EAL

COPD: Bone Density (2008)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To determine how exercise capacity correlates with bone mineral content in COPD versus controls.

Inclusion Criteria:

COPD patients were defined as those with FEV1/FVC ratio of less than 70% and response to bronchodilators less than 15%

Clinically stable COPD patients were healthy enough to undergo twelve minute walk test

COPD patients had been monitored for at least one year (except 2 patients who were monitored for 27 and 34 weeks)

All patients were treated with 200-600 mg/d theophylline

Exclusion Criteria:

History of: cor pulmonale, congestive heart failure, ventilatory failure with hypercapnia, active respiratory infection, steroid administration, malabsorption, or diabetes mellitus

Bedridden patients

Description of Study Protocol:

Recruitment No specific information on recruitment procedures for either COPD or control volunteers were described.

Design Short-term (upto and over 1 year) observational study of COPD patients and age-matched controls

Blinding used (if applicable) Not applicable

Intervention (if applicable) Not applicable

Statistical Analysis Bone mass and pulmonary function variables were analyzed with Student's t-test. Correlations between bone mass and other parameters were also conducted.

Data Collection Summary:

Timing of Measurements Baseline and approximately 1 year from baseline (exception to COPD patients who were retested at 27 and 34 weeks).

Dependent Variables

Body composition (bone mineral content, lean and fat mass) was measured by Norland XR-26 whole body dual energy x-ray absorptiometry (DEXA).
Twelve minute walking distance (TMD) measured by the recording the distance walked down a 50 meter air-conditioned corridor in the afternoon.
Pulmonary function tests (VC, FVC, FEV1, RV, TLC) were measured by Chestac 25 spirometry system.
Blood gasses (oxygen, carbon dioxide) and pH were measured by Instrumentation Laboratories Model 213 gas analyzer.

Independent Variables

Respiratory status (COPD or control)

Control Variables

Description of Actual Data Sample:

Initial N: 22 male COPD patients, 19 male age-matched controls

Attrition (final N): No attrition rate was reported for this observational study.

Age: COPD patients were 72.6 ± 7.2 years and Controls were 67 ± 10.1 years

Ethnicity: Ethnicity of participants was not described.

Other relevant demographics: see Results

Anthropometrics: No significant differences in age and body height between groups. Body weight and BMI were significantly lower in COPD patients than in controls.

Location: Kobe

Summary of Results:

Variable	COPD Group Mean ± Standard Deviation	Control Group Mean ± Standard Deviation	Statistical Significance
Bone mineral content (kg)	1.9±0.4	2.2±0.4	p<0.05 compared to control
Bone mineral content (% of body weight)	4.0±0.6	4.0±0.6
Lean mass (kg)	38.2±4.4	41.7±3.8
Lean mass ((% of body weight)	82.6±9.8	73.2±6.6
Fat mass (kg)	8.6±5.2	12.9±3.7	p<0.05 compared to control
Fat mass ((% of body weight)	17.4±9.8	23.5±6.1	p<0.05 compared to control
Body mass index (BMI)	18.9±2.1	22.1±1.3	p<0.05 compared to control
Change in body weight (kg)	-2.2±1.6
Change in body weight (kg/year)	-0.4±1.8
Change in bone mineral content (g)	-69±119		p<0.05 baseline compared with recent
Change in bone mineral content (g/year)	-70±117		p<0.05 baseline compared with recent
Percent change in bone mineral content (%)	-3.5±7.1
Change in fat mass (kg)	-1.4±3		p<0.05 baseline compared with recent
Change in fat mass (kg/year)	-1.7±3.7

Other Findings

There was a positive (but not significant) relation between bone mineral content and twelve minute walking distance in COPD patients (r=.39, p<0.07).

Absolute and percent change in bone mineral content was positively correlated with twelve minute walking distance in patients with COPD (r=0.53, p<0.02 and r=0.64, p<0.01 respectively.

Pulmonary function variables showed no significant changes during the observation period in COPD patients.

Bone mass variables were not significantly correlated with pulmonary function parameters or blood gasses in COPD patients.

Bone mineral content was positively correlated with body weight considering all subjects (r=0.75, p<0.01).

Bone mineral content was positively correlated with body weight and BMI in COPD subjects (r=0.75, p<0.001, r=0.57, p<0.01 respectively).

Change in bone mineral content and age, body height, body weight, or BMI were not significantly correlated.

Author Conclusion:

The lower body weight, bone mineral content, and twelve minute walking distance observed in the COPD patients in this study suggest that they are at increased risk for osteoporosis. Correlations between body weight and bone mineral content and changes in bone mineral content and twelve minute walking distance observed in COPD patients suggest that reduced exercise capacity may be, in part and independent of body weight, responsible for accelerated bone loss increased risk of osteoporosis in this population.
The relatively short length of the study and the lack physical activity assessment or intervention were identified by the authors as limitations of the study.

Funding Source:

Reviewer Comments:

While the study findings reinforce suppositions that reduced exercise capacity in COPD patients may increase their risk of osteoporosis, the lack of physical exercise assessment or intervention limits applicability.

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?		Yes
	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?	???
	2.3.	Were health, demographics, and other characteristics of subjects described?	No
	2.4.	Were the subjects/patients a representative sample of the relevant population?	Yes
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)	???
	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.)	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.)	???
	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?		???
	4.1.	Were follow-up methods described and the same for all groups?	???
	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%.)	???
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	???
	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?		N/A
	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?	N/A
	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?	N/A
	6.2.	In observational study, were interventions, study settings, and clinicians/provider described?	No
	6.3.	Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect?	???
	6.4.	Was the amount of exposure and, if relevant, subject/patient compliance measured?	No
	6.5.	Were co-interventions (e.g., ancillary treatments, other therapies) described?	No
	6.6.	Were extra or unplanned treatments described?	No
	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?	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?	No
	7.6.	Were other factors accounted for (measured) that could affect outcomes?	No
	7.7.	Were the measurements conducted consistently across groups?	???
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)?	???
	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