EAL

COPD: Bone Density (2008)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

The objectives of this study were to examine the influence of underweight and body composition on bone status and to explore the possible influence of vitamin D deficiency in the underweight patients with advanced pulmonary disease prior to lung transplantation.

Inclusion Criteria:

Underweight and normal weight patients with end-stage pulmonary diseases assessed for lung transplantation between August 1993 and August 1998
No current smokers

Exclusion Criteria:

Diagnosis of cystic fibrosis
Pulmonary hypertension
Body mass index > 25 kg/m²

Description of Study Protocol:

Recruitment

Subjects were recruited from the patients admitted to the Department of Thoracic Medicine, Rikshospitalet to be assessed for lung transplantation between August 1993 and August 1998.

Design: Cross-Sectional Study

Subjects with a body mass index (BMI) < 19 kg/m2 or a >19 and <25 kg/m2 with a weight loss >10% from their usual weight were defined as underweight.

Subjects with a BMI >19 and <25 with a weight loss equal to or less than 10% were defined as normal weight.

Studies were conducted comparing the 2 groups.

Blinding used (if applicable): not applicable

Intervention (if applicable): not applicable

Statistical Analysis

Multiple linear regressions were used to study the influence of underweight, body composition and vitamin D deficiency on bone mass density T scores.
An independent-samples t test was used to test differences for vitamin D intake between patients with and without vitamin D deficiency for underweight patients and for normal-weight patients.
P<0.05 was used to determine significance.

Data Collection Summary:

Timing of Measurements

Measurements were done while in hospital.

Dependent Variables

Body composition (anthropometric measurements, bone mineral density by DEXA)
Vitamin D status (vitamin D metabolites)
Bone status indicators (calcidiol, calcitriol, bone-specific alkaline phosphatase)

Independent Variables

Advanced pulmonary disease

Control Variables

Description of Actual Data Sample:

Initial N: 71 subjects, 32 males, 39 females (42 underweight, 29 normal weight)

Attrition (final N): as above

Age: Underweight: mean 47 years (range 25-60 years), Normal weight: mean 52 years (range 26-60 years)

Ethnicity: Not mentioned

Other relevant demographics:

63% of underweight were diagnosed with COPD, 52% of normal weight were diagnosed with COPD

Anthropometrics : see Results

Location: Osolo, Norway

Summary of Results:

Variables	Lunbar spine BMD T scores B (SE)	Lumbar spine BMD T scores P value	Femur Neck BMD T scores B (SE)	Femur Neck BMD T scores P value
Age (year)	-0.04 (0.02)	0.05	Excluded
Sex (male = 0, female = 1)	0.67 (0.32)	0.04	Excluded
AMC (%)	Excluded		0.03 (0.01)	0.01
Group (underweight = 1, normal weight = 2)	0.74 (0.33)	0.03	Excluded
Interaction term (underweight and vitamin D deficiency = 1, others = 0)	Excluded		-0.49 (0.26)	0.06
R² for the model	0.167		0.204

AMC %: arm muscle circumference % of standard, BMD: bone mineral density

Other Findings

Group, age and sex explained 16.7% of the total variation for lumbar spine T scores and group (p=0.002) and sex explained 19.4% of the total variation for femur neck T scores.

Intake of vitamin D was siginficantly lower (p<0.001) for those underweight patients with vitamin D deficiency than those underweight patients with a normal vitamin D level.

Author Conclusion:

Vitamin D deficiency was common in both underweight and normal-weight patients, but only in underweight patients was an association between vitamin D deficiency and reduced femur neck T scores indicated.

Funding Source:

Reviewer Comments:

Cross-sectional data collected over 5 year inclusion period
Previous/current use of bisphosphonates, exercise?
Statisical significance between the underweight and normal weight groups and dose of oral corticosteroids, osteoporosis at the lumbar spine and femur neck, etc was not shown.
Authors note limitation of not having data on cumulative steroid doses.

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?	N/A
	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?	???
	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.)	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.)	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?		???
	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?	No
	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?	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?		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?	???
	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