UWL: Association With Outcomes (2009)

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

To provide a systematic examination of specific sociodemographic characteristics and health performance variables associated with frailty in a large, well-defined sample of Mexican-American older adult males and females.

Inclusion Criteria:
  • Participants in the Hispanic Established Populations for Epidemiologic Study of the Elderly (EPESE) at Wave Three:
    • Mexican-American
    • 70 years of age or older
    • Residing in Texas, New Mexico, Colorado, Arizona and California
    • Non-institutionalized.
  • Reported having Medicare coverage at EPESE Wave One or Two.
Exclusion Criteria:
  • Refusal to participate
  • Proxy interviews, due to the physical nature of assessment required for the study.
Description of Study Protocol:


The sample from the current study is a sub-sample from the Hispanic Established Populations for Epidemiologic Study of the Elderly (EPESE).

  • The EPESE includes:
    • Longitudinal study of Mexican Americans
    • Aged 65 and over
    • Residing in Texas, New Mexico, Colorado, Arizona and California
    • Probability sampling based on counties, census tracts and households within those tracts
    • Total sample which is generalizable to 500,000 Mexican Americans in the southwest
    • Surveyed subjects in waves every two to three years beginning 1993 to 1994.
  • The sub-sample:
    • Was recruited from subjects in EPESE Wave Three, 1998 to 1999
    • Included only subjects who reported having Medicare coverage at either Wave One or Two
    • Were randomly selected from this group to participate in this study.


  • Participants who qualified were given survey questions in addition to those provided for them in Wave Four of the EPESE study in 2000 and 2001
  • Due to the physical nature of the questions, proxy interviews were not allowed
  • One year later, subjects were contacted and re-assessed using the same instruments and interview questions
  • Regression was used to come up with models that best predict frailty based on sociodemographic and health performance variables.

Statistical Analysis

Examined distribution of variables using descriptives and univariate statistics for all continuous variables and contingency tables (chi-square) for categorical variables

Two multi-variable linear regression models were computed to predict frailty score at baseline

  • First model included sociodemographic variables:
    • Gender
    • Age
    • Education
    • Marital status
    • Financial strain
    • Number of persons in household.
  • Second model included the first model sociodemographic variables as well as performance and health status variables:
    • Lower extremity strength (LE strength)
    • Upper extremity strength (UE strength)
    • Total number of comorbid conditions
    • Mini Mental State Examination (MMSE)
    • Disability score (ADL/IADL)
    • Body mass index (BMI).
  • Criteria of P<0.20 selected to identify predictor variables
  • Computed different regression models for males and females.
Data Collection Summary:

Timing of Measurements

The interview survey and measurements were administered initially. The same interview survey and instruments were used at the one-year follow-up.

Dependent Variables

How Measured
Frailty Fried and Walston Frailty Index, modified 0-4

Includes sub-scales on:

Variable How measured Scale
Weight loss Measured in pounds 1 More than 10 pounds unexplained weight loss between measurements (one-year)

Two items from Center for Epidemiological Studies - Depression (CES-D)

"I felt everything I did was an effort" and "I could not get going"

"How often in the last week did you feel this way"

0 "rarely or none of the time" or "some or a little of the time (one to two days)"
1 "a moderate amount of the time (three to four days)" or "most of the time (five to seven days)
Walking speed Assessed over an eight-foot walk 1 ≥9.0 seconds (≥75th percentile)
Grip strength   1 Men ≤21kg (≤25th percentile)
Women ≤14kg (≤25th percentile)

Independent Variables

How Measured
Muscle Strength Hand held device (Nicholas Manual Muscle Tester, Lafayette Instruments) 0.0 to 199.9
Disability: Activities of Daily Living (ADL) and Instrumental Activities of Daily Living (IADL) Katz Activities of Daily Living scale, modified; OARS Instrumental Activities of Daily Living scale; Rosow-Breslau scale 0: No limitation
1: Any IADL or mobility-related ADL limitation
2: Basic ADL limitation
Cognitive function The Mini Mental State Examination (MMSE) 0 to 30
Body Mass Index (BMI) Weight in kilograms/height in meters squared  
Sociodemographic Variables Age    
Gender Male/female
Marital status Married/unmarried
Years of schooling  
Prevalent medical conditions Physician diagnosis of heart attack, stroke, arthritis, cancer, hip fracture and diabetes
Financial strain How much difficulty meeting monthly payments
Household structure Members in household

Control Variables

None noted.

Description of Actual Data Sample:

Initial N

  • N=800 respondents selected from EPESE study
  • N=621 respondents interviewed at beginning of study
  • Attrition for initial interview due to:
    • Refusal to participate
    • Proxy interviews
    • Deceased
    • Lost to follow-up
    • In nursing home or too sick.

Attrition (Final N)

  • N=551 respondents with both initial and follow-up interview
  • Attrition for follow-up interview not noted.


78.1 (59%)
78.0 (41%)


All Mexican-American.

Other Relevant Demographics

Male and female groups did not differ based on age, education or household, but did statistically differ* on:

128 (35%)
189 (75%)



Males and female groups did not differ based on comorbid conditions, MMSE, BMI, frailty score, but did statistically differ* on:

LE strength (kg)
24.6 (8.5)
34.9 (11.7)
UE strength (kg)
12.6 (5.1)
19.9 (7.4)
Disability: None
166 (45%)
159 (63%)
Disability: IADL
138 (38%)
68 (27%)
Disability: ADL
64 (17%)
26 (10%)
Frailty: Non-Frail
148 (25%)
125 (50%)
Frailty: Pre-Frail
141 (38%)
83 (33%)
Frailty: Frail
80 (22%)
44 (17%)



EPESE was conducted in homes in the Southwest United States (Texas, New Mexico, Colorado, Arizona and California).

Summary of Results:
  • Regression Model One included sociodemographic variables
  • Regression Model Two added in health status and performance variables
    • Since gender was statistically different in Model One, Model Two was separated into two separate regression models: One for males and one for females.
  • There are seven variables that met the P<0.20 criterion and were considered potential predictor variables for examining frailty at the one-year follow-up:


Less than 0.01
UE Strength
  • The statistically significant independent variables explained 37% of the variance in the summary frailty score in males (Nagelkerke R²=0.37)
  • Age, LE strength and BMI were not significant for predicting fraility in males. 


Less than 0.01
LE Strength
  • The statistically significant independent variables explained 29% of the variance in the summary frailty score in females (Nagelkerke R²=0.29)
  • Age, comorbidity, UE strength and MMSE were not significant for predicting frailty in females
  • Results were further classified to see in how many subjects the gender specific regression equations actually predicted frailty at the one-year follow-up.


83% of males were correctly classified at follow-up.

Predicted Status Actual Status*
Frail Not frail
38 (23%)
19 (12%)
Not Frail
8 (5%)
99 (60%)

*Subjects with a score of one (pre-frail) were not included.


79% of females were correctly classified at follow-up.

Predicted Status Actual Status*
Frail Not frail
48 (21%)
29 (12%)
Not Frail
20 (9%)
131 (58%)

*Subjects with a score of one (pre-frail) were not included.

Other Findings

It is noted that:

  • Females tend to have both more comorbidity (77% versus 62%) and more disability (49% vs. 34%) than males in the sample
  • Females were also more likely to have all three conditions, comorbiditiy, disability and frailty, than men in the sample (23% vs. 16%).
Author Conclusion:

Using regression analysis of variables, the authors found different combinations of variables were statistically significant predictors of frailty in Mexican-American men and women over 70 years of age

  • Upper extremity strength, comorbidities, MMSE and disability were associated with frailty in men
  • Lower extremity strength, BMI and disability were associated with frailty in women
  • Disability (ADL/IADL) was the best single predictor of frailty status at one-year follow-up for both men and women.
Funding Source:
Government: National Institute on Aging, National Institutes of Health
Reviewer Comments:
  • Subject characteristics and demographics were noted for the initial sample that completed the initial interview (N=621), but not the final sample that completed the one-year follow-up (N=551)
  • Accounted for significant gender differences in the sample by running separate regression models for males and females
  • Attrition was accounted for in the initial sample, but not in the final one-year follow-up (N=621 at baseline interview and N=551 at one-year follow-up without citing reasons for the attrition)
  • Sample had some bias by only selecting individuals with Medicare, although it is noted that this was greater than 80% of the EPESE sample in Wave Three.
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) Yes
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? No
  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? No
  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%.) No
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? ???
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? ???
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? 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? 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? Yes
  10.2. Was the study free from apparent conflict of interest? Yes