GRENOBLE, France (AFP) - French doctors have started trying to bring Formula One legend Michael Schumacher out of his month-long induced coma, his spokesman said on Thursday.

The drugs used to keep Schumacher, 45, unconscious have begun to be reduced, though it may be some time yet before he comes to, the spokesman, Sabine Kehm, said in a statement.

"Michael's sedation is being reduced in order to allow the start of the waking up process which may take long time," the statement said.

"For the protection of the family, it was originally agreed by the interested parties to communicate this information only once this process was consolidated. Please note that no further updates will be given."

The spokeswoman asked the media to respect the privacy of Schumacher's family and to not disturb the doctors treating him.

Schumacher has been kept in intensive care in a hospital in the central Grenoble University Hospital, where he underwent surgery following a December 29 ski accident. He smashed his head against a rock in the French Alps, splitting the helmet he was wearing and causing critical head injuries.

Surgeons said he suffered bleeding and bruising in his brain and a scan showed "widespread lesions". It was unknown in what state he would be if the waking process is successful.

Experts said it was rare to keep a patient in an artificial coma for more than three weeks. In accidents of a similar severity, patients often had a disability after their emergence from coma, the experts noted.

Schumacher dominated Formula One for much of his racing career before his retirement in 2012. He won the F1 title seven times, more than any other driver, and notched up 91 victories between 1994 and 2004.