When anyone faints in public, it becomes a matter of curiosity. When a head of state faints in public, it arouses not only curiosity, but concern. So when President Shimon Peres momentarily lost consciousness Saturday night in the course of a question and answer session following his address to the Young Presidents Organization at the Rabin Center in Tel Aviv, there was curiosity, concern and even alarm. Peres was discharged from Sheba Medical Center at Tel Hashomer at 9 a.m. on Sunday after spending about 10 hours in the hospital's heart institute, undergoing tests and sleeping. Peres regained consciousness even before falling and insisted afterward he felt fine and did not need to be taken to the hospital, but his staffers insisted, and he was taken to Sheba for overnight observation. Initial and subsequent media reports were reassuring, and quoted the president's son-in-law and personal physician Prof. Rafi Walden as saying he was perfectly all right. Tests on his brain and heart showed that the health of the 86-year-old president was absolutely normal, Sheba doctors said. The president's cardiogram, pulse rate, blood pressure and sugar levels were all satisfactory. His fainting spell was apparently caused by a sudden decline in blood pressure from a long period of standing - which can occur in young soldiers as well, they added. Walden also attributed the president's fainting spell to the intense heat in the auditorium. While this may be true, it was just as likely that he was exhausted. Peres has always been a workaholic - he works seven days a week - and he has not allowed age to slow him down. Each week his office sends out his schedule to media outlets, often adding to it from day to day as he takes on extra tasks. The schedule includes only those events that are open for media coverage. Sometimes there are as many as three or four of these in a single day. But there are numerous other events of which the media, with the notable exception of Israel Radio's Shmulik Tal, remain unaware. Tal and Peres have a close and long-standing relationship and have a daily dawn conversation, to the frustration of the president's advisers and spokespeople, who prefer to be in control of what emanates from Beit Hanassi. Peres tells Tal things that his staff would not make public. The president requires little sleep. He goes to bed after midnight, frequently after returning from an evening engagement outside Jerusalem. He rises early to read several newspapers and a chapter or two of a book, performs his daily workout, has breakfast and starts with the business of the day at 8 a.m. and sometimes even earlier. He gives radio, television and print media interviews in Hebrew, English and French; meets with diplomats, politicians, brass from the security services, academics, entrepreneurs, representatives of special interest groups, et al, plus a variety of delegations from Israel and abroad. He also hosts receptions for local and foreign groups and organizations that he always addresses; hosts state receptions and dinners for visiting heads of state; and also finds time to regularly visit communities across the country, to go on state visits abroad and to attend numerous social events, where he spends long periods on his feet. When his security detail permits, he takes the stairs instead of an elevator. Peres's staff wanted to cancel everything that was on his agenda for Sunday. But he insisted on going ahead with his meeting with US special Middle East envoy George Mitchell. If it were solely up to Peres, nothing would have been canceled. Prime Minister Binyamin Netanyahu said he had spoken to Peres, who assured him he was well. "He sounded as excellent as always. Of course, it is impossible to stop Shimon," Netanyahu said at the start of Sunday's weekly cabinet meeting. "He spoke with me about what he plans to tell envoy Mitchell. I told him that aside from meeting Mitchell he should rest a bit, because I believe that every Israeli is genuinely concerned for our president." French President Nicolas Sarkozy also dispatched a letter to Peres saying how pleased he was to learn that he had recovered from the brief medical scare. Egyptian President Hosni Mubarak also called to wish him well. Peres's political career has spanned seven decades. He was a senior aide to the country's first prime minister, David Ben-Gurion, developed Israel's nuclear program, built up the military in the 1950s and has held every senior government post, including two stints as prime minister, 1984-86 and 1995-96. In 1994, he was awarded the Nobel Peace Prize for his efforts to achieve peace with the Palestinians. In 2007, he was elected to the country's ceremonial head of state. In addition to his official duties, Peres has also immersed himself in peacemaking efforts as president, traveling the world frequently as an unofficial adviser and envoy for the prime minister. Despite pleas from friends and colleagues to slow down, he maintains a grueling lifestyle. In an interview with The Associated Press upon assuming the presidency, Peres said that was the only way he knew how to work. "If you are healthy and clear-minded, what's wrong? I'm not in a hurry to pass away," he said. Judy Siegel and AP contributed to this report.