**5.2. Metabolic effects of air pollution and their relationship with pneumonia**

The relationship between diabetes, obesity, and susceptibility to lung infection and pneumonia has also been evaluated in several studies [175]. In these, an increased incidence and mortality from pneumococcal pneumonia, influenza, and tuberculosis was strongly associated with diabetes and obesity [176]. In this context, it is important to mention that obesity affects more women than men globally, and that a high body mass index has been directly associated with CAP risk in women [177, 178]. Animal models of bacterial infection using the leptin-deficient obese mouse have also shown higher susceptibility to pneumonia [179, 180]. Finally, an "obesity paradox" in CAP has also been reported extensively, in which obesity is associated with a higher incidence of bacterial pneumonia, but increased body mass index was associated with increased survival in patients hospitalized with CAP [181].
