COPD: Quality of Life (2007)


Monso E, Fiz JM, Izquierdo J, Alonso J, Coll R, Rosell A, Morera J. Quality of life in severe chronic obstructive pulmonary disease: correlation with lung and muscle function. Respir Med 1998;92:221-227.

PubMed ID: 9616516
Study Design:
Cross-Sectional Study
D - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:
The purpose of this study was to assess the quality of life (QL) impairment in severe COPD patients using long-term oxygen therapy and to investigate the physiological parameters related to QL in this population.
Inclusion Criteria:
COPD patients followed by the University Hospital in Catalonia Spain who had neither used long-term corticotherapy nor followed rehabiliation programs the previous year and who were able to answser a QL questionnaire and perform lung and muscle function tests.
Exclusion Criteria:
See above.
Description of Study Protocol:


Subjects were recruited from a university hospital in North Barcelona which periodically assesses all COPD patients on long-term oxygen therapy for assessment of their clinical status and monitoring of oxygen use.


A cross-sectional analysis was completed.

Blinding used (if applicable):  Not applicable 

Intervention (if applicable)

The Spanish version of the Nottingham Health Profile was used to measure Quality of Life (QL), lung function measurements were performed, muscle function and nutritional assessment.

Statistical Analysis

Pearson correlation coefficients were calculated to determine the relation between physiological variables and subjective patient-based variables. Stepwise regression analyses were performed using NHP and ADL scores as dependent variable and lung function, muscle function, nutrition status and VAS as independent variables. Results were considered statistically signficant when P< 0.05.

Data Collection Summary:

Timing of Measurements

QL assessments were done after 15 minutes of relaxation in a quiet room. Lung function measurements were performed when patients were clinically stable and following 15 minutes of rest. Respirator and peripheral muscle function were measured after a 15 minute rest.

Dependent Variables

  • QL as measured by mean score on the ADL questionnaire and the NHP
  • Muscle function measured by strength of the deltoid muscle and hand-grip strength
  • Nutritional status measured by skinfold measurements

Independent Variables

  • COPD and lung Function

Control Variables


Description of Actual Data Sample:

Initial N: 47

Attrition (final N): 47 (43 men, 4 women)

Age:  65.19 + 8.21 years

Ethnicity:  Not stated

Other relevant demographics: All lived in North Barcelona, Spain


Mean height: 162.47   7.99 cm

Mean weight:  68.91  13.51 kg

Location: North Barcelona, Spain


Summary of Results:

Other Findings

Significant correlations were found between years since initiating oxygen therapy and VAS, ADL scores and results on the NHP physical mobility dimension (P<0.05, r= 0.3).

Low FEV1 was associated with limitation in daily activities and high scores on the energy, physical mobility and social isolation NHP dimensions (r=0.3). No signficant correlations were found between QL and muscle function parameters or nutritional status.

VAS score was related to ADL score and to scores on most NHP dimensions (energy, pain, emotional reactions and physical mobility, r= 0.34 to 0.51).

Stepwise multiple regression analysis revealed that lung function explains 39-45% of the variance for some dependent variables (energy, physical mobiltiy, social isolation).


Author Conclusion:
COPD patients using long-term oxygn suffer from severe QL impairment affecting not only energy and mobility but also emotional reactions, social isolation and sleep. Lung fucntion is related to energy, mobility and social isolation dimensions, but muscle function is unrelated to QL in these patients.
Funding Source:
University/Hospital: FIS
Reviewer Comments:

Disparate sample size (many more men).  Did not look at BMI of patients - better indicator of nutritional status than just mid-arm circumferance and triceps skinfold.


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? ???
  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? ???
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? ???
  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) 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? ???
  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.) ???
  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? No
  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? N/A
  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? 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? No
  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? Yes
  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? No
  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)? ???
  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? ???
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