FNOA: Assessment of Overweight/Obesity (2012)

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

To compare body mass index (BMI), waist-hip ratio (WHR) and waist circumference as predictors of all-cause mortality among the elderly.

Inclusion Criteria:
  • Resident of Ommoord, a suburb of Rotterdam, the Netherlands
  • Age 55 or older at cohort entry
  • Full data available on all three body fatness measurements and smoking status.
Exclusion Criteria:
  • Age less than 55 years at cohort entry
  • Data missing for height, weight and BMI or waist to hip ratio or waist circumference
  • Smoking status unknown.
Description of Study Protocol:

Recruitment

All eligible participants in the geographic area selected were invited to participate. 78% of eligible participants responded to the invitation. 

Design

Prospective cohort study. 

Statistical Analysis

  • Sex-specific hazards ratios of all-cause mortality were calculated for BMI, WHR and waist circumference as continuous variables to study linear trends between body fatness measurements and mortality using Cox's proportional hazards model. A quadratic term was included in the model to calculate whether there was a U-shaped relation between body fatness measurements and mortality.
  • Hazard ratios were also calculated for quintiles of BMI, WHR and waist circumference
  • Hazard ratios were also calculated per predefined category of BMI and waist circumference
  • Analyses were performed for never, ex- and current smokers separately.
Data Collection Summary:

Timing of Measurements

  • Baseline examinations took place from March 1990 to July 1993. A home visit was conducted in which a trained interviewer administered a questionnaire including questions on smoking behavior. Two extensive clinical examinations followed the home visit, which included anthropometric measurements. Participants who were not able to leave their home to visit a research center for examination were examined in their homes.
  • Information on vital statistics was acquired at regular intervals from municipal authorities and general practitioners.

Dependent Variables

All-cause mortality.

Independent Variables

  • Measured height, weight and calculated BMI
  • WHR
  • Waist circumference

Control Variables

Smoking category:

  • Ex-smoker
  • Current smoker
  • Never smoker.

 

Description of Actual Data Sample:
  • Initial N: 6,296 (2,602 men, 3,694 women)
  • Attrition (final N): 6,296
  • Age: 55 to 102 years at baseline
  • Ethnicity: Dutch
  • Anthropometrics:
    • Average BMI was higher among women than among men
    • Mean WHR and waist circumference were higher among men than among women
  • Location: Ommoord, Rotterdam, The Netherlands.
Summary of Results:

Key Findings

  • BMI was not linearly related to increased mortality among never-smoking men (P=0.93) or women (P=0.26)
  • WHR was linearly related to increased mortality in never-smoking men (P=0.04), but not in never-smoking women (P=0.98)
  • Waist circumference was linearly related to increased mortality in never-smoking men (P=0.03), but not in never-smoking women (P=0.64)
  • In current and ex-smokers, BMI, WHR and waist circumference were not linearly related to increased mortality
  • A significant U-curved relationship between BMI and mortality was observed in never-smoking men (P=0.06). The U-curved relationship between BMI and mortality in never-smoking women did not reach significance (P=0.55).
  • No U-curve relationship was noted between waist circumference and mortality in never-smoking men or women
  • No significant relationships were noted between quintiles of BMI, WHR and waist circumference and increased all-cause mortality in men or women regardless of smoking status
  • A BMI greater than 30kg/m2 was related to increased mortality among never-smoking men when compared to a BMI between 18.5 and 25kg/m2.
  • Waist circumference between 94 and 102cm and waist circumference above 102cm were both related to increased mortality among never-smoking men.

 

Author Conclusion:
  • Among never-smoking elderly men, waist circumference may have more potential for detecting overweight than the BMI
  • The fraction of mortality attributable to a large waist circumference (more than 94cm) was almost three times higher than the fraction attributable to a high BMI (more than 30kg/m2) in never-smoking men
  • High levels of body fatness did not predict increased mortality in women or in ex- and current smoking men
  • Never-smoking men made up 16.3% of the men in the study. The proportion of never smokers among the elderly in society will increase in the future to more than 16.3% as the participants in the Rotterdam Study grew up in a time period in which smoking was much more common.
Funding Source:
Government: NESTOR Program for Geriatric Research (Ministry of Health and Ministry of Education) and the municipality of Rotterdam
Not-for-profit
The Netherlands Heart Foundation, The Netherlands Organization for Scientific Research
Reviewer Comments:
  • The duration of follow-up was fairly short, with a mean follow-up of 5.4 years. No data is available on life-threatening diseases at baseline or for weight change prior to baseline.
  • No significant relationships were noted between mortality and measures of body fatness in never-smoking women despite a larger sample (N=1,990) than never-smoking men (N=424). Women in the study were presumably post-menopausal, although this was not included in the analysis.
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? Yes
  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? 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? 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) Yes
  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? 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%.) N/A
  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? No
  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.) No
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? No
  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? 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? 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? No
  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? No
  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? No
  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