But more people are making it to 40 and thus surviving longer, making the average age of the population higher. The two prominent changes in age come at the end

But more people are making it to 40 and thus surviving longer, making the average age of the population higher. The two prominent changes in age come at the end of the 19th century when sanitary practice was introduced into medicine, and the middle of the 20th century when antibiotics began to be used. This indirectly increases the age of members of congress. I agree with what Alex3917 says above, that it has to do with needing to win votes from more and older voters. The graphs in the second half of the article also show that incumbency has increased, because longer living voters will support the familiar name. Then there was a dip in the '70s I assume from a combined factors of many of the older members retiring at the same time there was significant cultural change happening. Also on the graph of members of the House, there's a sudden rise in age at the start of the 21st century. The Senate graph has no corresponding change. I can only make a wild guess but that would be the amount of money that can be made in the private sector is so much more now that younger people are staying away from public service.