The male predominance in the incidence of infectious diseases in children: a postulated explanation for disparities in the literature.

In children, a male predominance in the incidence of symptomatic disease has been reported for some infectious agents and not for others. Not only are the factors underlying these sex differences poorly understood, but it is also not clear why the differences are described only for selected infectious diseases. In this study of sex- and age-specific incidence of infectious diseases in children, a possible explanation for the inconsistencies in the literature was explored. The sex ratio in reported disease incidence in Israel during a period of about 20 years was examined for various viral and bacterial infections. In addition, an hypothetical mathematical model was developed which assumes increased susceptibility to infectious disease (such as in relative immune deficiency) in a proportion of males. In children aged under 4 years, a higher incidence among males was consistently observed for all diseases, and the sex ratio varied between 1.16 (95% confidence interval (CI): 1.13-1.18) for shigellosis to 1.98 (95% CI: 1.79-2.17) for viral meningitis. The highest ratios were associated with the diseases which tend to present asymptomatically most often, which is consistent with the predictions of the model. The male excess in symptomatic disease appears to be present for most infectious diseases and this should be taken into account in studies comparing observed disease incidence between groups with different sex ratios. The inconsistencies in reports on the excess male morbidity for infectious diseases may be due to variations in symptomatic to asymptomatic infection ratios.