EAL

DLM: BMI (2001)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To examine the association between Body Mass Index (BMI) and death rates in US adults (white and African-American only).

Inclusion Criteria:

The study subjects were selected from the 1,184,657 participants in the Cancer Prevention Study II, a prospective study of mortality among men and women in the US begun by the American Cancer Society in 1982.

Exclusion Criteria:

Extremes of height and weight (less than 0.1 percentile or more than 99.9 percentile)
No information on race or race other than African-American or white
No information on smoking status or prior weight from mailed questionnaire sent to obtain information on demographics, personal and family history of disease, and various aspects of behavior, environmental and occupational exposure and diet.

Description of Study Protocol:

1,184,657 subjects in the Cancer Prevention Study II, a prospective study of mortality among men and women in the US that was begun in 1982 with follow-up for 14 years. Participants were identified and enrolled by more than 77,000 volunteers in all 50 states, the District of Columbia and Puerto Rico.

Data Collection Summary:

Outcome Measures: Deaths from all causes, deaths from cardiovascular disease (CVD) (ICD-9 codes 390-459).

Description of Actual Data Sample:

457,785 men, 488,369 women
Average age was 57 years
201,622 deaths.

Summary of Results:

Subgroups for analysis:

Current or former smoker with history of any of the following: Cancer, heart disease, stroke, respiratory disease, current illness of any type, weight loss of more than 10 pounds in previous year
Current or former smoker with no history of disease at enrollment
Those who never smoked but had history of disease
Those who never smoked and no history of disease
Reference category for BMI 18.5 to 24.9.

Among subjects who had never smoked and who had no history of disease, the higher mortality rates were among the heaviest men (RR, 2.68; 95% CI, 1.76 to 4.08) and heaviest women (RR, 1.89; 95% CI, 1.62 to 2.21).

A high BMI was most predictive of death from CVD, especially in men (RR 2.9, 95% CI, 2.37 to 3.56). Significantly increased risk of death from CVD were found at all BMI indexes more than 25.0 in women and more than 26.5 in men.

The risk of death from all causes, CVD, cancer or other diseases were higher throughout the range of moderate and severe overweight for both men and women in all age groups. The risk associated with a high BMI is greater for whites than African-Americans. The results of this study support the well-established higher risk of death associated with severe overweight as well as a gradient of increasing risk associated with moderate overweight. The consistency of our findings in men and women and in all age groups supports the use of a single recommended range of body weight throughout life.

Author Conclusion:

Findings from this study support that there is an increase risk of death associated with severe overweight men and women, and more for white men and women than African-American men and women.

The lowest rates of death from all causes were found at BMIs between 23.5 and 24.9 in men and 22.0 and 23.4 in women.

Funding Source:

Other:

Not disclosed.

Reviewer Comments:

Self-reported height and weight decreases the strength of the study. There were not enough deaths (not enough subjects?) among African-American men at high BMI to analyze risk at very high BMIs.

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?	Yes
	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%.)	Yes
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	Yes
	4.4.	Were reasons for withdrawals similar across groups?	Yes
	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
	5.1.	In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate?	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?	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?	Yes
	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?		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
	7.3.	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
	7.5.	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
	7.7.	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