title: A hypothesis for reactivation of pulmonary tuberculosis: How thoracic wall shape affects the epidemiology of tuberculosis.
abstract: This study was aimed at determining the cause for the high incidence of tuberculosis (TB) reactivation occurring in males with a low body mass index (BMI). Current thinking about pulmonary TB describes infection in the lung apex resulting in cavitation after reactivation. A different hypothesis is put forward for TB infection, suggesting that this occurs in subclinical apical cavities caused by increased pleural stress due to a low BMI body habitus. A finite element analysis (FEA) model of a lung was constructed including indentations for the first rib guided by paramedian sagittal CT reconstructions, and simulations were conducted with varying antero-posterior (AP) diameters to mimic chests with a different thoracic index (ratio of AP to the transverse chest diameters). A Pubmed search was conducted about gender and thoracic index, and the effects of BMI on TB. FEA modeling revealed a tenfold increase in stress levels at the lung apex in low BMI chests, and a four-fold increase with a low thoracic index, r(2)  = 0.9748 P < 0.001. Low thoracic index was related to BMI, P = 0.001. The mean thoracic index was statistically significantly lower in males, P = 0.001, and increased with age in both genders. This article is the first to suggest a possible mechanism linking pulmonary TB reactivation to low BMI due to the flattened thoracic wall shape of young male adults. The low thoracic index in young males may promote TB reactivation due to tissue destruction in the lung apex from high pleural stress levels.
authors: Department of Cardiothoracic Surgery, Mater Dei Hospital, L-Imsida, Malta.|Department of Anatomy, Faculty of Medicine, University of Malta, Msida MSD.
authors: Aaron R
authors: AR
authors: Casha
authors: Department of Statistics and Operations Research, Faculty of Science, University of Malta, Msida MSD, Malta.
authors: Liberato
authors: L
authors: Camilleri
authors: Department of Cardiothoracic Surgery, Mater Dei Hospital, L-Imsida, Malta.
authors: Alexander
authors: A
authors: Manché
authors: Metamaterials Unit, Faculty of Science, University of Malta, Msida MSD, Malta.
authors: Ruben
authors: R
authors: Gatt
authors: Metamaterials Unit, Faculty of Science, University of Malta, Msida MSD, Malta.
authors: Daphne
authors: D
authors: Attard
authors: Department of Physics and Astronomy, Uniwersytet Zielonogórski, Zielona Góra, Poland.
authors: Wiktor
authors: W
authors: Wolak
authors: Department of Physics and Astronomy, Uniwersytet Zielonogórski, Zielona Góra, Poland.
authors: Krzysztof
authors: K
authors: Dudek
authors: Department of Anaesthesia, Mater Dei Hospital, L-Imsida, Malta.
authors: Marilyn
authors: M
authors: Gauci
authors: Department of Cardiothoracic Surgery, Mater Dei Hospital, L-Imsida, Malta.
authors: Christopher
authors: C
authors: Giordimaina
authors: Metamaterials Unit, Faculty of Science, University of Malta, Msida MSD, Malta.
authors: Joseph N
authors: JN
authors: Grima
mesh_terms: D015992:Body Mass Index; D005260:Female; D020342:Finite Element Analysis; D006801:Humans; D015994:Incidence; D008297:Male; D008953:Models, Anatomic; D013902:Radiography, Thoracic / Q000379:methods; D012008:Recurrence; D012737:Sex Factors; D035441:Thoracic Wall / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed; D014397:Tuberculosis, Pulmonary / Q000453:epidemiology*; D055815:Young Adult
keywords: body mass index; epidemiology; reactivation;  tuberculosis