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 |
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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
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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 | |