The financial health of the large number of US leveraged buy-outs is deteriorating more than other parts of the debt market as the economy slows and the credit markets remain shut to debt-laden companies, Fitch Ratings says in a study to be released on Thursday.

Weak performance is already hurting loan-financed LBOs done in the boom years of 2004 to 2007, when investors from hedge funds to structured finance vehicles flocked to higher-yielding parts of the debt markets.