EAL

HTN: Potassium (2015)

Citation:

Kelly TN, Gu D, Rao DC, Chen J, Chen J, Cao J, Li J, Lu F, Ma J, Mu J, Whelton PK, He J. Maternal history of hypertension and blood pressure response to potassium intake. The GenSalt Study. Am J Epidemiol. 2012; 176(Suppl 7): S55-S63.

PubMed ID: 23035145

Study Design:

Non-Controlled Trial

Class:

D - Click here for explanation of classification scheme.

Quality Rating:

POSITIVE: See Quality Criteria Checklist below.

Research Purpose:

To examine the relationship between parental history of hypertension and both systolic blood pressure and diastolic blood pressure responses to potassium intake among participants of the Genetic Epidemiology Network of Salt Sensitivity (GenSalt) Study.

Inclusion Criteria:

Between the ages of 18 years and 60 years
Systolic blood pressure (SBP) between 130mm Hg and 160mm Hg or diastolic blood pressure (DBP) between 85mm Hg and 100mm Hg and no use of anti-hypertensive medications were recruited
Provided written, informed consent.

Exclusion Criteria:

Stage 2 hypertension
Secondary hypertension
Clinical cardiovascular disease
Chronic kidney disease
Diabetes
Used anti-hypertensive medications
Pregnant
Heavy alcohol consumption
Currently on a low-sodium diet.

Description of Study Protocol:

Recruitment

Han Chinese individuals with habitually high sodium intake from rural areas of northern China were recruited for the study
A community-based blood pressure screening was conducted among persons aged 18 years to 60 years in the study villages to identify potential probands and their families.

Design

Non-controlled trial.

Blinding Used

Implied with measurements.

Intervention

GenSalt 21-day feeding study:

Low-sodium diet (51.3mmol of sodium per day) for seven days
High-sodium diet (307.8mmol of sodium per day) for seven days
High-sodium diet plus 60mmol potassium supplementation for seven days; one 20mmol potassium pill was given during breakfast, lunch and dinner.

Statistical Analysis

The means and percentages of baseline characteristics were presented by parental history of hypertension
Statistical significance was determined by T-tests for continuous variables and chi-square tests for categorical variables
Differences in mean blood pressure responses to potassium intake according to parental, maternal and paternal history of hypertension; early onset hypertension were examined separately by using mixed linear regression models
To determine whether the use of differentially reported information on maternal and paternal history of hypertension may have influenced study findings, a sensitivity analysis including only those participants who had directly ascertained information on parental hypertension status from both parents
All reported P values are two-sided and all statistical analyses were conducted by using SAS version 9.2.

Data Collection Summary:

Timing of Measurements

Measurements were made at baseline and after the feeding study.

Dependent Variables

Systolic blood pressure and diastolic blood pressure responses to potassium intake:
- Three morning blood pressure measurements were obtained according to a standard protocol during each of the three days of baseline observation and on days five, six and seven of each intervention period
- Blood pressure was measured with the participant in the sitting position after five minutes of rest.
Parental history of hypertension was directly ascertained from parents of intervention participants at the GenSalt baseline examination
Body weight and height were measured twice in light indoor clothing without shoes during the baseline examination. Body mass index was calculated as weight (kg)/height (m)².

Independent Variables

GenSalt 21-day feeding study:
- Low-sodium diet (51.3mmol of sodium per day) for seven days
- High-sodium diet (307.8mmol of sodium per day) for seven days
- High-sodium diet plus 60mmol potassium supplementation for seven days; one 20mmol potassium pill was given during breakfast, lunch and dinner.
All study foods were cooked without salt, and prepackaged salt was added to the individual study participant’s meal when it was served by the study staff. To ensure study participants’ compliance with the intervention program, they were required to have their breakfast, lunch and dinner at the study kitchen under supervision of the study staff during the entire study period. The study participants were instructed to avoid consuming any foods that were not provided by study personnel. Three timed urinary specimens were collected at baseline and at the end of each phase of intervention (days five, six and seven) to monitor compliance with the dietary sodium and potassium interventions among all participants.

Control Variables

A standard questionnaire was administered by trained staff at the baseline examination to collect information on family structure, demographic characteristics, personal and family medical history and lifestyle risk factors including cigarette smoking, drinking and physical activity
Physical activity information obtained from the questionnaire was converted to metabolic equivalent hours per day.

Description of Actual Data Sample:

Initial N: N=1,871 participants
Attrition (final N): N=1,698 included in the analyses
Age: Aged 18 years to 60 years. Mean age of those with parental history of hypertension at 39.9 years, mean age of those without a parental history of hypertension at 36.5 years
Ethnicity: Chinese
Anthropometrics: Mean BMI (kg/m²⁾ of those with parental history of hypertension 23.3kg/m² vs. 23.5kg/m² in those without a parental history of hypertension
Location: China.

Summary of Results:

Key Findings

Stronger associations between early onset maternal hypertension and blood pressure responses were noted with systolic blood pressure decreases of -4.8mm Hg (95% CI: -5.65, -3.95) vs. -3.55mm Hg (95% CI:-4.17, -2.93) and diastolic blood pressure decreases of -2.25mm Hg (95% CI: -3.1, -1.50) vs. -1.42 mm Hg (95% CI: -1.99, -0.85) among those with early onset maternal hypertension vs. those without
Odds ratios for high potassium sensitivity were 1.36 (95% CI: 0.96, 1.92) and 1.6 (95% CI: 1.08, 2.36) for those with maternal hypertension and early onset maternal hypertension, respectively (P=0.08 and P=0.02 respectively).

Author Conclusion:

Potassium supplementation could help to reduce blood pressure among those with a maternal history of hypertension.

Funding Source:

Government:

National Heart Lung and Blood Institute Grant #'s: U01HL072507, R01HL087263, and R01HL090682

Reviewer Comments:

Quality Criteria Checklist: Primary Research
Relevance Questions
	1.	Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies)	Yes
	2.	Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about?	Yes
	3.	Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice?	Yes
	4.	Is the intervention or procedure feasible? (NA for some epidemiological studies)	Yes

Validity Questions
1.	Was the research question clearly stated?		Yes
	1.1.	Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified?	Yes
	1.2.	Was (were) the outcome(s) [dependent variable(s)] clearly indicated?	Yes
	1.3.	Were the target population and setting specified?	Yes
2.	Was the selection of study subjects/patients free from bias?		Yes
	2.1.	Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study?	Yes
	2.2.	Were criteria applied equally to all study groups?	Yes
	2.3.	Were health, demographics, and other characteristics of subjects described?	Yes
	2.4.	Were the subjects/patients a representative sample of the relevant population?	Yes
3.	Were study groups comparable?		N/A
	3.1.	Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT)	N/A
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	N/A
	3.3.	Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.)	N/A
	3.4.	If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis?	N/A
	3.5.	If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.)	N/A
	3.6.	If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")?	N/A
4.	Was method of handling withdrawals described?		Yes
	4.1.	Were follow-up methods described and the same for all groups?	Yes
	4.2.	Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.)	Yes
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	Yes
	4.4.	Were reasons for withdrawals similar across groups?	Yes
	4.5.	If diagnostic test, was decision to perform reference test not dependent on results of test under study?	N/A
5.	Was blinding used to prevent introduction of bias?		Yes
	5.1.	In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate?	N/A
	5.2.	Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.)	Yes
	5.3.	In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?	N/A
	5.4.	In case control study, was case definition explicit and case ascertainment not influenced by exposure status?	N/A
	5.5.	In diagnostic study, were test results blinded to patient history and other test results?	N/A
6.	Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described?		Yes
	6.1.	In RCT or other intervention trial, were protocols described for all regimens studied?	Yes
	6.2.	In observational study, were interventions, study settings, and clinicians/provider described?	N/A
	6.3.	Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect?	Yes
	6.4.	Was the amount of exposure and, if relevant, subject/patient compliance measured?	Yes
	6.5.	Were co-interventions (e.g., ancillary treatments, other therapies) described?	Yes
	6.6.	Were extra or unplanned treatments described?	Yes
	6.7.	Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups?	Yes
	6.8.	In diagnostic study, were details of test administration and replication sufficient?	N/A
7.	Were outcomes clearly defined and the measurements valid and reliable?		Yes
	7.1.	Were primary and secondary endpoints described and relevant to the question?	Yes
	7.2.	Were nutrition measures appropriate to question and outcomes of concern?	Yes
	7.3.	Was the period of follow-up long enough for important outcome(s) to occur?	Yes
	7.4.	Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures?	Yes
	7.5.	Was the measurement of effect at an appropriate level of precision?	Yes
	7.6.	Were other factors accounted for (measured) that could affect outcomes?	Yes
	7.7.	Were the measurements conducted consistently across groups?	Yes
8.	Was the statistical analysis appropriate for the study design and type of outcome indicators?		Yes
	8.1.	Were statistical analyses adequately described and the results reported appropriately?	Yes
	8.2.	Were correct statistical tests used and assumptions of test not violated?	Yes
	8.3.	Were statistics reported with levels of significance and/or confidence intervals?	Yes
	8.4.	Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)?	N/A
	8.5.	Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)?	Yes
	8.6.	Was clinical significance as well as statistical significance reported?	Yes
	8.7.	If negative findings, was a power calculation reported to address type 2 error?	N/A
9.	Are conclusions supported by results with biases and limitations taken into consideration?		Yes
	9.1.	Is there a discussion of findings?	Yes
	9.2.	Are biases and study limitations identified and discussed?	Yes
10.	Is bias due to study's funding or sponsorship unlikely?		Yes
	10.1.	Were sources of funding and investigators' affiliations described?	Yes
	10.2.	Was the study free from apparent conflict of interest?	Yes