A Possible, Single Explanation of the Increase and Flattening or Decreasing of Asthma

Copyright 2005, James Michael Howard, Fayetteville, Arkansas, U.S.A.

This is my response to the following editorial which appeared in the British Medical Journal.

British Medical Journal 2005; 330: 1037-1038 Editorial by Dr. H Ross Anderson:

“Prevalence of asthma s no longer increasing in some countries, but the reasons for this are unclear.

A broad consensus exists that in most Western countries the prevalence of asthma increased over the last four decades of the 20th century. This is based largely on repeat studies of school age children. Evidence is emerging that in recent years this trend has flattened or fallen in some countries. For example, as part of the UK arm of the international study of asthma and allergies in childhood (ISAAC), repeat studies found that self reported symptoms of asthma in 13-14 year old children had fallen by about 20% in the United Kingdom between 1995 and 2002. This trend was also observed in the health survey for England between 1996 and 2001. Over the same period a similar fall in symptoms of asthma in 6-7 year old children reported by parents was seen in Melbourne. On the other hand, the only available repeat survey of preschool children noted a major increase in prevalence between 1990 and 1998. A global picture of recent trends in children will soon be provided by the results of ISAAC phase 3, which has obtained trends in prevalence between 1995 and 2002 in more than 100 centres in 58 countries. Little information exists about long term trends in adults, but recent trends in the UK seem to be flat.

These data are limited by the lack of an objective measure of asthma in large populations and the reliance on surveys to elicit symptoms of wheezy breathlessness, which are likely to represent a heterogeneous group of disorders. Questions about lifetime prevalence are subject to serious recall bias, and the usual compromise is to rely on the 12 month period of prevalence in an attempt to capture the intermittent nature of symptoms experienced by most people with asthma, while limiting the recall entailed and avoiding problems with labelling. Trends in the cultural perception and naming of symptoms might explain the trends observed in prevalence studies, and while it remains true that without objective measures we cannot be certain how much is real and how much is artefact it seems unlikely that artefact would completely explain the observed trends.

Any single explanation would need to account for both the rise and fall of the prevalence of asthma.”

A Possible, Single Explanation of the Increase and Flattening or Decreasing of Asthma

It is my hypothesis that testosterone is involved in asthma.  Blacks exhibit more asthma than whites.  The testosterone effect may result from exposure to increased testosterone in utero, black women produce more testosterone than white women, or simply increased testosterone in blacks, black men and women produce more testosterone than white men and women.  This may be due to a combination of exposure in utero and increased testosterone at puberty.  (Please see http://anthropogeny.com/T%20DHEA%20Asthma.htm for more detail.)

It is my hypothesis that the "secular trend," the increase in size and earlier puberty in children is actually caused by an increased percentage of individuals of higher testosterone within the population with time.  This effect is probably driven by increased reproduction of women of higher testosterone; hence, this increases exposure of fetuses to higher testosterone.  With time, these individuals increase in percentage within a population.  Therefore, if testosterone is involved in asthma, asthma will increase with time, also, within a population.  (Some say the trend is due to increased calories; increased calories only accelerates reproduction, not cause the trend.)

Ironically, as testosterone increases to levels that are too high, the testosterone may actually reduce reproduction rates.  That is, too high levels of testosterone reduces sperm count and fertility in women.  (Please see http://anthropogeny.com/birth%20rate%20secular%20trend.htm for more detail.)  It is also my hypothesis that the current decrease in reproduction rates of certain groups in the United States is due to this process. The reason that the asthma prevalence may be leveling or decreasing is that the parents who produce children with asthma are not reproducing as rapidly as in the past or may be declining in reproduction.

These two hypotheses, based on the same single mechanism, may explain why asthma rates have increased but now show a decline in some countries.