EAL

FNOA: Assessment of Overweight/Obesity (2012)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To examine the cross-sectional associations of body mass index (BMI) with 43 health conditions, including serious diseases, cardiovascular risk factors, other diagnosed medical conditions, and health complaints in older adults using data from the Vitamins and Lifestyle (VITAL) cohort study.

Inclusion Criteria:

Adults aged 50-76 from western Washington State who completed a self-administered questionnaire on current height and weight, medical history and risk factors

Exclusion Criteria:

Underweight (BMI<18.5)
Missing or implausible height, weight, or BMI
Missing information on medical conditions.

Description of Study Protocol:

Recruitment

Using names purchased from a commercial mailing list, baseline questionnaires were mailed to men and women aged 50 to 76 in western Washington State, followed by a postcard reminder after two weeks. Recruitment was conducted from October 2000 to December 2002. The questionnaire used was 24 pages, self-administered, gender-specific and covered supplement use, diet, medical history, and risk factors.

Design

Cross-sectional analysis of cohort data

Blinding used

Not applicable

Intervention

Not applicable

Statistical Analysis

Odds ratios from separate logistic regression models were used to examine associations of the four BMI categories with health conditions. All analyses were gender-stratified and adjusted for age, education, race/ethnicity, and smoking status. The association of BMI with health conditions was assessed by a test for trend, using the logistic regression analog to the Mantel extension test.

Data Collection Summary:

Timing of Measurements

Data were collected once at the time when questionnaires were returned.

Dependent Variables

BMI (defined as weight in kg divided by the square of height in meters; based on self-reported height and weight) categorized into four categories: normal (18.5 to 25.0), overweight (25.0 to 30.0), obese I (30 to <35), and obese II/III (≥35).

Independent Variables

43 health conditions based on self-report (participants simply marked whether they had the condition), grouped into four categories:

Seven serious diseases such as stroke, cancer (not including nonmelanoma skin cancer), coronary artery disease (defined as self-report of any of the following: heart attack, coronary bypass surgery, angioplasty, or physician-diagnosed angina)
Two cardiovascular disease risk factors: hypercholesterolemia and hypertension
23 physician-diagnosed medical conditions such as ulcers and osteoarthritis (included self-report of conditions diagnosed by a physician, currently being treated with prescription medications, or conditions for which there has been a medical procedure)
11 health complaints such as chronic headaches and fatigue (defined as symptoms or conditions that participants experienced for at least half the days of the past year or were treating).

Control Variables

Age
Gender
Education
Race-ethnicity
Smoking.

Description of Actual Data Sample:

Initial N: 77,746 (21.7%) out of 364,418 questionnaires mailed were returned
Attrition (final N): 73,003 participants
- 37,005 women
- 35,999 men
- 77,746 passed eligibility and questionnaire quality control checks
- Other excluded: 679 underweight (BMI<18.5); 3,864 with missing or implausible height, weight, or BMI; 200 with missing medical conditions information
Age: 50 to 76 years (mean age was 61.8 years for women and 62.0 years for men)
Ethnicity: Primarily Caucasian (93.3% of women and 93.4% of men)
Other relevant demographics: Education (35.2% of women and 49.3% of men had ≥16 years); current smokers (7.7% of women and 8.6% of men)
Anthropometrics: 59.7 % of women and 72.7% of men were overweight or obese.

	Women %	Men %
Normal	40.3	27.3
Overweight	34.0	49.0
Obese I	15.7	17.8
Obese II	6.2	4.5
Obese III	3.9	1.5

Location: A 13-county area in western Washington State.

Summary of Results:

Key Findings

Among women, 34% were overweight, 16% in the obese I category, and 10% in obese categories II/III
Among men, 49% were overweight, 18% in the obese I category, and 6% in obese categories II/III
For women, 37 (90%) of the 41 health conditions examined were associated with increasing levels of obesity (P<0.05). The strongest associations (odds ratio [OR] greater than three for obese category II/III compared to normal weight) were:

Health condition	Odds ratio
Diabetes	12.5
Knee replacement	11.7
Congestive heart failure	5.6
Hypertension	5.4
Gallbladder removal	4.9
Pulmonary embolism	4.3
Fatigue/lack of energy	3.7
Insomnia	3.5

For men, 29 (71%) of the 41 health conditions examined were associated with increasing levels of obesity. The strongest associations were:

Health condition	Odds ratio
Diabetes	8.3
Knee replacement	6.1
Hypertension	5.6
Congestive heart failure	3.9
Fatigue/lack of energy	3.5
Pulmonary embolism	3.1
Insomnia	3.1

Other Findings

For women, there were significant though moderate inverse associations for osteoporotic fractures and constipation
For men, there was a modest significant inverse association with enlarged prostate.

Author Conclusion:

A broad range of diseases and health complaints are associated with obesity. Clinicians should be aware of the diverse ways in which being overweight or obese may affect the health of their patients when counseling them about weight loss.

Funding Source:

Government:

National Cancer Institute

Reviewer Comments:

Self-report on physician-diagnosed medical conditions might be inaccurate based on definitions by study protocol
Self-report on some health complaints might be subjective based on definitions
Higher percentage of overweight/obese men than women in sample, but fewer men in the obese II/III category
Sample not representative of target population
Low response rate.

Additional limitations noted by authors:

The direction of effect cannot be discerned due to nature of cross-sectional design, though the objective of this study was to characterize the health burden of obesity regardless of the mechanism of effects
Physical activity not controlled for
The volunteer nature of this sample; the study cohort were primarily Caucasian and well educated; smoking less common in the study cohort than in Washington State
All the data are based on self-reporting. Participants with some conditions were misclassified because they were not aware they had the condition or were not taking medication.

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?		???
	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?	???
	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?	No
3.	Were study groups comparable?		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
	3.3.	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?		Yes
	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%.)	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
	4.5.	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?	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?	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?		???
	7.1.	Were primary and secondary endpoints described and relevant to the question?	N/A
	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?	N/A
	7.4.	Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures?	No
	7.5.	Was the measurement of effect at an appropriate level of precision?	No
	7.6.	Were other factors accounted for (measured) that could affect outcomes?	Yes
	7.7.	Were the measurements conducted consistently across groups?	N/A
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