HTN: Potassium (2015)

Citation:
 
Study Design:
Class:
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Quality Rating:
Research Purpose:

To clarify the main dietary and non-dietary risk factors between hypertension and normal blood pressure of Chinese urban people.

Inclusion Criteria:

Living in Tianjin, China.

 

Exclusion Criteria:

Younger than 34 years on older than 64 years.

Description of Study Protocol:

Recruitment

Participants for this study were drawn from two previous cross-sectional studies, the baseline survey carried out in 1989 and a follow-up survey in 1992. 

Design

The study population was divided into two groups, those with normal BP and those with hypertension. A nutrition survey, a self-administered questionnaire and anthropometric measurement was conducted to gather information on height, weight, BP, diet, smoking, alcohol consumption, physical activity, family health history, education, income, commuting physical activity and leisure time sport.

Statistical Analysis

  • Data analyzed using the SPSS program
  • Differences of dietary factors between hypertension and normal BP subjects were tested by using general factorial ANOVA (adjusted for age, BMI, energy and time of survey)
  • To assess the relationship between hypertension and dietary and non-dietary risk factors, adjusted odds ratios (OR) were calculated by logistic regression. Analysis of association between hypertension and dietary factors was adjusted for age, BMI, energy and time of survey. When calculating the OR for risk factors between different levels of categorical variables, dummy variables were created by using the lowest group as reference category, i.e., low education, low income, no smoking, no family history, normal weight, less than one leisure time sport.

 

Data Collection Summary:

Timing of Measurements

  • Diet was assessed using a three-day food record plus weighing
  • Height and weight were measured twice and the mean values used for analysis
  • BP was measured twice and the mean used for analysis
  • Alcohol consumption was calculated from the food intake data
  • Physical activity was assessed using a questionnaire. 

Dependent Variables

Diet, age, BMI, BP, education, income, smoking, alcohol consumption, overweight, family history of hypertension, occupation activity, commuting physical activity, leisure time sports per week.

 


 

 

Description of Actual Data Sample:
  • Initial N: 2,068 (367 hypertensive males, 395 hypertensive females, 623 normal BP males, 683 normal BP females)
  • Attrition (final N): 2,068
  • Age: 35 to 64 years old
  • Ethnicity: Chinese

Anthropometrics

 
 
Men 
Women 
Normotension
Hypertension
Normotension
Hypertension
Subjects
623
367
683
395
Age (years)
47.4
54.1
47.4
54.1
Body Mass Index (kg/m2)
23.4
25.7
24.0
26.2
Diastolic BP
75.9
91.9
74.7
90.6
Systolic BP
117.6
148.8
117.1
150.7
Education (percentage) 0 to 6 years
21.5
33.2
35.6
61.1
7 to 12 years
63.5
54.8
57.2
35.1
13+ years
15.0
12.0
7.2
3.8
Income (percentage) Low
30.3
24.7
27.4
33.5
Medium
35.4
35.5
38.8
30.3
High
34.3
39.8
33.8
36.2
Smoking (percentage)
65.3
57.2
25.3
29.0
Alcohol Consumption (percentage)
26.6
27.7
2.8
3.8
Overweight (percentage)
30.7
57.8
33.8
63.4
Subjects
274
166
281
186
Family History of Hypertension (percentage)
45.6
48.6
44.8
51.1
Occupation Activity
15.1
13.0
14.5
14.8
Commuting Physical Activity
1.5
1.1
0.9
0.7
Leisure Time Sports per Week More than one 1 time
20.4
23.5
13.9
11.8
Less than one time or none
79.6
76.5
86.1
88.2

Location

Tianjin, China.

Summary of Results:

 Key Findings

  • Hypertensive group had higher mean values of daily sodium intake than normal BP group (P<0.05)
  • Hypertensive men and women had higher dietary sodium-to-potassium ratio than normotensive group. The difference was significant in women (P<0.01) and almost significant in men (P= 0.057).
  • Dietary sodium intake and dietary sodium-to-potassium ratio were positively associated with BP. Univariate OR for dietary sodium, dietary sodium-to-potassium ratio were 1.07 (P<0.05), 1.12 (P=0.061) in men and 1.07 (P<0.05), 1.18 (P<0.01) in women, respectively
  • Age and BMI had positive association with BP; the odds ration (OR) of hypertension for age and BMI were 1.09, 1.18 in men (P<0.001) and 1.08, 1.16 in women (P<0.001) respectively
  • Women with high education levels were less likely to be hypertensive compared with low level of education (P<0.05 for trend)
  • Overweight men were 3.14 times more likely to be hypertensive (P<0.001) compared with normal weight men. Overweight women showed 3.23 times the same risk (P<0.001).
  • Men with family history of hypertension had a nearly 60% increased probability to hypertension compared with men of no family history  (P<0.05); women with family history had 120% increase in probability (P<0.001)
  • Men going to and from work on foot or by bicycle were inversely associated with BP (OR 0.80, P<0.05)
  • Income, smoking, alcohol consumption, occupational and leisure time physical activity were not significantly associated with hypertension. 

Other Findings

  • There was a high sodium and low potassium consumption in the whole population
  • No significant associations were found between dietary intake of calcium, magnesium, total fat, saturated fat, sodium-to-potassium ratio, protein, cholesterol and different BP patterns.

 

Author Conclusion:
  • The present study has shown that there were high sodium and low potassium consumption levels in the whole of the Tianjian urban population, and the hypertensive group had a high dietary sodium intake and high dietary sodium-to-potassium ratio.
  • Limitations of the study include the collection of dietary data, which is known to be imprecise. Daily intake of nutrients is variable so using a cross-sectional nutritional survey may attenuate the relationships between dietary factors and BP, assessment of diet in a relatively homogeneous population may weaken or lack associates between hypertension status and many dietary variables.
Funding Source:
Industry:
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) N/A
  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? N/A
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) N/A
 
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? N/A
  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? ???
  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? ???
3. Were study groups comparable? Yes
  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? Yes
  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? Yes
  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? N/A
  4.1. Were follow-up methods described and the same for all groups? N/A
  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%.) N/A
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? N/A
  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? N/A
  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.) N/A
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? No
  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? N/A
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? N/A
  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? N/A
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? N/A
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? N/A
  6.6. Were extra or unplanned treatments described? N/A
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? N/A
  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? N/A
  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? N/A
  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? ???
  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