He was only 37.

Scottish Cycling confirmed the news on Tuesday ... Wardell died in his sleep two days after winning the championship race on Sunday in Dumfries and Galloway.

Wardell's partner, Olympic cycling medalist Katie Archibald, says she was lying in bed with him when it happened ... and she tried to save his life.

"I still don't understand what's happened; if this is real; why he'd be taken now? So healthy and happy," Archibald said on her Twitter page.

"He went into cardiac arrest while we were lying in bed. I tried and tried, and the paramedic arrived within minutes, but his heart stopped and they couldn't bring him back. Mine stopped with it."

Archibald says she is devastated over Wardell's death and the pain she's suffering is indescribable.

"I love him so much and need him here with me. I need him here so badly, but he's gone."

Wardell -- who started cycling in his teens -- made his last appearance on BBC Scotland's The Nine show on Monday, describing how he was able to win the race after three punctures.

"I guess I still felt confident that I'd be able to catch the leaders and win," Wardell said, "so I just gave it my best shot. What more can you do?"