Modified Mediterranean diet and survival: EPIC-elderly prospective coh
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《英国医生杂志》
1 Department of Hygiene and Epidemiology, University of Athens Medical School, Athens 11527, Greece, 2 Nutrition and Hormones Group, International Agency for Research on Cancer, Lyon, France, 3 Centre for Nutrition and Health, National Institute for Public Health and the Environment, Bilthoven, Netherlands, 4 Julius Center for Health Sciences and Primary Care, University Medical Center, Utrecht, Netherlands, 5 Department of Epidemiology, German Institute of Human Nutrition, Potsdam, Germany, 6 Division of Clinical Epidemiology, German Cancer Research Centre, Heidelberg, Germany, 7 Molecular and Nutritional Epidemiology Unit, CSPO-Scientific Institute of Tuscany, Florence, Italy, 8 Epidemiology Unit, National Cancer Institute, Milan, Italy, 9 Dipartimento di Medicina Clinica e Sperimentale Università Federico II, Naples, Italy, 10 Cancer Registry Azienda Ospedaliera "Civile M P Arezzo," Ragusa, Italy, 11 Environmental Epidemiology, Imperial College London, 12 Catalan Institute of Oncology, L'Hospitalet de Llobregat, Barcelona, Spain, 13 Andalusian School of Public Health, Granada, Spain, 14 Department of Epidemiology, Murcia Regional Health Council, Murcia, Spain, 15 Department of Public Health of Guipuzcoa, San Sebastian, Spain, 16 Cancer Research UK Epidemiology Unit, University of Oxford, 17 Medical Research Council Dunn Nutrition Unit, Cambridge, 18 Clinical Gerontology, University of Cambridge, 19 Equipe E3N-EPIC, Institut National de la Sante et de la Recherche Medicale, Institut Gustave Roussy, France, 20 Malmo Diet and Cancer Study, Department of Medicine, Lund University, Sweden, 21 Department of Public Health and Clinical Medicine, Umea University, Umea, Sweden, 22 Department of Odontology, Umea University, 23 Institute of Cancer Epidemiology, Danish Cancer Society, Copenhagen, Denmark, 24 Department of Clinical Epidemiology, Aalborg Hospital, Aarhus University Hospital, Aalborg, Denmark, 25 Department of Epidemiology, Harvard School of Public Health, Boston, MA, USA
Correspondence to: A Trichopoulou antonia@nut.uoa.gr
Objective To examine whether adherence to the modified Mediterranean diet, in which unsaturates were substituted for monounsaturates, is associated with longer life expectancy among elderly Europeans.
Design Multicentre, prospective cohort study.
Setting Nine European countries (Denmark, France, Germany, Greece, Italy, the Netherlands, Spain, Sweden, United Kingdom).
Participants 74 607 men and women, aged 60 or more, without coronary heart disease, stroke, or cancer at enrolment and with complete information about dietary intake and potentially confounding variables.
Main outcome measures Extent of adherence to a modified Mediterranean diet using a scoring system on a 10 point scale, and death from any cause by time of occurrence, modelled through Cox regression.
Results An increase in the modified Mediterranean diet score was associated with lower overall mortality, a two unit increment corresponding to a statistically significant reduction of 8% (95% confidence interval 3% to 12%). No statistically significant evidence of heterogeneity was found among countries in the association of the score with overall mortality even though the association was stronger in Greece and Spain. When dietary exposures were calibrated across countries, the reduction in mortality was 7% (1% to 12%).
Conclusion The Mediterranean diet, modified so as to apply across Europe, was associated with increased survival among older people.
The association of diet with several diseases has attracted much attention.1 2 Recently, interest has concentrated on dietary patterns, because they can accommodate the complex interplay of nutrients within a diet.3 4 Dietary patterns have often been studied in relation to the mortality of elderly people,5-9 because of interest in this important age group and because of methodological considerations—for example, the cumulative effects of diet over an extended period and the high frequency of deaths.
The Mediterranean diet has been used in many studies because several of its components have been related to common chronic diseases,2 10 ecological evidence suggests that such a diet may be beneficial to health,11 and variants of this diet have improved the prognosis of patients with coronary heart disease.12 13 The Mediterranean diet is characterised by a high intake of vegetables, legumes, fruits, and cereals (in the past largely unrefined); a moderate to high intake of fish; a low intake of saturated lipids but high intake of unsaturated lipids, particularly olive oil; a low to moderate intake of dairy products, mostly cheese and yogurt; a low intake of meat; and a modest intake of ethanol, mostly as wine.14 Adherence to a Mediterranean diet was operationalised through a 10 unit dietary score by Trichopoulou et al.4 15 Several studies have used variants of this score and have reported inverse associations with overall mortality.4 6 8 9 15 These studies, however, relied on small samples of mostly elderly participants or on the Greek population only.15
We calculated a score reflecting the Mediterranean diet.15 To allow the score to be applied to non-Mediterranean populations, in which intake of monounsaturates from olive oil is minimal, we substituted monounsaturated lipids with the sum of monounsaturated and polyunsaturated lipids in the numerator of the lipid ratio. We investigated the relation of this modified score with overall mortality in a large sample of elderly Europeans participating in EPIC (the European prospective investigation into cancer and nutrition study).16
Participants and methods
EPIC is a multicentre, prospective cohort study investigating the role of biological, dietary, lifestyle, and environmental factors in cancer and other chronic diseases, under the coordination of the International Agency for Research on Cancer.16 Briefly, between 1992 and 2000, 519 978 apparently healthy volunteers were recruited in 23 centres from 10 European countries (Denmark, France, Germany, Greece, Italy, the Netherlands, Norway, Spain, Sweden, and the United Kingdom). The criteria for sample selection and the methods are reported in detail elsewhere.16
Data for participants aged 60 or over at recruitment were included in the EPIC-elderly study. This study aims to identify dietary patterns among elderly Europeans and to investigate the associations of diet with survival.
Dietary intakes
Usual dietary intakes were assessed through compatible instruments (food frequency questionnaires and, in some centres, records of intake over seven or 14 days) that had been developed and validated within each centre.17-19 In addition, a computerised instrument for recall of dietary intake over 24 hours was developed to collect information from a stratified random sample of the aggregate cohort. The aim was to calibrate the measurements across countries.17
Nutrient intakes were calculated using food composition tables specific to the country.20 In the present study, 14 food groups and nutrients were considered: potatoes, vegetables, legumes, fruits, dairy products, cereals, meat and meat products, fish and seafood, eggs, monounsaturated lipids, polyunsaturated lipids, saturated lipids, sugar and confectionery, and non-alcoholic beverages. For each participant, daily intake (grams) of each of the groups and total energy intake (megajoules) were estimated.
Lifestyle, anthropometric, and medical variables
A precoded questionnaire was used to record data on lifestyle and health,16 which included educational achievement, history of illnesses, history of smoking, and physical activity. For participants still in work, the physical demand of their job was recorded. For leisure, time spent on each of several activities was multiplied by an energy cost coefficient; the products were then summed to produce a score of daily physical activity.21 Sex and centre specific thirds of the estimated physical activity score at leisure were used.
Anthropometric measurements were taken in all EPIC centres using similar, standardised procedures, except for France, Oxford (United Kingdom), and Norway. In these centres self reported values were recorded, but actual measurements were obtained for only a fraction of the participants.
Mediterranean diet scale
A scale indicating the degree of adherence to the traditional Mediterranean diet has been constructed by Trichopoulou et al.4 15 Values of zero or one were assigned to each of nine indicated components, using as cut-off values the sex specific medians among the participants. People whose consumption of presumed beneficial components (vegetables, legumes, fruits, cereals, fish) was below the median consumption were assigned a value of zero, and a value of one otherwise. People whose consumption of presumed detrimental components (meat and dairy products) was below the median consumption were assigned a value of one, and a value of zero otherwise. A value of one was given to men consuming from 10 g to less than 50 g of ethanol per day and to women consuming from 5 g to 25 g. For lipid intake, the ratio of the sum of monounsaturates and polyunsaturates to saturates was calculated. This modified Mediterranean diet score, as both monounsaturates and polyunsaturates are included in the numerator of the lipid ratio, can take a value from zero (minimal adherence) to nine (maximal adherence).
Follow-up
Information on the vital status of participants was obtained from mortality registries and by active follow-up. Earliest and latest years of follow-up were 1999 (some participants in the Netherlands) and December 2003 (most centres). Participants were classified as alive at last follow-up, dead, emigrated, refused to participate further, and unknown.
Overall, 100 442 participants of the EPIC cohort were aged 60 years or more at recruitment and had acceptable records of energy intakes (those in the top and bottom 1% of the ratio of energy intake to estimated energy requirement were excluded).22 Vital status has been ascertained for 100 309 (99.9%) of these participants; however, 15 362 were excluded from the EPIC-elderly study database because coronary heart disease, stroke, cancer, or a combination of these had been diagnosed at enrolment. Of the remaining 84 947 participants, 10 340 had missing information for one or more of the dietary, anthropometric, or lifestyle variables, or had died within the year after enrolment. Thus 74 607 individuals were included in the study.
Statistical analysis
Analyses were carried out with Stata 7.0 and SAS 8.2. Descriptive presentation relied on cross tabulations. Survival data were modelled through Cox's proportional hazards regression,23 with length of follow-up as the primary time variable. Adjustment was made for sex, age, self reported diabetes mellitus at enrolment, educational achievement, smoking status, physical activity, waist to hip ratio, body mass index, and total energy intake. In analyses that investigated the relation of the score with mortality, consumption of eggs, potatoes, and sugar and confectionery (which are not part of the score) were also controlled for continuously. Both fixed effects and random effects models were used. Separate proportional hazard models were used for all participants and for participants in each country. Models were stratified by country or by centre (for the country specific analyses).
Dietary exposures across centres were equilibrated using an additive calibration.18 Briefly, the differences between the sex and centre specific means of the values from the food frequency questionnaire and the means of the 24 hour recall values were calculated and added to the questionnaire values. The calibrated score was computed and its association to mortality was investigated using similar models.
Results
Table 1 shows the distribution of the participants in the EPIC-elderly study by country, sex, and age at enrolment. Participants from all countries involved in EPIC are included in the EPIC-elderly study database, except for Norway, which has a comparatively young cohort. These eligible participants were followed up for a median of 89 months (range 1 to 138 months) and contributed 541 872 person years. During follow-up, 4047 participants died. Most deaths occurred in the Swedish, Danish, and UK cohorts. These cohorts are larger than the other EPIC cohorts and have a higher mean age.
Table 1 Distribution of 74 607 participants in EPIC-elderly cohort, by country, sex, and age at enrolment. Values are numbers (percentages)
The patterns for deaths and accumulated person years by non-nutritional variables were generally as expected (table 2). Table 3 shows the cross classifications of broad categories of the score by non-nutritional variables. The score is higher among older people ( 70 years) and lower among current smokers.
Table 2 Number of deaths and accumulated person years among 74 607 participants in EPIC-elderly cohort by age, sex, sociodemographic, anthropometric, and lifestyle variables
Table 3 Baseline characteristics by categories of modified Mediterranean diet score among 74 607 participants in EPIC-elderly study and 4047 deaths
Table 4 shows the associations of food groups and nutritional variables with overall mortality. Mortality ratios are adjusted for non-nutritional variables (see table 2) as well as for country, sex, and diabetes mellitus. They were not mutually adjusted, however, because underlying strong associations among food groups create technical problems—one of the reasons for opting for a nutrition score. Some of the associations are both plausible and statistically significant, notably the inverse associations of overall mortality with intake of vegetables, fruits, and cereals, ratio of unsaturated to saturated lipids, and the positive association of overall mortality with saturated lipids.
Table 4 Median and mean (standard deviation) daily intake of selected food groups and associated mortality ratio (95% confidence intervals) for chosen increment in EPIC-elderly study
Table 5 shows the adjusted associations of non-calibrated and calibrated scores with overall mortality. The associations were investigated by comparing mortality of participants with scores of 6 to 9 and 4 to 5 with those scoring 0 to 3, and by estimating the mortality ratio in relation to two unit increments of the score. Evidence shows that an increase in the score is associated with reduced overall mortality, a two unit increment corresponding to a statistically significant 8% reduction in both fixed effects and random effects models. No statistically significant evidence exists of heterogeneity among countries in the effect of score on overall mortality even though the effect is stronger in Greece and Spain and absent in the Netherlands and Germany (table 6). After excluding the Greek data, the reduction of overall mortality with an increase in the score remained statistically significant (mortality ratio for a two unit score increase 0.93, 95% confidence interval 0.89 to 0.97). The results of the analysis over all countries changed little after calibration. A two unit increment of the score corresponds to a statistically significant 7% reduction in mortality in the fixed effects and random effects models.
Table 5 Mortality ratios (95% confidence intervals) for all countries (stratified by country) by category of modified Mediterranean diet score in 74 607 participants in EPIC-elderly study
Table 6 Mortality ratios (95% confidence intervals) by country (stratified by centre within country) by category of modified Mediterranean diet score in EPIC-elderly study
Discussion
De Groot LC, van Staveren WA, Burema J. Survival beyond age 70 in relation to diet. Nutr Rev 1996;54: 211-2.
World Cancer Research Fund and American Institute for Cancer Research. Food, nutrition and the prevention of cancer: a global perspective. Washington DC: WCRF and AICR, 1997.
Jacques PF, Tucker KL. Are dietary patterns useful for understanding the role of diet in chronic disease? Am J Clin Nutr 2001;73: 1-2.
Trichopoulou A, Kouris-Blazos A, Wahlqvist ML, Gnardellis C, Lagiou P, Polychronopoulos E, et al. Diet and overall survival in elderly people. BMJ 1995;311: 1457-60.
Huijbregts P, Feskens E, Rasanen L, Fidanza F, Nissinen A, Menotti A, et al. Dietary pattern and 20 year mortality in elderly men in Finland, Italy, and the Netherlands: longitudinal cohort study. BMJ 1997;315: 13-7.
Osler M, Schroll M. Diet and mortality in a cohort of elderly people in a north European community. Int J Epidemiol 1997;26: 155-9.
Kumagai S, Shibata H, Watanabe S, Suzuki T, Haga H. Effect of food intake pattern on all-cause mortality in the community elderly: a 7-year longitudinal study. J Nutr Health Aging 1999;3: 29-33.
Lasheras C, Fernandez S, Patterson AM. Mediterranean diet and age with respect to overall survival in institutionalised, nonsmoking elderly people. Am J Clin Nutr 2000;71(4): 987-92.
Knoops KT, de Groot LC, Kromhout D, Perrin AE, Moreiras-Varela O, Menotti A, et al. Mediterranean diet, lifestyle factors, and 10-year mortality in elderly European men and women: the HALE project. JAMA 2004;292: 1433-9.
Willett WC, ed. Diet and coronary heart disease. Nutritional epidemiology, 2nd ed. New York: Oxford University Press, 1998: 414-66.
Keys A. Seven countries. A multivariate analysis of death and coronary heart disease. Cambridge, MA: Harvard University Press, 1980.
De Lorgeril M, Renaud S, Mamelle N, Salen P, Martin JL, Monjaud I, et al. Mediterranean alpha-linolenic acid-rich diet in secondary prevention of coronary heart disease. Lancet 1994;343: 1454-9.
Singh RB, Dubnov G, Niaz MA, Ghosh S, Singh R, Rastogi SS, et al. Effect of an IndoMediterranean diet on progression of coronary artery disease in high risk patients (Indo-Mediterranean diet heart study): a randomised single-blind trial. Lancet 2002;360: 1455-61.
Willett WC, Sacks F, Trichopoulou A, Drescher G, Ferro-Luzzi A, Helsing E, et al. Mediterranean diet pyramid: a cultural model for healthy eating. Am J Clin Nutr 1995;61(suppl 6): S1402-6.
Trichopoulou A, Costacou T, Bamia C, Trichopoulos D. Adherence to Mediterranean diet and survival in a Greek population. N Engl J Med 2003;348: 2599-608.
Riboli E, Hunt KJ, Slimani N, Ferrari P, Norat T, Fahey M, et al. European prospective investigation into cancer and nutrition (EPIC): study populations and data collection. Public Health Nutr 2002;5: 1113-24.
Slimani N, Kaaks R, Ferrari P, Casagrande C, Clavel-Chapelon F, Lotze G, et al. European prospective investigation into cancer and nutrition (EPIC) calibration study: rationale, design and population characteristics. Public Health Nutr 2002;5: 1125-45.
Kaaks R, Riboli E. Validation and calibration of dietary intake measurements in the EPIC project: methodological considerations. European prospective investigation into cancer and nutrition. Int J Epidemiol 1997;26(suppl 1): S15-25.
Margetts BM, Pietinen P. European prospective investigation into cancer and nutrition: validity studies on dietary assessment methods. Int J Epidemiol 1997;26(Suppl 1): S1-5.
Deharveng G, Charrondiere UR, Slimani N, Southgate DA, Riboli E. Comparison of nutrients in the food composition tables available in the nine European countries participating in EPIC. European prospective investigation into cancer and nutrition. Eur J Clin Nutr 1999;53: 60-79.
James WPT, Schofield EC. Human energy requirements: a manual for planners and nutritionists. Oxford: Oxford University Press, 1990.
Department of Health. Dietary reference values for food energy and nutrients for the United Kingdom. UK Department of Health report on health and social subjects No 41. London: Stationery Office, 1991.
Breslow NE, Day NE. Statistical methods in cancer research. Vol II. The design and analysis of cohort studies. Lyons: International Agency for Research on Cancer, 1987. (IARC scientific publication No 82)
Willett WC, Stampfer MJ, Manson JE, Colditz GA, Speizer FE, Rosner BA, et al. Intake of trans fatty acids and risk of coronary heart disease among women. Lancet 1993;341: 581-5.(Antonia Trichopoulou, associate professo)
Correspondence to: A Trichopoulou antonia@nut.uoa.gr
Objective To examine whether adherence to the modified Mediterranean diet, in which unsaturates were substituted for monounsaturates, is associated with longer life expectancy among elderly Europeans.
Design Multicentre, prospective cohort study.
Setting Nine European countries (Denmark, France, Germany, Greece, Italy, the Netherlands, Spain, Sweden, United Kingdom).
Participants 74 607 men and women, aged 60 or more, without coronary heart disease, stroke, or cancer at enrolment and with complete information about dietary intake and potentially confounding variables.
Main outcome measures Extent of adherence to a modified Mediterranean diet using a scoring system on a 10 point scale, and death from any cause by time of occurrence, modelled through Cox regression.
Results An increase in the modified Mediterranean diet score was associated with lower overall mortality, a two unit increment corresponding to a statistically significant reduction of 8% (95% confidence interval 3% to 12%). No statistically significant evidence of heterogeneity was found among countries in the association of the score with overall mortality even though the association was stronger in Greece and Spain. When dietary exposures were calibrated across countries, the reduction in mortality was 7% (1% to 12%).
Conclusion The Mediterranean diet, modified so as to apply across Europe, was associated with increased survival among older people.
The association of diet with several diseases has attracted much attention.1 2 Recently, interest has concentrated on dietary patterns, because they can accommodate the complex interplay of nutrients within a diet.3 4 Dietary patterns have often been studied in relation to the mortality of elderly people,5-9 because of interest in this important age group and because of methodological considerations—for example, the cumulative effects of diet over an extended period and the high frequency of deaths.
The Mediterranean diet has been used in many studies because several of its components have been related to common chronic diseases,2 10 ecological evidence suggests that such a diet may be beneficial to health,11 and variants of this diet have improved the prognosis of patients with coronary heart disease.12 13 The Mediterranean diet is characterised by a high intake of vegetables, legumes, fruits, and cereals (in the past largely unrefined); a moderate to high intake of fish; a low intake of saturated lipids but high intake of unsaturated lipids, particularly olive oil; a low to moderate intake of dairy products, mostly cheese and yogurt; a low intake of meat; and a modest intake of ethanol, mostly as wine.14 Adherence to a Mediterranean diet was operationalised through a 10 unit dietary score by Trichopoulou et al.4 15 Several studies have used variants of this score and have reported inverse associations with overall mortality.4 6 8 9 15 These studies, however, relied on small samples of mostly elderly participants or on the Greek population only.15
We calculated a score reflecting the Mediterranean diet.15 To allow the score to be applied to non-Mediterranean populations, in which intake of monounsaturates from olive oil is minimal, we substituted monounsaturated lipids with the sum of monounsaturated and polyunsaturated lipids in the numerator of the lipid ratio. We investigated the relation of this modified score with overall mortality in a large sample of elderly Europeans participating in EPIC (the European prospective investigation into cancer and nutrition study).16
Participants and methods
EPIC is a multicentre, prospective cohort study investigating the role of biological, dietary, lifestyle, and environmental factors in cancer and other chronic diseases, under the coordination of the International Agency for Research on Cancer.16 Briefly, between 1992 and 2000, 519 978 apparently healthy volunteers were recruited in 23 centres from 10 European countries (Denmark, France, Germany, Greece, Italy, the Netherlands, Norway, Spain, Sweden, and the United Kingdom). The criteria for sample selection and the methods are reported in detail elsewhere.16
Data for participants aged 60 or over at recruitment were included in the EPIC-elderly study. This study aims to identify dietary patterns among elderly Europeans and to investigate the associations of diet with survival.
Dietary intakes
Usual dietary intakes were assessed through compatible instruments (food frequency questionnaires and, in some centres, records of intake over seven or 14 days) that had been developed and validated within each centre.17-19 In addition, a computerised instrument for recall of dietary intake over 24 hours was developed to collect information from a stratified random sample of the aggregate cohort. The aim was to calibrate the measurements across countries.17
Nutrient intakes were calculated using food composition tables specific to the country.20 In the present study, 14 food groups and nutrients were considered: potatoes, vegetables, legumes, fruits, dairy products, cereals, meat and meat products, fish and seafood, eggs, monounsaturated lipids, polyunsaturated lipids, saturated lipids, sugar and confectionery, and non-alcoholic beverages. For each participant, daily intake (grams) of each of the groups and total energy intake (megajoules) were estimated.
Lifestyle, anthropometric, and medical variables
A precoded questionnaire was used to record data on lifestyle and health,16 which included educational achievement, history of illnesses, history of smoking, and physical activity. For participants still in work, the physical demand of their job was recorded. For leisure, time spent on each of several activities was multiplied by an energy cost coefficient; the products were then summed to produce a score of daily physical activity.21 Sex and centre specific thirds of the estimated physical activity score at leisure were used.
Anthropometric measurements were taken in all EPIC centres using similar, standardised procedures, except for France, Oxford (United Kingdom), and Norway. In these centres self reported values were recorded, but actual measurements were obtained for only a fraction of the participants.
Mediterranean diet scale
A scale indicating the degree of adherence to the traditional Mediterranean diet has been constructed by Trichopoulou et al.4 15 Values of zero or one were assigned to each of nine indicated components, using as cut-off values the sex specific medians among the participants. People whose consumption of presumed beneficial components (vegetables, legumes, fruits, cereals, fish) was below the median consumption were assigned a value of zero, and a value of one otherwise. People whose consumption of presumed detrimental components (meat and dairy products) was below the median consumption were assigned a value of one, and a value of zero otherwise. A value of one was given to men consuming from 10 g to less than 50 g of ethanol per day and to women consuming from 5 g to 25 g. For lipid intake, the ratio of the sum of monounsaturates and polyunsaturates to saturates was calculated. This modified Mediterranean diet score, as both monounsaturates and polyunsaturates are included in the numerator of the lipid ratio, can take a value from zero (minimal adherence) to nine (maximal adherence).
Follow-up
Information on the vital status of participants was obtained from mortality registries and by active follow-up. Earliest and latest years of follow-up were 1999 (some participants in the Netherlands) and December 2003 (most centres). Participants were classified as alive at last follow-up, dead, emigrated, refused to participate further, and unknown.
Overall, 100 442 participants of the EPIC cohort were aged 60 years or more at recruitment and had acceptable records of energy intakes (those in the top and bottom 1% of the ratio of energy intake to estimated energy requirement were excluded).22 Vital status has been ascertained for 100 309 (99.9%) of these participants; however, 15 362 were excluded from the EPIC-elderly study database because coronary heart disease, stroke, cancer, or a combination of these had been diagnosed at enrolment. Of the remaining 84 947 participants, 10 340 had missing information for one or more of the dietary, anthropometric, or lifestyle variables, or had died within the year after enrolment. Thus 74 607 individuals were included in the study.
Statistical analysis
Analyses were carried out with Stata 7.0 and SAS 8.2. Descriptive presentation relied on cross tabulations. Survival data were modelled through Cox's proportional hazards regression,23 with length of follow-up as the primary time variable. Adjustment was made for sex, age, self reported diabetes mellitus at enrolment, educational achievement, smoking status, physical activity, waist to hip ratio, body mass index, and total energy intake. In analyses that investigated the relation of the score with mortality, consumption of eggs, potatoes, and sugar and confectionery (which are not part of the score) were also controlled for continuously. Both fixed effects and random effects models were used. Separate proportional hazard models were used for all participants and for participants in each country. Models were stratified by country or by centre (for the country specific analyses).
Dietary exposures across centres were equilibrated using an additive calibration.18 Briefly, the differences between the sex and centre specific means of the values from the food frequency questionnaire and the means of the 24 hour recall values were calculated and added to the questionnaire values. The calibrated score was computed and its association to mortality was investigated using similar models.
Results
Table 1 shows the distribution of the participants in the EPIC-elderly study by country, sex, and age at enrolment. Participants from all countries involved in EPIC are included in the EPIC-elderly study database, except for Norway, which has a comparatively young cohort. These eligible participants were followed up for a median of 89 months (range 1 to 138 months) and contributed 541 872 person years. During follow-up, 4047 participants died. Most deaths occurred in the Swedish, Danish, and UK cohorts. These cohorts are larger than the other EPIC cohorts and have a higher mean age.
Table 1 Distribution of 74 607 participants in EPIC-elderly cohort, by country, sex, and age at enrolment. Values are numbers (percentages)
The patterns for deaths and accumulated person years by non-nutritional variables were generally as expected (table 2). Table 3 shows the cross classifications of broad categories of the score by non-nutritional variables. The score is higher among older people ( 70 years) and lower among current smokers.
Table 2 Number of deaths and accumulated person years among 74 607 participants in EPIC-elderly cohort by age, sex, sociodemographic, anthropometric, and lifestyle variables
Table 3 Baseline characteristics by categories of modified Mediterranean diet score among 74 607 participants in EPIC-elderly study and 4047 deaths
Table 4 shows the associations of food groups and nutritional variables with overall mortality. Mortality ratios are adjusted for non-nutritional variables (see table 2) as well as for country, sex, and diabetes mellitus. They were not mutually adjusted, however, because underlying strong associations among food groups create technical problems—one of the reasons for opting for a nutrition score. Some of the associations are both plausible and statistically significant, notably the inverse associations of overall mortality with intake of vegetables, fruits, and cereals, ratio of unsaturated to saturated lipids, and the positive association of overall mortality with saturated lipids.
Table 4 Median and mean (standard deviation) daily intake of selected food groups and associated mortality ratio (95% confidence intervals) for chosen increment in EPIC-elderly study
Table 5 shows the adjusted associations of non-calibrated and calibrated scores with overall mortality. The associations were investigated by comparing mortality of participants with scores of 6 to 9 and 4 to 5 with those scoring 0 to 3, and by estimating the mortality ratio in relation to two unit increments of the score. Evidence shows that an increase in the score is associated with reduced overall mortality, a two unit increment corresponding to a statistically significant 8% reduction in both fixed effects and random effects models. No statistically significant evidence exists of heterogeneity among countries in the effect of score on overall mortality even though the effect is stronger in Greece and Spain and absent in the Netherlands and Germany (table 6). After excluding the Greek data, the reduction of overall mortality with an increase in the score remained statistically significant (mortality ratio for a two unit score increase 0.93, 95% confidence interval 0.89 to 0.97). The results of the analysis over all countries changed little after calibration. A two unit increment of the score corresponds to a statistically significant 7% reduction in mortality in the fixed effects and random effects models.
Table 5 Mortality ratios (95% confidence intervals) for all countries (stratified by country) by category of modified Mediterranean diet score in 74 607 participants in EPIC-elderly study
Table 6 Mortality ratios (95% confidence intervals) by country (stratified by centre within country) by category of modified Mediterranean diet score in EPIC-elderly study
Discussion
De Groot LC, van Staveren WA, Burema J. Survival beyond age 70 in relation to diet. Nutr Rev 1996;54: 211-2.
World Cancer Research Fund and American Institute for Cancer Research. Food, nutrition and the prevention of cancer: a global perspective. Washington DC: WCRF and AICR, 1997.
Jacques PF, Tucker KL. Are dietary patterns useful for understanding the role of diet in chronic disease? Am J Clin Nutr 2001;73: 1-2.
Trichopoulou A, Kouris-Blazos A, Wahlqvist ML, Gnardellis C, Lagiou P, Polychronopoulos E, et al. Diet and overall survival in elderly people. BMJ 1995;311: 1457-60.
Huijbregts P, Feskens E, Rasanen L, Fidanza F, Nissinen A, Menotti A, et al. Dietary pattern and 20 year mortality in elderly men in Finland, Italy, and the Netherlands: longitudinal cohort study. BMJ 1997;315: 13-7.
Osler M, Schroll M. Diet and mortality in a cohort of elderly people in a north European community. Int J Epidemiol 1997;26: 155-9.
Kumagai S, Shibata H, Watanabe S, Suzuki T, Haga H. Effect of food intake pattern on all-cause mortality in the community elderly: a 7-year longitudinal study. J Nutr Health Aging 1999;3: 29-33.
Lasheras C, Fernandez S, Patterson AM. Mediterranean diet and age with respect to overall survival in institutionalised, nonsmoking elderly people. Am J Clin Nutr 2000;71(4): 987-92.
Knoops KT, de Groot LC, Kromhout D, Perrin AE, Moreiras-Varela O, Menotti A, et al. Mediterranean diet, lifestyle factors, and 10-year mortality in elderly European men and women: the HALE project. JAMA 2004;292: 1433-9.
Willett WC, ed. Diet and coronary heart disease. Nutritional epidemiology, 2nd ed. New York: Oxford University Press, 1998: 414-66.
Keys A. Seven countries. A multivariate analysis of death and coronary heart disease. Cambridge, MA: Harvard University Press, 1980.
De Lorgeril M, Renaud S, Mamelle N, Salen P, Martin JL, Monjaud I, et al. Mediterranean alpha-linolenic acid-rich diet in secondary prevention of coronary heart disease. Lancet 1994;343: 1454-9.
Singh RB, Dubnov G, Niaz MA, Ghosh S, Singh R, Rastogi SS, et al. Effect of an IndoMediterranean diet on progression of coronary artery disease in high risk patients (Indo-Mediterranean diet heart study): a randomised single-blind trial. Lancet 2002;360: 1455-61.
Willett WC, Sacks F, Trichopoulou A, Drescher G, Ferro-Luzzi A, Helsing E, et al. Mediterranean diet pyramid: a cultural model for healthy eating. Am J Clin Nutr 1995;61(suppl 6): S1402-6.
Trichopoulou A, Costacou T, Bamia C, Trichopoulos D. Adherence to Mediterranean diet and survival in a Greek population. N Engl J Med 2003;348: 2599-608.
Riboli E, Hunt KJ, Slimani N, Ferrari P, Norat T, Fahey M, et al. European prospective investigation into cancer and nutrition (EPIC): study populations and data collection. Public Health Nutr 2002;5: 1113-24.
Slimani N, Kaaks R, Ferrari P, Casagrande C, Clavel-Chapelon F, Lotze G, et al. European prospective investigation into cancer and nutrition (EPIC) calibration study: rationale, design and population characteristics. Public Health Nutr 2002;5: 1125-45.
Kaaks R, Riboli E. Validation and calibration of dietary intake measurements in the EPIC project: methodological considerations. European prospective investigation into cancer and nutrition. Int J Epidemiol 1997;26(suppl 1): S15-25.
Margetts BM, Pietinen P. European prospective investigation into cancer and nutrition: validity studies on dietary assessment methods. Int J Epidemiol 1997;26(Suppl 1): S1-5.
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