Classify the players' smiles, from none to light-up-the-locker-room. Then see how long the players lived. I haven't read the research article, and I agree that

Classify the players' smiles, from none to light-up-the-locker-room. Then see how long the players lived. I haven't read the research article, and I agree that smiling doesn't hurt, but this post surely doesn't make it sound very scientific. I wouldn't drop the "Correlation is not causation" bomb, but they seem to have missed it.