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COPD: Effectiveness of Therapies (2007-2008)

Citation:

Tabak C, Smit HA, Rasanen L, Fidanza F, Menotti A, Nissinen A, Feskens EJM, Heederik D, Kromhout D.  Dietary factors and pulmonary function:  a cross-sectional study in middle aged men from three European countries.  Thorax 1999;54:1021-1026.

PubMed ID: 10525562
 
Study Design:
Cross-Sectional Study
Class:
D - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:
To evaluate the cross-sectional association of dietary factors with pulmonary function.
Inclusion Criteria:
Middle aged men in the Seven Countries Study from Finland, Italy and the Netherlands.
Exclusion Criteria:
Some men were excluded from spirometric testing because they suffered from severe conditions including COPD as judged by the examining physician, and had lower energy intakes.
Description of Study Protocol:

Recruitment

16 population samples of men aged 40 - 59 years from 7 countries were enrolled and examined at baseline for the Seven Countries Study.  Men were reexamined 5 and 10 years later.  Data were collected from middle aged men in 3 European countries in the 1960s:  Finland, the Netherlands and Italy.

Design

Cross-Sectional Study.

Blinding used (if applicable)

Not applicable.

Intervention (if applicable)

Not applicable.

Statistical Analysis

Cross-sectional relation between FEV and dietary factors was analyzed using multiple regression analysis.  Several models for the dependence of FEV on height and age were evaluated.

Data Collection Summary:

Timing of Measurements

Measurements compared.  Information of dietary intake and pulmonary function were only available for the 2 Finnish cohorts in 1969 and for the Italian and Dutch cohorts in 1965.

Dependent Variables

  • Pulmonary function:  forced expiratory volume measured by spirometry, but measured with different methodology among the countries 
  • Data missing for 29 subjects in Finland, 149 subjects in Italy, and 28 subjects in the Netherlands

Independent Variables

  • Dietary intake estimated using the cross-check dietary history method
  • Interviews were carried out by extensively trained dietitians and nutritionists

Control Variables

  • Age
  • Height
  • Smoking
  • BMI
  • Alcohol consumption
  • Energy intake
Description of Actual Data Sample:

Initial N: Middle aged men in Finland (n=1248), Italy (n=1386) and the Netherlands (n=691).

Attrition (final N):  As above

Age:  aged 40 - 59 at baseline for men in all countries

Ethnicity:  not reported

Other relevant demographics:

Anthropometrics:

Location:  Finland, Italy and the Netherlands

 

Summary of Results:

 

  Finland (n=1248)

Italy (n=1386)

Netherlands (n=691)
Age (years) 59.0 +/- 5.5 54.5 +/- 5.0 54.8 +/- 5.5

Height (m)

1.70 +/- 0.06

1.66 +/- 0.06

1.74 +/- 0.07

Smoking (pack years)

21.4 +/- 17.0

15.1 +/- 15.0

19.5 +/- 13.9

BMI 24.7 +/- 3.8 25.8 +/- 3.8 24.8 +/- 2.7
Alcohol (g) 6.5 +/- 13.0 86.8 +/- 58.3 6.8 +/- 12.5
Energy intake (MJ) 15.6 +/- 4.7 12.5 +/- 3.1 12.4 +/- 2.7
Energy excluding alcohol (MJ) 15.4 +/- 4.6 10.0 +/- 2.6 12.2 +/- 2.8
FEV (ml) 2703 +/- 733 2742 +/- 719 2960 +/- 699
Vitamin C (mg) 91.7 +/- 35.3 45.9 +/- 24.0 91.8 +/- 39.5
Vitamin E (mg) 6.7 +/- 2.4 9.9 +/- 3.6 17.9 +/- 6.6
Beta-carotene (mg) 2.0 +/- 1.9 0.8 +/- 0.6 1.1 +/- 0.4
Fruit (g) 174 +/- 183 191 +/- 180 152 +/- 109
Vegetables (g) 79 +/- 60 53 +/- 50 176 +/- 69
Fish (g) 39 +/- 46 21 +/- 20 17 +/- 23

Other Findings

FEV was positively associated with intake of vitamin E in Finland, with intake of fruit in Italy, and with intake of beta-carotene in the Netherlands.

In all 3 countries, men with intakes of both fruit and vegetables above the median had a higher FEV than those with a low intake of both foods.

The difference in FEV ranged from 110 to 169 ml before and from 53 to 118 ml after energy adjustment.

Differences in FEV for intake of 3 antioxidants (vitamins C and E and beta-carotene) above versus below the median ranged from 61 to 181 ml before and from -35 to 58 ml after energy adjustment.

Intake of fish was not associated with FEV. 

Author Conclusion:
In conclusion, intake of both fruit and vegetables above the median level was positively associated with pulmonary function in 3 European countries.  Intake of the 3 studied antioxidants (vitamin C, vitamin E and beta-carotene) above the median level tended to be positively associated with pulmonary function before but not after adjustment for energy intake.  The associations of the individual dietary factors with pulmonary functionwere not consistent across countries.  We postulate that the larger and more consistent joint effect of fruit and vegetable intake on pulmonary function might be the result of a more relevant and more stable difference in exposure.
Funding Source:
Reviewer Comments:
Pulmonary function measurements not done consistently among the countries.  Data available for different time periods: the 2 Finnish cohorts in 1969 and for the Italian and Dutch cohorts in 1965.  Samples not similarly sized.
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? ???
  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? ???
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) No
  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? N/A
  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? No
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? Yes
  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? Yes
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? No
  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? Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  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)? 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