FNOA: Assessment of Overweight/Obesity (2012)
This research examines the association between body-weight-change and mortality, particularly according to self-reported dieting status, among middle aged people.
Participant survivors in the Israeli Ischemic Heart Disease Study from 1963 that were followed-up in 1968.
Participant survivors from the Israeli Ischemic Heart Disease Study who did not have a follow-up assessment in 1968.
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.
- 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.
- 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.
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.
- 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.
University/Hospital: | Bar-Ilan University and Tel Aviv University |
- 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
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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 | |