Urinary Sodium Excretion and Salt Intake Are Not Associated With Blood Pressure Variability in a White General Population

Background Salt restriction may lower blood pressure variability (BPV), but previous studies have shown inconsistent results. Therefore, we investigated in an observational study and intervention trial whether urinary sodium excretion and salt intake are associated with 24-hour BPV. Methods and Results We used data from the cross-sectional population-based Maastricht Study (n=2652; 60±8 years; 52% men) and from a randomized crossover trial (n=40; 49±11 years; 33% men). In the observational study, we measured 24-hour urinary sodium excretion and 24-hour BPV and performed linear regression adjusted for age, sex, mean blood pressure, lifestyle, and cardiovascular risk factors. In the intervention study, participants adhered to a 7-day low- and high-salt diet (50 and 250 mmol NaCl/24 h) with a washout period of 14 days, 24-hour BPV was measured during each diet. We used linear mixed models adjusted for order of diet, mean blood pressure, and body mass index. In the observational study, 24-hour urinary sodium excretion was not associated with 24-hour systolic or diastolic BPV (β, per 1 g/24 h urinary sodium excretion: 0.05 mm Hg [95% CI, -0.02 to 0.11] and 0.04 mm Hg [95% CI, -0.01 to 0.09], respectively). In the intervention trial, mean difference in 24-hour systolic and diastolic BPV between the low- and high-salt diet was not statistically significantly different (0.62 mm Hg [95% CI, -0.10 to 1.35] and 0.04 mm Hg [95% CI, -0.54 to 0.63], respectively). Conclusions Urinary sodium excretion and salt intake are not independently associated with 24-hour BPV. These findings suggest that salt restriction is not an effective strategy to lower BPV in the White general population. Registration URL: https://clinicaltrials.gov/ct2/show/NCT02068781.