My H-index

It’s a silly number, perhaps, but I tried to calculate my H-index today. The H-index lists your publications in order from the most cited to the least cited and then finds the value where rank order equals the number of citations. My h-index is 24 which means that I have 24 papers that have been cited 24 or more times. Confused? Here’s a better explanation from Wikipedia. Anyway, I used Research Gate to get an approximation to this (I’m not sure if Research Gate has an accurate citation count).

Looking over the list of publications in order of citation, I see that I have had the opportunity to work with a lot of very good researchers. I do not show the authors in the list, but the top two articles were written by Andrea Gaedijk, a genetics researcher at Children’s Mercy Hospital. A large number of the articles were secondary data analyses that Vidya Sharma, also of Children’s Mercy Hospital, had taken the lead on (though in her unassuming ways, she often let someone else be the lead author). Another source of articles with a high number of citations was my work on male reproductive toxicology, mostly with Steve Schrader at the National Institute of Occupational Safety and Health.

Okay, here’s the list of publications in order of citation.

1. The CYP2D6 Activity Score: Translating Genotype Information into a Qualitative Measure of Phenotype. Cited in 213 publications.

2. Optimization of cytochrome P4502D6 (CYP2D6) phenotype assignment using a genotyping algorithm based on allele frequency data. Cited in 121 publications.

3. Vagal nerve stimulation in refractory epilepsy: the first 100 patients receiving vagal nerve stimulation at a pediatric epilepsy center. Arch Pediatr Adolesc Med 157: 560-564. Cited in 95 publications.

4. High incidence of focal segmental glomerulosclerosis in nephrotic syndrome of childhood. Cited in 91 publications.

5. Resource Utilization and Expenditures for Overweight and Obese Children. Cited in 85 publications.

6. Effect of rapid diagnosis of influenza virus type A on the emergency department management of febrile infants and toddlers. Cited in 70 publications.

7. Adverse effects of systemic glucocorticosteroid therapy in infants with hemangiomas. Cited in 69 publications.

8. Atopic dermatitis in children in the United States, 1997-2004: Visit trends, patient and provider characteristics, and prescribing patterns. Cited in 59 publications.

9. Low Levels of Tissue Inhibitors of Metalloproteinases With a High Matrix Metalloproteinase-9/Tissue Inhibitor of Metalloproteinase-1 Ratio Are Present in Tracheal Aspirate Fluids of Infants Who Develop Chronic Lung Disease. Cited in 56 publications.

10. Abanses JC, Dowd MD, Simon SD, et al. Impact of rapid influenza testing at triage on management of febrile infants and young children. Cited in 55 publications.

11. Factors Influencing Infant Visits to Emergency Departments. Cited in 52 publications.

12. Normal urinary calcium/creatinine ratios in African-American and Caucasian children. Cited in 44 publications.

13. A breast-feeding assessment score to evaluate the risk for cessation of breast-feeding by 7-10 days of age. Cited in 42 publications.

14. Quality of Care for Common Pediatric Respiratory Illnesses in United States Emergency Departments: Analysis of 2005 National Hospital Ambulatory Medical Care Survey Data. Cited in 42 publications.

15. X chromosome gene expression in human tissues: Male and female comparisons. Cited in 41 publications.

16. Timing of follow-up voiding cystourethrogram in children with primary vesicoureteral reflux: Development and application of a clinical algorithm. Cited in 41 publications.

17. Semen analysis of military personnel associated with military duty assignments. Cited in 32 publications.

18. Longitudinal study of semen quality of unexposed workers. I. Study overview. Cited in 32 publications.

19. Tracking Trichophyton tonsurans through a large urban child care center: Defining infection prevalence and transmission patterns by molecular strain typing. Cited in 28 publications.

20. Transitioning Preterm Infants With Nasogastric Tube Supplementation: Increased Likelihood of Breastfeeding. Cited in 28 publications.

21. A time to be promoted. The Prospective Study of Promotion in Academia (Prospective Study of Promotion in Academia). Cited in 26 publications.

22. A Four-Site Study of Stress, Strain, and Coping for Inpatient Registered Nurses. Cited in 26 publications.

23. Interindividual variability in acetaminophen sulfation by human fetal liver: Implications for pharmacogenetic investigations of drug-induced birth defects. Cited in 25 publications.

24. Double probing of human spermatozoa for persistent histones, surplus cytoplasm, apoptosis and DNA fragmentation. Cited in 24 publications.

25. Comparison of the Burkard and Allergenco MK-3 volumetric collectors. ??? Cited in 24 publications.

26. Semen quality and hormone levels among radiofrequency heater operators. Cited in 23 publications.

27. Measuring Male Reproductive Hormones for Occupational Field Studies. Cited in 23 publications.

28. Influence of the News Media on Diagnostic Testing in the Emergency Department. Cited in 21 publications.

29. Duration of breast-feeding patterns established in the hospital: Influencing factors. Results from a national survey. Cited in 21 publications.

30. Comparison of two formulae for estimation of glomerular filtration rate in children. Cited in 20 publications.

31. Predicting accrual in clinical trials with Bayesian posterior predictive distributions. Cited in 19 publications.

32. Reproductive function in relation to duty assignments among military personnel. Cited in 19 publications.

33. Longitudinal study of semen quality of unexposed workers. Sperm motility characteristics. Cited in 19 publications.

I won’t list the articles beyond here. I have around a hundred publications. Needless to say, many of my publications have very few citations.

If you look at the 23rd article in the list, that was cited 25 times. The 24th article was cited 24 times and the 25th article was also cited 24 times. So my H-index is 24.

Is 24 a good number? Well, first you have to ask yourself whether the H-index is a valid measure of research productivity. It has good face validity. If you have only one or two articles that are cited a lot, you won’t score high and if you have a lot of articles, none of which a cited a lot, you won’t score well. You need to have some consistency–the ability to produce a large number of highly cited articles. Given that many research articles are rarely read, much less cited (see this Smithsonian article for real data on this), an index of 24 sounds pretty good.

Quoting from the Wikipedia article mentioned earlier, “The London School of Economics found that (full) professors in the social sciences had average h-indices ranging from 2.8 (in law), through 3.4 (in political science), 3.7 (in sociology), 6.5 (in geography) and 7.6 (in economics).” No statisticians in that group, but I’m well above the average of a bunch of other disciplines. On the other hand, the article also states that “Among 36 new inductees in the National Academy of Sciences in biological and biomedical sciences in 2005, the median h-index was 57.” So I have a ways to go.

Also worth noting is that in none of the articles among the top 24 most cited articles was I the first author. I sincerely disagree with people who make distinctions between among author order, as this is biased against the Statistics discipline as a whole, but there are too many of them to argue with.

So, for the record, the best publications I have where I am the first author is “Benchmarking numerical accuracy of statistical algorithms” which was cited 15 times, “Is the randomized clinical trial the gold standard of research?” also cited 15 times, and “Understanding the odds ratio and the relative risk” also cited 15 times. The remaining first author articles were cited 14,10, 8, 5, 1, and 1 times.

So my H-index looking only at first author publications is 6. Note that one of the articles cited only once was actually cited just by another one of my publications. Obviously, I need to do more self-citations! Seriously, though, an H-index of 6 for first author publications is not too bad.

As a statistician, you would think that I’d be more careful than to spend a morning calculating a number that has limited validity. But be sure to read all of the criticisms of the H-index (and citation indices in general) mentioned in the Wikipedia article.

Still, I’m convinced that I deserve a huge raise on the basis of my H-index. Now I just have to figure out a way to get my boss to read this blog post.

You can find an earlier version of this page on my blog.