Predictors of short- and long-term adherence with a Mediterranean-type diet intervention: the PREDIMED randomized trial.
BACKGROUND
Dietary intervention success requires strong participant adherence, but very few studies have examined factors related to both short-term and long-term adherence. A better understanding of predictors of adherence is necessary to improve the design and execution of dietary intervention trials. This study was designed to identify participant characteristics at baseline and study features that predict short-term and long-term adherence with interventions promoting the Mediterranean-type diet (MedDiet) in the PREvención con DIeta MEDiterránea (PREDIMED) randomized trial.


METHODS
Analyses included men and women living in Spain aged 55-80 at high risk for cardiovascular disease. Participants were randomized to the MedDiet supplemented with either complementary extra-virgin olive oil (EVOO) or tree nuts. The control group and participants with insufficient information on adherence were excluded. PREDIMED began in 2003 and ended in 2010. Investigators assessed covariates at baseline and dietary information was updated yearly throughout follow-up. Adherence was measured with a validated 14-point Mediterranean-type diet adherence score. Logistic regression was used to examine associations between baseline characteristics and adherence at one and four years of follow-up.


RESULTS
Participants were randomized to the MedDiet supplemented with EVOO (n = 2,543; 1,962 after exclusions) or tree nuts (n = 2,454; 2,236 after exclusions). A higher number of cardiovascular risk factors, larger waist circumference, lower physical activity levels, lower total energy intake, poorer baseline adherence to the 14-point adherence score, and allocation to MedDiet + EVOO each independently predicted poorer adherence. Participants from PREDIMED recruiting centers with a higher total workload (measured as total number of persons-years of follow-up) achieved better adherence. No adverse events or side effects were reported.


CONCLUSIONS
To maximize dietary adherence in dietary interventions, additional efforts to promote adherence should be used for participants with lower baseline adherence to the intended diet and poorer health status. The design of multicenter nutrition trials should prioritize few large centers with more participants in each, rather than many small centers.


BACKGROUND
This study was registered at controlled-trials.com (http://www.controlled-trials. com/ISRCTN35739639). International Standard Randomized Controlled Trial Number (ISRCTN): 35739639. Registration date: 5 October 2005.


METHODS
parallel randomized trial.
Department of Epidemiology, Harvard T.H. Chan School of Public Health, 677 Huntington Avenue, Boston, MA, 02115, USA.|Channing Division of Network Medicine, 181 Longwood Avenue, Room 345, Boston, MA, 02115, USA.
Mary Kathryn
MK
Downer
Department of Epidemiology, Harvard T.H. Chan School of Public Health, 677 Huntington Avenue, Boston, MA, 02115, USA.|Department of Preventive Medicine and Public Health, Faculty of Medicine, University of Navarra, C/Irunlarrea, No. 1. Research Building, 2nd floor, Local 2520, 31008, Pamplona, Navarra, Spain.|Centro de Investigación Biomédica en Red Fisiopatología de la Obesidad y Nutrición (CIBERobn), Instituto de Salud Carlos III, 28029, Madrid, Spain.|IdiSNA, Navarra Institute por Health Research, 31008, Barcelona, Navarra, Spain.
Alfredo
A
Gea
Department of Epidemiology, Harvard T.H. Chan School of Public Health, 677 Huntington Avenue, Boston, MA, 02115, USA.|Channing Division of Network Medicine, 181 Longwood Avenue, Room 345, Boston, MA, 02115, USA.
Meir
M
Stampfer
Department of Preventive Medicine and Public Health, Faculty of Medicine, University of Navarra, C/Irunlarrea, No. 1. Research Building, 2nd floor, Local 2520, 31008, Pamplona, Navarra, Spain.|Centro de Investigación Biomédica en Red Fisiopatología de la Obesidad y Nutrición (CIBERobn), Instituto de Salud Carlos III, 28029, Madrid, Spain.|IdiSNA, Navarra Institute por Health Research, 31008, Barcelona, Navarra, Spain.
Ana
A
Sánchez-Tainta
Department of Preventive Medicine, University of Valencia, AVDA,Vicente Blasco Ibanez, 15, 46010, Valencia, Spain.|Centro de Investigación Biomédica en Red Fisiopatología de la Obesidad y Nutrición (CIBERobn), Instituto de Salud Carlos III, 28029, Madrid, Spain.
Dolores
D
Corella
Human Nutrition Unit, Biochemistry and Biotechnology Department, IISPV, Hospital Universitari de Sant Joan de Reus, Universitat Rovira i Virgili, C/Sant Llorenç, 21, 43201, Reus, Spain.|Centro de Investigación Biomédica en Red Fisiopatología de la Obesidad y Nutrición (CIBERobn), Instituto de Salud Carlos III, 28029, Madrid, Spain.
Jordi
J
Salas-Salvadó
Lipid Clinic, Department of Endocrinology and Nutrition, Institut d'Investigacions Biomediques August Pi Sunyer (IDIBAPS), Hospital Clinic, University of Barcelona, C/Villarroel, 170, 08036, Barcelona, Spain.|Centro de Investigación Biomédica en Red Fisiopatología de la Obesidad y Nutrición (CIBERobn), Instituto de Salud Carlos III, 28029, Madrid, Spain.
Emilio
E
Ros
Department of Internal Medicine, Institut d'Investigacions Biomediques August Pi Sunyer (IDIBAPS), Hospital Clinic, University of Barcelona, C/Villarroel, 170, 08036, Barcelona, Spain.|Centro de Investigación Biomédica en Red Fisiopatología de la Obesidad y Nutrición (CIBERobn), Instituto de Salud Carlos III, 28029, Madrid, Spain.
Ramón
R
Estruch
Cardiovascular and Nutrition Research Group, Institut de Recerca Hospital del Mar, Carrer Dr. Aiguader, 88, 08003, Barcelona, Spain.|Centro de Investigación Biomédica en Red Fisiopatología de la Obesidad y Nutrición (CIBERobn), Instituto de Salud Carlos III, 28029, Madrid, Spain.
Montserrat
M
Fitó
Department of Preventive Medicine, University of Malaga, Campus de Teatinos, 29071, Malaga, Spain.|Centro de Investigación Biomédica en Red Fisiopatología de la Obesidad y Nutrición (CIBERobn), Instituto de Salud Carlos III, 28029, Madrid, Spain.
Enrique
E
Gómez-Gracia
Department of Cardiology, University Hospital of Araba, C/Jose Atxotegi, s/n, 01009, Vitoria-Gasteiz, Araba, Spain.|Centro de Investigación Biomédica en Red Fisiopatología de la Obesidad y Nutrición (CIBERobn), Instituto de Salud Carlos III, 28029, Madrid, Spain.
Fernando
F
Arós
Palma Institute of Health Research (IdISPa), University of Balearic Islands and Hospital Son Espases, Carretera de Valldemossa, 79, 07120, Palma, Illes Balears, Spain.|Centro de Investigación Biomédica en Red Fisiopatología de la Obesidad y Nutrición (CIBERobn), Instituto de Salud Carlos III, 28029, Madrid, Spain.
Miquel
M
Fiol
Department of Family Medicine, Research Unit, Distrito Sanitario Atencion Primaria Sevilla, Avda. de Jerez s/n, 41007, Sevilla, Spain.|Centro de Investigación Biomédica en Red Fisiopatología de la Obesidad y Nutrición (CIBERobn), Instituto de Salud Carlos III, 28029, Madrid, Spain.
Francisco Jose Garcia
FJ
De-la-Corte
Research Institute of Biomedical and Health Sciences, University of Las Palmas de Gran Canaria, Juan De Quesada 30, 35001, Las Palmas, Spain.|Centro de Investigación Biomédica en Red Fisiopatología de la Obesidad y Nutrición (CIBERobn), Instituto de Salud Carlos III, 28029, Madrid, Spain.
Lluís
L
Serra-Majem
Head of Lipid and Vascular Risk Unit, Internal Medicine Department, Hospital Universitari de Bellvitge-IDIBELL. Universidad de Barcelona, C/Freixa Larga s/n, 08907 - Hospitalet de Llobregat, Barcelona, Spain.|Centro de Investigación Biomédica en Red Fisiopatología de la Obesidad y Nutrición (CIBERobn), Instituto de Salud Carlos III, 28029, Madrid, Spain.
Xavier
X
Pinto
Human Nutrition Unit, Biochemistry and Biotechnology Department, IISPV Universitat Rovira i Virgili, C/Sant Llorenç, 21 Planta baja del edificio 4 de la Facultat de Medicina i Ciències de la Salut, 43201, Reus, Tarragona, Spain.|Centro de Investigación Biomédica en Red Fisiopatología de la Obesidad y Nutrición (CIBERobn), Instituto de Salud Carlos III, 28029, Madrid, Spain.
Josep
J
Basora
Department of Preventive Medicine, University of Valencia, AVDA,Vicente Blasco Ibanez, 15, 46010, Valencia, Spain.|Centro de Investigación Biomédica en Red Fisiopatología de la Obesidad y Nutrición (CIBERobn), Instituto de Salud Carlos III, 28029, Madrid, Spain.
José V
JV
Sorlí
Jordi Gol Primary Care Research Institute, Gran Via de les Corts Catalanes 587, àtic, 08007, Barcelona, Spain.|Centro de Investigación Biomédica en Red Fisiopatología de la Obesidad y Nutrición (CIBERobn), Instituto de Salud Carlos III, 28029, Madrid, Spain.
Ernest
E
Vinyoles
Department of Preventive Medicine and Public Health, Faculty of Medicine, University of Navarra, C/Irunlarrea, No. 1. Research Building, 2nd floor, Local 2520, 31008, Pamplona, Navarra, Spain.|Centro de Investigación Biomédica en Red Fisiopatología de la Obesidad y Nutrición (CIBERobn), Instituto de Salud Carlos III, 28029, Madrid, Spain.|IdiSNA, Navarra Institute por Health Research, 31008, Barcelona, Navarra, Spain.
Itziar
I
Zazpe
Department of Preventive Medicine and Public Health, Faculty of Medicine, University of Navarra, C/Irunlarrea, No. 1. Research Building, 2nd floor, Local 2520, 31008, Pamplona, Navarra, Spain. mamartinez@unav.es.|Centro de Investigación Biomédica en Red Fisiopatología de la Obesidad y Nutrición (CIBERobn), Instituto de Salud Carlos III, 28029, Madrid, Spain. mamartinez@unav.es.|IdiSNA, Navarra Institute por Health Research, 31008, Barcelona, Navarra, Spain. mamartinez@unav.es.
Miguel-Ángel
MÁ
Martínez-González
D000368:Aged; D002318:Cardiovascular Diseases / Q000209:etiology; D038441:Diet, Mediterranean; D002149:Energy Intake; D015444:Exercise; D005247:Feeding Behavior; D005260:Female; D015438:Health Behavior; D006293:Health Promotion; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009754:Nuts; D000069463:Olive Oil; D010349:Patient Compliance; D012307:Risk Factors; D013030:Spain; D055105:Waist Circumference
D000069463:Olive Oil
Dietary adherence; Dietary intervention; Dietary predictors; Long-term dietary adherence; Mediterranean Diet; PREDIMED trial; Short-term dietary adherence