NEW YORK (Reuters) - Consumer sentiment tumbled to a nine-month low in April, with Americans especially gloomy about the long-term health of the economy, a survey released on Friday showed. The Thomson Reuters/University of Michigan's preliminary reading on the overall index of consumer sentiment fell to 72.3 in April, a level last seen in July, 2012, and below economists' forecasts of 78.5. The index stood at 78.6 last month. The barometer of current economic conditions fell to 84.8 this month from 90.7, while the gauge of consumer expectations hit 64.2, down from 70.8. ...