EAL

Mediterranean Diet and the Prevention and Treatment of CVD

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To investigate the association between specific dietary patterns and peripheral arterial disease in Italian type 2 diabetes patients.

Inclusion Criteria:

Eligible if they were Italian citizens from the Abruzzo region
Fulfilled the WHO criteria for type 2 diabetes

Exclusion Criteria:

Excluded if presence of concomitant major disease

Description of Study Protocol:

Recruitment

From a cohort of 944 patients with type 2 diabetes, who were consecutively seen at the Diabetes Care Center of the General Hospital of Pescara in Italy from 1996 until 2000, 144 patients with peripheral arterial disease were selected and matched for age and sex with 288 type 2 diabetic controls without microvascular complications.

Design: Cohort/Case-Control Study

Blinding used (if applicable): not applicable

Intervention (if applicable): not applicable

Statistical Analysis

Each case was matched to 2 controls. Data for continuous variables were expressed as means with standard deviations. Means were compared using ANOVA, controlling for matching. Odds ratios and 95% confidence intervals were calculated as estimators of relative risk. Odds ratios were obtained by univariate and multivariate conditional to matching logistic regression analysis. Covariates included in multiple analyses were duration of diabetes, smoking habits, history of hyperlipidemia, hypertension, BMI and physical activity. Logistic regression analyses were performed after dividing subjects into 6 groups based on diabetes duration longer or shorter than 10 years, presence or absence of hypertension and dietary score.

Data Collection Summary:

Timing of Measurements

Prevalence of thrombotic complications and dietary scores completed in cases and controls and compared.

Dependent Variables

Prevalence of thrombotic complications was evaluated by a trained monitor who reviewed the medical records of all patients
Peripheral arterial disease vs absence of microvascular complications

Independent Variables

Dietary score was elaborated from a semiquantitative food frequency questionnaire
Validity of the FFQ preliminarily assessed against a 7-day food record in 34 volunteers
Correlation between scores obtained between FFQ and 7-day food record was 0.71 (P = 0.001)

Control Variables

Patient information was collected by a standardized questionnaire
Age
Sex

Description of Actual Data Sample:

Initial N: 144 patients with peripheral arterial disease (103 men, 41 women) were selected and matched for age and sex with 288 type 2 diabetic controls without microvascular complications (206 men, 82 women)

Attrition (final N): as above

Age: in both groups: 25% were < 60 years, 42% were aged 60 - 69 years, 33% were aged > 70 years

Ethnicity: not mentioned

Other relevant demographics:

Anthropometrics: Controls were matched for age and sex. There were no significant differences between groups in terms of history of hyperlipidemia, smoking habits, BMI and levels of glycated hemoglobin.

Location: Italy

Summary of Results:

	Odds Ratio	95% Confidence Interval
Dietary Score: 0 - 8	1.0	--
Dietary Score: 9 - 10	0.73	(0.42, 1.26)
Dietary Score: >11	0.44	(0.24, 0.83)
Diabetes Duration: <5 years	1.0	--
Diabetes Duration: 6 - 14 years	1.75	(1.05, 2.90)
Diabetes Duration: >15 years	2.52	(1.45, 4.39)
Hypertension - No	1.0	--
Hypertension - Yes	2.30	(1.39, 3.79)
Dyslipidemia - No	1.0	--
Dyslipidemia - Yes	0.89	(0.54, 1.45)
BMI < 25	1.0	--
BMI > 25	1.50	(0.82, 2.74)
Smoking: Never	1.0	--
Smoking: Former	0.70	(0.37, 1.33)
Smoking: <10 cigarettes/day	1.16	(0.47, 2.86)
Smoking: >10 cigarettes/day	1.20	(0.54, 2.65)
Physical activity: minimal	1.0	--
Physical activity: moderate	0.58	(0.27, 1.25)
Physical activity: intense	0.45	(0.14, 1.44)

Other Findings

Cases had longer diabetes duration, higher prevalence of hypertension and lower physical activity.

In multivariate analysis, a higher score was independently associated with a significant reduction in peripheral arterial disease risk (odds ratio = 0.44, 95% confidence interval = 0.24, 0.83).

Diabetes duration (odds ratio > 15 years = 2.49, 95% confidence interval = 1.45, 4.25), hypertension (odds ratio = 2.12, 95% confidence interval = 1.31, 3.45) and butter consumption (odds ratio = 2.6, 95% confidence interval = 1.15, 3.68) were also significantly associated with peripheral arterial disease.

The dietary score significantly improved the predictive value of models based on duration of diabetes and hypertension (LSR = 2.19, DF = 7, P < 0.001).

The effect of a high dietary score on the risk of peripheral arterial disease was independent of diabetes duration and hypertension.

Author Conclusion:

In conclusion, this study shows that rather than individual items, a high-score dietary pattern may have a protective role on peripheral arterial disease in Italian patients with type 2 diabetes, living in a traditionally Mediterranean region. The combination of different types of food with healthy characteristics might be necessary to express their protective effect on atherosclerosis development. Therefore, in order to prevent peripheral arterial disease, repeated dietary advice should be given, together with careful blood pressure and other risk factor control, to type 2 diabetic patients, also in populations traditionally consuming a Mediterranean diet.

Funding Source:

Reviewer Comments:

Cases matched with 2 controls from same cohort.

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.)	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?	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?		???
	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.)	???
	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?		N/A
	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?	N/A
	6.4.	Was the amount of exposure and, if relevant, subject/patient compliance measured?	N/A
	6.5.	Were co-interventions (e.g., ancillary treatments, other therapies) described?	N/A
	6.6.	Were extra or unplanned treatments described?	N/A
	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?	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?	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