Infant mortality and diminished entelechy in three European countries

Individual-level research reports that adverse environmental conditions during infancy increase the risk of mortality later in life. Extending this model to populations implies what we call the "diminished entelechy" hypothesis in which birth cohorts subjected to virulent environmental insults early in life experience increased mortality at older ages and do not realize their otherwise expected lifespan. Controversy remains as to whether the individual-level findings generalize to populations. We test the "diminished entelechy" hypothesis by measuring the association between infant mortality and life expectancy at age one for males and females born in Sweden (1751-1912), Denmark (1835-1913), and England and Wales (1841-1912). Time-series methods control for trends and other forms of autocorrelation that could confound the associations. Results support diminished entelechy in Sweden and England and Wales, but not in Denmark, in that environmental insults during infancy appear associated with reduced cohort lifespan. We then explored when in the life course the sequelae of infancy appear most salient. We examined cohort associations between infant mortality and mortality during childhood (1-4 years), youth (5-19 years), adulthood (20-54 years), and old-age (55-79 years). We generally find that infant cohort effects appear to "program" the mortality experience in youth, but not in adulthood or old-age. These findings conflict with the notion that improved conditions during infancy shaped the historical decline of old-age mortality.