(Reuters) - Bernard J. Tyson, chairman and chief executive officer of not-for-profit health insurer Kaiser Permanente, died unexpectedly in his sleep on Sunday, aged 60, the company said in a statement.

Tyson, who held the top job since 2013, was Oakland, California-based Kaiser Permanentes first black chief executive and a strong proponent for affordable and accessible healthcare.

The company did not give a cause of death. A company spokesperson did not immediately respond to a request for comment.

A day earlier on Saturday, the San Francisco native took to Twitter to post about high-tech and high-touch healthcare.

Tyson was described by colleagues in a company statement as an outstanding leader, visionary and champion for high-quality, affordable health care for all Americans.