© 2008 American Thoracic Society
Vitamin D and Tuberculosis Incidence in SpainTo the Editor:We read the article by Dr. Martineau and colleagues on the in vitro effect of vitamin D on tuberculosis immunity with great interest (1). These authors' results seem to be supported by the distinct incidence of tuberculosis in the various regions of Spain and by a study performed in the region with the highest rates of tuberculosis in the Basque Country (northern Spain) (A. Alberto García-Zamalloa, unpublished work). Vitamin D is synthesized by humans and synthesis is related to exposure to the sun. Spain is famous for its sun, but the amount of hours of sunshine differs throughout the country (2). To determine the association between rates of tuberculosis incidence and sunlight exposure in Spain, we used incidence data from a prospective study performed between 1996 and 1997 in 11 regions of continental Spain (3) and the mean number of hours of sunshine in each region for the years 2002–2003 (2). When the Basque Country was excluded, due to its wide use of the BCG vaccine (4), the correlation between disease rates (regional range rate: 16.22 to 70.75 per 100,000 inhabitants) and annual hours of sunshine (range, 1,761–2,950) was significant for the tuberculosis population as a whole (Pearson's correlation coefficient [r] = –0.7946, P = 0.0060) and bacilliferous pulmonary patients (r = –0.7518, P = 0.0122) and was highly significant for patients aged > 34 years old (r = –0.8945, P = 0.0005). In another study performed in the Bajo-Deba valley region of the Basque Country between 1995 and 2003, very different incidence rates were observed in neighboring populations with similar levels of income and education. Ermua-Mallabia and Mendaro, which are inland towns with 19,754 inhabitants, showed an annual incidence rate of 95.6 per 100,000 inhabitants in contrast with a rate of 26 per 100,000 inhabitants for Deba and Mutriku, coastal towns with 9,816 inhabitants. The first two towns are located in narrow valleys, which are colder and receive less sunshine than the other two towns, which are situated on the coast, have more hours of sunshine, and provide greater opportunities for being outdoors. The mean serum concentrations of 25-hydroxy-vitamin-D3 in a randomized sample of 76 parturient women (40 and 36 from inland and coastal areas, respectively) obtained in 1998–2002 were, in ng/ml: 18.6 (95% CI, 15.5–21.8) and 28.3 (95% CI, 23.6–32.9), respectively (ANOVA F = 11.8, P = 0.001). The possibility of reducing the prevalence of tuberculosis by correcting vitamin D deficiency, a simple and inexpensive measure, highlights the importance of the study by Martineau and coworkers.
Hospital Donostia FOOTNOTES Conflict of Interest Statement: None of the authors has a financial relationship with a commercial entity that has an interest in the subject of this manuscript. REFERENCES
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