[Secular trends in cardiovascular risk factors: developments are not encouraging].

The study and evaluation of trends in cardiovascular risk factors in the population can be carried out by repeated transverse studies in sample populations over time. This is perhaps the strategy that has been most used by health care institutions by means of national health surveys and also by research groups using cross-sectional design studies, undertaken either on an autonomous regional level or on a national level. However, longitudinal studies following persons over a particular period of time are the optimal design with which to evaluate the secular trend of risk factors and to observe the phenomenon of tracking or persistence, also known as tracing. This technique enables us to evaluate whether persons with high degrees of risk factors maintain these levels over time, and also to determine the overall evolution of these risk factors in the same persons. This permits us to see to what extent it is worth while detecting high-risk persons at an earlier age and providing them with a closer follow-up and a more intense intervention if these same persons remain in the high quintiles. Observation of the whole population enables us to see whether environmental factors are having a negative influence on the evolution of the risk factors. If this were indeed the case, it would in theory increase the risk of persons in this population for cardiovascular disease or death in the near future, and this increase would be greater than expected from just the worsening risk factors with age. Longitudinal studies carried out in children and adolescents, such as the classic study by Bogalusa,1 are useful to evaluate the changes in risk factors with age Secular Trends in Cardiovascular Risk Factors: Developments Are Not Encouraging