EAL

COPD: Effectiveness of Therapies (2007-2008)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

The purpose of the current study was to investigate the independent effects of fruits, vegetables, fish, alcohol and whole grains on pulmonary function and COPD symptoms in 13651 men and women examined between 1994 and 1997 in the MORGEN (monitoring project on risk factors and health in The Netherlands) study.

Inclusion Criteria:

participants of the MORGEN study
technically acceptable, reproducible forced expiratory volume (FEV) in 1 s measurement

Exclusion Criteria:

pregnant women
those with technically unacceptable or nonreproducible FEV
those with missing values for one or more potential confounders

Description of Study Protocol:

Recruitment

MORGEN study participants.

Design

Cross-sectional analysis.

Blinding used (if applicable)

Not applicable

Intervention (if applicable)

Not applicable

Statistical Analysis

SAS (version 6.12, Cary, NC,USA)

multiple linear regression to study relation between FEV and dietary factors
logistic regression analysis to study associations between COPD symptoms and dietary factors
adjusted average FEV and prevalence of COPD symptoms per category of food intake by PROC LSMEANS
smoothed spline-plots for association between assessment of additivity of effects of foods independently associated with COPD

Data Collection Summary:

Timing of Measurements

Single measurement.

Dependent Variables

prevalence of COPD symptoms as evidenced by European Community Respiratory Health Survey questionaire
FEV by pulmonary function measurements, reproducible by European Respiratory Society criteria

Independent Variables

Intake by food frequency questionaire (MORGEN as component of European Prospective Investigation into Cancer and Nutrition (EPIC)):

fruit (juices)
whole grain
alcohol
fish
vegetable
fruit intake plus intake of whole grains
fruit intake plus intake of alcohol

Control Variables

lifestyle factors; physical activity, educational level, nationality
pack years of smoking
additive effects of foods
age
gender
height (for pulmonary function)
BMI
energy intake

Description of Actual Data Sample:

Initial N: 17025

Attrition (final N): 13651, 46% male

Age: 41.2 + 10.8

Ethnicity: not specified

Other relevant demographics:

Dutch nationality

Anthropometrics

n=9072 smoking history; n=4572 never smoked

Location:

Bilthoven and Utrecht, the Netherlands

Summary of Results:

Other Findings

In subjects with low alcohol consumption (1-30 g/day) the forced expiratory volume in 1 second was higher and the prevalence of COPD symptoms lower than in non-drinkers (p<0.001).

Intake of fruit (juices) and whole grains was positively associated with the FEV and inversely associated with the prevalence of COPD symptoms. (p < 0.001)
Adjusted FEV was lower in non-drinkers compared with drinkers. (p < 0.001)
Prevalence of COPD symptoms was lower in subjects with a low alcohol consumption compared with both non-drinkers and those with a moderate or heavy alcohol consumption. (p < 0.001)
The effects of favorable vs unfavorable intake of fruit (juices), whole grains and alcohol on pulmonary function were additive. (p < 0.001)
The joint effect of fruit (juices), whole grains and alcohol on FEV was marginally smaller than the sum of the individual effects. Similar results were observed for COPD symptoms.
Fish and vegetable intake did not show independent beneficial associations with COPD.

Author Conclusion:

The current cross-sectional study showed independent beneficial associations of fruit (juices), whole grains and alcohol with COPD. The effects of a favorable intake of fruits (<180 g/day), whole grains (<45 g/day) and alcohol (1-30 g/day) were observed to be largely additive. In subjects with a favorable intake (n=2998) of the three foods, the FEV₁ was 139 mL higher and the prevalence of COPD symptoms lower than in subjects (n=1406) with unfavorable intakes of fruit juices, whole grains and alcohol (p < 0.001).

Funding Source:

Reviewer Comments:

Controlled for many variables. Authors note the lack of an association between fish intake and COPD may be explained by the low level of fish consumption in the Dutch population.

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)	Yes
	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.)	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?	Yes
	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.)	N/A
	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?		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?	N/A
	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?	Yes
	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?	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?	Yes
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