(Circulation. 1999;99:779-785.)
© 1999 American Heart Association, Inc.
Clinical Investigation and Reports |
From Explorations Fonctionnelles Cardiorespiratoires et Métaboliques, CHU de Saint-Etienne (M.d.L., P.S., I.M.), Saint-Etienne; and INRETS Epidemiology Unit (J.L.M.), Hôpital Cardiovasculaire (J.D.) and INSERM Unit 265 (N.M.), Lyon, France.
Correspondence to Dr M. de Lorgeril, Explorations Fonctionnelles Cardiorespiratoires et Métaboliques, Niveau 6, CHU Nord, 42055 Saint-Etienne Cedex 2, France. E-mail lorgeril{at}univ-st-etienne.fr
| Abstract |
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Methods and ResultsThree composite outcomes (COs) combining either cardiac death and nonfatal myocardial infarction (CO 1), or the preceding plus major secondary end points (unstable angina, stroke, heart failure, pulmonary or peripheral embolism) (CO 2), or the preceding plus minor events requiring hospital admission (CO 3) were studied. In the Mediterranean diet group, CO 1 was reduced (14 events versus 44 in the prudent Western-type diet group, P=0.0001), as were CO 2 (27 events versus 90, P=0.0001) and CO 3 (95 events versus 180, P=0.0002). Adjusted risk ratios ranged from 0.28 to 0.53. Among the traditional risk factors, total cholesterol (1 mmol/L being associated with an increased risk of 18% to 28%), systolic blood pressure (1 mm Hg being associated with an increased risk of 1% to 2%), leukocyte count (adjusted risk ratios ranging from 1.64 to 2.86 with count >9x109/L), female sex (adjusted risk ratios, 0.27 to 0.46), and aspirin use (adjusted risk ratios, 0.59 to 0.82) were each significantly and independently associated with recurrence.
ConclusionsThe protective effect of the Mediterranean dietary pattern was maintained up to 4 years after the first infarction, confirming previous intermediate analyses. Major traditional risk factors, such as high blood cholesterol and blood pressure, were shown to be independent and joint predictors of recurrence, indicating that the Mediterranean dietary pattern did not alter, at least qualitatively, the usual relationships between major risk factors and recurrence. Thus, a comprehensive strategy to decrease cardiovascular morbidity and mortality should include primarily a cardioprotective diet. It should be associated with other (pharmacological?) means aimed at reducing modifiable risk factors. Further trials combining the 2 approaches are warranted.
Key Words: diet trials coronary disease myocardial infarction
| Introduction |
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-3 fatty acids2 3 and
were not intended primarily to reduce blood cholesterol.
Two of these trials2 3 also included a high intake of
fresh fruits and vegetables, legumes, and cereals containing large
amounts of fibers, antioxidants, minerals, vegetable proteins, and
vitamins of the B group. The credibility of these recent trials was
considerably reinforced by a number of recent studies showing major
cardioprotective effects of most of these foods and
nutrients,5 6 7 8 9 10 11 12 13 14 with a particular emphasis on
-3 fatty
acids8 9 and on folates for their role in
hyperhomocysteinemia and in the argininenitric
oxidetetrahydrobiopterin pathway,10 11 12 13 14 2
possible major mediators in the development of CHD. The Lyon Diet Heart Study is a randomized, single-blind secondary prevention trial aimed at testing whether a Mediterranean-type diet, compared with a prudent Western-type diet, may reduce recurrence after a first myocardial infarction.3 We previously reported a significant reduction of the rates of cardiovascular complications,3 15 and no major bias was detected in the trial.16 However, despite confluent epidemiological and clinical data supporting the results,5 6 7 8 9 10 11 12 13 14 certain commentators put forth the relatively small number of events, the wide CIs of the risk ratios at the intermediate analysis, and hence the uncertainty regarding the true reduction of risk. In this report, we present data resulting from an extended follow-up, providing a total of 275 events over a mean follow-up of 46 months per patient. We also examined the relationships between traditional risk factors, dietary patterns, and the occurrence of complications.
| Methods |
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Inclusion of patients was based on a modified Zelen design.17 Briefly, during their stay in hospital, patients were asked to participate in a cohort study with a follow-up of 5 years. They were not fully informed about the design of the study, especially regarding the comparison of 2 diets. Patients assigned to the experimental group were asked to comply with a Mediterranean-type diet and had to sign a second consent form. Patients of the control group received no dietary advice from the investigators but nonetheless were advised to follow a prudent diet by their attending physicians.3
An intermediate analysis was proposed by the Scientific
Committee to be performed in March 1993, clinical data being frozen
after a minimum follow-up of 1 year for each patient. Because of a
statistically significant result, the decision was made to stop the
trial. The first report was published in June 1994.3 For
ethical, medical, and scientific reasons, all patients were invited to
come to the Research Unit for a final visit, during which they were
fully informed about the main results of the trial. Hence, given the
delay after the clinical status of the 2 groups in March 1993, the
decision to invite the patients to a new assessment, and the time
needed to see each patient, an additional follow-up of
19 months was
available in the 2 groups to perform the final analyses. This
offered the opportunity to evaluate the long-term (mean, 4 years)
effect of the diet tested in the trial and whether the patients
continued to comply with it.
As in the previous analysis, only clinical events requiring hospital admission were considered. The End-Point Committee met for a final and blinded evaluation of the raw data obtained from hospital files and, for patients who had died, from the civil status office of the patient's birthplace. Definitions of the end points were reported previously,3 15 16 and the basic principles of the experimental diet have been described.3 15 16 In practical terms, the dietary instructions were detailed and customized to each patient,16 and a dietary survey at each visit allowed us to check for adhesion and compliance to the experimental diet. In addition, plasma fatty acids were analyzed (gas-liquid chromatography) in the 2 groups as described3 and used as objective biomarkers.
Analyses were done on the intention-to-treat principle. Event-free survival for myocardial infarction, cardiovascular death, and 3 composite outcomes (COs) were estimated by the Kaplan-Meier method. The censoring date was the date of the earliest event or the end of follow-up. The Cox proportional-hazards model was used to calculate the risk ratios and to quantify the associations between each traditional risk factor and the different COs, namely myocardial infarction plus cardiovascular death (CO 1); myocardial infarction plus cardiovascular death plus major secondary events including episodes of unstable angina, as previously defined,3 15 episodes of overt heart failure, stroke, or pulmonary or peripheral embolism (CO 2); or the preceding plus minor events requiring hospital admission, including recurrent stable angina, postangioplasty restenosis, surgical or medical myocardial revascularization, and thrombophlebitis (CO 3). Also considered in a separate analysis were the medications recorded 2 months after randomization. Because the use of lipid-lowering drugs varied considerably during the study in France, these drugs were not included in these analyses. This point has been described and analyzed elsewhere.16
| Results |
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Main cardiovascular risk (or prognosis) factors and the
mean daily nutrient intake recorded on the final visit are given in
Tables 2
and 3
. Data are quite similar to those
recorded at and 2 months after randomization.3
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Univariate associations between major risk factors
recorded 2 months after randomization (data not shown) and the 3
composite outcomes are shown in Table 4
.
Among the medications used (data not shown), only aspirin was
significantly (and inversely) associated with the outcomes and was then
included in the multivariate analyses. A
threshold effect was observed with leukocyte count (quartile
analyses), with a markedly increased risk when the count was
>9x109/L. Thus, leukocyte count was used as a
categorical variable, whereas total cholesterol and
blood pressure (no J-shaped curve) were used as continuous
variables in further analyses.
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With regard to any association between the plasma concentration of
major fatty acids and recurrence, only 18:3(
-3) and
22:6(
-3) tended to be inversely associated with recurrence
(P=0.11 and P=0.16, respectively, versus CO
1).
Then, the effect of traditional risk factors on recurrence was
analyzed with the multivariate Cox
proportional-hazards model (Table 5
).
When the plasma fatty acid concentrations were entered into the model,
18:3(
-3) was the only fatty acid significantly associated with CO 1
(risk ratio, 0.20; 95% CIs, 0.05 to 0.84 after adjustment for age,
sex, smoking, total cholesterol, blood pressure, leukocyte
count, and aspirin use). With regard to the effect of 18:3(
-3) on CO
2 and CO 3, the associations were borderline nonsignificant
(P=0.08 and P=0.12).
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| Discussion |
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Mediterranean Dietary Pattern and Recurrence
The rate of cardiac death and nonfatal infarction in the
experimental group after 46 months (1.24 per hundred patients per year)
is similar to that observed after 27 months (1.32). The rate in control
subjects was 4.07 after 46 months, whereas it was 5.55 after 27
months.3 Hence, the data confirm the impressive protective
effect of the Mediterranean diet.
It has been argued that it is easier to prescribe drugs than to change the dietary habits of patients, a task often considered to be difficult; and unfortunately, after some attempts, many physicians do give up. This study shows that several years after randomization, most experimental patients were still closely following the Mediterranean diet recommended to them. This suggests, in contrast to the current opinion, that the adoption of and compliance with new dietary habits is not so difficult, provided that the instruction of patients (and of their families) and surveillance are properly (professionally) conducted.16 Of course, the new dietary habits need to be financially and gastronomically acceptable and practically feasible for patients (and their relatives) who often have to adapt to a difficult working environment and the stressful urban way of life. Finally, it should be emphasized that taking 1 or several drugs prescribed by their attending physician, as most of the patients did in the 2 groups of the present trial, is not incompatible with the adoption of new dietary habits. This trial even supports the view that pharmacological treatment (for instance, with aspirin) and dietary prevention had additional and independent beneficial effects.
Blood Pressure, Smoking, Cardiovascular
Medications, and Recurrence
In multivariate analyses, blood pressure,
but not smoking, was significantly and independently associated with
recurrence. It should be noted, however, that we did not
analyze the effect of the true blood pressure of each patient
because many of them were taking at least 1 pressure-lowering drug as
part of a systematic secondary prevention treatment.
In secondary prevention, it is usually the effect of current (and not past) smoking that is analyzed. In the present cohort, <20% of the patients in the 2 groups were current smokers on the final visit. It is therefore likely that, in this population with a low prevalence of smoking, the number of events was too small and the length of follow-up too short to allow an actual evaluation of the true effect of persistent smoking.
The effects of cardiac medications in this study were quite disappointing, because only aspirin was consistently associated with a protective effect. However, the study was not designed primarily to test these medications, and data should be interpreted cautiously. It is nonetheless noteworthy that, in secondary prevention, the effect of ß-blockers was shown to be quite small18 and that such low efficacy was probably difficult to demonstrate in a low-risk population. The same reasoning can apply to calcium channel blockers, whose effect (either protective or deleterious) is the object of a bitter controversy.19
Plasma Fatty Acids and Recurrence
Major difficulties in randomized dietary trials are the prevention
of "attending physician bias"16 and between-group
contamination during follow-up. For that purpose, patients were not
fully informed that they were participating in a dietary trial with the
comparison of 2 diets. The lack of knowledge of that comparison by the
patients of both groups (and by their attending physicians) may
minimize the physician bias.16 Thus, in the first part of
the study, the dietary habits of the control patients were not
investigated and recorded so as not to influence them.
Consequently, we cannot include their dietary parameters in
the Cox model to prospectively analyze their relationships with
recurrence. Instead, we used the plasma fatty acids measured 2
months after randomization as crude estimates of dietary data. Only
-linolenic acid was significantly associated with an
improved prognosis, which is in agreement with a recent study reporting
a negative correlation between the intake of
-linolenic acid
and the risk of myocardial infarction.20 Conversely, we
did not find any correlation between long-chain
-3 fatty acid and
recurrence. Several animal21 and
clinical1 2 3 8 9 studies, however, have shown the
beneficial effects of these fatty acids on CHD, whereas a few studies
were apparently inconsistent, even putting forth the hypothesis
that high dosages may be noxious.22 In moderate amounts,
such as are consumed in the traditional Mediterranean diet, the
protective effects of
-3 fatty acids are probably related to their
multiple actions on the various factors that modulate the cascade of
events leading to acute myocardial ischemia and its acute
complications, in particular sudden death.23 It is likely
that the lack of significant correlations (although a trend toward
protection was observed) in this study may be partly explained by the
relatively small number of sudden deaths and fatal myocardial
infarctions, which are apparently the main types of complications
prevented by moderate consumption of these fatty
acids.8 9
Blood Cholesterol, Leukocyte Count, and
Recurrence
As expected, total cholesterol and leukocyte count
were major independent and joint predictors of recurrence,
along with the dietary pattern. A leukocyte count
>9x109/L increased the risk by a factor of 1.6
to 2.9, and each increase of 1 mmol/L of total
cholesterol increased the risk of recurrence by
20% to 30%. Epidemiological studies have consistently shown a
positive correlation between plasma cholesterol levels and
the incidence of (and mortality from) CHD in various
populations.24 25 Thus, our population does not appear to
be different from other low-risk populations.25 26 In
other words, the data indicate that neither the Mediterranean dietary
pattern nor any major bias has altered the usual and expected
relationships between the major risk factors of CHD and
recurrence.
Leukocyte count also has been shown to be a marker for increased risk
of CHD mortality in many studies.27 In most studies, this
effect is partly independent of smoking. A plausible mechanism to
explain this relationship is that leukocytes are involved not only in
the inflammation and ulceration of the arterial
lesion28 but also in the exacerbation of acute myocardial
ischemia. This may ultimately result in an increased infarct
size, the major determinant of postinfarction survival. Experimental
studies have indeed suggested the implication of leukocytes in acute
myocardial ischemia,29 and human and animal
studies have consistently shown that leukocytes play a role in
the severity of ventricular arrhythmias during
ischemia.29 30 In this study, high leukocyte count
was associated with an increased risk of major acute coronary
events, such as cardiac death and acute infarction (risk ratio,
3),
whereas the association was lower (risk ratio, 1.6) when recurrent
stable angina and the need for myocardial
revascularization were considered, suggesting that
leukocytes are more important in acute myocardial complications than in
the development of subacute coronary artery lesions.
| Acknowledgments |
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Received June 14, 1998; revision received October 14, 1998; accepted October 26, 1998.
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