It is my hypothesis that testosterone is increasing in our population and that this increase is the cause of the "secular trend," the increase in size and earlier puberty in our children. Therefore, as the continuum progresses, phenomena will increase if caused by increased testosterone, and possibly decrease if other phenomena are increased which counteract the earlier phenomena. This sounds really contradictory but it may explain the earlier increase in childhood ear infections and the current decline.

Testosterone decreases the immune system. Blacks produce more testosterone than whites and blacks exhibit more infections, bacterial and viral, than whites. Therefore, based on the explanation in the paragraph above, ear infections should increase.

As testosterone levels increase, I suggest this produces earlier changes in the growth of the head which might increase development of the eustachian tubes. It is known that the incidence of childhood ear infections decline upon achievement of a certain level of development in young children, that is, the eustachian tubes reach a level of growth which allows drainage of the ear and this reduces infections.

It is known that black children, at 2-3 years, exhibit increased head circumference growth compared to White and Asian children in a study of growth after birth (Paediatr Perinat Epidemiol. 2000 Jan;14(1):4-13). Head circumference growth may include development of the eustachian tubes. Therefore, one might predict that Black children will exhibit fewer ear infections than whites; this is the case (Laryngoscope. 2010 Aug;120(8):1667-70).

Now, I suggest that, as the increase in testosterone progresses, the increase in ear infections as a result of the adverse effect of testosterone of the past are counteracted by the increase in growth of the eustachian tubes. This may explain why the incidence of ear is currently decreasing. I suggest this may explain the current decrease in childhood ear infections as secular trend has been ongoing for a much longer time than the current decline in smoking, which has been advanced as the reason for the decline.