Experts say Americans’ lifespans have increased substantially since the late 1700s, with life expectancy roughly doubling since 1776. Multiple outlets attribute the gains to public health and medical advances that reduce deaths from infectious diseases. They point to improvements in sanitation and cleaner water, which lower exposure to water- and food-borne illnesses. They also cite the development and wider use of antibiotics, which help treat bacterial infections that previously caused high mortality. Vaccines are highlighted as another major factor, preventing outbreaks of diseases that historically killed large numbers of people. In addition, sources mention changes in smoking behavior over time, which has helped reduce deaths from smoking-related conditions such as heart and lung diseases. While the overall trend is described as a long-term improvement rather than a single cause, the reporting converges on the same broad set of drivers: better prevention and treatment of infectious illness, improved environmental and sanitation conditions, and reduced tobacco exposure.