UWL: Association With Outcomes (2009)

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

To determine the key predictors of aspiration pneumonia in a nursing home population with the hope that health care providers could identify those residents at highest risk and focus more efforts on prevention of this serious disease.

Inclusion Criteria:
  • Nursing home residents aged 65 years or more
  • Most recent full (not quarterly) assessment
  • Unduplicated.
Exclusion Criteria:

None specifically mentioned.

Description of Study Protocol:


Data from the Minimum Data Set (MDS) nursing home assessment data for three states from 1993 to 1994 was used.


Cross-sectional analysis of a retrospective cohort. 

Statistical Analysis

  • Analyses began with bivariate statistical tests
  • Chi-square tests were examined to assess the association of the risk factors with the presence of pneumonia
  • Intercorrelations between the variables were investigated via a Pearson's correlation coefficient matrix
  • Variables significantly associated at the bivariate level were then entered into a multivariate logistic regression model using a backward elimination procedure
  • Interaction terms were calculated to account for any moderating effects on the dependent variable.
Data Collection Summary:

Timing of Measurements

Standardized MDS summary scales and their component items were used.

Dependent Variables

Aspiration pneumonia assessed via the ICD-9-CM code 486 for pneumonia (any type).

Independent Variables

  • Activities of Daily Living (ADL) Hierarchy Index
  • Cognitive Performance Scale (CPS)
  • Resource Utilization Groups (RUGs)


Description of Actual Data Sample:
  • Initial N: 102,842 nursing home residents
  • Attrition (final N): 102,755 residents had data available for prevalence of pneumonia, 74.9% female
  • Age: Aged 65 or more years, 49.4% were aged 85 years or older.


  • 85.3% white
  • 10.9% African American
  • 3.8% Hispanic, Native American or Asian/Pacific Islander.


New York, Mississippi, Maine.


Summary of Results:

Predictors of Aspiration Pneumonia (Logistic Regression Model with Backward Elimination Procedure)

Independent Variables

Odds Ratio (95% CI)

Suctioning 2.55 (2.06, 3.15)
COPD 2.49 (2.27, 2.72)
CHF 1.75 (1.61, 1.90)
Feeding tube 1.73 (1.51, 1.98)
Bedfast 1.72 (1.53, 1.92)
Case mix index 1.67 (1.55, 1.79)
Indicators of delirium/less alert 1.63 (1.38, 1.92)
Weight loss 1.60 (1.47, 1.74)
Swallowing problem/dysphagia 1.46 (1.31, 1.62)
Urinary tract infection 1.39 (1.25, 1.53)
Mechanically altered diet 1.24 (1.14, 1.36)
Dependence, eating 1.17 (1.05, 1.31)

Dependence, bed

1.07 (0.96, 1.19)

Dependence, locomotion 1.05 (0.94, 1.17)
Number of medications 1.04 (1.03, 1.04)
Age 1.01 (1.00, 1.01)
CVA 0.83 (0.75, 0.91)
Tracheotomy care 0.38 (0.25, 0.60)

Other Findings

  • Results of these analyses showed the prevalence of pneumonia among this population was 3% (N=3,118)
  • Results from the logistic regression models indicated 18 significant predictors of aspiration pneumonia
  • The strongest to weakest predictors of pneumonia were: Suctioning use, COPD, CHF, presence of feeding tube, bedfast, high care mix index, delirium, weight loss, swallowing problems, urinary tract infections, mechanically altered diet, dependence for eating, bed mobility, locomotion, number of medications and age, while both CVA and tracheotomy care were inversely predictive of pneumonia.


Author Conclusion:

The emergence of these significant predictors suggested a different pathogenesis of pneumonia in the elderly nursing home resident from the acute care patient or the outpatient. Nursing home residents have chronic medical conditions that gradually lead to "decompensation" in functional status, nutritional status, and pulmonary clearance. Dysphagia and aspiration are common complications of their medical conditions and may slowly worsen as their status deteriorates. Alternatively, a sudden adverse event may dramatically increase the amount aspirated or the ability to resist infection and lead to sudden decompensation. Clinical staff must identify residents with dysphagia and aspiration and work to prevent decline in functional status in all residents. They must be aware of the dangers of adverse events that lead to sudden inactivity or illness and increase the risk of aspiration pneumonia. Prevention of this disease whenever possible will reduce costs, improve health outcomes and improve our quality of care.

Funding Source:
University/Hospital: University of Michigan, Institute of Gerontology
Reviewer Comments:

ICD-9-CM code for pneumonia was not specific to aspiration pneumonia. Authors note that although the project was able to examine many variables by benefit of the MDS data set, it did not complete the profile of all possible risk factors. The current study included only nursing home residents and cannot be generalized to persons in other settings.

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? 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? ???
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? 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? Yes
  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? N/A
  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? N/A
  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? ???
  7.6. Were other factors accounted for (measured) that could affect outcomes? ???
  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