As has been widely reported, there were two deaths at the Tromso Olympiad, both occurring at the end of the event. The first was Kurt Meier, a 63-year-old player from the Seychelles, who died during his final round game. The second was Alisher Anarkukov, an Uzbek player who wasn't part of the country's national team but a participant on a special team for the hearing impaired. (Why being hearing impaired counts as a disability for chess is something I don't know, but assume it has to do with the Kirsan Ilyumzhinov's longstanding and so far futile hope to have chess included in the larger Olympic movement.)
This is sadly not unheard of, and a number of famous players have died "with their boots on" over the years. Is chess a risky sport, even an "extreme" sport? Maybe so, at least as the stress levels rise for one in iffy health. (But parents of young kids, don't worry. The dangers for your children are many decades away - this isn't like boxing, football or even soccer.)