Apple has announced that product marketing executive Philip Schiller, rather than CEO Steve Jobs, will deliver the keynote speech at January's Macworld Conference & Expo, and revealed that the iPhone-maker will no longer exhibit at the event after next month.

The news that Jobs won't deliver the keynote will spark fears over the Apple co-founder's health, which has been a matter of concern for some Wall Street analysts, and a topic of discussion among Apple users and investors, for months.

The speculation started in June, when Jobs appeared gaunt at the company's Worldwide Developers Conference. In 2004, Jobs announced that he had had surgery to remove a cancerous tumour in his pancreas.

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However, Ezra Gottheil, an analyst with Technology Business Research, said the move was it's part of the continuity that they attempted to establish when they rolled out the MacBooks, when Jobs didn't do a solo."

During the October MacBook event, Jobs shared the stage with other senior executives, including Tim Cook, the company's chief operating officer. Over the years, Jobs has used his time on stage to unveil numerous new products, including the company's MacBook Air laptop earlier this year, and the first iPhone in January 2007.

"Clearly, Apple wants to showcase their top management, but this is an interesting time to do it, when the stock is under pressure," Gottheil said. "But I think they want to communicate that the company is a good deal more than Jobs, and that its ongoing health and prosperity is not connected to him."

It was not immediately clear what effect Apple's decision to pull out of Macworld would have on the event. Macworld has been held annually in San Francisco since 1985, and Apple has exhibited each year at the trade show. Next year's show comes just ahead of the 25th anniversary of the introduction of the first Mac in 1984.

Apple is not the only one lowering its Macworld profile. Adobe said earlier this month that it had decided not to exhibit at the Expo, although it will still have a presence at the event.