Human life expectancy and season of birth in Taiwan: A retrospective cohort study

Prior research has indicated a correlation between the birth season and life expectancy; however, many of these studies did not sufficiently account for comorbidities. In this comprehensive investigation, we aimed to meticulously explore the association between the birth month and life expectancy, giving due consideration to comorbidities. We used a robust dataset derived from Taiwan's National Health Insurance Research Database (2000-2013), which allowed us to conduct a thorough examination. We divided our participants into four groups based on their season of birth: spring, summer, autumn, and winter. Propensity score matching was used to ensure an equitable distribution of demographic and clinical characteristics across the groups. Propensity scores were computed using logistic regression. Our model incorporated a broad range of demographic factors and comorbidities, providing rigorous adjustment for potential confounders. Our findings revealed a significantly increased risk of all-cause mortality among individuals born in spring, even after stringent adjustment for demographic factors and comorbidities. People born in spring demonstrated a 1.05-fold increase in the risk of all-cause mortality, with a hazard ratio of 1.05 and a 95% confidence interval of 1.01-1.09. Our study provides compelling evidence that helps understand the potential long-term impacts of a person's birth season, which acts as a proxy for pregnancy / early-life environmental exposure, on life expectancy. These findings underscore the crucial need for additional research to illuminate the underlying biological and environmental mechanisms linking the birth season and lifespan of a person. The elucidation of these links could guide the development of innovative health promotion and disease prevention strategies that are tailored to an individual's birth season.