Arch Ophthalmol. 2009;127(12):1632-1639
It is my hypothesis that the "secular trend," the increase in size and
earlier puberty occurring in children, is caused by an increase in the
percentage of individuals of higher testosterone. More specifically, I think
this is driven by an increase in the percentage of women of higher
testosterone giving birth within the population. Exposure to increased
maternal testosterone may be the cause of the parallel increase in numerous
phenomena such as diabetes, obesity, breast cancer, etc., including myopia.
Black maternal testosterone is known to be higher than white and this fact
may explain the higher incidence of morbidity in blacks as well as this
increase in myopia among blacks.
Blacks exhibit less myopia than whites. Blacks produce more testosterone
than whites. It is known that infant mortality is high in the United States
and may be increasing, relative to other countries. While this is occurring
in blacks and whites, the rate in blacks is 2.4 times that of whites (NCHS
Data Brief. 2008 Oct;(9):1-8. "Recent trends in infant mortality in the
United States.") Increased testosterone has been connected with sudden
infant death syndrome (J Pediatr. 2005 Nov;147(5):586-91). I suggest that
the percentage of "lethally" high testosterone blacks is decreasing within
the United States while the percentage of black individuals of
less-than-lethal testosterone levels is increasing. This may account for the
increased obesity, diabetes, etc. in the black population and the
coincidently increased infant mortality in the black population. It may also
explain why myopia is increasing in blacks. That is, as testosterone levels
decrease in the black population, the percentage of individuals with myopia
increases. The same pattern is occurring in whites, but the result is less
because whites exhibit less infant mortality.
(This is a clarified explanation of my earlier explanation.)
James Michael Howard
Fayetteville, Arkansas, U.S.A.
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