Psychological Stress and the Diurnal Patterns of Sodium Excretion and Blood Pressure: Results From the SABRE Study

BACKGROUND: Psychological stress is associated with reduced blood pressure (BP) dipping, but the underlying mechanisms are unclear. This study examined the associations among stress-induced sodium excretion, diurnal sodium excretion, and BP dipping. METHODS: Apparently healthy adult participants underwent a laboratory session during which urinary sodium excretion was measured before and after mental stress tasks. Participants then completed 24-hour ambulatory BP monitoring and separate awake and asleep urine collections. The change in urinary sodium excretion rate with stress was defined as the difference in urinary sodium excretion rate before and after stress. The awake-to-asleep ratio of the urinary sodium excretion rate and systolic BP dipping were calculated from the 24-hour urine and BP measurements. RESULTS: In an adjusted model including age, sex, race, ethnicity, body mass index, mean systolic BP, mean diastolic BP, parental history of hypertension, fasting glucose, and 24-hour creatinine clearance, a smaller stress-induced urinary sodium excretion rate was associated with a lower awake-to-asleep ratio of urinary sodium excretion rate (n=180, B=0.2253 [95% CI, 0.0490-0.4016]). In an adjusted model including age, sex, race, ethnicity, body mass index, current smoking, alcohol use, fasting glucose, 24-hour sodium excretion, 24-hour potassium excretion, 24-hour creatinine clearance, and fractional excretion of sodium, a lower awake-to-asleep ratio of the urinary sodium excretion rate was associated with lower systolic BP dipping (n=175, B=1.0127 [95% CI, 0.0599-1.9656]). CONCLUSIONS: A lower stress-induced urinary sodium excretion rate was associated with a worse diurnal pattern of urinary sodium excretion, which was associated with lower systolic BP dipping. REGISTRATION INFORMATION: clinicaltrials.gov. Identifier: NCT03636490.