EAL

FNOA: Assessment of Overweight/Obesity (2012)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

The study examined the association between BMI and subsequent disability and mortality among older Americans. The effect of BMI on life expectancy and disability-free life expectancy was also estimated.

Inclusion Criteria:

Participants enrolled from five sites of the Established Populations for Epidemiologic Studies of the Elderly (EPESE) of community-dwelling persons 65 years and older in the United States:

East Boston, Massachusetts (1982-1989)
Two rural counties in Iowa (1982-1989)
New Hampshire, Connecticut (1982-1989)
Durham, North Carolina (1986-1993)
Subjects from the Hispanic EPESE, collected from Texas, California, Arizona, Colorado and New Mexico (1993-2000).

Exclusion Criteria:

Subjects that reported at least one limitation in activities of daily living (ADLs) at baseline
Subjects with missing BMI values
Subjects with other missing values used as covariates in the study.

Description of Study Protocol:

Recruitment

Subjects were recruited through the EPESE and H-EPESE.

Design

Prospective cohort study

Height, weight (calculated BMI), and functional disability were assessed at baseline. Sociodemographic information collected included: Age, sex, years of formal education, smoking status, the presence of medical conditions (cancer, hypertension, diabetes mellitus, hip fracture, heart attack or stroke)

Follow-up data was collected annually for seven years by in-person interviews (at baseline, third, and sixth follow-ups) and telephone interviews (at the first, fourth, and fifth follow-ups).

At baseline and at each follow-up interview at EPESE sites, information was gathered on health conditions, sociodemographics, and psychosocial characteristics of subjects. Also blood pressure, anthropometric measurements and upper and lower body physical function measures were obtained.

Investigators were looking for:

Association between BMI and mortality
Association between BMI and disability
Estimated effect of BMI on life expectancy
Estimated effect of BMI on disability-free life expectancy.

Blinding used

Implied with measurements

Intervention

Not applicable

Statistical Analysis

Cox proportional hazards regression analysis was used to estimate the hazard ratio of incidence of ADL disability and the hazard ratio of mortality at each follow-up as a function of BMI at baseline
Analyses were controlled for age, sex, marital status, smoking status, years of formal education, and selected medical conditions
BMI was a continuous variable on disability and BMI using Martingale residuals, and the locally weighted scatterplot smooth method was used to find associations, and fit into three Cox proportional hazards models to estimate the hazard ratios of BMIs
Total life expectancy and disability-free life expectancy was estimated using the interpolation of Markov chain method.

Data Collection Summary:

Timing of Measurements

Baseline surveys occurred between 1982 and 1993, depending on site, and participants were interviewed yearly at follow-ups for the next seven years.

Dependent Variables

Mortality
- Confirmed via death certificates, obituaries, reports from relatives or through the National Death Index
Disability
- Measured as a dichotomous variable (needed no help vs. needed help on one or more ADLs).

Independent Variables

BMI
- Categorized according to the National Institutes of Health obesity standards.

Control Variables

All analysis were controlled for age, sex, marital status, smoking status, years of formal education, and selected medical conditions.

Description of Actual Data Sample:

Initial N: N=12,725
- 5,219 male
- 7,506 female
Attrition (final N): N=12,725 (noted that 1,455 were lost to follow-up at some point, but study analysis reports final N=12,725)
Age: Average age for four baseline groups varied from 70.9 years of age to 75.7 years of age
Ethnicity:
- White, N=8,359
- African American, N=1,931
- Mexican American, N=2,435
Other relevant demographics:
- Married, N=6,522
- Years of formal education, for four baseline groups varied from 8.2 years to 9.4 years
- Smoking status
  - Never, N=7,052
  - Former, N=3,503
  - Current, N=2,170
- Comorbidity
  - Heart attack, N=1,563
  - Stroke, N=631
  - Hypertension, N=7,510
  - Cancer, N=1,532
  - Hip fracture, N=313
  - Diabetes mellitus, N=2,061
Anthropometrics:
- BMI
  - <18.5, N=387
  - 18.5 to <25, N=4,547
  - 25 to <30, N=5,082
  - 30 to <35, N=2,031
  - 35 to <40, N=517
  - ≥40, N=161
Location: EPESE sites:
- East Boston, Massachusetts, N=2,536
- Rural Iowa, N=2,655
- New Haven, Connecticut, N=2,092
- Durham, North Carolina, N=3,007
- H-EPESE sites in Texas, California, Arizona, Colorado, New Mexico), N=2,435.

Summary of Results:

Key Findings

Study participants who became disabled or died during the study follow-up of seven years were older and reported more comorbid diseases than others who did not develop disability and who were not lost to follow-up. Mean BMI for baseline characteristic groups (non-disabled, disabled, dead, lost to follow-up) were similar across groups.
Predicting hazards for ADL disability and mortality as a function of BMI demonstrated that:
- The hazard for disability was highest among the <18.5 and >30 groups
- The hazard for mortality was highest among the <25 and ≥35 groups
When hazards were treated as a continuous variable, using three different models:
- BMIs associated with minimum hazard of subsequent disability ranged from 24.1 to 24.2, with a fairly steep increase with lower and higher BMIs
- BMIs associated with minimum hazard of mortality ranged from 25.1 to 27.2, with a steep rise with lower BMIs and a more gradual rise with higher BMIs
In calculating total life expectancy and disability-free life expectancy as a function of BMI:
- For men, both total life expectancy and disability-free life expectancy was higher among the BMI group 25 to <30
- For women, total life expectancy was higher among the BMI group 30 to <35 and disability-free life expectancy was higher among the BMI group 25 to <30
Also estimated are percentages of total life expectancy that will be disability free, which fell sharply for subjects with BMIs of 30 or higher.

Findings

Cox Hazards Models Predicting HR of ADL Disability and Mortality as a Function of BMI:

BMI Category	ADL Disability	Mortality
<18.5	1.52	1.53
18.5 to <25	1.00	1.00
25 to <30	1.02	0.78
30 to <35	1.31	0.80
35 to <40	1.94	1.02
≥40	2.49	1.13

Differences were looked at when combining hazards estimates along with the continuous variable model across various subgroups of subjects (characteristics of groups), and all were similar in all subgroupings.

Author Conclusion:

Assessment of obesity and ideal BMIs in older adults have typically examined associations between BMI and mortality. This study suggests that the association between BMI and subsequent disability should also be considered in evaluation of ideal BMIs in older adults.

Funding Source:

Government:	National Institute on Aging
University/Hospital:	Center for Population Health and Health Disparities, University of Texas Medical Branch

Reviewer Comments:

Self-reported weights and heights were used at some study sites, which may produce lower BMIs
Information not available for all variables at all sites
Self-assessments of ADLs and the presence of comorbidities could mean errors in data classification, however it is noted that historically research suggests good agreement among self-reports on comorbidities and actual medical events
Comorbid conditions did not include arthritis, which could contribute significantly to ADLs and function/loss of function
The sample studied may not be representative of all older adults, although the baseline characteristics show patterns similar to those in older adult population (per article author).

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?	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?	???
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.)	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?	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?	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?	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?		No
	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?	No
	7.5.	Was the measurement of effect at an appropriate level of precision?	???
	7.6.	Were other factors accounted for (measured) that could affect outcomes?	Yes
	7.7.	Were the measurements conducted consistently across groups?	No
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