Natalie is a scientific illiterate. Of course it’s the demographics of old people choosing to live in an oldster-convenient place, not actually people living longer just because they live in NYC. What an idiot.
Manhattan below 110th Street is one of the wealthiest areas in the United States, with a per capita income above $100,000. (The rest of NYC is a fraction of that. NYC's overall median is less than New York State's median.)
Rich people (everywhere, not just in NYC) live longer than poor people. For many of the same reasons that they are rich people, and not poor people. They make better use of the information that is widely available to them.
One can live very well in Manhattan, but it takes a lot of money! That's why most in the middle need to commute in from the suburbs.