To the Editor,

We read with interest the article by León et al1 who studied a sample of workers aged 25 to 64 years recruited during their routine medical checkup exams undertaken by the prevention services of FREMAP during 2003 and estimated an overall prevalence of the metabolic syndrome (MS) of 13.4%, higher in men (15.9%) than in women (5.2%). What really caught our attention, though, was that the greatest prevalence of MS in the various autonomous regions in Spain corresponds to men in Extremadura: 22.15% (95% confidence interval [CI], 21.7%-22.5%), whilst the prevalence in women is also the highest in Spain: 9.1% (95% CI, 8.1%-10.2%).

This high prevalence of MS in Extremadura, by far the highest in Spain, is surprising. As the authors point out, the prevalence not only of MS, but also of other cardiovascular risk factors, like hypertension, diabetes and obesity, and even ischemic heart disease, is greater in regions of southern Spain,1 including Extremadura. Our group (GERIVA: Grupo de Estudio del Riesgo Vascular de Extremadura [Group for the Study of Vascular Risk in Extremadura]) recently published a study analyzing the prevalence of MS according to various different criteria in the province of Caceres (also in the region of Extremadura). The study involved the general population over the age of 24 years, and was based on a population sample of 1314 subjects (55.4% women), with a mean age of 52.8 (18) years.2 The prevalence of MS according to the ATP-III (2001) criteria,3 which we understand to be those used for the diagnosis of MS by León et al, was 18.6% (95% CI, 16.5-20.8), and was similar in men (18.3%; 95% CI, 15.2-21.4) and women (19%; 95% CI, 16.2-21.8). This prevalence is similar or just slightly higher than that of other similar studies carried out in Spain and with which we compared our findings.2 Thus, a prevalence, especially in men, of 22.15% would seem high, both in absolute terms and in comparison with the prevalence seen in the other autonomous regions of Spain, particularly when these authors only include a population up to the age of 64 years, and it is well known, as our study clearly shows, that the prevalence of MS is much higher with effect from this age.

Also surprising were the great differences found in the study by León et al between sexes. The study by our group found no differences between men (18.3%) and women (19%), a finding that was also seen in most of the recent reports referred to in our article.2 This difference may be due to the large variation in the sample between the numbers of men and women in the study by León et al.1

Finally, another recently published study carried out in the province of Badajoz (again in Extremadura) among persons who attended their primary health care center4 reported a prevalence similar to that of León et al1 (23.8%). However, this very high prevalence was explained by the fact that the study was not done in the general population but rather in an elder population, as is that of persons attending their health center.

In view of these points, we believe that the prevalence in Extremadura of MS, and probably of other cardiovascular risk factors, may be slightly above the national mean, but not so much as suggested by León et al.1