EAL

COPD: Bone Density (2008)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

The purpose of this study was to identify the main correlates of low bone mineral density (BMD) and to verify whether, and to what extent, the acid-base balance correlates with BMD in a COPD population carefully characterized with regard to variables affecting BMD.

Inclusion Criteria:

COPD diagnosed according to the American Thoracic Society criteria
After the resolution of acute exacerbation provided they were in stable condition as follows:
Performance of activities of daily living (ADL) had to be comparable to that reported to be usual for the individual patient at home
Patients on oxygen had to maintain arterial oxygen saturation of at least 90%

Exclusion Criteria:

Premenopausal status
Previous or actual post-menopausal hormone replacement therapy or any kind of therapy (diphosphonates, or co-morbid conditions such as chronic renal failure known to affect bone turn over)
Cancer or near terminal illness

Description of Study Protocol:

Recruitment

Subjects were recruited from those admitted to the respiratory ward of the University Hospital, Catholic Hospital Rome, Italy for an exacerbation of COPD in a 9 month period of time.

Design: Cross-Sectional Study

Patients were grouped according to whether they did (group 0) or did not (group N) have a BMD at the lumbar column and/or the femoral neck >2.5 standard deviations (SD) belows the adult mean value (diagnosis of osteoporosis).

Blinding used (if applicable): Not applicable

Intervention (if applicable): Not applicable

Statistical Analysis

Differences between the 2 groups were assessed by the Chi-Squared test for dichotomous vairables and by a Student's t-test or Mann-Whitney test for continuous variables according to whether the variable did or did not have, both normal distribution and homeogenous variance, respectively.
Variables significantly or near significantly different between groups at the univariate analysis were entered in to a logistic regression model having the presence of osteoporosis as dependent variable and ajusted for age and gender. Arterial CO₂was forced into the model in order to evaluate the effect of hypercapnia on BMD. The independent variable was considered to be significantly associated with the outcome if one was not enclosed between the 95% confidence intervals (95% CI) and the odds ratio (OR).

Data Collection Summary:

Timing of Measurements

One time measurements were done while inpatient.

Dependent Variables

Bone Mineral density (DEXA)
Health Related variables (behavioral variables, physical function, cognitive function, etc)
Body composition (anthropometrics, BMI)
Affect of hypercapnia

Independent Variables

Compared COPD patients with and without BMD >2.5 SD below the young adult mean value for BMD at the lumbar column and/or the femoral neck

Control Variables

Description of Actual Data Sample:

Initial N: 104 subjects with COPD, 68 males

Attrition (final N): 104 (62 in group 0, 42 in group N)

Age: Group 0: 71.31 ± 7.55 years, Group N 70.24 ± 6.92 years (P = NS)

Ethnicity: not stated

Other relevant demographics:

There were no signficant differences between groups 0 and N in regards to number of males, pack years of smoking, daily wine intakes, daily calcium intakes, serum albumin, hemoglobin, physical or cognitive function.

Anthropometrics:

There were no signficant differences between groups 0 and N in regards to pulmonary function tests, arterial oxygen and carbon dioxide tension, years duration of COPD, or number of subjects defined as frequent users of systemic steroids, inhaled steroids or diuretics.

Location: Rome, Italy

Summary of Results:

Variables	Odds Ratio	95 % CI	Coefficient	Standard Error	P value
BMI << 22 kg/m²	4.18	1.19-14.71	1.43	0.64	0.026
PaC0₂> 6.93 kPa	0.60	0.23- 1.61	- 0.50	0.49	0.313

Other Findings

Group O was characterized by worse nutritional status, as reflected by indices of either lean or fat mass, and by a trend towards lower FEV1/FVC ratio.

Arterial tension of carbon dioxide lacked any correlation with BMD.

According to the logistic regression analysis, BMI < 22 qualified as the only and positive independent correlate of osteoporosis (odds ratio 4.18, 95% confidence interval 1.19 to 14.71).

Author Conclusion:

In conclusion, malnutrition characterizes COPD patients with osteoporosis, while mild to moderate hypercapnia lacks either a positive or negative effect on bone mineral density.

Funding Source:

Reviewer Comments:

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?	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?	Yes
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)	N/A
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	Yes
	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.)	Yes
	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.)	N/A
	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?	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?	Yes
	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?	Yes
	7.6.	Were other factors accounted for (measured) that could affect outcomes?	Yes
	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)?	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