Was there a different method of counting of age at the time of events of Old Testament? (Catholic perspective) Genesis 5:6-32(RSVCE) gives an account of the generations of Adam. Prima facie,  eldest sons were born to  the forefathers when some of them had  completed or were about to complete a hundred years of age! For instance, Genesis  says:  When Seth had lived a hundred and five years, he became the father of Enosh. 
 When Enosh had lived ninety years, he became the father of Kenan. 
 When Lamech had lived a hundred and eighty-two years, he became the father of a son,  and called his name Noah. After Noah was five hundred years old, Noah became the father of Shem, Ham, and Japheth.

All that puts one is serious doubt whether there was a different method of counting of age, during the ancient times. My question is: has the Catholic Church made any studies into the system of counting of age that was prevalent at the time of events of the OT?
As far as "from a Catholic perspective", I had a similar question when going through school.  It was answered by my professor, a priest of the Basilian Order, in a two-fold manner.  He stated that, when it comes to the Old Testament, the Church is happy to allow its followers to believe it is "historically accurate" or "stories told to tell a moral Truth and lay the groundwork for the coming of Jesus Christ."  In this way, one must decide to take the numbers given as literal, or given as a moral example to their holiness.  The other point made was that in the Hebrew language, characters are both letters and numbers.  In this manner, certain numbers may be equal to certain words and the other way around.  This is something which the Western mind can have trouble grasping. An example being the Hebrew word for "having completed" or "completeness" equaling the number 40. So, when the People of Israel wandered the desert for 40 years, did they truly wander that long, or until they had completed their imposed tasks by God for their actions at Mount Sinai? I find it to be an interesting notion to contemplate! And as far as from a Catholic perspective, both are correct. This could apply to ages as well. So, did they live that long, literally? Does the longer they lived represent their being Holy and in fellowship with God? Or could these ages be numbers akin to a word, descriptive of the person to whom the age is attached, that would have been easily recognized by those using the ancient Hebrew language? Each of these could be "True" in the sense that, no matter which you use, they are morally true in the context of the Books and stories they are found and in laying groundwork for the coming of Jesus Christ. Since then, I have kept this in mind whenever examining such things as age in the Old Testament and I have made sure to put this before the minds and hearts of those I have taught or conversed with concerning this topic.