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UWL: Association With Outcomes (2009)

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

This study focuses on the role of nutritional status in influencing the risk of institutionalization of frail, cognitively intact people while controlling for health, burden or specific disease, functional and social variables likely to influence outcome.

Inclusion Criteria:
  • Elderly subjects receiving publicly financed home help services offered by six local community service centers in the area of Sherbrooke (Quebec, Canada)
  • Receiving assistance any time from 1991 to 1993
  • Ability to provide signed informed consent.
Exclusion Criteria:
  • No official a priori exclusions
  • However, the following were asked not to participate according to clinical judgment of health professionals of home care team:
    • Subjects not appropriate for signing informed consent
    • Subjects unable to perform an interview (interview questions and a 24-hour dietary recall).
Description of Study Protocol:

Recruitment

  • Recruited elderly subjects receiving publicly financed home help services from six local community service centers in the area of Sherbrooke (Quebec, Canada)
  • Subjects received services from 1991 to 1993.

Design

  • Prospective cohort of one group of study subjects
  • Baseline interview for survey data collected in-home by two research dietitians included.
Variables
Type
Characteristic
Control Variables Sociodemographic Age
Gender
Education
Social support and lifestyle factors Marital status
Living alone or not
Frequency of social contacts
Self-reported isolation
Health-related variables Functional autonomy
Burden of disease
Perceived health status
Medications used
Nutrition Variables Anthropometrics Height
Weight
Arm muscle circumference
BMI
MAC
TSF
MAMA
Reported Three-day dietary recall
Weight loss

The observation period was from the time of the baseline interview and examination, defined as the study entry point, until September 1, 1996 or until entry into an institution, if earlier: "Institution" is defined as "any establishment providing long-term care on a sustained and prolonged basis to meet the physical, social and personal needs of individuals such as chronic care hospitals, nursing homes or very small facilities referred to as foster families."

Statistical Analysis

  • Cox proportional hazards model was used to investigate the relationship between nutritional status indicators and institutionalization
  • Hazard ratio and 95% confidence intervals were calculated as measures of increased risk and statistical significance, using separate bivariate models
  • In order to control for confounding, any covariate that was significantly related (alpha of 0.10 or lower) to the outcome was entered into a preliminary model using a forward selection procedure. Covariates at a significance level of 0.05 were then retained.
  • Predictive values of nutritional indices were adjusted for gender, age at baseline and functional autonomy score
  • Linearity of relationships was tested by visual inspection of data plots
  • Proportionality was tested by incorporating into the model an interaction term between the log of the survival time and the predictors.
Data Collection Summary:

Timing of Measurements

  • All subject information obtained at interview and measurements taken at baseline, upon inception into the study between 1991 and 1993
  • Monitored for institutionalization up to September 1996.

Dependent Variables

Living in an institutional or non-institutional establishment

Independent Variables

  • Nutritional status indicators:
    • Energy and protein intake assessed by three non-consecutive 24-hour recalls, including one weekend day conducted over a three-week period 
    • Height and weight measured using a level platform with measuring tape and electronic scale 
    • BMI
    • Mid-upper-arm muscle area
    • Mid-arm circumference measured with flexible non-stretch tape
    • Triceps skin fold thickness measured using Harpenden skin fold calipers
    • Involuntary weight loss based on self-report. 

Control Variables

  •  Social network variables
    • Marital status
    • Living alone or not
    • Frequency of contacts
    • Self-reported isolation.
  • Pre-disposing factors
    • Age
    • Gender
    • Level of education
    • Perceived health status
    • Burden of disease
    • Medications used.
  • Functional autonomy.
Description of Actual Data Sample:

Initial N

288 subjects (81 men, 207 women)

Attrition (Final N)

  • 202 subjects (46 men, 156 women)
  • Exclusions:
    • Early death (N=7)
    • Early institutionalization (N=7)
    • Lost to follow-up (N=7)
    • Died before institutionalization (N=65).

Age

60 to 94 years of age.

Ethnicity

Not described.

Other Relevant Demographics

Period of observation varied from 3.6 to 63.7 months with a mean of 41.1±18.1.

Location

Area of Sherbrooke (Quebec, Canada).

Summary of Results:

 Baseline Characteristic Differences

Variables
Institutionalized
(N=108)
Living in the Community
(N=94)
Gender (Percentage of Men)
17

30, P<0.05
Involuntary Weight Loss (Percentage)
31

44, P<0.05
Functional Autonomy (Score)

21.3±9.1

24.4±10.4
Perceived Isolation
("Almost Never Alone")
29
 44, P<0.01
  • Rate of institutionalization was 46% and was higher in men (61%) than in women (41%)
  • No significant differences were reported between institutionalized and free-living subjects in regard to baseline energy or protein intake. 

Unadjusted Relative Hazards of Institutionalization

Variables
Relative Hazards
95% Confidence Interval
Involuntary Weight Loss (≥5kg)
1.59
 1.02-2.47, P=0.04
Functional Autonomy (+1 standard deviation)
1.28
 1.04-1.57, P=0.02
Living Alone ("Yes")
0.66
 0.44-0.99, P=0.05
Perceived Isolation ("Often with Others")
2.66
 1.33-5.30, P=0.006
  • Energy or protein intake and anthropometric indices (BMI, MAMA) were not associated with the risk of institutionalization
  • Those who were living with others were more likely to be admitted to a long-term care establishment compared to those who were living alone.

Other Findings

  • In the multivariate model, which adjusted for age, gender and functional status, weight loss remained a significant independent predictor of institutionalization [hazard ratio, 1.71 (95% confidence interval, 1.08 to 2.73)] as did limited functional capacities [hazard ratio, 1.26 (95% confidence interval, 1.02 to 1.55)]
  • Given the same age, gender and level of functional autonomy, an elderly person having lost at least five kg of body weight during the year preceding the baseline interview increased his or her likelihood of institutionalization by 1.7 times.
Author Conclusion:

Weight loss of five kg or more is a significant predictor of early institutionalization in community-living frail elderly, independent of individual functional or physical health characteristics. This association suggests that intervention strategies aimed at improvement of food intake and nutritional status may be effective in preventing or retarding institutionalization. However, until further evaluation of specific nutritional interventions is done, it remains unclear whether weight loss is a marker or a cause of institutionalization.

Funding Source:
Government: Quebec Ministry of Health and Social Services; Medical Research Council of Canada
Reviewer Comments:
  • Weight loss was self-reported and not measured
  • Only baseline weight loss was used with no re-assessment of subjects' weight lost once enrolled in the study, in some cases, for up to five years
  • Nutrition analysis was based on Canadian Nutrition Recommendations and the Canadian nutrient profile
  • Omission of the cognitively impaired and absence of measure of depression may limit generalization of findings.
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) Yes
  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) Yes
 
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? Yes
  2.2. Were criteria applied equally to all study groups? N/A
  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? N/A
  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? N/A
  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? N/A
  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? ???
  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? ???
  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? ???
  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? ???
  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? N/A
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