Cross-Over Trial: How Much Does Dietary Sodium Impact Blood Pressure?
BACKGROUND AND PURPOSE:
- The blood pressure (BP) response to sodium intake can vary widely even within individuals
- Gupta et al. (JAMA, 2023) examined the BP response to dietary sodium within and between individuals
METHODS:
- Prospective, multicenter, observational cohort study
- CARDIA study: Goal to identify the factors in young adulthood influencing development of CVD
- Enrollment occurred in 1985 to 1986
- Participants
- Current study
- US adults aged 50 to 75
- Exclusion: Systolic BP outside 90 to 160 mm Hg | Diastolic BP outside 50 to 100 mm Hg
- Current study
- Exposures
- Normotension | Controlled hypertension | Uncontrolled hypertension | Untreated hypertension
- Interventions
- 1-week usual diet
- 1-week high-sodium diet: 2200 mg/day in addition to daily diet
- 1-week low sodium diet: 500 mg daily total
- Study design
- Community cross-over trial
- 4 study visits: Enrollment | Baseline | End of the first diet week | End of the second diet week
- Latter 3 occurring over consecutive 1-week intervals
- Salt sensitive: Defined as ≥5 mm Hg decline in mean arterial pressure between a high-sodium and a low-sodium diet
- 24-hour urine collections for assessment of dietary adherence
- Subgroup analysis: Age | Sex | Race | Hypertension | Baseline BP | Diabetes | BMI
- Primary outcomes
- Average 24-hour ambulatory systolic and diastolic BP
- Mean arterial pressure (MAP)
- Pulse pressure
RESULTS:
- 213 participants
- Normotension: 25% | Controlled hypertension: 20% | Uncontrolled hypertension: 31% | Untreated hypertension: 25%
- Median age: 61 years | Female: 65% | Black: 64%
- Median systolic BP measures
- Usual diet: 125 mm Hg
- High-sodium: 126 mm Hg
- Low-sodium: 119 mm Hg
- The median within-individual change MAP between high- and low-sodium diets was not impacted by hypertension status
- 4 mm Hg (IQR, 0 to 8) | P<0.001
- 46% met criteria met traditional definition of ‘salt sensitive’ based on ≥5 mm Hg change
- There was a decrease in within-individual MAP in the majority of participants with lower dietary sodium intake
- Low-sodium MAP decline: 73.4%
- Mean systolic BP difference between individuals allocated to a high-sodium vs a low-sodium diet
- 8 mm Hg (95% CI, 4 to 11) | P<0.001
- Not statistically different between subgroups
- Adverse events were mild
CONCLUSION:
- The majority of older adults who lowered dietary sodium experienced a reduction in mean arterial pressure
- This decline was not associated with hypertension status or use of antihypertensive medication
- The authors state
That none of the classes of antihypertensive medications was consistently associated with the BP response to dietary sodium emphasizes the importance of continued lifestyle modification even among individuals with treated hypertension
Learn More – Primary Sources:
Effect of Dietary Sodium on Blood Pressure: A Crossover Trial
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