With more than half of the world’s population currently living in cities, there is a need to understand how city-level factors, such as city size, can influence health in cities. However, there are numerous ways to define and delineate city boundaries. We explored whether years of life lost (YLL), a measure of premature mortality, scales with population size in the United States (US) from 2010 to 2015 and examined whether these scaling patterns vary by city definition, using eight different definitions. Across all city definitions, YLL displayed a sublinear scaling behavior: larger cities...