Steve Jobs takes six months' sick leave

Apple has confirmed that chief executive Steve Jobs will step down from his post while recuperating from a hormone imbalance. His absence will stretch until the end of June.

Tim Cook, Apple's chief operating officer, will run the company during Jobs's absence, according an email Jobs sent to Apple employees that was released to the media.

Jobs wrote in the email: "Unfortunately, the curiosity over my personal health continues to be a distraction not only for me and my family but everyone else at Apple as well. In addition, during the past week, I have learned that my health-related issues are more complex than I originally thought.

"In order to take myself out of the limelight and focus on my health, and to allow everyone at Apple to focus on delivering extraordinary products, I have decided to take a medical leave of absence until the end of June."

Trading in Apple's stock was halted following the announcement but resumed later, falling more than 8 per cent, as investors digested the news.

Jobs, 53, has been the subject of heated speculation regarding his health since last June's Worldwide Developers Conference, when he appeared to have lost a great deal of weight. At the time, Apple insisted that Jobs's health was a private matter, but revealed in early January that Jobs was suffering from a hormone imbalance that impeded his body's ability to absorb certain proteins.

In August 2004, Jobs underwent successful surgery to treat a rare form of pancreatic cancer, which sidelined him until September of that year. Much of the speculation over the past year has been over whether that cancer has returned -- that was not made clear in the email written on Wednesday by Jobs, an intensely private man.

Since his return to Apple in 1997, the mercurial founder has resurrected Apple from the depths, reviving the Mac, changing the music industry with the introduction of the iPod and iTunes, and turning the mobile-phone industry on its head with the 2007 introduction of the iPhone. He is considered to be one of the most influential executives in the technology industry, if not in US business itself; Barron's Magazine in the US once estimated that Apple would lose between $16bn and $20bn in market capitalisation on the day Jobs decides to leave Apple for good.

Apple has been criticised over the past few years for seeming to lack a succession plan for Jobs, whom some feel can never truly be replaced. But it has never been clear whether the company is just playing its cards close to its chest regarding that plan.

Cook has been regarded as the short-term solution for a long time, having run the company during Jobs's absence in 2004. He is respected as a detail-orientated manager who can keep the ship on course.

The long-term plan is what will have investors and the media talking for the rest of the year, however. Apple has used Jobs as its chief spokesman and leading figure ever since his return to the company, and few people associate Apple with anyone other than Jobs.

Over the past few months, the company has started familiarising the public with other executives, such as Mac hardware chief Bob Mansfield, design guru Jony Ive, and iPhone software head Scott Forstall. In a move that had many wondering if Jobs was suffering from ill health, the company had Phil Schiller, senior vice president of marketing, give the keynote speech at this year's Macworld Expo, a role usually taken by Jobs, to introduce new products such as the iPhone and the MacBook Air.

Jobs said in the email that he plans "to remain involved in major strategic decisions" while on his leave of absence, which implies that he'll still be playing his usual role to some degree, green-lighting some future projects and scuttling others. But that also implies he will not be negotiating on Apple's behalf during that time, and probably won't make an appearance at Apple's June Worldwide Developers Conference or any other events the company holds in the interim.