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DLM: Energy Balance, Obesity and Anthropometric Measurement (2005)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:

To determine whether baseline measures, weight changes (weight or waist circumference) or weight and waist circumference cycling were associated with CHD and mortality.

Inclusion Criteria:

Women who had been enrolled in the Heart and Estrogen/Progestin Replacement Study (HERS) were invited to enroll in a prospective cohort study for an additional two years (HERS II).

Exclusion Criteria:

BMI less than 18.5kg m2.

Description of Study Protocol:

Recruitment

Women who had been enrolled in the Heart and Estrogen/Progestin Replacement Study (HERS) and HERS II.

Design

  • Mortality analysis was done on data obtained from HERS I, a randomized, blinded, placebo-controlled trial evaluating the use of conjugated estrogens/progestins and HERS II, a prospective cohort study. Total follow-up was 6.8 years.
  • Baseline characteristics assessed were: Age, race or ethnicity, smoking habits, alcohol consumption, exercise or walking activity
  • Baseline and annual measures were: Body weight, height, waist, hip circumference, systolic blood pressure and diastolic blood pressure during HERS
    • Weight was measured in kilograms using a standard balance beam scale
    • Height was measured in centimeters using the rod attached to the scale, which was calibrated monthly
    • Waist and hip circumference were measured by using a flexible tape measure
    • Two consecutive measurements were taken at the level between the iliac crests and lower ribs, usually at the level of the navel
    • Hip circumference was measured twice at the area of greatest girth
  • Blood was also drawn at baseline.

Blinding Used

For original study, yes.

Intervention

Not applicable.

Statistical Analysis

  • Pearson correlations
  • Cox proportional hazards models.
Data Collection Summary:

Timing of measurements: Baseline and annually.

 

Description of Actual Data Sample:
  • Initial N: 2,739 females
  • Attrition (final N): 2,739 females (2,359 contributed to mortality analyses)
  • Age: 66.6 years (SD 6.6 years)
  • Ethnicity: 88.7% white
  • Anthropometrics mean (SD)
    • Weight: 73kg (14.5)
    • BMI: 28.7kg per m2 (5.4)
    • WHR: 0.87 (0.08)
    • Waist circumference: 91.9cm (13.3)
  • Location: 20 outpatient clinical centers in the United States.
Summary of Results:

Risk of CHD

HERS Study 1993 to 2001

Variables

CHD Mortality

BMI alone

Hazard Ratio (95% CI)

Waist Circumference Alone 

Hazard Ratio (95% CI)

BMI  (kg/m2) and Waist Circumference Together

Hazard Ratio (95% CI)

Age-adjusted

1.19 (1.06, 1.35)

1.32 (1.16, 1.50)

BMI 0.86 (0.68, 1.10)

WC 1.49 (1.16,1.91)

Multivariate Model 1

1.17 (1.03, 1.33)

1.28 (1.12,1.47)

BMI 0.86 (0.67, 1.10)

WC 1.47 (1.14,1.89(

Multivariate Model 2

1.01 (0.88, 1.15)

1.07 (0.93,1.24)

BMI 0.85 (0.66,1.10)

WC 1.23 (0.95,1.60)

  • Model 1 adjusted for:
    • Age
    • Non-white ethnicity
    • Current smoking
    • Assignment to hormone therapy
    • Self-report of poor/fair health
    • Creatinine clearance of at least 40ml per minute
    • Hospitalization for congestive heart failure
    • New York Heart Association class I-IV congestive heart failure
    • At least two prior myocardial infarctions
    • Any cancer diagnosis
    • Self-report of other serious medical condition
    • Medication use: Aspirin, statins, beta blockers, and angiotensin-converting enzyme inhibitors
  • Model 2 adjusted for all of the above and for potential mediators:
    • Diabetes
    • Hypertension
    • Lipoprotein (a)
    • HDL- and LDL-cholesterol, as time-dependent covariates.
Author Conclusion:
  • "Among post-menopausal women with established CHD, higher levels of baseline waist circumference were associated with an increased risk of CHD and total mortality, whereas higher levels of baseline BMI were associated with a lower risk of the outcomes studied."
  • "Traditional cardiac risk factors did not fully explain the association between these baseline obesity measures and total mortality. Contrary to findings reported for men and for younger women, weight and waist circumference cycling were not associated with mortality. Our findings argue for the inclusion of both BMI and waist circumference as independent cardiac risk factors for predicting total mortality among women with established heart disease."
Funding Source:
Government: NIH, US Dept of Veterans Affairs, Royal Netherlands Academy of Arts and Sciences
Industry:
Wyeth-Ayerst Research
Pharmaceutical/Dietary Supplement Company:
University/Hospital: University of California
Reviewer Comments:

By their own admission, these findings may be exclusive to older women.

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? 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? 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? 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? 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? 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? 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? 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? N/A
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? Yes
  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? Yes
  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? 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? N/A
  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