Aging in Office

<b>Barack Obama</b> Is the 44th and current President of the United States. (Getty/AP)

<b>George W. Bush</b> Served as the 43rd President of the United States, from 2001 to 2009. (AP)

<b>Bill Clinton</b> Served as the 42nd President of the United States from 1993 to 2001. (AP)

<b>George H. W. Bush</b> Served as the 41st President of the United States, from 1989 to 1993.  (AP)