Swedish Parental Birth Age Study: shows sensitivity to confounding factors

Read an interesting study this morning on various psychological and academic outcomes based on age of Dad at birth.  http://www.wrrh308.com/wp-content/uploads/2014/03/JAMA-Study.pdf

It’s interesting to see how much the conclusion can change based on the factors that the researchers take into account.  For example, a kid is half as likely to fail a grade if born to a Dad older than 45.  But, once you take into account a variety of factors like parental income and more, the likelihood returned to 1 (same as overall population).  If you go further, and take into account siblings to try to control for all the genetic/environmental factors, then the kid is now 50% more likely to fail a grade.  Note – it’s not clear to me how they took into account birth order for the last, although they seem to have done something with first-cousins of similar birth order.

In other words, the world is complex and there are many factors that affect us.  It’s hard to isolate them, and our conclusions are sensitive to how we take into account the various possible factors. 

However, while it’s difficult to make any conclusions about causality without a controlled study, this study did seem to have a robust and relatively large dataset, approach the problem from multiple directions, and explain what they could not conclude.  This is much, much better than several other studies I’ve read recently which were also based on observed data and were trying to answer questions about causality.

And, from the content, it seems that (for these particular outcomes) it’s better to have a older Dad who generally has his life together (income, maturity, etc) than a younger Dad who doesn’t.  But, a younger Dad who is responsible and stable is perhaps the best of all.  Surprise?

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