EAL

DLM: Energy Balance, Obesity and Anthropometric Measurement (2005)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To assess to what extent the incidence of coronary events and death related to smoking, hypertension, hyperlipidemia and diabetes is modified by obesity.

Inclusion Criteria:

Males from the city of Malmo, Sweden born between 1921 and 1949.

Exclusion Criteria:

Those with a previous history of myocardial infarction (N=180) or stroke (N=53)
Those with missing values on smoking habits, blood pressure, blood lipids, fasting glucose or body mass index (BMI) (N=186).

Description of Study Protocol:

Definitions

Coronary event (CE) – acute MI and deaths due to chronic ischemic heart disease.

Protocol

Subjects were instructed to abstain from food, alcohol and tobacco for 12 hours prior to the examination. Height, weight, blood pressure, pulse rate, triglycerides, cholesterol, glucose and fasting insulin were measured.
Self-administered questionnaire to categorize smoking status, angina, cancer, health, physical activity, occupation and drinking behavior
Social class and civil status were obtained by data linkage with the Swedish National Population Census Register
Incidence of CE and death were based on record linkage with the National Inpatient Register, the Swedish Causes of Death Register and the Malmo Heart Infarction Register.

Statistical Tests

General linear model and logistic regression to assess the age-adjusted relationships between body weight and other risk factors for CVD
A direct method was used to calculate age-standardized rates of coronary events and mortality per 1,000 person-years in the different weight categories
Cox’s proportional hazards model was used to study the influence of body weight on the incidence of coronary events, total mortality, CVD mortality and non-CV mortality after adjustment for potential confounders. Age and heart rate were modeled as continuous variables. Hypertension, hyperlipidemia, diabetes mellitus, smoking habits, self-reported health, the absence of physical activity during leisure-time, civil status, occupational level, history of angina pectoris, history of cancer and problematic drinking were categorical variables.
Interactions between BMI and these variables were investigated in terms of a synergy index. Values above one indicate a positive interaction or synergy.
Relative risks (RR) were based on a comparison with non-smoking men who had normal body weight and who were not exposed to hypertension, hyperlipidemia or diabetes.
Significance: P<0.05
Confidence Interval (CI) 95%.

Data Collection Summary:

Exposures measured at baseline exam (1974 to 1984) with follow-up for endpoints through 1997.

Description of Actual Data Sample:

N=22,025 males (70 to 75% population of Malmo)

Summary of Results:

There was a linear relationship between BMI and incidence of MI and a J-shape relationship with overall mortality.

After 23 years of follow-up:

12% (N=2,674) died, 38% due to CVD, 34% due to cancer, 28% due to other causes
20% of the obese men died and 13% had a CE. Incidence of CE was 76% (RR 1.76, 95% CI 1.49-2.08) higher among obese men (N=1,343) than among men of normal weight (N=11,738)
After adjustment for potential confounders, the risk remained statistically significant for overweight (RR 1.18, 95% CI 1.07 to 1.31) and obese (RR 1.39, 95% CI 1.17-1.65).

Author Conclusion:

“Obesity is associated with an increased incidence of coronary events and death. This risk is substantially increased by exposure to other atherosclerotic risk factors, of which smoking seems to be most important.”

Funding Source:

Government:

Malmo City Council; Swedish Council for Social Research

University/Hospital:

Malmo University Hospital (Sweden)

Not-for-profit

Foundation associated with industry:

Reviewer Comments:

Strengths:

Strong power with large sample size
Credible use of statistics with multivariate analysis
Data corroborated with national data registries.

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?	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
	1.1.	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?	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
	3.5.	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?		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.)	N/A
	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?	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
	6.6.	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?		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?	N/A
	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?	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