53 Rev Esp Cardiol. 2005;58(7):797-806 797 Introduction and objectives. To assess the prevalen- ce of metabolic syndrome in the active Spanish working population and to describe differences related to work type. Subjects and method. Data were collected on 7256 in- dividuals [82.4% male; mean age (SD), 45.4 (9.8) years] actively employed in a large car factory and a department store. Metabolic syndrome was diagnosed according to modified ATP-III criteria (using body mass index instead of waist circumference). Results. Overall, the prevalence of metabolic syndro- me was 10.2%. When data were adjusted to match the age and gender of the general population (age range, 20- 60 years), the prevalence was 5.8% (95% CI, 4.1%- 7.6%). Moreover, it was significantly higher in men than women, at 8.7% (95% CI, 7.3%-10.0%) vs 3.0% (95% CI, 0.8%-5.1%), respectively. All the components of the me- tabolic syndrome were significantly more common in males, except a low HDL-cholesterol level. Prevalence increased with age and male gender (OR=1.7), obesity (OR=9.6), hypertension (OR=3.4), and diabetes (OR=15.4). The prevalence was highest in manual workers (11.8%), and lower in office workers (9.3%) and managers (7.7%), E PIDEMIOLOGY AND P REVENTION Prevalence of Metabolic Syndrome in the Spanish Working Population: MESYAS Registry Eduardo Alegría, a Alberto Cordero, a Martín Laclaustra, b Alberto Grima, c Montserrat León, b José A. Casasnovas, b Emilio Luengo, d Alfonso del Río, b and Ignacio Ferreira b , for the researchers of the MESYAS Registry* a Departamento de Cardiología, Clínica Universitaria de Navarra, Pamplona, Navarra, Spain. b Unidad de Investigación Cardiovascular, Hospital Clínico Universitario, Zaragoza, Spain. c Servicio de Cardiología Preventiva, Asepeyo, Valencia, Spain. d Servicio de Cardiología, Hospital Militar, Zaragoza, Spain. *The members of the MESYAS research team are listed at the end of the article. Martín Laclaustra holds a research contract at the Instituto Aragonés de Ciencias de la Salud, as part of the contract support program for researchers who have finished their medical specialty training at the Instituto de Salud Carlos III. The MESYAS Registry has a grant from the Spanish Society of Cardiology (Seville, 2003) and the Section of Preventive Cardiology and Rehabilitation. Correspondence: Dr. E. Alegría Ezquerra. Departamento de Cardiología. Clínica Universitaria de Navarra. Avda. Pío XII, 36. 31008 Pamplona. Navarra. España. E-mail: ealegria@unav.es Received October 5, 2004. Accepted for publication March 18, 2005. which indicates an inverse relationship with social class. The likelihood of presenting with metabolic syndrome, irrespective of age or gender, was highest in manual wor- kers (OR=1.3). This phenomenon seemed to depend on the serum triglyceride level. Conclusions. One in ten active workers had metabolic syndrome. The prevalence rose with age, male gender, and blood pressure, and was greatly increased by obesity and diabetes. Manual workers had the highest prevalen- ce, whereas managers had a more favorable profile. Key words: Prevalence. Metabolic syndrome. Working population. Prevalencia del síndrome metabólico en población laboral española: registro MESYAS Introducción y objetivos. Estudiar la prevalencia del síndrome metabólico (SM) en la población laboral activa española y analizar sus diferencias según las categorías laborales. Sujetos y método. Se recogieron los datos de 7.256 trabajadores activos (un 82,4% varones), con una edad media de 45,4 ± 9,8 años, empleados en una factoría de coches y unos grandes almacenes. El diagnóstico del SM se realizó mediante los criterios modificados del ATP-III (se utilizó el índice de masa corporal en lugar del períme- tro abdominal). Resultados. La prevalencia bruta del SM fue del 10,2%. Ajustada por edad y sexo en una población plana (20-60 años) fue del 5,8% (intervalo de confianza [IC] del 95%, 4,1-7,6%), significativamente más alta en varones que en mujeres (el 8,7%; IC del 95%, 7,3-10,0 frente al 3,0%; IC del 95%, 0,8-5,1). Todos los componentes del SM fueron significativamente más prevalentes en varo- nes, excepto las concentraciones de lipoproteínas de alta densidad, que fueron más bajas. La prevalencia aumentó con la edad y el sexo masculino (odds ratio [OR] = 1,7), la obesidad (OR = 9,6), la hipertensión (OR = 3,4) y la diabetes (OR = 15,4). Los trabajadores manuales presen- taron la mayor prevalencia de SM (11,8%), seguidos por los trabajadores de oficina (9,3%) y los directivos (7,7%) SEE EDITORIAL ON PAGES 768-71