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The Birth-Order Gap May Begin With Germs
Danish registry data link early respiratory illness in younger siblings to later health, education and earnings differences.
Summary
Danish registry data link early respiratory illness in younger siblings to later health, education and earnings differences.
Northwestern University researchers used Danish records covering first- and second-born siblings from 1981 through 2017. Younger siblings were two to three times more likely to be hospitalized for respiratory illness in their first months, and controlling for that exposure cut the estimated later-born earnings penalty roughly in half. The analysis also linked early illness with chronic respiratory and mental-health outcomes. Registry evidence supports a biological pathway but cannot guarantee the same effect size in other health systems.
Why it matters
Danish registry data link early respiratory illness in younger siblings to later health, education and earnings differences.
Limits and context
- Registry evidence supports a biological pathway but cannot guarantee the same effect size in other health systems.
Key claims
Danish registry data link early respiratory illness in younger siblings to later health, education and earnings differences.
Qualification: Registry evidence supports a biological pathway but cannot guarantee the same effect size in other health systems.
Evidence: source-2026-07-27-013
Sources
- Northwestern University via Medical Xpress: Respiratory illness and birth orderNorthwestern University via Medical Xpress · official announcement
Corrections
No corrections have been recorded for this story.