Analyzing Genetic Factors Involved in Blood Pressure Changes Due to Salt and Potassium Intake (The GenSalt Study)

High blood pressure is one of the most common health problems among adults. If left untreated, it can lead to heart failure, kidney failure, or stroke. Common causes include stress, diet, diabetes, kidney disease, or obesity. Typical treatments include taking medication, losing weight, and quitting smoking. It is also recommended that people with high blood pressure or those at risk of developing high blood pressure modify their diets to decrease sodium intake and increase potassium intake. Research has shown that genetics may play a role in the development of high blood pressure and may affect fluctuations of blood pressure levels, including blood pressure changes brought on by sodium and potassium. This study will identify and analyze the genetic factors that may be responsible for blood pressure changes due to dietary salt and potassium intake. Blood samples collected in this study may also be used for future genetic research on blood pressure.

This study will enroll people who have mildly elevated blood pressure and their siblings, spouses, and children. Participants will first take part in a 3-day observation period. At a Day 1 study visit, participants' weight, height, waist size, and blood pressure will be measured. There will be three separate blood pressure measurements. Study staff will then interview participants to collect information on family and personal medical history, cigarette smoking habits, alcohol consumption, physical activity, and diet. Finally, blood samples will be collected. For 24 hours after the first study visit, participants will collect their urine. At study visits on Days 2 and 3, participants will undergo three blood pressure measurements and a cold pressor test, which measures blood pressure at different body temperatures. Participants will also collect a urine sample each night.

After the 3-day observation period, participants will take part in a 3-week treatment period. Each day, all participants will eat breakfast, lunch, and dinner in the study kitchen. For Days 1 through 7, participants will eat a low sodium diet; for Days 7 through 14, participants will eat a high sodium diet; and for Days 14 through 21, participants will eat a high sodium diet and receive potassium supplements. Blood pressure will be measured three times per day and urine will be collected at several times during this period. Blood samples will be collected at the end of each week.

Parents of participants will also be enrolled in this study, and they will complete the same study procedures that participants complete during the 3-day observation period except for the urine collection.

The study completion date listed in this record was obtained from the "Completed Date" entered in the Query View Report System (QVR).

Inclusion criteria

Inclusion criteria

for Primary Participants:

• Between 18 and 60 years old
• Systolic blood pressure level of 130 to 160 mm Hg and/or diastolic blood pressure level of 85 to 100 mm Hg
• Both parents (2-generation nuclear family) or at least one parent (at least a 3-generation family) is available and willing to participate in the study
• At least one sibling meets eligibility criteria for participation

Inclusion criteria

for Sibling/Spouse/Child Participants:

• Siblings and spouses must be between 18 and 60 years old; children must be more than 16 years old
• Lives in the same village as the main study participant

Exclusion criteria

for All Participants:

• Current stage 2 hypertension (systolic blood pressure level greater than or equal to 160 mm Hg and/or diastolic blood pressure level greater than or equal to 100 mm Hg)
• Current or recent (i.e., less than 1 month before the screening visit) use of antihypertensive medications or medications that affect blood pressure
• Secondary hypertension
• History of clinical cardiovascular disease, including heart attack, congestive heart failure, stroke, and peripheral arterial disease
• Chronic kidney failure or urinary albumin concentration of greater than or equal to 20 mg/dL
• Current diabetes (i.e., fasting serum glucose level greater than or equal to 126 mg/dL) or use of insulin or oral hypoglycemic agents
• Peptic ulcer disease requiring treatment in the 2 years before study entry
• Liver disease requiring treatment in the 2 years before study entry
• Pregnant
• Heavy alcohol drinker (i.e., more than 14 drinks per week)
• Currently adhering to a low sodium diet