Coronary Artery Risk Development in Young Adults–Salt Sensitivity of Blood Pressure - CARDIA-SSBP
Contribution To Literature:
The CARDIA-SSBP trial showed that in a community-based cohort of middle-aged patients, a low-sodium diet was associated with a median 7 mm Hg reduction in SBP, regardless of HTN status or anti-HTN medication use.
The goal of the trial was to determine the effect of a high- vs. low-sodium diet on blood pressure (BP) among middle-aged patients with variable rates of hypertension (HTN) and anti-HTN medication use.
- Crossover design
Following 1 week of usual diet, participants were randomized to 1 week of a high- (~2,200 mg sodium daily added to usual diet, n = 118) or low-sodium (500 mg daily total, n = 95) diet followed by crossover to the alternate arm the following week. Ambulatory 24-hour BP monitoring was performed on day 7 of each diet.
- Total number of enrollees: 213
- Duration of follow-up: 21 days
- Median patient age: 61 years
- Percentage female: 65%
- Age 50-75 years
- Normotension or controlled HTN on ≤3 anti-HTN medications
- Enrollment systolic BP (SBP) <90 or >160 mm Hg
- Enrollment diastolic BP (DBP) <50 or >100 mm Hg
- Use of ≥4 anti-HTN medications
- Uncontrolled BP despite ≥3 anti-HTN medications including a diuretic
- Contraindication to high- (e.g., heart failure) or low-sodium (e.g., orthostatic hypotension) diet
- Rheumatologic or immunocompromising conditions
Other salient features/characteristics:
- Median body mass index: 31 kg/m2
- Percentage with HTN: 48%
- Percentage with diabetes mellitus (DM): 21%
- Percentage using ≥2 anti-HTN medications: 19%
- Percentage enrolled from CARDIA (Coronary Artery Risk Development in Young Adults) cohort: 73%
- Median enrollment SBP: 128 mm Hg
- Median 24-hour urine sodium: Usual diet, 4.62 g; high-sodium diet, 5.48 g; low-sodium diet: 1.70 g
Primary endpoint, mean 24-hour ambulatory SBP difference between high- and low-sodium diets:
- At week 1: 8 mm Hg (95% confidence interval [CI] 4-11 mm Hg, p < 0.0001)
- At week 2: 7 mm Hg (95% CI 3-11 mm Hg, p < 0.0001)
Mean ambulatory SBP difference from usual diet: High-sodium diet first: +1 mm Hg (p = 0.14)
- Low-sodium diet first: -5 mm Hg (p <0.0001)
24-hour urinary sodium excretion for usual vs. high- vs. low-sodium diet: 4.6 vs. 5.5 vs. 1.7 g
Subgroup analysis of mean ambulatory SBP difference between high- and low-sodium diets:
- No anti-HTN vs. anti-HTN medication use: 7.90 (95% CI 4.50-11.30) vs. 7.78 (95% CI 3.40-12.16) mm Hg
- Baseline SBP ≤125 vs. >125 mm Hg: 5.91 (95% CI 2.60-9.23) vs. 10.37 (95% CI 6.00-14.75) mm Hg
- No DM vs. DM: 5.69 (95% CI 3.21-8.17) vs. 17.59 (95% CI 7.16-28.03) mm Hg
Median within-patient SBP reduction from high- to low-sodium diet: 7 mm Hg (interquartile range 0-14 mm Hg), p < 0.001 (p = 0.32 for normotensive vs. controlled vs. untreated vs. uncontrolled HTN); percentage of patients with SBP reduction from high- to low-sodium diet: 74.4%
Adverse events with high- vs. low-sodium diet:
- Headache: 2.8% vs. 1.4%
- Edema: 2.3% vs. 0%
- Cramping 0.5% vs. 2.3%
Among middle-aged patients, the CARDIA-SSBP trial demonstrated a median 7 mm Hg reduction in 24-hour ambulatory SBP with a low-sodium diet (500 mg/day) compared with high sodium intake, which did not significantly increase SBP compared with usual diet. Importantly, this decrease was consistent across patients regardless of HTN status or anti-HTN medication use. Subgroup analysis trends suggest that this effect may be more pronounced in patients with SBP >125 mm Hg or comorbid DM, who may correspondingly be at greater risk of cardiovascular complications from poorly controlled HTN. The increased incidences of edema and cramping with high- and low-sodium diets, respectively, were low but not unexpected.
These results extend the findings of the original DASH diet study (2001), which enrolled a younger cohort and notably excluded patients with anti-HTN medication use, DM, and known cardiovascular disease, i.e., patients likely to benefit clinically from aggressive BP control. A notable limitation of this trial is the short duration of each intervention (7 days). Further research may be warranted into longer-term dietary regimens in this population to determine not only the sustainability and magnitude of SBP change over time but also the tolerability of and adherence to a low-sodium diet.
Presented by Dr. Deepak Gupta at the American Heart Association Scientific Sessions, Philadelphia, PA, November 11, 2023.
Keywords: AHA23, Hypertension, Sodium Chloride, Dietary
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