: 1.24-1.41; and hypertension: 2.31-2.71) do not overlap, meaning that the difference between these groups was also statistically significant. Therefore, compared to patients without hypertension, patients with hypertension had a greater increase in systolic blood pressure (steeper slope of association) per 1-g increase in urine sodium excretion. (Choice A) There was a significant association between sodium excretion and change in systolic blood pressure for every 1-g increase in urine sodium excretion (P-value for interaction <0.001). However, association does not imply causation. (Choice B) On average, non-hypertensive individuals had a statistically significant increase in systolic blood pressure of 1.38 mm Hg per 1-g increase in urinary sodium excretion. (Choice D) Young patients (age <45) had a statistically significant increase in systolic blood pressure, but the increase was less than that seen in older individuals. The CIs do not overlap, meaning that the differences between the age groups were statistically significant. Older patients had a steeper association with (ie, more susceptibility to) change in blood pressure for every 1-g increase in urine sodium excretion. (Choice E) No information was provided about the association between age and urinary sodium excretion. The results show that young individuals (age <45) had a statistically significant increase in systolic blood pressure for every 1-g increase in urinary sodium excretion. Educational objective: Non-overlapping confidence intervals suggest statistically significant differences between groups.

A Study Examines the Relationship Between Urine Sodium Excretion and Systolic