I found a related article on New York Times but not a exact research paper. 
<a href="http:&#x2F;&#x2F;www.nytimes.com&#x2F;2007&#x2F;01&#x2F;03&#x2F;health&#x2F;03aging.html?pagewanted=all" rel="nofollow">http:&#x2F;&#x2F;www.nytimes.com&#x2F;2007&#x2F;01&#x2F;03&#x2F;health&#x2F;03aging.html?pagewa...</a>