1. National Program for Cardiovascular Prevention, Ministry of Public Health and Social Welfare , Pettirossi & Brasil, Asuncion, PC 1548 , Paraguay
2. Imperial Clinical Trials Unit, Imperial College London , Stadium House, 68 Wood Lane, London W12 7RH , UK
3. Department of Primary Care and Public Health, Imperial College London , St Dunstan's Road, London W6 8RP , UK