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 study the relationship between body mass index (BMI) and non-coronary mortality.

Inclusion Criteria:

Insured men of the Korean Medical Insurance Corporation
40 to 64 years of age
Undergone biennial multiphasic health examinations, starting in 1986.

Exclusion Criteria:

Those who had not undergone the follow-up health examination in 1990
Those with a weight loss of more than 5% compared with their weight in 1986
Those with inadequate or missing data.

Description of Study Protocol:

Since heights were not measured in 1986, heights measured in 1990 were used to calculate BMI. Subjects were divided into eight categories according to BMI levels: 18, 18 to 19, 20 to 21, 22 to 23, 24 to 25, 26 to 27, 28 to 29 and greater than or equal to 30kg per m².
Information on smoking, alcohol intake and physical exercise was obtained from a self-administered questionnaire completed during the health examination in 1990. Subjects were divided into four groups according to smoking habits (never, former, light [less than 20 per day] and heavy [at least 20 per day] and three categories related to alcohol drinking habits (non, occasional and frequent). There were two categories of exercise (regular or not) and four economic status categories based on monthly salary.
Mortality was followed up in 1990 to 1991 using:
- The death certificate data of the Korea National Statistical Office
- The death benefit record of the Korean Medical Insurance Corporation
- 1992 to 1998 based on the death certificate data of the Korea National Statistical Office
Utilization review records were cross-checked for corroboration
BMI 22 to 23kg per m² was used as the reference point for relative risk (RR).

Anthropometrics

Height was measured
Weight was measured
Fat-free mass was not measured
BMI was measured.

Statistical Tests

Analysis of covariance to obtain age-adjusted average levels of diastolic blood pressure (DBP) and systolic blood pressure (SBP), serum total cholesterol and fasting serum glucose
Relative risk of BMI was estimated by the Cox proportional hazard regression analysis, adjusting for age, DBP level, serum total cholesterol, serum glucose level, smoking, alcohol consumption, physical exercise and economic status (BMI 22 to 23kg per m² reference)
Two models were compared: Considering and not considering the effect of obesity.

Data Collection Summary:

Outcome Masures

DBP and SBP
Serum total cholesterol
Fasting serum glucose
Causes of death:
- All cause
- Cancer
- Coronary
- Cerebrovascular non-cancer
- Non-coronary
- Non-cerebrovascular.

Blinding Used

No.

Description of Actual Data Sample:

N=235,398 males.

Summary of Results:

During the 12.4 year follow-up period, 4.5% (600 deaths) were attributed to coronary heart disease
There was a positive relation between coronary mortality and BMI, and that became more obvious after the elimination of early follow-up ( i.e., first eight years). The age-adjusted coronary mortality rate among men with BMI 28 to 29kg per m² was three times higher than that among men with the lowest BMI. The positive relation was more obvious before the adjustment of cholesterol, glucose and DBP levels. The increased risk of coronary mortality in the 28 to 29kg per m² group after adjusting age, monthly salary, smoking, alcohol consumption and exercise (see column 1 below) was substantially attenuated after the adjustment also included cholesterol, fasting glucose and DBP (see column 2 below). The relative risk (RR) is compared to BMI 22 to 23kg per m².

During the first eight years of follow-up:

BMI	Column 1*	Column 2**
Kg/m²	RR (95% CL)	RR (95% CL)
<18	0.44	0.53
18-19	0.69	0.78
20-21	0.96	1.04
22-23	1	1
24-25	1.03	0.95
26-27	1.19	1.02
28-29	1.81	1.42
>30	0.45	0.34

After early follow-up:

BMI	Column 1*	Column 2**
Kg/m²	RR (95% CL)	RR (95% CL)
<18	0.70	0.82
18-19	0.61	0.68
20-21	0.97	1.04
22-23	1	1
24-25	0.99	0.92
26-27	1.07	0.94
28-29	1.56	1.27
>30	1.35	1.05

* adjusted for age, monthly salary, smoking, alcohol consumption and exercise

**adjusted for age, monthly salary, smoking, alcohol consumption, exercise, cholesterol, fasting glucose and DBP

Anthropometric

Mean±SD
BMI: 23.1 (±2.54) kg per m².

Author Conclusion:

Adjustment for the possible biological effects of obesity attenuated the effect of obesity on cardiovascular disease risk considerably
This finding suggests that part of the BMI-related cardiovascular mortality was mediated by the known cardiovascular risk factors.

Funding Source:

University/Hospital:

Sungkyunkwan University School of Medicine, National University College of Medicine (Korea)

Reviewer Comments:

Strengths:

Strong power with large sample size
Credible use of statistics
Early follow-up was eliminated.

Generalizability/Weaknesses:

Limitations were not discussed.

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?	N/A
	1.2.	Was (were) the outcome(s) [dependent variable(s)] clearly indicated?	N/A
	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?	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)	???
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	???
	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?		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?	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?	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?	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)?	???
	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?	???
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