Oprah going off the air clearly will be a major moment in television

TV Guide editor Matt Roush

Her show has consistently been the number one daytime chat show since it first appeared nationally in 1986 and it is currently aired on 280 US TV stations and is shown in more than 100 countries worldwide.

Winfrey's name has become practically synonymous with daytime television talk shows since she began her broadcasting career in Nashville, Tennessee, before taking up residence at her current base in Chicago.

Matt Roush, editor with TV Guide in the US, said it was a huge decision by the talk show host.

Winfrey was interviewed by Michael Parkinson in 2000

"Oprah going off the air clearly will be a major moment in television," he said.

"She's just so popular. She's become such an icon, whereas some of these other talk shows are more distractions."

He added Winfrey had helped pioneer the daytime talk show genre with her serious demeanour and her thoughtful way of tackling issues.

"What distinguishes Oprah is the fact that she has been able to do this sort of television without having to stoop and pander."

Appeal

Winfrey's show recently suffered a dip in ratings.

But is still well ahead of its nearest rival, Live with Regis and Kelly, the long-running ABC morning show hosted by Regis Philbin and Kelly Ripa.

Raphael has been on air for about 20 years

The power of Winfrey's appeal cannot be underestimated. Any time she nominates a novel for her book club, sales rocket.

She has also branched out into magazines and made-for-television movies.

Winfrey is also an acclaimed actress, with an Oscar nomination for her portrayal of Sofia in the Steven Spielberg drama The Color Purple in 1985.

Her most recent big screen appearance was in Beloved in 1998.

Meanwhile one of Winfrey's rivals, Sally Jessy Raphael, has announced she is to leave her talk show at the end of the current season.

The Sally Jessy Raphael Show has been on the air for about 20 years, making it the longest-running talk show now airing on daytime television in the US.

She said in a statement: "I've been proud of many of the shows we've produced over the last two decades."