SAN FRANCISCO — Apple Inc. saw its shares slip yesterday morning after the company's dramatic decision to pull out of the highly visible, annual Macworld trade show, which also raised fresh speculation about the health of Chief Executive Steve Jobs.

At the closing bell yesterday, Apple shares were down more than 6 percent at $89.16. The stock has lost half its value over the past four months.

After Tuesday's close, Apple announced that the Jan. 6 Macworld event coming up in San Francisco will be its last. The company said the event no longer met its needs and followed several moves over the past few years to reduce its reliance on trade events to showcase new products.

However, the company also renewed concerns about Jobs' health with its announcement that he'll skip his traditional keynote appearance at the upcoming event. Jobs, who was treated successfully for the pancreatic cancer in 2006, has fueled rumors and speculation since appearing gaunt at another company event earlier this year.

Oppenheimer analyst Yair Reiner downgraded Apple's stock to a market perform, or neutral, rating on the news.

"We don't know why Steve Jobs has pulled out of his annual address at Macworld. ... Maybe he's not feeling well, or maybe he just has nothing new to say," Reiner wrote in a note to clients. "Whatever the reason, the unexpected announcement has underscored the greatest risk to Apple's long-term success — its dependence on Jobs' health and its apparent lack of a succession plan."

The analyst called on the company to either disclose more information about Jobs' health or "elaborate a viable plan for eventually transferring power."

"Until such time, we can no longer continue to recommend Apple as a long-term investment," he wrote.

In Jobs' place, Apple said senior vice president Philip Schiller will give the opening keynote at the upcoming Macworld at San Francisco's Moscone Center.

Other analysts had a more positive take, citing sources who described Jobs' as healthy and noting that Apple has made past moves to pull out of trade events so it can better introduce products on its own schedule.

The Macworld show is owned and operated by media company IDC, not Apple.

"I think Apple wants to get away from the tyranny of Macworld where it is forced to introduce new products on IDG's schedule, rather than its own," wrote Charlie Wolf of Needham & Co. in a report yesterday.

He added that he had "reliable sources" who said Jobs is "cancer-free."

Keith Bachman of BMO Capital Markets said investors may conclude that Jobs is leaving the company sometime in the near term, but that he believes Jobs plans to stay with the company at least through the 2009 calendar year.

However, he also noted that the absence of Jobs on stage next month may also suggest that the company won't have any compelling new products to unveil.

"We believe that not having Mr. Jobs lead the 2009 Macworld does suggest, consistent with our note of Dec. 4, that this event will not be terribly meaningful," Bachman wrote. "Hence, the downside in the stock for a disappointing Macworld is probably realized near-term rather than at Macworld."

Apple says it has relied less on trade shows over the years. The company has lately begun introducing more products at its own events. Executives at IDG, which runs the Macworld show, told MarketWatch that the show will go on without Apple.

Gene Munster of Piper Jaffray said he didn't think the decision was related to Jobs' health. But he said the fact that Jobs is not doing the keynote suggests the actual news out of the event will be less significant.

"We're not expecting as much today as we were yesterday," Munster said in an interview. "The reality is, if they had something big to show, Steve Jobs would probably be showing it."