COPD: Quality of Life (2007)


Katsura H, Yamada K, Kida K. Both generic and disease specific health-related quality of life are deteriorated in patients with underweight COPD. Respiratory Medicine 2005;99:624-30.

PubMed ID: 15823461
Study Design:
Cohort study
B - 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 evaluate the effects of of body weight on both generic and disease-specific health-related quality of life (HRQoL) of patients with COPD.

Inclusion Criteria:
  • Stable COPD patients who received monthly regular follow-up in the outpatient clinic of the Pulmonary Division of Tokyo Metropolitan Geriatric Medical Ceter between January 2000 and December 2000
  • FEV1/FVC ratio of < 70%
  • BMI <26 kg/m2
Exclusion Criteria:

Patients with comorbidities affecting nutritional status and body weight such as:

  • malignancies
  • malabsorption
  • endocrine disorders
  • chronic renal failure
  • cardiac diseases
  • neuromuscular diseases
  • Cognitive disorder was assessed by Mini Mental State Examination and those patients with an MMSE <24 were excluded.
Description of Study Protocol:


Patients were recruited from those stable COPD patients who received monthly regular follow-up in the outpatient clinic of the Pulmonary Division of Tokyo Metropolitan Geriartric Medical Center


Subjects were divided into 2 groups based on BMI:

  • Normal weight (BMI >20kg/m2, < 26 kg/m2)
  • Underweight (BMI < 20 kg/m2)

Dyspnea, disease-specific and generic HRQoL were compared between the 2 groups.

Blinding used (if applicable):  Not applicable 

Intervention (if applicable):  Not applicable 

Statistical Analysis

Unpaired Student's t-tests and confidence intervals were used for comparisons between the NW and UW groups. Pearson's correlation coefficient was used to determine the relationship between HRQoL measures and clinical values. Stepwise multiple regression analysis was perfomred to determine independent variables of HRQoL measures. P values less than 0.05 were considered signficant.


Data Collection Summary:

Timing of Measurements

Measurements made and compared between the 2 groups. 

Dependent Variables

  • Degreee of dyspnea (Oxygen cost diagram) 
  • Exercise capacity (6 minute walking distance test) 
  • Heath-related quality of life (Japansese version of St. George's Respiratory Questionnaire and Medical Outcomes Study Short Form 36-item Questionnaire)
  • Lung Function (FEV1 and FVC)

Independent Variables

  • BMI

Control Variables


Description of Actual Data Sample:

Initial N: 83

Attrition (final N): (83) 49 in NW group, 34 in UW group

Age: 74.6+  0.7 years

Ethnicity: Not stated

Other relevant demographics:

Anthropometrics: There were no significant differences between groups in terms of lung function or body height. The UW group had significantly lower body weight 45.8 +  0.9 vs. 58.4  +  1.0 than the NW group (p< 0.0001) and lower BMI 17.9  +  0.3 vs 22.9   + 0.3 (p<0.0001).

Location: Tokyo, Japan


Summary of Results:



Pt characteristics NW group UW group  p value

6 MWD(m)

396.0 + 


348.7 + 


OCD 77.6 +   2.3 62.4 +   3.3 <0.001

Comparison of the HRQol Measures


UW group had greater impairment in activity (p<0.05), impact (p<0.05), symptoms (p<0.05) and total score (p<0.05) than the NW group.


The UW group had greater impairment in physical functioning (p<0.05), role emotional (p<0.05), bodily pain (p<0.001) and general health (p<0.05) than the NW group.

Correlation between th HRQoL measures and clincal variables

OCD and 6 MWD were significantly correlated with BMI (BMI vs. OCD; r = -0.35, p<0.01), (BMI vs. 6 MWD; r = 0.34, p<0.01)

BMI was signficantly correlated with 4 components of the  SF-36: physical functioning (p<0.05), role emotional (p<0.01), bodily pain (p<0.01) and general health (p<0.01)

Author Conclusion:
Low body weight in patients with COPD is related to a worsening of dyspnea and deterioration of both general and disease-specific HRQoL. Nutritional intervention may be important for improving dyspnea an HRQoL in patients with COPD.
Funding Source:
Foundation associated with industry:
Reviewer Comments:
Did not state if patients were on oxygen which might change quality of life indicators. SES information and information about signficant other/other support at home was not stated. No explanation of how the QOL tests were administered.
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? 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? ???
  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? 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.) Yes
  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? ???
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? ???
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? ???
  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? Yes
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? ???
  6.6. Were extra or unplanned treatments described? ???
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? ???
  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? 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? Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes? ???
  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