His death was announced by the Cesena hospital on Monday afternoon, with doctors explaining that Hayden had suffered “a serious polytrauma” following the accident.The hospital's statement read: “The medical team has verified the death of the patient Nicholas Patrick Hayden, who has been undergoing care since last Wednesday 17 May in the intensive care unit of the Bufalini Hospital in Cesena following a very serious polytrauma which occurred the same day.” Hayden upset the odds to claim the 2006 Moto GP championship in one of the most entertaining seasons in recent memory, edging Valentino Rossi to the title to end the Italian's five-year streak of wins After news of Hayden's accident broke last week, Rossi paid tribute to his competitor and described him as “one of the best friends I've ever had in the paddock”.Dani Pedrosa, Hayden's team-mate in 2006 when he won the world title, posted a photo of the American on his Twitter account, writing: "Always in my heart, champ. #69." The 2006 victory would be Hayden's only championship, but 'The Kentucky Kid' remained in Moto GP until 2015.The following year, he switched to the World Superbike Championship and finished fifth in the overall standings, winning that year's race in Malaysia.
Members of the rider's family, including his mother Rose and brother Tommy, had flown out from the United States to be beside him during his time in hospital.
Hayden held 13th place in the current season's standings following last Sunday's race at Imola.
There were two reasons why the death of Nicky Hayden hurt so much.
The 35-year-old American was hit by a car while training south of the Italian seaside resort of Rimini on Wednesday and was rushed to hospital with severe chest and head injuries.
"Nicky Hayden's clinical condition remains extremely critical," said a statement from the Maurizio Bufalini Hospital in Cesena.