This study finds that being born during periods with high infant mortality, reflecting poor disease environments and limited healthcare access, is linked to higher mortality rates later in life, particularly after age 70. For example, as infant mortality declined by about 58% between 1915 and 1940, this improvement is associated with a roughly six-year increase in life expectancy at age 60. The study also shows that poor early-life conditions are associated with lower education, income, and greater rates of disability, which help explain the long-term health effects.