EAL

FNOA: Assessment of Overweight/Obesity (2012)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To test the hypothesis that high cardiorespiratory fitness and high body mass index are independently and jointly associated with a lower risk for death among healthy elderly men.

Inclusion Criteria:

Participant in The Veterans Exercise Testing Study
Male gender
Age 65 years or older
Completed a baseline medical examination
Completed a maximal exercise test.

Exclusion Criteria:

Abnormal exercise test
Documented cardiovascular disease (including coronary artery disease, myocardial infarction, heart failure, stroke).

Description of Study Protocol:

Recruitment

Participants in The Veterans Exercise Testing Study cohort were referred to two university-affiliated Veterans Affairs medical centers between 1987 and 2003 for clinical exercise testing.

Design

Prospective cohort study.

Blinding Used

Inherent in measurements.

Statistical Analysis

The independent effects of BMI and cardiorespiratory fitness were assessed using two proportional hazards models, the first adjusting for age, ethnicity and cardiovascular disease risk factors (hypertension, hypercholesterolemia and current smoking) and the second by adding cardiorespiratory fitness (for BMI) and BMI (for cardiorespiratory fitness), entered as continuous variables
In joint analysis, nine cardiorespiratory-fitness and BMI categories were assessed using a single proportional hazards model adjusting for age, ethnicity and cardiovascular disease risk factors.

Data Collection Summary:

Timing of Measurements

A baseline examination was completed at time of cohort entry. Mortality data was collected from the Social Security Death Index and California Death Registry. Vital status was determined as of December 31st, 2004.

Dependent Variables

All-cause mortality.

Independent Variables

Cardiorespiratory fitness (symptom-limited maximal exercise test using an individualized ramp treadmill protocol)
Body mass index (calculated using measured height and weight).

Control Variables

Age
Ethnicity
Cardiovascular disease risk factors (hypertension, hypercholesterolemia, current smoking).

Description of Actual Data Sample:

Initial N: 2,469 consecutive men who completed a baseline medical exam and maximal exercise test
Attrition (final N): 981 men after application of exclusion criteria
Age: 65 to 88 years
Ethnicity: 75% non-Hispanic White, 9% Hispanic, 10% African-American, 6% Asian American
Anthropometrics: Underweight participants represented 2.1% of the cohort, normal weight 26.3%, overweight 46.6% and obese 25.0%
Location: Long Beach, CA and Palo Alto, CA, USA.

Summary of Results:

Key Findings

Each one-unit increase in BMI was associated with reductions in mortality risk
The HR (95% CI) for mortality associated with underweight, overweight and obesity were 2.51 (1.26 to 4.98), 0.66 (0.48 to 0.90) and 0.48 (0.32 to 0.74), respectively
Each one-unit increase in MET (metabolic equivalent; measure of cardiorespiratory fitness) was associated with reductions in mortality risk
Multivariate analysis:
- In the fully adjusted multivariate model, the association of the interaction of BMI and cardiorespiratory fitness to all-cause mortality was significant (P=0.005)
- Among men having low cardiorespiratory fitness, all-cause mortality did not differ by BMI groups
- Among men with moderate cardiorespiratory fitness, overweight and obese men were 61% and 63% less likely to die compared with the low cardiorespiratory fitness, normal BMI reference group
- Among men with high cardiorespiratory fitness, normal weight, overweight and obese participants had reduced mortality risks of 51%, 64% and 74% respectively.

Multivariate Hazard Ratios of All-cause Mortality Within Strata of Cardiorespiratory Fitness Groups According to BMI for 981 Healthy Elderly Veterans

Fitness/BMI Category	N	Number of deaths (%)	HR (95% CI)	p
Low (<5.0 METs)
BMI <20.0*	3	3 (100)	---	---
BMI 20.0-24.9	56	17 (30)	1.00 (reference)	---
BMI 25.0-29.9	103	32 (31)	0.96 (0.57-1.63)	0.89
BMI ≥30.0	65	12 (19)	0.56 (0.28-1.13)	0.11
Moderate (5.0-8.0 METs)
BMI <20.0*	10	5 (50)	---	---
BMI 20.0-24.9	107	35 (33)	0.85 (0.51-1.42)	0.54
BMI 25.0-29.9	205	36 (18)	0.39 (0.23-0.64)	<0.001
BMI ≥30.0	124	17 (14)	0.37 (0.20-0.71)	0.003
High (>8.0 METs)
BMI <20.0*	8	2 (25)	---	---
BMI 20.0-24.9	95	19 (20)	0.49 (0.27-0.91)	0.03
BMI 25.0-29.9	149	25 (17)	0.36 (0.20-0.63)	<0.001
BMI ≥30.0	56	5 (9)	0.26 (0.10-0.69)	0.007

*Too few participants for stratified analysis; MET (metabolic equivalents); model adjusted for age, ethnicity, cardiovascular disease risk factors (HTN, hypercholesterolemia, current smoking).

Author Conclusion:

Both higher BMI and higher cardiorespiratory fitness reduced the risk of all-cause mortality in healthy elderly veterans who were referred for exercise testing for clinical reasons but determined to be free of cardiovascular disease
Mortality risk was reduced as BMI increased within groups having moderate or high cardiorespiratory fitness, but BMI was not significantly associated with mortality within the low-cardiorespiratory fitness group
Our obese, highly fit participants had the lowest mortality risk of any group.

Funding Source:

University/Hospital:

Winston-Salem State University; VA Palo Alto Health Care System; Stanford University

Reviewer Comments:

Subjects were all veterans. Extrapolating data to the general population of elderly men must be done with caution due to the inherent differences in this population (all subjects met selection criteria at time of enlistment; excluding pre-existing health problems; including height and weight requirements indicating that obesity developed later in life after term of service was concluded)
Patient were recruited among elderly veterans who were referred by their healthcare providers for clinical exercise testing only
Subjects with known cardiovascular disease were excluded, leaving a "healthy" obese population
Age range from 65 to 88 years; subjects surviving until inclusion in the study were possibly less susceptible to the negative effects of overweight
Body fat distribution and lean body mass was not measured
The reference group in the multivariate analysis was made up of participants with normal weight BMI, but low cardiorespiratory fitness.

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
	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
	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?	Yes
	2.2.	Were criteria applied equally to all study groups?	Yes
	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?	No
	2.4.	Were the subjects/patients a representative sample of the relevant population?	No
	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)	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?	Yes
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	Yes
	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?	Yes
4.	Was method of handling withdrawals described?		Yes
	4.1.	Were follow-up methods described and the same for all groups?	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
	4.2.	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
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	Yes
	4.4.	Were reasons for withdrawals similar across groups?	N/A
	4.4.	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
	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.	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
	5.1.	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
	5.2.	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
	5.3.	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
	5.4.	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?	Yes
	6.4.	Was the amount of exposure and, if relevant, subject/patient compliance measured?	Yes
	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?	Yes
	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
	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)?	N/A
	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
	8.5.	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?	Yes
	10.1.	Were sources of funding and investigators' affiliations described?	Yes
	10.2.	Was the study free from apparent conflict of interest?	Yes
	10.2.	Was the study free from apparent conflict of interest?	Yes