UWL: Association With Outcomes (2009)

Study Design:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:

To determine if weight change over a two-year period in Mexican Americans aged 65 or older is associated with increased risk of lower body disability over a subsequent five-year follow-up period.

Inclusion Criteria:
  • Participation in the Hispanic Established Population for the Epidemiological Study of the Elderly Cohort
  • Resident of Texas, California, Arizona, Colorado or New Mexico
  • Mexican American
  • No limitation at baseline in four activities of daily living: Walking across a small room, bathing, transferring from a bed to a chair and toileting. Able to perform a walk test at a two-year follow-up.
  • Weight measurements available at baseline and two-year follow-up.
Exclusion Criteria:
  • Disabled in any of the following ADLs: Walking across a small room, bathing, transferring from a bed to a chair or using the toilet
  • Institutionalized
  • Unable to perform walk test at two-year follow-up.
Description of Study Protocol:


Area probability sampling procedure used.


Cohort study 

Statistical Analysis

Chi square, analysis of variance, post-hoc Tukey test, General Estimation Equation.



Data Collection Summary:

Timing of Measurements 

Baseline, two years, five years, seven years.

Dependent Variables

  • Weight change: Weight change was assessed by comparing baseline weight with weight at two-year follow-up. Weight was measured using a calibrated Metro 9800 measuring scale. 
  • Lower body disability: Lower body disability was defined as the presence of any ADL limitation and onset of walking limitation
  • ADL Limitation: Respondents were asked whether they could perform without help, with help or were unable to do the following activities of daily living (walking across a small room, bathing, transferring from a bed to a chair and toileting). Lower body ADL limitation was dichotomized as no help needed vs. needing help with or unable to perform one or more of the activities.  
  • Walking limitation: Mobility was assessed with an eight-foot timed walk at normal pace. Walking limitation was defined as being unable to walk or walking this distance at a speed of 9.0 seconds or more. 

Independent Variables and Control Variables

  • Time
  • Sociodemographics
  • Age
  • Sex
  • Years of education
  • Marital status
  • History of DM, arthritis, heart attack, stroke, hip fracture or cancer
  • Depression
  • Cognitive function
  • Body mass index
  • Hand grip strength
  • Overnight hospitalization over time interval.



Description of Actual Data Sample:
  • Initial N: 1,737  (735 males, 1,002 females)
  • Attrition (final N): 1,246 at seven-year follow-up.


65 years or older:

  • For those who lost more than 5% body weight at two-year follow-up, mean age was 75.1±6.2
  • For those who had stable body weight at two-year follow-up, mean age was 73.9±5.5
  • For those who gained more than 5% body weight at two-year follow-up, mean age was 73.1±5.5.


Mexican American.

Other Relevant Demographics

Descriptive Sample Characteristics by Two-year Weight Change in Older Non-disabled Mexican Americans at Two-year Follow-up   (N=1737)

Statistical significance key: *P<0.001,  #P<0.01

Explanatory Variables >5% loss Stable >5% gain
Total, N (%) 377 (21.7) 1,003 (57.7) 357 (20.6)
Education, years, mean±SD# 4.5±3.7 5.2±4.1 5.0±3.8
Weight, pounds, baseline, mean±SD* 161.3±30.2 160.3±30.4 151.2±29.0
Weight, pounds, at two-year follow-up, mean±SD* 143.2±27.6 160.0±30.5 168.6±31.6
BMI at baseline, kg/m2, mean±SD* 28.1±5.0 28.3±4.9 26.9±4.8
BMI at 2-year follow-up, kg/m2, mean±SD* 25.2± +/- 4.4 28.3±4.9 30.0±5.4
Arthritis# N (%) 145 (38.5) 458 (45.7) 154 (43.1)
Cancer# N (%) 31 (8.2) 147 (14.7) 59 (16.5)
Mini-mental state exam score, mean±SD* 23.5±4.5 24.6±4.2 24.0±4.2


Texas, New Mexico, Colorado, Arizona and California.


Summary of Results:

Other Findings

Using general estimation equation to evaluate any lower body disability (LBD) as a function of a two-year weight change in non-disabled Mexican Americans at two-year follow-up and controlling for time, age, sex, education, marital status and BMI at baseline,  the odds ratio (OR) for any LBD was 1.43 (95% confidence interval (CI) (1.06 to 1.95) for subjects who lost weight and the OR was 1.39 (95% CI, 1.02 to 1.89) for subjects who gained weight. After hand grip strength, presence of medical condition and cognitive function were add to the equation, the OR for LBD for subjects with weight change decreased.


Author Conclusion:

Independent of sociodemographic variables and BMI at baseline, change in body weight in initially non-disabled Mexican Americans older that 65 years of age was significantly predictive of subsequent lower body disability over five years. However, health conditions and muscle strength partially mediate the association between weight loss or gain and future loss of ability to walk and independently perform ADLs. Potential modifiable risk factors for weight fluctuations should be identified and treated to decrease or slow the onset of disability, reduce medical care costs and improve the health and quality of life of older Mexican Americans.

Funding Source:
Reviewer Comments:

From the initial Hispanic EPESE cohort  (N=3,050), 1,013 subjects had incomplete information at the two-year follow-up due to death, lost to follow-up or re-interview refusal. This group of 1,013 subjects was significantly different from study participants at baseline in that they were more likely to be older; to have ever had a heart attack, diabetes, stroke, hip fracture, cancer and depression; and to be disabled at baseline.  Moreover, this group was more likely to have lower BMI, body weight and hand muscle strength and have a lower cognitive function score than those included in the study. This suggests that the actual study population may have been skewed to represent a healthier segment of the older Mexican American population than the population as a whole.   

Also, the researchers did not know whether weight loss or gain was intentional or unintentional in the study subjects.

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) N/A
  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.) 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? Yes
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? No
  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? Yes
  6.6. Were extra or unplanned treatments described? Yes
  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)? Yes
  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