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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:

The Chinese population has a lower mean level of body mass index (BMI) and the rates of overweight are significantly lower than those in Western populations. This study investigates whether the variation of BMI within this lower range is still associated with the metabolic risk factors of cardiovascular disease and whether overweight is an independent risk factor for cardiovascular disease in the Chinese population.

Inclusion Criteria:

The data were obtained from a multicentre collaborative study on cardiovascular epidemiology.

Fourteen target populations studied were selected on the basis of the main geographical regions of China, i.e. northeast, north, south-west, south, middle-east and middle-west, as well as the main characteristics of the populations, e.g. city residents, rural farmers, factory workers and fisherman.

Originally surveyed participants had no history of CHD or stroke and were between 35-59 years old.

Exclusion Criteria:

Younger than 35 or older than 59.

History of CHD or stroke.

Description of Study Protocol:

Recruitment:

A population of ~100,000 residents was drawn from each of the 14 target populations.

The 14 populations were not randomly selected from the general Chinese population but comprised populations located in different regions of the country and included various workers.

Design The causes of death were monitored in ~100,000 residents from 1991 to 1995 using the Monica procedure. Risk factors were surveyed in a random cluster sample of 1,000 subjects (35-59 years of age) from each population under surveillance using internationally standardized methods and a centralized system to ensure quality control.

Blinding used (if applicable) N/A

 

Intervention (if applicable) N/A

 

Statistical Analysis Cox regression models were used to explore the association of BMI and RR of storoke, CHD and total death. Cross-sectional stratified analyses were used to analyze the relationship of BMI or waist circumference to other metabolic risk factors

 

Data Collection Summary:

Timing of Measurements: Baseline levels surveyed from 1982 to 1985, followed-up every 9 years

 

Dependent Variables

              

  • Waist and hip circumference (measured in standing position with a measuring tape at the middle point betyween the lowest point of the costal arch and the crest of the iliac bone on both sides of the body, and through the mid-point between umbilicus and xyphoid process on the abdominal side of the body)
  • Height (nearest cm using verticle ruler)
  •  Body weight (nearest kg with use of spring balance, wearing usual clothing and no shoes)

Independent Variables

        Risk factors: Lipids, glucose (after a 12 h fast), BP

        Incidence of stroke (intracerebral haemorrhage, cerebral infarction, cerebral embolism,
             subarachnoid haemorrhage and unclassified)

        CHD (acute MI, coronary sudden death and chronic coronary death)

        All causes of death

Control Variables

      Priniciple physicians were trained and certified centrally before the beginning of the follow-up period.

     After a cardiovascular event, detailed clinical information was collected from the hospital, family members and checked for completeness and acuracy by the prinicple physician.

Description of Actual Data Sample:

Initial N: ~100,000

Cohort Follow-up: 24,734 participants from the cohort were surveyed for risk factors

Survey of Risk Factors: 1,000 (500 men and 500 women) were drawn as a random cluster sample from each of the populations under surveillance.  9,200 men and 10,531 women were included in the study.

Attrition (final N): Cohort Follow-up: 24,734 participants.  Risk Factor: Complete data on RF available in 7,454 men and 9,012 women (?)

Age: 35-59 years of age

Ethnicity: Chinese

Other relevant demographics: Target populations studied were selected on the basis of the main geographical regions of China, i.e. northeast, north, south-west, south, middle-east and middle-west, as well as thr main characteristics of the populations, e.g. city residents, rural farmers, factory workers and fisherman.

Anthropometrics:

Mean body weights ranged from 55.3-70.4 for men and from 52 to 65.9 kg for woemn

Mean heights were 162.9-171.2 cm for men and 152.8-158.3 cm for women

Mean waist circumferences were 69.6-86.7cm  for men and 67.8-82.6 for women

Means of BMI were 20.8-24.6 for men and 20.9-25.1 for women

Location:

 

Summary of Results:

Risk Factors

Rate of overweight ranged friom 2.7-45.4% for men and from 6.3-49.7% for women

Rate of obesity ranged friom 0-4.3% for men and from 0.2-9.5% for women, much lower than Western populations.

Prevelance of HTN, hypercholesterolemia, low HDL-C and high serum glucose all increased with strata increments of BMI.

Incidence of CHD, stroke and total mortality

Results from the prospective study on 10 cohorts during a follow-up of 9 years, 90 cases of coronary events and 256 cases of stroke occurred.

Compared with the lowest quintile, the incidence of CHD events in the highest quintile increased 1.4 times and the incidence of stroke increased 2.5 times.

After controlling for age, gender, BP, Total cholesterol, smoking and alcohol drinking status, BMI was associated significantly with the RR of CHD with each 2 unit increase in BMI being associated wityh a 23% increase (95% CI: 1.08-1.41) with the risk of CHD.

After controlling for age, gender, BP, Total cholesterol, smoking and alcohol drinking status, each 2 unit increase in BMI being associated with a 9% increase in RR for total stroke (95% CI: 1.04-1.13) and a 13% increase in the RR for ischaemic stroke (95% CI: 1.08-1.17). 

All the association were statistically significant and independent of other classical risk factors.

 

Women

   <18.9 18.9-20.2 20.3-21.7 21.8-23.8 >/=23.9
CHD incidence, age adjusted 2.5       2.6 3.4 3.9 6.0
Stroke 5.2 7.8 7.8 12.6 18.0

Men

    <19.1 19.1-20.2 20.3-21.4 21.5-23.1 >/=23.2
CHD incidence, age adjusted 2.5 2.6 3.4 3.9 6.0
Stroke 5.2 7.8 7.8 12.6 18.0

Variables

Treatment Group

Measures and confidence intervals

Control group

Measures and confidence intervals

Statistical Significance of Group Difference

Dep var 1

Mean, CI.

e.g., 4.5±2.2

Mean, CI.

e.g., 1.5±2.0

Stat signif difference between groups

e.g., p=.002

Dep var 2

 

 

 

etc

 

 

 

 

Other Findings

 

Author Conclusion:

The average BMI values and ther rates of overweight in the Chinese population are reportedly much lower than those in Western populations. The analysis showed that thr variability of BMI and waist circumference, even within the lower range, was associated with the prevalence of other risk factors.

The prospective study in 10 cohorts with 24,734 participants revealed that the incidence of both CHD and stroke rose with each quintile increment of BMI. After adjusting for classic RF, the association still remained significant.

Funding Source:
Government: NABIR, USDOE
Reviewer Comments:

The 14 populations were not randomly selected from the genral Chinese population. However, as authors pointed out, the cohort comprised populations located in different regions of the country and included various workers.

No description of exclusion criteria. Poor description of includion criteria.  Appears that participants were not included or excluded based on other risk factors/diseases, which may impact outcomes. Health status of the participants was not decribed.

Difficulty in determining final N. No description of how withdrawls (participants lost inTarget populations studied were selected on the basis of the main geographical regions of China, i.e. northeast, north, south-west, south, middle-east and middle-west, as well as thr main characteristics of the populations, e.g. city residents, rural farmers, factory workers and fisherman.  follow-up) are being handled.

 

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
  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
  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
  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) 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. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? 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
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
  1.3. Were the target population and setting specified? Yes
  2. Was the selection of study subjects/patients free from bias? No
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
  2.1. 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? ???
  2.2. Were criteria applied equally to all study groups? ???
  2.3. Were health, demographics, and other characteristics of subjects described? No
  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? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? Yes
  3. Were study groups comparable? 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
  3.1. 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
  3.2. 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
  3.3. 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
  3.4. 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
  3.5. 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
  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? ???
4. Was method of handling withdrawals described? ???
  4.1. Were follow-up methods described and the same for all groups? ???
  4.1. Were follow-up methods described and the same for all groups? ???
  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%.) ???
  4.2. 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? ???
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? ???
  4.4. Were reasons for withdrawals similar across groups? ???
  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
  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? ???
5. Was blinding used to prevent introduction of bias? ???
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? 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
  5.2. 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? ???
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? ???
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? 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
  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. 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
  6.1. 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
  6.2. 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? Yes
  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
  6.4. 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
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? N/A
  6.6. Were extra or unplanned treatments 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
  6.7. 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
  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. 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
  7.1. 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
  7.2. 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
  7.3. 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
  7.4. 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
  7.5. 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
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.7. Were the measurements conducted consistently across groups? 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. 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
  8.1. 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
  8.2. 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
  8.3. 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)? No
  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)? No
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? Yes
  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
  8.6. 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
  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. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? 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. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? No
  10.1. Were sources of funding and investigators' affiliations described? No
  10.2. Was the study free from apparent conflict of interest? Yes
  10.2. Was the study free from apparent conflict of interest? Yes