The NIH director on why Americans aren't getting healthier, despite medical advances

It's Dr. Francis Collins' last few weeks as director of the National Institutes of Health after 12 years, serving under three presidents.

Collins made his name doing the kind of biomedical research NIH is famous for, especially running The Human Genome Project, which fully sequenced the human genetic code. The focus on biomedicine and cures has helped him grow the agency's budget to over $40 billion a year and win allies in both political parties.

Still, in a broad sense, Americans' health hasn't improved much in those 12 years, especially compared with...