ORIGINAL ARTICLE
Japan’s share of research output in basic medical science
Mahbubur Rahman, Junichi Sakamoto and Tsuguya Fukui1
Department of Epidemiological and Clinical Research Information Management, 1Department of General
Medicine and Clinical Epidemiology, Kyoto University Graduate School of Medicine, Kyoto, Japan(Received for publication on March 19, 2004)

Abstract. Objective: To investigate the degree of Japan’s contribution to the research in basic biomedical science in the last decade. Methods: Articles published during 1991–2000 in highly reputed
basic biomedical science journals (10 journals from each of the 16 categories related to basic biomedical science) were accessed through Medline database. The number of articles having afﬁliation with aJapanese institution was then determined using appropriate search strategies. Results: In total 312,748
articles were published in the selected journals and Japan’s share was 20,665 articles (6.6% of total)
with an upward trend over time (p F 0.01). Japan’s share was higher in the journals, which publish
mostly original articles (6.9%) than that in the journals, which publish only review articles (2.6%). The
former group showed an upward trend (p F 0.01) over time (1991–2000) while the latter did not(p F 0.08). Among the 16 categories, Japan had signiﬁcantly positive trend in 7 categories while others
remained unchanged. Conclusions: Japan’s share of original articles for basic medical science has
increased in the last decade. On the other hand, its share of review articles was low and has remained
stagnant in the same period. (Keio J Med 53 (3): 172–177, September 2004)
Key words: Medline, basic science, biomedical research, research productivity

Introduction
In a study which included only journal articles published during 1990–2000 in Medline database, we
demonstrated that Japan is the second highest research articles producer (9.4% of total) in biomedical
ﬁeld following the USA (40.8%).1 However, based onhighly reputed top 6 basic science journals, its position
slipped to 4th (3.1% of total articles) and went downheavily to 14th place for both general medicine (0.7%of total articles),2,3 and epidemiology journals (1.1% of
total),4 although remained 3–11% for other categories5–14. But up to now, little is known about Japan’scontributions to the speciﬁc basic science ﬁelds. We
conducted this investigation to determine Japan’s shareof research articles for each of the categories related tobasic medical science in the last decade and the timetrend as well in this period of time.
Materials and Methods
Institute for Scientiﬁc Information15 listed most of
the standard journals published in different countries

and grouped into some broad categories. Sorted by impact factor, ten journals from each of the categories related to basic medical science were selected based on
the following criteria: (1) the journal is available inMedline database, (2) the journal’s articles are available for at least 5 consecutive years in 1991–2000 period in the Medline database, (3) the journal publishedat least 100 articles in 1991–2000 period, and (4) thejournals publish articles only in English. Maximum
number of journals, which publish only review articles,
included per category was 6. In case, if the number
was more than that, it was omitted, and other journal,
which publishes mostly original articles, was chosen.
Only journal articles were included for the analysis, i.e.,
letter, correspondence, and news were excluded. Medline database was searched in November 2002 to elicit
the number of articles (journal-articles) originating fromJapanese Institutions and published from 1991 through2000. After that, the number of articles from Japan toeach of the journals was generated and summed up toﬁnd the Japan’s share in each category of journals.
Again its contribution was divided into two subgroups:(1) for the journals, which publish only review articles,

Reprint requests to: Dr. Mahbubur Rahman, Department of Epidemiological and Clinical Information Management, Kyoto University Graduate School of Medicine, Yoshidakonoe-cho, Sakyo-ku, Kyoto 606-8501, Japan, telephone: 81-75-752-1519, facsimile: 81-75-752-1532, e-mail:rahman@pbh.med.kyoto-u.ac.jp172Keio J Med 2004; 53 (3): 172–177
Table 1

173

Japan’s Share of Srticles in Each Category

Category**

Anatomy and Morphology
Biochemistry and Molecular Biology
Biotechnology and Applied
Microbiology
Medicinal Chemistry
Genetics and Hereditory
Immunology
Medicine, Research and Experimental
Microbiology
Neuroscience
Oncology
Parasitology*
Pathology
Pharmacology
Physiology
Toxicology
Virology

Journal articles published in 1991–2000

Japan’s share in 1991–2000

Total

Non-review Journals

Review Journals

Overall

Non-review Journals

Review Journals

7,854
14,582
12,383

7,854
11,655
10,818

-#
2,927
1565

11.9
3.8
6.0

11.9
4.3
6.5

-#
1.8
2.1

15,271
21,212
26,046
19,47633,277
15,471
36,764
10,64815,15919,15040,68014,686
29,76814,89917,30722,601
19,08230,332
12,70636,192
10,64814,883
16,92040,01414,30928,755

372
3,905
3,445
394
2,945
2,765
572
-#
276
2,230
666
377
1,013

8.6
5.6
4.9
6.4
5.6
3.9
10.7
4.5
7.4
8.8
5.8
6.8
5.5

8.7
6.3
5.3
6.5
6.0
4.0
10.8
4.5
7.5
9.6
5.9
6.9
5.4

4.0
2.5
2.6
1.5
1.5
3.4
2.6
-#
0.4
2.8
2.3
2.4
8.0

* Only 8 eligible journals were found in this category. ** Some journals are listed in more than one category. Although we included them in therespective category, when net Japanese contribution was calculated, they were counted only once. # Journals publish only review articles are
not available for these categories.
Anatomy and Morphology: Journal of Pineal research, Developmental Dynamics, Microscopy Research and Technique, Anatomy and Embryology, Anatomical Record, Journal of anatomy, Journal of Morphology, Tissue & Cell, European Journal of Morphology, and ClinicalAnatomy.
Biochemistry & Molecular Biology: Annual Review of Biochemistry, Cell, Nature Medicine, Annual Review of and Developmental Biology,
Annual review of Biophysics and Biomolecular Structures, Trends in Biochemical Sciences, Current Opinion in Genetics & Development,
Embo Journal, Current Opinion in Structural Biology, and Nature Structural Biology.
Biotechnology and Applied Microbiology: Current Opinion in Genetics & Development, Nature Biotechnology, Genome Research, Current
Opinion in Biotechnology, Gene Therapy, Human Gene Therapy, Trends in Biotechnology, Pharmacogenetics, Critical Reviews in Eukaryotic
Gene Expression, Gene Expression, and Genomics.
Genetics and Hereditory: Nature Genetics, Gene Development, Annual review of Genetics, Trends in Genetics, American Journal of Human
Genetics, Human Molecular Genetics, Genome Research, Oncogene, Human Mutations, and Gene Therapy.
Immunology: Annual review of Immunology, Advances in Immunology, Immunity, Journal of Experimental Medicine, Current Opinions in
Immunology, Immunology Today, Journal of Immunology, Immunological Reviews, AIDS, and Critical Reviews in Immunology.
Medicinal Chemistry: Natural Product Reports, Medicinal Research Reviews, Journal of Medical Chemistry, Chemical Research in Toxicology,
Anti-Cancer Drug Design, Journal of Pharmaceutical Sciences, Bioorganic and Medicinal Chemistry, Journal of Natural Products, ChemicoBiological Interactions, and Chirality.
Medicine, Experimental: Nature Medicine, Journal of Experimental Medicine, Journal of Clinical Investigation, Molecular Medicine Today,
Gene Therapy, Human Gene Therapy, Molecular Therapy, Laboratory Investigation, Journal of Molecular Medicine-JMM, and Experimental
Hematology.
Microbiology: Annual Reviews of Microbiology, Clinical Microbiology Reviews, FEMS Microbiology Reviews, Trends in Microbiology, Molecular Microbiology, Journal of Bacteriology, Journal of Clinical Microbiology, Applied and Environmental Microbiology, and Current Topics
in Microbiology and Immunology.
Neuroscience: Annual Reviews of Neurosciences, Trend in Neurosciences, Frontiers in Neuroendrocrinology, Neuron, Current Opinion in
Neurobiology, Progress in Neurobiology, Brain Pathology, Annals of Neurology, Journal of Neurosciences, and Brain.
Oncology: Journal of National Cancer Institute, Advances in Cancer Research, Cancer Research, Oncogene, Experimental Cell Research,
Seminar in Cancer Biology, Carcinogenesis, Genes Chromosomes & Cancer, Leukemia, and International Journal of Cancer.
Parasitology: International Journal of Parasitology, Molecular and Biochemical Parasitology, Parasitology and Immunology, Journal of Parasitology, Experimental Parasitolgy, Annals of Tropical Medicine and Parasitology, Parasitology Research, and Journal of Helminthology.
Pathology: Brain Pathology, American Journal of Pathology, Journal of Neuropathology and Experimental Neurology, Journal of Pathology,
American Journal of Surgical Pathology, Modern Pathology, American Journal of Clinical Pathology, Human Pathology, Neuropathology andApplied Neurobiology, and Seminar in Diagnostic Pathology.
Pharmacology: Pharmacological Reviews, Annual Reviews of Pharmacology, Trends in Pharmacological Science, Antiviral Therapy, Pharmacology and Therapeutics, Neuropsychopharmacology, Pharmacogenetics, Neuropharmacology, Journal of Pharmacology and Experimental
Therapeutics, and British Journal of Pharmacology.
Physiology: Physiology Reviews, Annual Reviews of Physiology, Journal of General Physiology, American Journal of Physiology, Journal of
Physiology-London, Journal of Cell Physiology, Journal of Pineal Research, Journal of Mammary Gland Biology and Neoplasia, Journal of
Neurophysiology, and Psychophysiology.

174

Rahman M, et al: Research in biomedical science in Japan

Table 1 Continued
Toxicology: Annual Reviews of Pharmacology, Critical Reviews in Toxicology, Drugs, Drug Safety, Chemical Research in Toxicology, Toxicology and Industrial Health, Toxicology and Applied Pharmacology, Mutation Research-Fundamental and Molecular Mechanisms of Mutagenesis, Neurotoxicology and Teratology, and Environmental and Molecular Mutagenesis.
Virology: Antiviral Therapy, AIDS, Journal of Virology, Advances in Virus Research, Virology, Journal of General Virology, Journal of
Medical Virology, Journal of Neurovirology, AIDS Research and Human Retroviruses, and Antiviral Research.

and (2) for the journals, which publish mostly originalarticles. Finally net Japan’s share for basic science research output was determined. Japan’s share was also
generated for each year (1991–2000) for each categoryof journals to examine the time trend.

nals and journals with original articles was examined bychi-square test. Tests of signiﬁcance were two-tailed
and value of p < 0.05 was considered signiﬁcant.

Statistical Analyses

In total, 312,748 articles in the 16 categories journals
related to basic medical science were published from1991 through 2000. Among these, Japan’s contributions
were 20,655 articles (6.6%). Japan’s share was higher
in the journals, which publish mostly original articles(6.9%) than that in the journals, which publish only
review articles (2.6%). Contributions ranged from 3.8%
to 11.9% (Table 1) in different categories. When thejournals were divided into ‘‘journals mostly publish
original articles’’ and ‘‘journals publish only review
articles’’, the ranges were 4.0% to 11.9% and 0.4% to
8.0%, respectively in different categories (Table 1).
Japan’s contribution was signiﬁcantly higher in each of
the categories (except virology where the reverse istrue; and anatomy and parasitology where journals forreview articles were not available) for journals, which
publish mostly original articles than that for journals,
which publish only review articles.
Year-wise, as a whole, Japan’s contribution has increased from 6.2% in 1991 to 7.2% in 2000 (Fig. 1).
This upward trend was statistically signiﬁcant (p ¼ 0.01)
over the period of time. However, for journals, which
publish only review articles, the trend was not signiﬁcantly upward (p ¼ 0.08), although it went up from
1.9% in 1991 to 3.2% in 2000. On the other hand, journals, which publish mostly original articles showedstrongly signiﬁcant upward trend (p ¼ 0.01) (Fig. 1).
Figure 2 shows the trend of Japan’s share in eachof the 16 categories of journals. Among the 16 categories, Japan had signiﬁcantly positive trend over thelast decade in Biotechnology & Molecular Biology(p ¼ 0.05), Genetics & Hereditary (p ¼ 0.01), Immunology (p ¼ 0.01), Microbiology (p ¼ 0.03), Pathology(p ¼ 0.01), Physiology (p ¼ 0.01) and Pharmacology(p ¼ 0.05) while contribution to the remaining 9 categories were stagnant in the last decade.
Japan’s contribution was lower in the journals withhigher impact factor as derived from GEE regression
model (coefﬁcient ¼ 0.13, p ¼ 0.01) which means thatits contribution decreases 0.13% [95% conﬁdence interval (CI): 0.06%–0.2%] if impact factor of a journal
increases by one point. Same relationship was also

Nonparametric tests for trend were performed using
STATA 7.0 (STATA Corporation, College Road, Texas, USA) to determine any signiﬁcant change in Japan’sshare in different categories and also as a whole overthe period of time. Besides, relationship between contribution to each journal, and journal impact factor was
ﬁtted into generalized estimating equation (GEE) regression model. In this model, percentage of contribution of Japan to each journal in a year was considered
as dependent variable and impact factor of individualjournal in a particular year was considered as independent variable. Five years data (1996–2000)15 were ﬁtted
into the model, as data on impact factor before that
period were not available from the known sources. Besides, Japan’s total contribution to each of the journal
during 1991–2000 was also regressed by journal impact
factor during 2001 by simple linear regression. Relative
contribution of Japan regarding articles in review jour-8Japan's Contribution (% of Total)

76Overall

5

Journals publish only
review articles

4

Journals publish mostly
original articles

3
2
1
0
91

92

93

94

95

96

97

98

99

2000

Year of Publication
Fig. 1 Trend of Japan’s share of articles in basic medical sciencejournals during 1991–2000.

Results

Keio J Med 2004; 53 (3): 172–177
16

16

Anatomy and Morphology
Z=0.67
P=0.50

12

11

13

12.3

16
10.5

12.7

10.7

12

9.9
9.7

8.4

8

175

Biochemistry & Molecular Biology
Z=1.98P=0.0512

4.2

4
3.5 2.9

2.8 3.1 3.1

3.1

6.7

4.8

4

3.6

3.1

7.2

7.7

6.7

4.2

4
4

7.7

8

8

7.5

Biotechnology and Applied Microbiology
Z=1.82
P=0.07

3.1

4.9

3.2

0
0

00

6.5

5.2 5.6

6

12

5.5

93

94

95

96

97

98

99

2000

16

Microbiology
Z=2.20P=0.03

8
5.3

6.6

5.9

4

92

16

8.3

12

5.4 5.3 5.5

6.5

5.5

92

93

94

95

96

97

98

6.7

4.4

4

3.5
91

99 2000

92

93

94

95

96

97

98

99 2000

128

Oncology13
Z=1.00P=0.32
10.7
10.4
10.4 10.5 10.6
10.7
9.3

16
11.1

12

4

12

5.2

3.4
0

16
12

4.6
4.1

4.2

3.7

3.1

93

94

95

96

97

98

99 2000

16

Physiology
Z=2.64
P=0.01

12

8
5.5

5.3

5.5

5.9

6.2

92

93

94

95

96

97

98

99 2000

Toxicology
Z=-0.13
P=0.90

16

7.1

6.9

5.6

5.8

8

6.3

92

93

94

95

96

92

93

94

95

96

97

98

99 2000

7.9

7.9

7.9

7.8

96

97

98

99 2000

Pathology
Z=2.75
P=0.01

99 2000

97

98

9.2

9.4 9.2

6.2 6.4

6.8

6.9

7

91

93

94

95

5.1

5.4

92

8.4

Virology
Z=0.29P=0.77
5.9

5.8

5.1

6.5
6.1

4

0
91

4.8

5

5

95

96

97

0

91

92

93

94

95

96

97

98

99

91

92

93

94

98

99 2000

Pharmacology
Z=1.99P=0.05
9.2

8

5.5

4

0

12

7.3

12

7.5

8
5.9

5.9

5.5

4

6.4

5.9

3.5

0
91

8.7

16

4

4.5

0
92

3.1

8

6.1

6.2

4

91

3.7

3.4

9.6
8

5.6

0

16

Parasitology
Z=-1.07
P=0.28

5.2

3.8

3.7

3.7

91

16

3.9

Neurosciences
Z=1.58P=0.11

0
91

6.1

8

5.6
5.7

4

0

5.7

98

91

7.3

7

8

4.8 5

2000

3.9
91

99
20
00

98

97

96

95

94

93

92

91
12

4.9

0

0

Medicine, Research and Experimental
Z=1.87
P=0.06

5.2

4

4

16

4.5

99

4.4
6.2

5.3

4

0

99 2000

98

8

7

6.1

5.1

97

97

99

20

98

12

6.2

5.2

4.7

96

Immunology
Z=2.71
P=0.01

94

4

4.4

95

96

5.9

94

95

8

8.7

8.3

7.2

93

93

8

92

16

Genetics&Hereditory
Z=2.49P=0.01

12

10.3

10.4

9.1

91

92

12

99 2000

98

16

Medical Chemistry
Z=1.80P=0.07
8.4
8.5 8

16

97

97

96

96

95

95

94

94

93

93

92

92

91

91

0

8.4

8.4

8.5

9.5

8.3

8.2

4
0
91

92

93

94

95

96

97

98

99

2000

Fig. 2 Trends of Japan’s share in each category of basic medical
science. Y axis indicates percentage of contribution and x axis year of
publication. Z and p values for non-parametric test for trend are also
shown for each category.

176

Rahman M, et al: Research in biomedical science in Japan1814th)2,3 epidemiology (1.1%, 14th),4 nuclear medicine(11.4%, 2nd),5 orthopedics (8.3%, 3rd),6 ophthalmology (6.5%, 3rd),7 urology and nephrology (6.0%, 2nd),8
anesthesia (7.3%, 4th),9 dermatology (9.5%, 3rd),10 infectious diseases (3.4%, 6th),11 rheumatology (5.7%,4th),12 hematology (7.9%, 4th)13 and cardiovasculardiseases (8.3%, 2nd)14. These ﬁgures are comparablewith the results we obtained from this study, except
general medicine and epidemiology, in which Japan’scontribution was terribly meager. Remedial measures
are necessary for the categories of basic science inwhich Japan’s contribution is comparatively lower.
Grants and the number of scientist, which are essential
to increase research productivity,16 should be directedto those ﬁelds.
In our previous study, which dealt with only 6
basic science journals with the highest impact factor,
Japan’s share was much lower (3.1%)3 than the overall
share of basic science articles elicited in this study(6.6%). Average impact factor for the 6 basic sciencejournals (26.0) selected in the previous study was muchhigher than that in this study (7.7). GEE regression
model also revealed that Japan’s contribution signiﬁcantly decreases with the increase of journal impact
factor. This features reveals that Japan’s contribution
was comparatively lower to the high impact factor
journals. On the plus side, since many of the review
journals have higher impact factor and Japan’s contribution to those journals is lower, it might contribute, tosome extent, to this negative relationship.
In conclusion, Japan’s overall share of original articles has increased in the last decade while its share ofreview articles was lower and has remained stagnant in
the last decade.

Japan's Contribution (% of Total)

16
14
12
10
8
6
4
2
0
0.5

2.5

3.5

5.0

8.2

14.2

46.2

Journal Impact Factor (from lower to higher)*Fig. 3 Japan’s contribution (1991–2000) to individual journal versus
the impact factor of journals in 2001. *In total, 144 journals’ impact
factors were placed on the x-axis. Journal impact factors labeled outside x-axis are for 1st, 25th, 50th, 75th, 100th, 125th, 144th journal
from lower to higher impact factors.

found [0.18% decrease (CI: 0.11–0.26%) for one point
increase of impact factor] in a linear regression between
Japan’s contribution to different journals during 1991–
2000 and impact factor of journals for the year 2001
(Fig. 3).
Discussion
The number of publications elicited from theseselected journals is only a gross estimate of the proportion of Japan’s contribution to the high quality basic
medical science journals. We included journals from 16
categories only, although there are many more journals
in the selected categories with lower impact factor.
Moreover, a good number of clinical journals also publish few articles on basic science. On the ﬂip side, journals selected for this study could also include somearticles not related to basic science, rather to clinical,
behavioral or social sciences. Actually there is no automatic search strategy to elicit all the basic science articles included in Medline database. And therefore, weused search command for journal articles only. Thus theabsolute number of high quality journal articles originating from Japan is certainly different from our ﬁndings. However, the proportion of contribution obtained
here is likely to reﬂect the real situation.
Although Japan’s ranking was 2nd in the world,1 interms of overall number of articles based on journal
articles included in Medline database, its contributions
and rankings in different categories had wide range ofvariation: high quality basic medical science (3.1%,4th),2,3 general and general internal medicine (0.7%,

References
1. Rahman M, Fukui T: Biomedical publication – global proﬁle andtrend. Public Health 2003; 117: 274–280
2. Rahman M, Fukui T: A decline in the U.S. share of research
articles. N Engl J Med 2002; 347: 1211–1212
3. Fukui T, Rahman M: Contribution of research in basic and clinical sciences in Japan. Intern Med; 41: 626–628
4. Rahman M, Sakamoto J, Fukui T: Publications in epidemiology
journals: Japanese perspectives. J Epidemiol 2003; 13: 96–98
5. Rahman M, Sakamoto J, Fukui T: Japan’s contribution to
nuclear medical research. Ann Nucl Med 2002; 16: 383–385
6. Rahman M, Sakamoto J, Fukui T: Japan’s share of articles inorthopedics. J Orthop Sci 2002; 7: 607–609
7. Rahman M, Sakamoto J, Fukui T: Japan’s share of publishedresearch in ophthalmology. Jpn J Ophthalmol 2003; 47: 221–224
8. Rahman M, Sakamoto J, Fukui T: Japan’s share of research
output in urology and nephrology. Int J Urol 2003; 10: 353–355
9. Rahman M, Sakamoto J, Fukui T: Research output in anaesthesia: a quantitative ranking. Anaesthesia 2002; 57: 1213–1214
10. Rahman M, Sakamoto J, Fukui T: Share of research output indermatology: a quantitative ranking. Br J Dermatol 2003; 149:
218–220

Keio J Med 2004; 53 (3): 172–177
11. Takahashi O, Rahman M, Fukui T: Japan’s contribution to research on infectious disease. Jpn J Infect Dis 2002; 55: 139–141
12. Hayashino Y, Rahman M, Fukui T: Japan’s contribution to theresearch on rheumatology. Mod Rheumatol 2003; 13: 168–172
13. Morimoto T, Rahman M, Fukui T: International comparison ofresearch productivity in hematology. Int J Hematol 2003; 77:
192–195

177
14. Hayashino Y, Rahman M, Fukui T: Japan’s contribution to research on cardiovascular disease. Circ J 2003; 67: 103–106
15. ISI Journal Citation Reports. Institute for Scientiﬁc Information,
Philadelphia, USA, 2001
16. Rahman M, Fukui T: Biomedical research productivity: factors
across the countries. Int J Technol Assess Health Care 2003; 19:249–252