EAL

FNOA: Assessment of Overweight/Obesity (2012)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To determine how obesity affects the average length of life for men and women aged 70 years and older
To determine how obesity affects the length of non-disabled life among older men and women in the United States.

Inclusion Criteria:

Participants in the first three waves of the Asset and Health Dynamics Among the Oldest Old (AHEAD).

Exclusion Criteria:

Participants in the AHEAD study whose dates of birth, death and initial functioning status could not be determined.

Description of Study Protocol:

Recruitment

Subjects were from the Asset and Health Dynamics Among the Oldest Old (AHEAD) study. Recruitment procedures for this study were not described.

Design

Prospective cohort study:

Data from the AHEAD study was reviewed and analyzed. The sample was followed through three waves of the study. Estimates were made of total, active and disabled life expectancy for obese and non-obese older men and women.
Active life was defined as having no difficulty performing any functions necessary for day-to-day personal care (ADLs). Disabled was defined as having difficult in one or more of six ADLs (walking across a room, bathing or showering, eating, dressing, toileting or transferring in or out of bed).
The original sample consisted of community-dwelling adults but during the second and third waves some participants were in nursing homes. These subjects were defined as disabled.
Obesity was based on calculations of BMI determined by self-reports of height and weight at the first wave and was defined as a BMI higher than 30.

Statistical Analysis

A multi-state life table method was used to estimate total and active life expectancy appropriate for use with longitudinal data
The Interpolation of Markov Chains (IMaCH) approach to estimation of transition schedules and life expectancy was used. This method uses a multi-nomial logistic regression approach to estimating age-specific health transitions. Gender and obesity were included as covariates.

Data Collection Summary:

Timing of Measurements

Data for AHEAD was collected as follows: The first wave began in 1993 to 1994, the second wave in 1995 and 1996 and the third wave in 1998. There was an average interval of two years between the first and second waves and 2.25 years between the second and third waves.

Dependent Variables

Length of life as determined by the National Death Index (NDI) and reports of survivors
Length of non-disabled life as measured by residence in a nursing home during wave two or three or difficulty in performance of one or more ADLs. Method of assessing ability to performance of ADLs was not described.

Independent Variables

Obesity as measured by BMI based on self-reported height and weight.

Control Variables

Gender.

Description of Actual Data Sample:

Initial N: 7,381 individuals in 1993. The gender breakdown was not provided.
Attrition (final N): All participants were accounted for at the end of the third wave, although 1,894 had died
Age: All participants were aged 70 or older at baseline
Anthropometrics: 13.2% of the study population (973 participants) were classified as obese at baseline
Location: United States.

Summary of Results:

Key Findings

Obese older adults of both genders were less like to remain active than non-obese adults (41.5% vs. 50.5%) but were more likely to remain disabled (14.5% vs. 6.4%)
Obese older adults were less likely to die (20.5% vs. 26.4%), more likely to become disabled (16.7% vs. 12.7%) and slightly more likely to recover to active status (6.8% vs. 4.0%)
For both men and women, those who were obese had a significantly higher probability of becoming disabled across the older ages. The likelihood of becoming disabled for women (both obese and non-obese) was higher than men.
For men at age 70, life expectancy was estimated to be 12.3 years for non-obese and 12.4 years for obese. For women at age 70, life expectancy for non-obese women was 15.3 years and for obese women 15.5 years.

Number of Health Transitions for Adults Aged 70 and Older, by Obesity Status

Sample State in 1993 and 1998	All N=7,381	Obese N=973	Not Obese N=6,408
Remained active in 1998	3,637 (49.3)	404 (41.5)	3,233 (50.5)
Became disabled in 1998	987 (13.3)	162 (16.7)	816 (12.7)
Became active in 1998	322 (4.4)	66 (6.8)	256 (4.0)
Remained disabled in 1998	550 (7.5)	141 (14.5)	409 (6.4)
Died by 1998	1,894 (25.5)	200 (20.5)	1,694 (26.4)
Total	7,381 (100)	973 (100)	6,408 (100)

(Percentages appear in parenthesis.)

Total, Active, and Disabled Life Expectancy, in Years and Percent Remaining Life for Obese and Not Obese Adults Aged 70, 80 and 90 Years: AHEAD 1993-1998

Gender	Total	95% CI	Active	95% CI	Disabled	95% CI	Disabled (%)
Male, not obese
70	12.3	11.9-12.8	9.9	9.4-10.2	2.5	2.3-2.8	20.7
80	6.7	6.4-7.1	4.5	4.2-4.7	2.3	2.1-2.5	33.7
90	3.9	3.6-4.1	2.1	2.0-2.3	1.7	1.6-1.9	45.1
Male, obese
70	12.4	11.4-13.3	8.4	7.7-9.1	4.0	3.4-4.5	32.0
80	6.8	6.1-7.5	3.3	3.0-3.7	3.5	3.0-4.0	51.1
90	4.3	3.8-4.8	1.8	1.6-2.0	2.4	2.0-2.9	57.1
Female, not obese
70	15.3	14.8-15.7	10.5	10.1-10.8	4.8	4.5-5.1	31.4
80	8.9	8.6-9.3	4.8	4.5-5.0	4.2	3.9-4.4	46.6
90	5.1	4.8-5.5	2.0	1.8-2.1	3.2	2.9-3.5	62.0
Female, obese
70	15.5	14.4-16.6	8.1	7.4-8.8	7.4	6.5-8.3	47.7
80	9.6	8.7-10.5	3.7	3.3-4.1	5.9	5.1-6.7	61.5
90	5.8	5.1-6.6	1.5	1.3-1.7	4.3	3.6-5.0	74.2

Other Findings

Women lived more years, more active years and more disabled years then men. The group with the longest expected disabled life was obese women, with 7.4 years at age 70.

Author Conclusion:

The authors conclude that obesity had little effect on life expectancy for either older men or women, once people had reached age 70. However, the obese are more likely to become disabled, impeding their ability to function independently.

Funding Source:

Government:	National Institute on Aging
University/Hospital:	University of South Florida Research Council

Reviewer Comments:

Height and weight (and therefore BMI) in this study were self-reported. The authors recognize this as a limitation of the study.
It appears that the BMI was only collected during the first wave of the study. Over the study period (approximately four years), some of the non-obese could have changed to the obese category and the obese could have changed to the non-obese, skewing the results.
There are many things besides obesity that could contribute to a decrease in ADL function and lifespan, including mental and physical health conditions, use of medications and surgery. None of these factors were accounted for in the statistical analysis or considered in the discussion section of this study.

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?		No
	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?	No
	2.2.	Were criteria applied equally to all study groups?	N/A
	2.3.	Were health, demographics, and other characteristics of subjects described?	No
	2.4.	Were the subjects/patients a representative sample of the relevant population?	???
3.	Were study groups comparable?		???
	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?	???
	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?	???
	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?		N/A
	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?	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?	N/A
	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?	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?		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?	No
	7.6.	Were other factors accounted for (measured) that could affect outcomes?	No
	7.7.	Were the measurements conducted consistently across groups?	???
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)?	???
	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