PDM: Metabolic Syndrome (2013)


Aizawa K, Shoemaker JK, Overend TJ, Petrella RJ. Effects of lifestyle modification on central artery stiffness in metabolic syndrome subjects with pre-hypertension and/or pre-diabetes. Diabetes Res Clin Pract. 2009; 83: 249-256.

PubMed ID: 19097666
Study Design:
Case Control Study
C - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:

To examine the effects of lifestyle modification (aerobic exercise and Mediterranean-style diet) on central artery stiffness in metabolic syndrome (MS) subjects with pre-hypertension and pre-diabetes.

Inclusion Criteria:
  • Subjects with either
    • Pre-hypertension [systolic blood pressure (SBP) 130 to 139mm Hg and diastolic blood pressure (DBP) 85 to 90mm Hg]
    • Pre-diabetes (IFG 6.1 to 7.0mmol per L and IGT 7.8 to 11.0mmol per L following an oral glucose tolerance test)
    • Both pre-hypertension and pre-diabetes
    • All subjects were otherwise healthy and none were taking medications that would affect blood pressure or glucose levels
  • All patients were referred from their family physician.


Exclusion Criteria:

Individuals not meeting the inclusion criteria.

Description of Study Protocol:


All patients were referred to the study by their family physician.


Case-control study.

Blinding Used

Implied with measurements.


  •  Baseline, at eight weeks and at 24 weeks, the following tests were taken after an overnight fast:
    • Blood lipids
    • Blood glucose
    • Anthropometrics
    • Blood pressure
    • Doppler ultrasound: arterial stiffness of the carotid artery
    • Treadmill exercise test
  • Subjects were divided in two groups:  MS and non-MS
  • Lifestyle intervention (referred to as SNAC) contained four components:
    • Aerobic exercise: Most days of the week, moderate intensity and for 30 minutes
    • Mediterranean-style diet: Fish, whole grains, fruits, vegetables, olive oil, red wine
      • Subjects received five dinner meals per week from the University of Western Ontario Food Service for the first eight weeks and sample menus throughout the 24-week intervention 
    • Activity diet prescription: Linked the diet and amount of exercise together specific to each individual
    • Stage of change: Survey was used to asses the subjects' behavior change. 

Statistical Analysis

  • Descriptive statistics were used to describe the population
  • Repeated measures ANOVA were used to compare the differences at baseline, eight weeks and 24 weeks
  • Chi-square was used for categorical data
  • ANCOVA was used to measure changes in mean arterial pressure (MAP) as a covariate.


Data Collection Summary:

Timing of Measurements

Baseline, eight weeks and 24 weeks.

Dependent Variables

  • Components of metabolic syndrome:
    • Blood pressures
    • Blood lipids
    • Blood glucose
    • Anthropometric measures
  • Modification on carotid artery parameters
  • Heart rate.

Independent Variables

  • Aerobic exercise
  • Mediterranean-style diet
  • Metabolic syndrome vs. non-metabolic syndrome. 
Description of Actual Data Sample:
  • Initial N: N=63 (31 males, 32 females)
  • Age: 53.9±8.7 years
  • Ethnicity: Canadians
  • Other relevant demographics:
    • MS: N=29
    • Non-MS: N=34
  • Anthropometrics: MS subjects were heavier and had a greater BMI than the non-MS subjects (P<0.05)
  • Location: London, Canada.
Summary of Results:

Key Findings

  • Carotid artery distensibility significantly increased in the MS group at 24 weeks post-intervention compared with baseline (0.191±0.012 to 0.143±0.011, 1/mm Hg x 10-2; P<0.05)
  • β stiffness index decreased in the MS group at 24 weeks post-intervention (9.8±1.1 to 12.51.1 AU; P<0.05)
  • Mean change in waist circumference (-3.3±5.8), SBP (-6.9±16.1) and DBP (-5.6±9.2) significantly (P<0.05) decreased in the MS group after the 24-week intervention
  • Fasting glucose significantly decreased in the MS group from baseline to post-intervention at 24 weeks (6.120.98 to 5.81±0.67; P<0.05).


Author Conclusion:

The study results showed a reduction of carotid artery stiffness following a 24-week lifestyle modification intervention in MS subjects, and that the reduction was accompanied by improvements of some MS components including waist circumference, SBP, DBP and fasting glucose.

Funding Source:
Heart & Stroke Foundation of Ontario
Other non-profit:
Reviewer Comments:
  • The authors did not clearly state where the study was conducted
  • It was unclear if the subject selection was free from bias because all of the subjects were physician referrals and no other means of advertising were mentioned by the authors
  • Authors indicated that the MS and the non-MS groups did have significant differences in weight and BMI at baseline
  • The authors neglected to indicate whether all of the study participants actually did participate from baseline to 24 weeks post-intervention. Attrition rate was not mentioned.
  • Diet and exercise monitoring was not mentioned in the intervention, so participant compliance was unclear and not documented
  • Family physicians instructed the subjects on the diet and exercise intervention. No registered dietitians or nutritionists were mentioned in the study
  • Frequency for physician and subject contact was not indicated in the intervention
  • Each subject's family physician educated their own patient, so it was unclear how many physicians were involved with the study and what type of materials (if any) were provided by the physician to the subject
  • It was unclear how the family physicians were selected to take part in the study and if they were from the same practice group or various other clinic settings.
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? ???
  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? ???
  2.3. Were health, demographics, and other characteristics of subjects described? No
  2.4. Were the subjects/patients a representative sample of the relevant population? ???
3. Were study groups comparable? No
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) Yes
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? No
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) Yes
  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.) No
  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? No
  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%.) ???
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? ???
  4.4. Were reasons for withdrawals similar across groups? ???
  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? Yes
  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? Yes
  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? ???
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? ???
  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? No
  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? 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