Ashlee Simpson's Collapse Due To Exhaustion

Singer back in U.S. with her family.

After being hospitalized in Japan over the weekend, Ashlee Simpson is back in the U.S. with her family. The official reason for her collapse? Exhaustion, according to her rep.

The singer was slated to headline MTV Japan's fifth annual Cool Christmas concert on Friday in Yokohama, Japan. Simpson took the Pacifico Yokohama stage after three local acts — Kumi Koda, Ayaka, and Melody — and started singing, but left the stage after one and a half songs into her five-song set. She later came back to apologize, saying that she was losing her voice (see "Ashlee Simpson Collapses In Japan").

Cutting her performance short and ending the show, according to an MTV Japan programming manager, was a collective decision made by Simpson, her staff and the channel. Despite Simpson not finishing her set, the Cool Christmas concert (which was not broadcast live) will air December 23 at 9 p.m. in Japan.

While earlier reports had Simpson collapsing in the elevator at the channel's offices, the singer actually left the venue of the event — which is about 30 minutes away from MTV Japan's offices in Tokyo's Roppongi nightlife district — prior to her collapse. According to eyewitnesses, she then went back to her hotel before she was taken to the hospital, around midnight local time. She left the hospital Saturday morning around 4 a.m.

Bo Bice was picked to replace Simpson during her scheduled appearance Monday (December 19) at the Radio Music Awards in Las Vegas, but he has since fallen ill as well (see "Bo Bice Rushed To Hospital, Won't Be Able To Fill In For Ashlee"). The Goo Goo Dolls will now perform in Ashlee's slot, according to NBC.