Sexual dimorphism in tuberculosis incidence: children cases compared to adult cases in Tuscany from 1997 to 2011.

In most countries, men seem to be more susceptible to tuberculosis (TB) than women, but only few studies have investigated the reasons of this gender incidence difference. The effect of sexual hormones on immunity is possible.Data from children and adults, living in Tuscany, hospitalized for TB in all the thirty-one regional hospitals from January 1st 1997 to December 31st 2011, were analyzed using the International Classification of Disease, 9th Revision, Clinical Modification.During the study period, 10,744 patients were hospitalized with TB diagnosis, precisely 279 (2.6%) children [0-14 years], 205 (1.9%) adolescents [15-18 years] and 10,260 (95.5%) adults [≥ 18 years]. The male population ranged from 249 patients (51.4%) in children and adolescents, to 6,253 (60.9%) in adults. Pulmonary TB was the most common form both in children and adults. Men were more likely than women to have pulmonary TB after puberty, while no significant differences were found between males and females in the hospitalized children. The male gender also resulted the most affected for the extra-pulmonary disease sites, excluding the lymphatic system, during the reproductive age.Our findings suggest a possible role of sexual hormones in the development of TB. No significant male-female difference was found in TB incidence among children, while a sex ratio significantly different from 1:1 emerged among reproductive age classes. An increased incidence difference also persisted in older men, suggesting that male-biased risk factors could influence TB progression. Some limitations of the study are the sample size, the method of discharge diagnosis which could be deficient in accuracy in some cases, the increasing number of immigrants and the lack of possible individual risk factors (smoke and alcohol). Further studies are needed to investigate the possible hormone-driven immune mechanisms determining the sexual dimorphism in TB.