Unhooking the past: Early-life exposure to hookworm eradication and later-life longevity.

Early-life exposure to the RSC hookworm eradication campaign increased later-life longevity by approximately 1.3 months per one-standard-deviation increase in county-level treatment intensity.

• The study used Social Security Administration death records linked to the 1940 full-count census.
• A two-way fixed effect approach was employed to examine effects of early-life exposure.
• Exposure period examined was in-utero and early life during the campaign initiated in the 1910s.
• Treatment intensity was measured at the county level.

The longevity effects of the hookworm eradication campaign were substantially larger among nonwhites, children of illiterate mothers, and those born in urban areas.

• These subgroup analyses suggest heterogeneous treatment effects by race, maternal literacy, and urbanicity.
• Nonwhites showed substantially larger effects compared to the overall average of 1.3 months.
• Children of illiterate mothers represented a particularly vulnerable subgroup with larger effects.
• Urban-born individuals experienced larger effects than the overall sample.

Dynamic complementarity was observed in the effects of hookworm eradication on longevity, with larger effects in counties exposed to the Rosenwald school construction movement.

• Counties exposed to the Rosenwald school construction movement showed larger longevity effects from hookworm eradication.
• States with more stringent child labor laws also showed larger effects.
• This pattern of dynamic complementarity suggests that the health intervention's effects were amplified by complementary educational and labor policies.
• The findings indicate interactions between public health, educational infrastructure, and labor market regulations.

Improvements in educational attainment, income, and cognitive ability were identified as possible pathways through which hookworm eradication affected longevity.

• Evidence for these pathways was drawn from the 1940 census and World War II enlistment data.
• The authors describe this pathway evidence as 'suggestive.'
• Three distinct pathway mechanisms were examined: educational attainment, income, and cognitive ability.
• World War II enlistment data provided the cognitive ability measures.

The Rockefeller Sanitary Commission's hookworm eradication campaign was initiated in the American South in the 1910s and serves as the natural experiment for this study.

• The RSC campaign targeted hookworm infection, which was prevalent in the American South.
• The campaign's geographic and temporal variation provided the basis for a quasi-experimental design.
• County-level variation in treatment intensity was used as the key independent variable.
• The study links this historical intervention to long-run outcomes observable in mid-20th century administrative records.