NIH Funding, Research Productivity, and Scientific Impact: a 20-Year Study.

Background: The Research Project Grant (R01) is the oldest grant mechanism used by the National Institutes of Health (NIH). Receiving an R01 award is often taken as a sign of scientific success. We presented normative data on multiple productivity and impact metrics for a more objective assessment of funded grants' scientific success.

Methods: All initial R01 grants awarded by NIH in the year 2000 were prospectively followed and evaluated using the numbers of publications and citations, as well as the h-indices at the grant level. We examined the variability, time trends, and relations among these metrics to better understand the funded projects' cumulative output and impact.

Results: In the 20 years since initial funding, 4451 R01 grants generated a total of 55,053 publications. These publications were cumulatively cited 3,705,553 times over 736,811 citation years. The median number of publications was 8 (25, 75 percentiles 4, 17) per grant for the entire 20-year duration. The median number of citations and the median h-index were 441 (25, 75 percentiles 156, 1061) and 7 (25, 75 percentiles 4, 13) per grant, respectively. The time courses of publication, citation, and accumulation of h-index were highly variable among the awarded grants. Although the metrics were correlated within an award, they reflected the grant's success in different domains.

Conclusion: Numbers of publications, citations, and h-indices vary greatly among funded R01 grants. When used together, these metrics provide a more complete picture of the productivity and long-term impact of a funded grant.