Lewis Hamilton and Nicole Scherzinger Lewis Hamilton and Nicole Scherzinger

Nicole Scherzinger and her boyfriend, race car driver Lewis Hamilton, have called it quits after four years together, People reports.

Distance was a primary reason for the split, a source told the magazine. The X Factor judge, 33, is based in Los Angeles while Hamilton, 26, has a house in Switzerland and travels the world frequently.

Check out photos of Nicole Scherzinger

In July, Scherzinger's father was quoted as telling The Daily Mail that the couple had gotten engaged, but she quickly shot down the rumors and said he was misquoted.

Scherzinger and Hamilton met at the European Music Awards in November 2007.