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<< The prevalence of asthma is measured as a proportion; that is, existing cases of asthma divided by the total population at a point in time. This slide demonstrates the increase in asthma prevalence from 1982 to 1994. The white line indicates the U.S. population under the age of 18 affected by asthma. In 1982, roughly 4% of people younger than 18 years old had asthma. By 1994, this rate had increased to almost 7%, or approximately five million people under the age of 18. Furthermore, from 1982 through 1994, the overall annual age-adjusted prevalence rate of asthma for people younger than 18 years old increased by 72%. >>
So we're talking about going from 4% of the population to 7% from '82-'94. While technically nearly a 100% increase, this is a good example of how numbers and statistics can be easily manipulated.
<< An important accomplishment of the second half of the 20th century has been the reduction of smoking prevalence among persons aged greater than or equal to 18 years from 42.4% in 1965 to 24.7% in 1997. >>
So here we are going from ~42% to ~24.7%. A significant decrease, I'll admit, but look at the date range. '65-'97. You're comparing apples and oranges here.
You also have to look at other causes of asthma and see if those sources have gone up - for example, if more children are being exposed to high levels of air pollution, you might see a rise in the number of people with asthma even if smoking is eliminated altogether. Again, all you're "proving" is that parental smoking is not THE ONLY factor. That doesn't mean it's not a factor. It could still be a significant factor. That's why you need to use a study such as the one I outlined previously which would help to isolate all other possible variables. >>
Sorry, but now you're just denying reality to fit a preconception you have. And I submit that the ambiguous studies you have presented do the same thing.
Air pollution has decreased in the same period. I don't know about you, but I grew up before CCs and unleaded gas. I remember the LA air being so thick with smog that my lungs hurt and I couldn't catch my breath just riding my bike the mile home from grade school during the mid 70s, and that no longer happening by the time I entered highschool and rode three miles home on my ten speed. I didn't know it then, but I was having asthma-esque attacks brought on by smog, even though nothing else causes asthma attacks in me, and I've never been diagnosed with it. Everyone I knew suffered the same thing, even though most of them were not diagnosed with asthma either. I've never felt it since. Why? Because the smog of the 60s and 70s just isn't there in that concetration anymore.
Both smog and ETS have decreased, with ETS decreasing by a huge factor considering that smoking is no longer allowed in nearly all public buildings, and the rate of smoking was cut in half yet Asthma rates have nearly doubled.
With numbers going in exactly the opposite direction, I cannot believe you would even dare to suggest that it's a significant factor. I posit that smoking triggers already existing asthma that had yet to be diagnosed, and therefore it is mistakenly blamed for "causing" it.
The most viable explanation I have seen for the most signifigant causes of asthma are genetics, and a "too clean" lifestyle that was sparked by irrational fear of AIDS in the mid to late eighties when we saw the introduction of "antibacterial" everything and the abuse of antibiotics. Nothing else makes sense. Especially when you consider the environmental triggers of asthma have DECREASED and are obviously not the CAUSE.