Apple CEO Jobs fought pancreatic cancer four years ago, and has appeared increasingly gaunt at Apple events this year.
Apple has not commented on the decision by Jobs not to present a keynote at January's Macworld Expo, which is his traditional opportunity to present the company's latest products.
Phillip Schiller, Apple's senior vice-president of worldwide product marketing, will take Jobs' place at the event.
Apple told the BBC that shows like Macworld "were no longer relevant" for the company, and that it was reaching its current and potential customers through its expanding store network and through webcasts.
That won't read very well for the loyal Macworld show exhibitors.
IT publisher IDG runs the Macworld Expo event, which has been going for 25 years. Apple fans will have to wait to see whether future Macworld events take place without the participation of Apple. If they do, that might somewhat defeat the object of them.