Apple also said 2009 will be the last year it exhibits at Macworld, claiming that trade shows are now a "minor" way it reaches customers.
Analysts said Apple's withdrawal from Macworld after next year did not necessarily mean that Jobs was sick, but could indicate that the company has no blockbuster product announcements.
Instead of Jobs, Philip Schiller, the senior vice president of worldwide product marketing, will deliver the keynote.
Asked whether the move was related to Jobs' much-discussed health, Apple spokesman Steve Dowling said: "Phil is giving the keynote because this will be Apple's last year at the show, and it doesn't make sense for us to make a major investment in a trade show we'll no longer be attending."
Macworld is a cultural event that draws thousands of Apple fans and technology aficionados to San Francisco, where they have been treated to major announcements from Jobs in past years, including the launch of the iPhone in 2007. The many blogs that follow Apple's every move have been buzzing for weeks about possible product launches at this year's event.
A showman, Jobs often took to the Macworld stage amid cheers and applause from thousands of software developers, customers and employees and ended presentations by saying "One more thing..." as a prelude to something unexpected.
Pacific Crest Securities analyst Andy Hargreaves said it's not surprising that the company would pull out of the event, especially if they don't have a blockbuster product announcement. He said the company's customer base has broadened and it no longer needs a huge event to rally its fans.
"I don't think this announcement has a big impact on the company's valuation, or it shouldn't," Hargreaves said.
However, Samuel Wilson, an analyst at JMP Securities, said Jobs' absence at the event was important. "It's like the first time in a long time he hasn't spoken in Macworld. Why is he not speaking this year would be the question."
Investors have been concerned about the cancer survivor's health after he appeared thin at another product launch in June. In 2004, Jobs, 53, said he had undergone successful surgery to remove a rare type of pancreatic cancer.
In September, Jobs, who is often perceived as irreplaceable as Apple's leader, appeared thin but jaunty as he introduced new iPod digital music players.
Apple has also been hit by investor concerns about weakened consumer spending amid a struggling US economy. Goldman Sachs downgraded the company's shares earlier this week, saying it expects the company to face a tougher environment in the coming quarters.
Apple shares have lost about half their value since June.
IDG World Expo, which owns Macworld, released a statement saying it was disappointed with Apple's decision to pull out, but said "we look forward to many more successful years of Macworld to come."
Apple also said it will continue to hold product launch events.
Last year, Macworld saw the launch of the MacBook Air, the company's ultrathin portable computer. The iPhone mobile phone and iTunes music store were also both unveiled at Macworld in recent years.
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