Idanna Appio spent 15 years at the Federal Reserve Bank of New York analysing the history of sovereign debt crises. Now, as a fund manager at the $138 billion First Eagle Investments, she’s reached a conclusion: US Treasury bonds are too risky to hold.The call looks far beyond the timing of much-anticipated Federal Reserve rate cuts. It’s tied to a new era of faster inflation, higher government health spending and bigger deficits. And behind all of that? The fact that the world is getting older,...