Rationale and Objectives
Despite rapid adoption of the Hirsch index ( h -index) as a measure of academic success, the correlations between the h -index and other metrics of productivity remain poorly understood. The aims of this study were to determine whether h -indices were associated with greater National Institutes of Health (NIH) funding success among academic radiologists.
Materials and Methods
Using the Scopus database, h -indices were calculated for a random sample of academic radiologists with the rank of professor. Using the NIH tool Research Portfolio Online Reporting Tools Expenditures and Reports, we determined the number, classification, and total years of NIH grant funding as principal investigator for each radiologist. Differences in h -index, sorted by funding status, were determined using Wilcoxon’s tests. Associations between h -index and funding status were determined using logistic regression. Significant correlations between h -index and grant metrics were determined using Spearman’s ρ.
Results
Among 210 professors of radiology, 48 (23%) secured at least one NIH grant. The mean h -index was significantly higher among individuals who secured at least one NIH grant (19.1) compared to those who did not (10.4) ( P < .0001). Professors with h -indices < 10 compared to those with h -indices > 10 were significantly less likely to receive NIH funding (odds ratio, 0.07; P = .0321). However, h -indices > 10 were not significantly predictive of greater funding. No significant relationships were observed between h -index and the number of grant awards, years of prior funding, the amounts of grant awards, or grant classification.
Conclusion
Having obtained at least one NIH grant was associated with a higher h -index, yet multiple or large grants, such as those for program projects, were not predictive of higher h -indices.
The publication of peer-reviewed journal articles remains one of the primary currencies by which one can assess productivity and success among academic physicians. A successful publication track record is essential for obtaining promotion at academic medical centers. Success can be defined by several measures, including the impact factor of the journal that publishes the work and the frequency with which peers cite the article in their own work. The Hirsch index ( h -index) is a relatively novel metric of academic productivity that incorporates both number of publications as well as number of citations into a single value . Briefly, the h -index equals the number of publications with at least n citations. The h -index is rapidly gaining favor as a means to assess the academic and scientific success of physicians and scientists, because it monitors the perceived importance of the authors’ work through citation frequency rather than the importance of the journal as a whole .
Despite extensive interest in the h -index, efforts to establish this publication measure as a metric of academic performance are incomplete. Previous work has shown that among academic radiologists, the h -index was positively correlated with academic rank , yet the relationship between the h -index and the propensity to secure research funding at academic radiology centers remains unclear. We focused this study on academic radiologists who had attained the rank of professor, because they represent the most experienced form of academic radiologist and thus are most likely to have contributed to the medical and scientific literature and to have sought research funding support. In the present study, we sought to determine if National Institutes of Health (NIH) grant funding status, including the type of awarded grant and the number of awarded grants, was correlated with the h -index among professors of radiology.
Materials and methods
Data Selection
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NIH Funding Data
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h -index Determination
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Statistical Analysis
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Results
Study Population
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Grant Data
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Table 1
h -Indices and Funding Characteristics of Radiology Professors
Variable NIH Funding ( n = 48 [23%]) No NIH Funding ( n = 162 [77%])h -index Mean ± SD 19.1 ± 12.6 10.4 ± 9.0 Median (IQR) 19.5 (9–28.5) 7.5 (4–16) Number of grant awards Mean ± SD 3.1 ± 4.0 Median (IQR) 2 (1–3) Duration of funding (y) Mean ± SD 6.9 ± 6.4 Median (IQR) 5 (2–9.5) Sum of grant awards Mean ± SD $6,689,727 ± $12,836,102 Median (IQR) $2,253,190 ($632,951–$6,154,095) Breakdown of NIH grants R01 49 R21 11 M01 11 S 15 P 27 Other 35
IQR, interquartile range; M, General Clinical Research Centers program grants; NIH, National Institutes of Health; P, program project/center grants; R01, NIH Research Project Grant Program grants; R21, NIH Exploratory/Developmental Research Grant Award grants; S, instrumentation grants; SD, standard deviation.
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h -index Data
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Relationship Between h -index and NIH Funding
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Table 2
Relationship Between Grant Identify and h -Index
NIH Grant Type Median h -Index (IQR) M 19 (7–28) P 16.4 (7.5–27.5) R 21.5 (11–34) R01 22.0 (10.5–31.5) S 12.5 (4.25–18.25) Other 17 (1–21.5)
IQR, interquartile range; M, General Clinical Research Centers program grants; NIH, National Institutes of Health; P, program project/center grants; R, research and resource grants; R01, NIH Research Project Grant Program grants; S, instrumentation grants.
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Discussion
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Conclusions
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