Baroreflex Function and Salt Sensitivity Among Normotensives

High degrees of salt sensitivity among normotensive individuals increases the risk for cardiovascular disease and death. Salt sensitive rodent models display impaired baroreflex sensitivity, a trait thought to contribute to poor cardiovascular health. Thus, we hypothesized that increased salt sensitivity (SS) in normotensive humans would be associated with decreased cardiac baroreflex sensitivity (CBRS) and decreased high frequency heart rate variability (HF‐HRV). Eighty‐seven healthy normotensive men and women completed 1 week of high (300mmol/day) and 1 week of low (20mmol/day) dietary sodium (random order) with 24hr mean arterial pressure (MAP) assessed on the last day of each diet. The change in 24hr MAP from low to high sodium was used as an index of SS. Of these 87 individuals, 50 agreed to return to the lab for testing under a habitual sodium intake condition. Eight were excluded from this analysis due to the presence of ectopic heart beats. Thus 42 (24 males) are presented in this analysis (age 39±2yrs [range 22–60yrs], BMI 24.3±0.5kg/m 2 , MAP 83±1mmHg, HR 59±1bpm, habitual urine sodium 93±7mmol/24hr). Electrocardiogram derived R‐R interval and beat‐by‐beat systolic blood pressure (SBP) were measured during 5 minutes of supine rest. Cardiac baroreflex analysis via the sequencing method was used to determine up sequence (concurrent increase in R‐R interval and SBP) and down sequence (concurrent decrease in R‐R interval and SBP) baroreflex sensitivity. Time domain heart rate variability analysis was performed using a fast Fourier transformation focusing on high frequency power. Linear regression analysis between SS and the variables of interest was performed. Among this cohort of normotensive adults, SS was associated with decreased HF‐HRV (r = −0.349, p = 0.046) and tended to be associated with decreased up sequence CBRS (r = −0.309, p = 0.096). However, multiple regression analysis accounting for age revealed that there was no relationship between SS and either HF‐HRV (age adjusted p=0.369) or up sequence CBRS (age adjusted p=0.712). Thus, these data suggest that the relation between increased SS and decreased HF‐HRV and CBRS is largely driven by the association of SS with age. Support or Funding Information Research supported by NIH R01 HL104106, & ACSM Foundation Research Grant.