EAL

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

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To evaluate clinical measures of obesity for their ability to predict death from cardiovascular disease (CVD) and coronary heart disease (CHD) with conventional cardiovascular risk factors.

Inclusion Criteria:

Registered voters

Exclusion Criteria:

Not reported

Description of Study Protocol:

Recruitment

Residents of 9 metropolitan centers across Australia, aged 20-69, who were registered voters of December 1988 were randomly selected.

Study Design

Subjects were selected by systematic probability by sex and 5-year age groups. The target was 1500 subjects in each group. They were invited to attend a local survey center after an overnight fast of >12 hours. Of 15,164 persons selected, 9,309 attended and data were completed on 9,206.

Participants completed a self-administered questionnaire after their fasting status was confirmed. Physical measurements taken were height, weight, waist circumference, hip circumference. Two consecutive readings were made and averaged. Subjects reported smoking status, heart disease, and diabetes. Blood pressure was taken, and blood drawn.

Statistical tests

Mortality rate was evaluated until December 31, 2000, by linking the records of the original survey to The Australian Institute of Health and Welfare National Death Index. Causes of death were ascertained from ICD-9 codes.

Baseline measures and risk factors were included in Cox proportional hazards regression analysis for survival time from survey to day of death or December 31, 2000. Since the death rates and the risk factors showed strong association with age, the subject variables were age-standardized with age and the square of age to account for linear and non-linear relationships. Hazard ratios were estimated with 95% CI. “The hazard ratios indicated the incremental risk of 1 SD above the mean for any continuous risk factor. For categorical risk factors, hazard ratios were calculated for the presence of the risk factor. Age-standardized univariate associations between candidate risk factors and CVD and CHD deaths were estimated. Finally, all of the risk factors were included in a multivariate Cox regression analysis using a forward step-wise variable selection procedure to determine significant independent associations with CVD deaths and CHD deaths.”

Data Collection Summary:

Timing of measurements

Measurements taken in 1989 and compared to mortality data through December 2000.

Dependent Variables

Mortality from CHD or CVD; deaths from other causes were not included in analysis.

Independent Variables

Hazard ratios for the risk factors predicting CVD mortality and CHD mortality: blood pressure, fasting serum lipid levels, smoking, history of heart disease or diabetes, and obesity as measured by BMI, waist circumference and WHR.

Control variables

Age

Description of Actual Data Sample:

Sample Size: 9206 men and women

Age: 20-69 years

Anthropometric Data

Men

4508 men, age 43+13

BMI 25.9 +3.6

Waist circumference (cm) 90+11

WHR 0.89+0.06

Women

4698 women, age 43+13

BMI 24.9 +4.8

Waist circumference (cm) 77+11

WHR 0.76+0.06

All are mean + 1 SD

Demographic Data: not reported

Location: Australia

Summary of Results:

Univariate cardiovascular disease mortality 1988-2000. Age-standardized hazard ratios for risk factors by Cox regression. The hazard ratios (with 95% CI) refer to risk at 1 SD above the mean for each variable.

	Men	Women
BMI	1.23*	1.26
Waist,cm	1.39*	1.37*
WHR	1.63*	1.58*

Multivariate cardiovascular disease mortality 1988-2000. Age-standardized hazard ratios for risk factors by Cox regression. The hazard ratios (with 95% CI) refer to risk at 1 SD above the mean for each variable.

	Men	Women
WHR	1.60*	1.59*

Univariate coronary heart disease mortality 1988-2000. Age-standardized hazard ratios for risk factors by Cox regression. The hazard ratios (with 95% CI) refer to risk at 1 SD above the mean for each variable.

	Men	Women
BMI	1.26	1.34*
Waist,cm	1.43*	1.54*
WHR	1.74*	1.77*

Multivariate coronary heart disease mortality 1988-2000. Age-standardized hazard ratios for risk factors by Cox regression. The hazard ratios (with 95% CI) refer to risk at 1 SD above the mean for each variable

	Men	Women
WHR	1.47*	1.88*

*statistically significant

Author Conclusion:

“Measurements of waist-hip ratio, using a carefully standardized technique proved far superior to the other indices of obesity in determining the future risk of death from CVD or CHD. The multivariate analyses confirm that WHR are independent of other risk factors, including self-reported coronary heart disease.” “WHR..is less dependent on body size and height. Furthermore, hip circumference is an index of muscle mass and may reflect exercise status and insulin sensitivity.” “WHR may prove to be a more appropriate and universal indicator of risk for ethnically diverse populations”…..including large or small framed groups.

Funding Source:

Not-for-profit

Foundation associated with industry:

Reviewer Comments:

Strengths:

There were adjustments for variables.
WHR appeared to be an indicator independent of other variables.
Mixed population, gender-wise and ethnically.
Credible use of statistics.
Power with larger sample.

Generalizability/Weaknesses:

Only one survey with no follow-up to end point of death or date of December 31, 2000.
only registered voters were included, but no data were given as to the percent of Australian citizens who are registered to vote. Some groups may not be represented, such as immigrants, elderly, or native populations.

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?		No
	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?	No
	2.2.	Were criteria applied equally to all study groups?	N/A
	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?	No
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?		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?	N/A
	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?		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?	Yes
	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?	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?	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?	Yes
	7.2.	Were nutrition measures appropriate to question and outcomes of concern?	N/A
	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?	???
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