To the Editor,

The high prevalence of the metabolic syndrome found in this study in men from Extremadura is not surprising if we bear in mind, as already mentioned, the agreement with other studies on cardiovascular risk factors, mainly obesity and diabetes mellitus, in different geographical areas of Spain. In addition, the methods used in our study were correct and rigorous, and the prevalence was standardized for age and sex.

The comparison of prevalence figures of cardiovascular risk factors in different studies is very complex and the methodological base is sometimes weak. The lack of a homogenous system, both in the protocol used to obtain the data and in their later treatment, is a generalized problem that makes comparison much more difficult, which is reflected in the difficulty involved in producing valid and general conclusions. It is for this reason that the methods of the various studies should be carefully reviewed before actually comparing the results.

As we stated in the section on limitations, we were unable to control certain factors that may have influenced the later results, such as the socioeconomic level of the workers or the type of activity they carried out, though we know that the mutual insurance company deals with workers employed in different activities. In spite of the fact that the study involved a large sample (600 workers), they are not necessarily representative of the general population of Extremadura.

About 90% of the sample in our study came from the province of Badajoz, in Extremadura. In the study mentioned by the authors of the letter, undertaken with a sample of patients in the same province, the authors found a very similar prevalence to that of our study. Accounting for the high prevalence solely by the inclusion of persons older than 65 years of age and the sample type is questionable, given that 80% of that sample were younger than 65 years of age.

The low prevalence of the metabolic syndrome in female workers, in all the autonomous regions studied and in all the age ranges, as compared with the figures published for the general female population is almost certainly the result of differences in the socioeconomic profile.

What is obvious, though, is the presence of large differences in the prevalence of the metabolic syndrome depending on the geographical area studied, as occurs with mortality from ischemic heart disease. Further research using methodologically rigorous studies is required to attempt to explain this difference if we wish to increase our understanding of cardiovascular prevention, more so if we aim to establish effective measures adapted to the situation in each region.