COPD: Bone Density (2008)

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

To quantify the baseline rates of comorbidities in COPD and asthma patients and to compare the risks to the general population.

Inclusion Criteria:
  • COPD and asthma cases were defined by identification of compatible terms in READ codes
  • Incident cases were individuals with either COPD or asthma in 1998 and who had at least 1 year of follow-up before and after diagnosis
  • Control patients were matched by age, gender, practice, and a time band of ± 1 year of follow-up around the case index date
Exclusion Criteria:
  • Control patients were allowed to have any medical condition including allergies and rhinitis or any other significant disease, except COPD (if matched to the non-COPD cohort) or except asthma (if matched to the nonasthma cohort)
Description of Study Protocol:

Recruitment

Patients with COPD (n=2,699) and patients with asthma (n=7,931) in the UK General Practice Research Database, compared with age-, gender-, time- and practice-matched cohorts.

Design:  Retrospective Cohort study. 

Blinding used (if applicable):  not applicable

Intervention (if applicable): not applicable 

Statistical Analysis

  • Yearly event rate per 10,000 patients within the year after index date was obtained
  • Ratio of event rates were calculated and relative risks were estimated for comorbidities in major organ systems and selected medical events
  • 95% confidence intervals were calculated
Data Collection Summary:

Timing of Measurements

Retrospective database review.

Dependent Variables

  • Comorbidities in major organ systems and 9 selected medical events:  angina, cataracts, fractures, glaucoma, myocardial infarction, osteoporosis, pneumonia, respiratory infection, and skin bruises

Independent Variables

  • COPD, asthma, or control

Control Variables

 

Description of Actual Data Sample:

 

Initial N: 2,699 cases of COPD (51.1% female), 7,931 cases of asthma (53.6% female)

Attrition (final N):  as above

Age:  mean age COPD cases:  65.0 ± 15.0 years, mean age asthma cases:  29.8 ± 23.9 years

Ethnicity: not mentioned

Other relevant demographics:

Anthropometrics:  crosslabeling of COPD and asthma in the same patient was allowed

Location: United Kingdom

 

Summary of Results:

Other Findings

In both COPD and asthma, the total sum of diagnoses related to major organ systems was higher than in their matched population controls.

Among incident COPD patients, a frequency >1% within the first year after diagnosis was observed for angina, cataracts, bone fractures, osteoporosis, pneumonia, and respiratory infections.

Compared to the non-COPD cohort, COPD patients were at increased risk for pneumonia (RR = 16.0, 95% CI: 8.7 to 29.3), osteoporosis (RR = 3.1, 95% CI: 2.3 to 4.0), respiratory infection (RR = 2.2, 95% CI: 1.8 to 2.7), myocardial infarction (RR = 1.7, 95% CI: 1.2 to 2.5), angina (RR = 1.7, 95% CI: 1.4 to 2.0), fractures (RR = 1.6, 95% CI: 1.3 to 1.9) and glaucoma (RR = 1.3, 95% CI: 0.9 to 1.8), all but glaucoma were P < 0.05.

2.0% of COPD patients had cataracts recorded, but this rate was no different than that of the non-COPD cohort (RR = 0.9, 95% CI: 0.7 to 1.1).

Among incident asthma patients, the occurrence of events was generally lower, likely due to the younger age distribution, except for 4.0% with respiratory infection (RR = 1.84, 95% CI: 1.6 to 2.2) and 1.7% with fractures (RR = 1.5, 95% CI: 1.2 to 1.9).

Angina prevalence was 0.7% in the asthma cohort and 1.4 times more common than in patients without asthma (RR = 1.4, 95% CI: 1.0 to 2.0).

Author Conclusion:

We conclude that COPD and asthma are conditions associated with many comorbidities at the time of diagnosis, particularly cardiovascular, bone and other smoking-related diseases.  Further research is needed to elucidate the role of smoking, medication use, and the interrelationships between asthma and COPD and other comorbidities.

Funding Source:
Reviewer Comments:
  • Authors note that the GPRD database is broadly representative of the UK population in terms of age and gender, but that selection bias could have played a role in current design
  • Medications were not searched and analyses were not corrected by drug use
  • Authors note limitations of distinguishing COPD vs asthma in primary care, as these diagnoses are established without spirometry in UK and elsewhere, as well as limiting follow-up to only 1 year after diagnosis, and limited info on smoking
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? ???
  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? ???
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) 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.) Yes
  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.) 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? 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? ???
  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)? N/A
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? No
  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