Being the leader of a country is tough.
The job requires tenacity, and strength in the face of criticism. Your decisions can affect millions of people, and that pressure can become too much for one person.
While the natural passage of time introduces wrinkles and crows-feet, the ageing process may very well be accelerated if you are the leader of a country - it's a bit stressful.
Here are some leaders pictured before they took office (left), and after (right):
1. Barack Obama, 2008-2016
2. George W Bush, 2001-2009
Under two years into his presidency, and the presidential seat is already too much for George W Bush.
3. Bill Clinton, 1993-2001
The right image - with just one year left of his presidency, Bill Clinton seems tired.
And it's not just the oval office that seems to age you quickly. Here are some of Britain's Prime Ministers, too...
4. David Cameron, 2010-2016
5. Tony Blair, 1997-2007
6. Margaret Thatcher, 1979-1990