Nighttime blood pressure dipping under controlled sodium conditions: effect of sex and race

Blunted nighttime blood pressure (BP) dipping is related to increased cardiovascular risk. Altered dietary sodium can influence short‐term and long‐term BP, but studies that have assessed nighttime BP dipping have not controlled for sodium intake in normotensives. We therefore measured nighttime BP dipping during a controlled sodium diet in normotensive adults (n=96; age= 38±1 yrs, BP= 119±1 / 75±1 mmHg), and examined sex (women n=48, age= 41±2 yrs, BP= 115±2 / 73±2 mmHg vs. men n=48, age= 35±2 yrs, BP= 123±1 / 76±1 mmHg) and racial differences (Caucasians n=75, age=39±2 yrs, BP= 120±1 / 75±1 mmHg; African American n=13, age= 35±3 yrs, BP= 116±3 / 71±2 mmHg) in subgroup analyses. All subjects consumed a recommended sodium diet (100 mmol/day) for 7 days and 24‐hour ambulatory BP was measured on the 7 th day of the diet. BP was assessed every 20 minutes during daytime (wake) and every 30 minutes during nighttime (sleep). Nighttime BP dipping was assessed by measuring the percent (%) difference between mean systolic daytime BP and mean systolic nighttime BP. Twenty‐four‐hour urine sodium excretion was 82.9±4.2 mmol/24 hrs for all subjects; no difference was observed between sex and race (p>0.05). Nighttime BP dipping under a controlled sodium condition was 10.9±0.6% for all subjects. No differences were observed in nighttime BP dipping between sexes (women= 10.9±0.8% vs. men= 10.8±0.9%, p>0.05) or between races (Caucasian= 10.7±0.7% vs. African American= 9.6±1.3% p>0.05). These data suggest that under controlled sodium conditions, there are no sex or race differences in nighttime BP dipping.