> "The overall risk to a man in his 40s or older is in the range of 2 percent, at most"
Which is much more comforting to know. I never heard any risk percentage from earlier articles I've read.
My father was 48 when I was born.
There are entire industries that depend on you not knowing the difference between these two concepts, which makes it all the more important that you actually learn it.
In the book The Emperor's New Drugs, about the efficacy of anti-depressants (or lack thereof), Kirsch gives the example that if you had a group of 500,000 people and found that smiling frequently increases life expectancy by 10 seconds on average, this may well be statistically significant because the study population is so large. However, it's not clinically significant because no one really cares if they live an extra 10 seconds, certainly not enough to change some major aspect of their behavior at least.
In this case, if the chances of having kids with autism or schizophrenia increase by/to? at most 2%, as the article states, then in practice this shouldn't really deter anyone from having kids. Thus, while the findings are statistically significant, they are not clinically significant.
Keep in mind that the overall risk of autism is 1 in 88, or 1.1%, and the overall risk of schizophrenia is about 1%. So it's not like you get a free pass if you have kids earlier. Also, there are other benefits to having a child later in life in terms of things that benefit the child, even if there are more neurodevelopment risks and disadvantages at the biological level.
It's determined entirely by perceived significance. For each type of drug, there is usually some agreed on metric within the field that determines what constitutes clinical significance. E.g. a blood pressure drug might have to lower blood pressure by 5% or 10% or whatever. And often times the metric isn't even relevant, as in the case of a reduction in blood pressure vs. a reduction in total mortality / morbidity.
However, at the end of the day what the academic community considers clinically significant doesn't really matter, it's your own preferences and values that should be your guide. Especially since in practice everyone is basically out to trick you in order to make more money, from pharma companies to newspapers to academic journals to professional organizations (AMA, APA, etc.), etc. That's why it's important to really understand this stuff forwards and backwards and to keep your wits about you.
So for non-fundamentalist women, there is fear of having a Downs child, but it gets rolled into the package of "worried about getting to have a successful pregnancy at all".
A part of that is because the risk is a lot higher for women than men.
http://www.notsuperhuman.com/2010/02/pregnancy-chronicles-wi...
"University of California-Davis researchers studied close to 5 million births during the ’90s, a decade when autism spiked in the state.
"A woman’s risk for having an autistic child rose 18% for every five years she aged.
"40-year-old women had... a 77% greater risk (of autistic child) than women who gave birth before 25."
Being a new mom at 40 increases autism risk by 77%, vs. the 2% increase in autism risk from being a new dad at 40 or older.
I am guessing, since the article you link doesn't actually link to the scientific study, that it is referring to: http://pediatricbioscience.com/publications/pdf/Pub16.pdf This did not examine any form of causality, as the currently-linked study did, nor did it evaluate the children themselves. By not controlling for evaluation mechanisms, the study you link only addresses patterns of early diagnosis and treatment. While it is interesting, the researchers themselves say that the data is hardly conclusive. The current study, on the other hand, explores not just correlation but causation, and thus is far more persuasive.
Second, you are comparing increase in risk to total overall risk. The percentage increase for men going from age 25 to 40 is 110%, not 2%. The study you link found a comparable number for women over age 40 of 0.4%.