EAL

FNOA: Assessment of Overweight/Obesity (2012)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

This research examines the association between body-weight-change and mortality, particularly according to self-reported dieting status, among middle aged people.

Inclusion Criteria:

Participant survivors in the Israeli Ischemic Heart Disease Study from 1963 that were followed-up in 1968.

Exclusion Criteria:

Participant survivors from the Israeli Ischemic Heart Disease Study who did not have a follow-up assessment in 1968.

Description of Study Protocol:

Recruitment

No recruitment was needed due to study design; analyzed participants came from the Israeli Ischemic Heart Disease Study.

Design

Retrospective cohort study

A follow-up study of participants aged 45 to 63 in 1963
From the prior study, participants were assessed on a variety of measurements, which were identical and repeated in surviving participants in 1968
The current study classified participant mortality which was tracked and analyzed for a period of 18 years, to 1986.

Intervention

Measurements from the prior study included:

Body Mass Index (BMI)
Blood pressure
Total cholesterol
Manifestations of atherosclerosis in cardiovascular and non-cardiovascular diseases:
- Clinically recognized myocardial infarction
- Diabetes Mellitus
- Cancer
- Chronic obstructive lung disease
- Angina.

Statistical Analysis

BMI classification into five categories (less than 22, 22 to 25, 25 to 27, 27 to 30, at least 30)
Weight change from 1963 to 1968 in five groups:
- Extreme weight loss: At least five kg
- Modest weight loss: Two kg to four kg
- Stable weight: Between -1kg and +1kg weight change
- Modest weight gain: Two kg to four kg
- Extreme weight gain: At least five kg.
Pooled risk of coronary heart disease in extreme weight-loss to stable weight estimated by the Cochran-Mantel-Haenszel method. Stratification in five groups, advanced individually for each subject.
Multivariate analysis of mortality using Cox's life table proportional hazards model; Breslow's modification for tied data. Adjusted relative risks and 95% confidence intervals for death from all causes and coronary heart disease by weight categories.
Took into account age, smoking status, BMI, pre-weight changes, serum total cholesterol, systolic blood pressure, diabetes, cancer, angina, intermittent claudication and myocardial infarction
Excluded deaths occurring in the first five years of follow-up (1968 to 1973), to limit the effect of pre-existing conditions
Weight change on survival was assessed using Kaplan-Meier and Cox-adjusted survival estimates.

Data Collection Summary:

Timing of measurements: Intervention measurements from the Israeli Ischemic Heart Disease Study occurred in 1963 and 1968. Study investigators followed up with mortality classification for 18 years (1986).
Dependent variables: Mortality.
Independent variables: Voluntary and involuntary weight loss.
Control variables: Repeated analysis removing deaths occurring during the first five years of follow-up (1968 to 1973) to eliminate a possible effect of pre-existing diseases on weight change and mortality.

Description of Actual Data Sample:

Initial N: 10,034 males assessed initially in 1963 via the Israeli Ischemic Heart Disease Study
Attrition (final N): 9,228 males
Age: 40 years to 65 years in 1963
Ethnicity: Not noted
Anthropometrics: The model adjusted for age, smoking status, BMI, serum total cholesterol, systolic blood pressure, diabetes, cancer, angina pectoris, intermittent claudication and myocardial infarction
Location: Israel.

Summary of Results:

Key Findings

Out of the 9,228 men, 2,471 reported being on a diet in 1963. 636 were dieting primarily "to lose weight" and 1,835 were dieting "for health reasons."
During the 18-year follow-up, 2,983 study subjects died.

Mortality

The "extreme loser" (loss of at least five kg) category had age-pooled risks compared to the stable weight group.

Variable	Age Pooled Risk of Mortality	Confidence Interval, 95%
Total Mortality	1.36	1.20-1.55
All Cardiovascular Disease Mortality	1.40	1.16-1.69
All Non-Cardiovascular Disease Mortality	1.33	1.11-1.59
Coronary Heart Disease Mortality	1.55	1.25-1.93
Cancer Mortality	0.90	0.65-1.24

After adjustments at the end of the weight-change period (1968), excess risks associated with extreme weight-loss declined by one-third. They declined further after adjustments for pre-weight-change morbidity and risk factors.
A conscious effort of weight-loss "to lose weight" after 18 years had about a doubling of excess mortality in men with at least five kg weight loss over the initial five-year period
Weight-loss, in general, from 1963 to 1968 was also associated with an increase in incidence of coronary heart disease and diabetes, as well as declining serum total cholesterol.

Mortality by BMI

Increased mortality existed across all weight-loss groups. The most marked increased risk was the age-adjusted mortality rate among lean men (BMI below 22 at baseline), which was almost double their stable weight counterparts (31.0 vs. 18.7). Men with a BMI of at least 30 had a risk of 22.8.
The model was adjusted for the three dieting categories and an additional model to test the relative weight reduction vs. absolute, neither of which made a significant difference to the original models.

Mortality by Reported Diet

Of the three diet categories (diet for medical reasons; diet to lose weight; no diet), the 18-year mortality was 23.5 per 1,000 person-years in extreme weight-losers (at least five kg), compared with 12.7 in men with stable weight. In men not on a diet, the mortality rate was half as large at 19.9 in the Extreme Weight-Loss Group vs. 14.9 in the Stable Weight Group.

Multivariate Analysis of Mortality

Analysis of relative risks for all-cause and coronary heart disease mortality compared to the stable weight group, adjusting for risk factors at the end of the weight-change period, showed that for each cause of death, a decrease of five kg or more was associated with a statistically-significant increase adjusted risk
A multivariate analysis of all-cause mortality adjusting for self-reported dieting was nearly the same
The Kaplan-Meier survival curves, and covariate-adjusted curves also showed the Extreme Weight-Loss Group at an increased risk for mortality.

Author Conclusion:

Weight-loss during a five-year period coincided with an increased incidence of coronary heart disease and diabetes mellitus
Both voluntary and involuntary weight-loss may be associated with a small increased risk of all-cause mortality
There is a need for a better understanding of involuntary weight-loss, particularly when it comes to weight reduction in preventative health.

Funding Source:

University/Hospital:

Bar-Ilan University and Tel Aviv University

Reviewer Comments:

The study only examined men, likely of Middle Eastern origin, which limits its generalization to other populations
Diet, weight-change and intentions over the 18-year follow-up period were not assessed, which may have provided other significant influences on mortality
Differences in study groups at baseline were discussed and adjusted for in analysis.

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?	No
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)	N/A
	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.)	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
	3.6.	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?	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
	5.1.	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
	5.3.	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
	5.5.	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?	No
	10.2.	Was the study free from apparent conflict of interest?	Yes