Kobe J. Med. Sci., Vol. 69, No. 2, pp. E64-E78, 2023

Gender Disparities in First Authorship at Three Medical Universities
in an Area Affected by the Great East Japan Earthquake
YUKO ONO1,2,3,*, MASAFUMI SAITO1, KENJU SHIMOMURA2,
KAZUAKI SHINOHARA3, NAOTO YAMADA4, YUDAI IWASAKI5,
SHIGEAKI INOUE1, and JOJI KOTANI1
1

Department of Disaster and Emergency Medicine, Kobe University Graduate School of Medicine, Kobe, Japan;
2
Department of Bioregulation and Pharmacological Medicine, School of Medicine, Fukushima Medical
University, Fukushima, Japan;
3
Department of Anesthesiology, Ohta General Hospital Foundation, Ohta Nishinouchi Hospital, Koriyama,
Japan;
4
Department of Anesthesiology, Iwate Medical University, Morioka, Japan;
5
Department of Anesthesiology and Perioperative Medicine, Tohoku University Graduate School of Medicine,
Sendai, Japan;*Corresponding author
Received March 30, 2023/Accepted June 15, 2023

Keywords: Academic promotion process, Grant acquisition, Natural disaster, Tohoku-Oki earthquake, Work-life
conflicts
The Great East Japan Earthquake that occurred on March 11, 2011, was one of the largest natural disasters
in modern times. Publication in medical journals is important aspects of the academic promotion process,and is thus important for all scientists. However, little is known about whether and how substantial natural
disasters affect gender disparities in academic productivity in disaster-affected areas. We hypothesized that
the Great East Japan Earthquake widened the existing disparities in scientific publishing between male andfemale researchers. To test this hypothesis, this retrospective observational study using existing databases
was conducted. We extracted from the MEDLINE database all types of biomedical articles published fromMarch 11, 2007, to March 11, 2015, by three medical universities in a disaster-affected area of Japan.
Differences in the proportion of female first authorship during the 4 years before and after the Great East
Japan Earthquake were compared. A total of 5,873 papers were analyzed. The proportion of female firstauthors significantly declined after the Great East Japan Earthquake (20.5% vs. 14.1%; odds ratio 0.64;
95% confidence interval 0.56–0.73). A similar trend was identified across all prespecified subgroups,
including clinical department; original article; public medical university; and prestigious journal with
impact factor >6. Reference data from two medical universities minimally affected by the Great East Japan
Earthquake showed the opposite trend. These results collectively suggest that large natural disasters canreinforce existing gender disparities in first authorship in biomedicine.
INTRODUCTION
The Great East Japan Earthquake that occurred on March 11, 2011, was one of the largest natural disasters inmodern times (1, 2). This magnitude 9.0 earthquake, and the subsequent tsunamis and nuclear power plant accident
in Fukushima, caused substantial damage to the Pacific coast of northeastern Japan (3, 4). According to a recent
estimate, this complex disaster resulted in more than 19,000 deaths, 6,000 injuries, and 1,150,000 collapsedbuildings (5). Therefore, this unprecedented event had both acute and chronic detrimental health effects on the
inhabitants of areas affected by the disaster (6, 7). To address these disaster-related healthcare problems, theworkload of medical professionals in areas affected by the Great East Japan Earthquake considerably increased
following the earthquake. Researchers were responsible for recording and disseminating what they had learned
from the earthquake, tsunamis, and nuclear power plant accident; applying their experience of the disaster toscientific developments; and training professionals who specialize in disaster and emergency radiation. The
disaster destroyed a large amount of laboratory equipment, stock agents, and experimental animal cages, which
considerably disrupted normal research activities. As frontline physicians and biomedical researchers working at
medical universities in a disaster-affected area, the authors have firsthand experience of these huge changes.
It is well known that women, children, older people, and people in poverty are disproportionately affected bynatural disasters. For example, women are more likely to die or be injured during disasters, and more likely toexperience negative effects of a disaster (e.g., loss of livelihood, longer recovery time, greater recovery effort
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GENDER AND FIRST AUTHORSHIP AFTER THE GREAT EARTHQUAKE
burden) than men (8–12). Large disasters therefore have discriminatory health and economic effects. However,
little is known about whether and how natural disasters affect gender disparities in academic productivity indisaster-affected areas. Previous studies have shown that work-life conflicts are more prevalent in female
healthcare professionals (especially those with children) than in their male counterparts (13, 14). In Japan, female
healthcare professionals often spend more time than their male counterparts engaging in unpaid domestic work
(e.g., childrearing and housekeeping) (15), and tend to experience more difficulty finding time for their researchand balancing their work and personal lives (14). The considerable changes to personal lives, disruption of normal
research activities, and increased workload and responsibilities caused by the Great East Japan Earthquake may
have made it even harder for female healthcare professionals and scientists to balance their research activity andfamily responsibilities. We hypothesized that this major disaster widened the existing gap in academic productivity(e.g., scientific publishing and grant acquisition) between male and female researchers. Both publication in medical
journals and grant acquisition are important aspects of the academic promotion process and academic employment
retention, especially in the field of medicine, and are thus important for all scientists (16–22). Rigorous testing of
this research hypothesis is therefore warranted.
The goal of this study was to clarify the effects of the Great East Japan Earthquake on gender differences infirst authorship and public funding acquisition at three medical universities in a disaster-affected area.
MATERIALS AND METHODS
Study design, setting, participants, data source, search strategy, and measured variables
This retrospective observational study using existing databases was conducted from August 2021 to February
2022 at three medical universities in an area affected by the Great East Japan Earthquake. We identified relevant
studies that similarly assessed the prevalence of female first authorship in selected journals (17–21) or evaluatedthe effect of the COVID-19 pandemic on female academic output (23–26). The search strategy was determined apriori by the survey team, which comprised clinicians (YO, NY, KaS, YI, SI, and JK), basic scientists (MS and
KeS), and a librarian (MJ, listed in the Acknowledgments). All types of biomedical articles published from March
11, 2007, to March 11, 2015, from Fukushima Medical University, Iwate Medical University, and Tohoku
University School of Medicine and Graduate School of Medicine were included in the analysis. Biomedical articles
were acquired from the MEDLINE database; no language restrictions were applied. The following search terms
were used: Fukushima medical university [ad] OR Fukushima medical university hospital [ad] OR Iwate medical
university [ad] OR Iwate medical university hospital [ad] OR Tohoku university graduate school of medicine [ad]OR Tohoku university school of medicine [ad] OR Tohoku university hospital [ad]. PubMed®
(https://pubmed.ncbi.nlm.nih.gov/) was used to search the MEDLINE database. Articles were excluded from theanalysis if the gender of the first author could not be determined; the first author did not belong to the three study
facilities; or the article had been retracted after publication.
The following data were extracted from this systematic PubMed® search: article type, disaster-related topic,
first author’s department, number of authors, and first author’s affiliation type. Journal impact factors wereobtained using InCites Journal Citation Reports® (Clarivate Analytics, Philadelphia, PA, USA) and categorized
into three levels: 0–3, 3–6, and >6. Type of article was categorized as original article, case report, review, andothers (e.g., letter, commentary, editorial). Papers on the Great East Japan Earthquake and similar topics wereidentified using a set of disaster-related keywords (e.g., the Great East Japan Earthquake, the Tohoku-Oki
earthquake, tsunamis, nuclear power plant accident) that appeared in the article titles or abstracts. First author’s
department was dichotomized into clinical and preclinical departments. The total number of authors was definedas the number of named authors listed in an article. If a group author [e.g., the Fukushima Health Management
Survey Group (27)] was listed at the end of a list of named authors, the group was not included in the total count(18). Fukushima Medical University and Tohoku University are public medical universities. Iwate Medical
University is a private medical university. All three institutions were substantially affected by the Great East Japan
Earthquake. Therefore, if the first author belonged to the two former universities, their affiliation type wascategorized as “public medical university.” If the first author belonged to the latter university, their affiliation type
was categorized as “private medical university.”
Outcome measures
The primary outcome measure was female first authorship in articles in the biomedical journals included in
the MEDLINE database. The other outcomes of interest were female corresponding authorship and last authorshipin published articles. Publication in medical journals is an important measure of academic productivity. Firstauthorship usually indicates the researcher who made the greatest contribution to the work; corresponding
authorship and last authorship indicate successful group leadership (21, 28). Most previous studies that haveassessed female authorship in biomedical literature have used similar measures (17, 19–21, 23–25, 28).
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Y. ONO et al.
Differences in these outcomes during the 4 years before and after the Great East Japan Earthquake (March 11,
2007, to March 10, 2011, and March 11, 2011, to March 11, 2015) were compared. Four years was deemed areasonable time for publication because most biomedical articles tend to be published within this period (29). In
addition, most doctoral courses in Japan, including those at the three study facilities, specify 4 years as a reasonable
time in which to complete a doctoral dissertation. For single-author articles, the author was categorized as both thefirst and last author.
All eligible articles were initially evaluated by the first author (YO) between August 2021 and December 2021
using a standardized recording format. To identify the author’s gender, we used a modified version of the method
previously reported by Jagsi et al. and Filardo et al. (17, 18). In brief, the author’s gender was initially determinedusing his or her first name. If an author’s gender was unclear, attempts were made to confirm it by checking withthe coauthors who belonged to Fukushima Medical University (KeS), Iwate Medical University (NY), and Tohoku
University (YI); by consulting institutional websites or social media accounts (e.g., Resarchmap®, Resarchgate®,
LinkedIn®); and by performing Internet searches using search engines (e.g., Google Image®). If the first author’s
gender remained unclear after these sources were exhausted, the article was classified as “gender of first author
could not be determined” and excluded from the analysis.
Primary analysis and subgroup analysis
All analyses were performed according to an a priori statistical analysis plan. Initially, all survey items were
evaluated using descriptive statistics. Predisaster and postdisaster differences in categorical variables wereassessed using chi-square followed by residual analysis. Differences in continuous variables between the twogroups (predisaster and postdisaster) were compared using Student’s t-test or the Mann-Whitney U test fornormally and non-normally distributed data, respectively, after application of the Shapiro-Wilk test for normality.
Univariable logistic regression models were fitted to produce a crude odds ratio (OR) and 95% confidence interval(CI) for female first and last authorship after the occurrence of the Great East Japan Earthquake. To further clarify
the transition in female first authorship, the percentage and simple moving average of female first authorship were
calculated for 6 months from 11 March 11, 2007, to March 11, 2015. A simple moving average is an arithmetic
average of data points divided by the number of time periods. We calculated the simple moving average of female
first authorship using two consecutive data points. For instance, if the proportion of female first authorship was
calculated at the two consecutive data points of P1 and P2, the simple moving average equals P1 + P2 divided by
2. A simple moving average was computed using the trendline function in Microsoft Excel®.
To evaluate the robustness of the primary analysis described above, the logistic regression analysis was
repeated for prespecified subgroups of original articles, articles from clinical departments, articles from public
universities, and articles in prestigious journals with impact factors >6. All statistical analyses were performed
using SPSS Statistics for Windows, version 25.0 (IBM Corp., Armonk, NY, USA). A P value of <0.05 wasconsidered to indicate statistical significance.
Subanalyses
It is likely that determining the factors associated with female first authorship would increase understandingof gender disparities in research output before and after the occurrence of the Great East Japan Earthquake. Thus,
differences in characteristics of female and male first authors at three medical universities in a disaster-affectedarea were also compared.
Funding acquisition plays a fundamental role in supporting the publication cycle and is an important marker
of scientific productivity (30, 31). Therefore, we also compared gender disparities in the number and amount ofgrants obtained during the 4 years before and after the occurrence of the Great East Japan Earthquake. To assess
this, all research projects at Fukushima Medical University, Iwate Medical University, and Tohoku University
School of Medicine from March 11, 2007, to March 11, 2015, were searched using the Grants-in-Aid for Scientific
Research database (Japan Society for the Promotion of Science [JSPS] KAKEN database:https://kaken.nii.ac.jp/en/). The JSPS is the largest public funder of academic research in Japan.
Reference dataset
To further confirm the effect of the Great East Japan Earthquake on the gender gap in first authorship, all typesof biomedical articles in the MEDLINE database published from March 11, 2007, to March 11, 2015, by Kobe
University School of Medicine and Hyogo Medical University were acquired as a reference. Kobe University
School of Medicine is a public medical university and Hyogo Medical University is a private medical university;
both institutions were minimally affected by the Great East Japan Earthquake. These universities were chosen asa reference because several of the present coauthors (YO, SI, and JK) belong to or used to belong to these
institutions and thus were able to confirm the gender of the researchers. PubMed® was searched using the
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GENDER AND FIRST AUTHORSHIP AFTER THE GREAT EARTHQUAKE
following search terms: Kobe university graduate school of medicine [ad] OR Kobe university school of medicine[ad] OR Kobe university hospital [ad] OR Hyogo college of medicine [ad] OR Hyogo college of medicine hospital[ad] OR Hyogo medical university [ad] OR Hyogo medical university hospital. The same primary analysis wasused to determine the gender gap in academic productivity before and after the Great East Japan Earthquake.
Power analysis
The retrospective nature of the study predetermined the sample size. Therefore, a priori estimation of statisticalpower was not possible. The observed power was computed posthoc using G*Power 3 for Windows (Heinrich
Heine University, Dusseldorf, Germany).
Ethics approval and consent to participate
Current Japanese ethical guidelines do not mandate ethical review for studies involving analysis of publicly
available data. This study was therefore exempt from ethical evaluation by the institutional review boards of theauthors’ institutions. Because this study did not involve human participants, the need for informed consent was
waived. All methods were carried out in accordance with the relevant guidelines and regulations, such as SAGER
guidelines (32) and STROBE statement (33).
RESULTS
Study flow
The initial MEDLINE search detected 6,504 eligible biomedical articles from three study sites for March 11,
2007, to March 11, 2015 (Figure 1). Of these, 145 (2.2%) articles for which the first author’s gender could not be
determined, 484 articles (7.4%) for which the first author did not belong to the study site, and 2 articles (0.03%)
that were retracted after publication were excluded from the analysis. The remaining 5,873 articles were includedin the final analysis. Of these, 2,317 (39.5%) articles were published during the 4 years before the Great East Japan
Earthquake, and 3,556 (60.5%) articles were published during the 4 years after the disaster. Complete records wereavailable for all articles, and no data were missing from the analyses.

Figure 1. Study flow diagram

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Differences in research output before versus after the occurrence of the Great East Japan Earthquake
Although there were significant differences in type of article, first author’s department, and number of authors
before versus after the Great East Japan Earthquake, these differences were small (Table I). Other characteristics,
including journal impact factor and first author’s affiliation type, were similar between the two groups.
Table I. Differences in biomedical articles published from three medical universities in a disaster-affected
area: before versus after the Great East Japan Earthquake

Journal impact factor
0–3
3–6
>6
Type of article
Original article
Case report
Review
OtherscDisaster-related topicd
Yes
No
First author’s department
Clinical department
Preclinical department
Number of authors
First author’s affiliation type
Public university
Private university

All (n = 5,873)

Before disaster(n = 2,317)a

After disaster(n = 3,556)b

3,261 (55.5)
1,997 (34.0)615 (10.5)

1,253 (54.1)
805 (34.7)
259 (11.2)

2,008 (56.5)
1,192 (33.5)
356 (10.0)

P
0.143

<0.001
4,340 (73.9)818 (13.9)
596 (10.1)
119 (2.0)

1,741 (75.1)
301 (13.0)
249 (10.7)
26 (1.1)*

2,599 (73.1)
517 (14.5)
347 (9.8)
93 (2.6)**

96 (1.6)
5,777 (98.4)

0 (0)2,317 (100)96 (2.7)
3,460 (97.3)

4,176 (71.1)
1,697 (28.9)
7 (4–10)

1,588 (68.5)
729 (31.5)
6 (4–9)2,588 (72.8)
968 (27.2)
7 (4–10)

4,712 (80.2)
1,161 (19.8)

1,834 (79.2)
483 (20.8)

2,878 (80.9)
678 (19.1)<0.001<0.001
0.094

Data are expressed as n (%) or median (interquartile range). aBiomedical articles published during the 4 years before
the Great East Japan Earthquake (March 11, 2007, to March 10, 2011). bBiomedical articles published during the 4
years after the Great East Japan Earthquake (March 11, 2011, to March 11, 2015). cLetter, commentary, editorial, etc.
dPapers on the Great East Japan Earthquake and related topics. Identified by a set of keywords (e.g., Great East Japan
Earthquake, tsunamis, nuclear power plant accident) that appeared in their titles or abstracts. **Adjusted standardized
residual >1.96. *Adjusted standardized residual ≤1.96.

Primary and subgroup analysis
As shown in Figure 2a, the proportion of female first authors significantly declined after the Great East Japan
Earthquake (20.5% vs. 14.1%; OR 0.64; 95% CI 0.56–0.73). The proportion of female corresponding authors also
declined (12.2% vs. 8.8%; OR 0.69; 95% CI 0.59–0.82), whereas the proportion of female last authors was similar
before and after the disaster (3.4% vs. 3.3%; OR 0.96; 95% CI 0.71–1.28). A decline in female first authorship
was particularly pronounced in the first 2 years after the disaster (Figure 2b).

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GENDER AND FIRST AUTHORSHIP AFTER THE GREAT EARTHQUAKE

Figure 2. Female authorship at three medical universities in a disaster-affected area: before versus after the Great
East Japan Earthquake(a) Odds ratios for female first, corresponding, and last authorships: before versus after the Great East Japan
Earthquake.
(b) Percentage of female first authorship over 6 months. Red points represent the percentage of female first authors;vertical lines represent 95% CI; the dotted line represents the simple moving average (2 consecutive points toaverage). aBiomedical articles published during the 4 years before the Great East Japan Earthquake (March 11,
2007, to March 10, 2011). This group is the reference set. bBiomedical articles published during the 4 years after
the Great East Japan Earthquake (March 11, 2011, to March 11, 2015). CI, confidence interval; OR, odds ratio.

There was a similar trend in all prespecified subgroups (Figure 3): clinical department (OR 0.71; 95% CI 0.58–0.84); original article (OR 0.60; 95% CI 0.51–0.70); public medical university (OR 0.64; 95% CI 0.55–0.75); andprestigious journal with impact factor >6 (OR 0.65; 95% CI 0.41–1.05).

Figure 3. Subgroup analysis of female first authorship at three medical universities in a disaster-affected
area: before versus after the Great East Japan Earthquake
aBiomedical articles published during the 4 years before the occurrence of the Great East Japan
Earthquake (March 11, 2007, to March 10, 2011). This group is the reference set. bBiomedical
articles published during the 4 years after the occurrence of the Great East Japan Earthquake(March 11, 2011, to March 11, 2015). CI, confidence interval; OR, odds ratio.

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Y. ONO et al.

Subanalyses
There were substantial differences between female and male first authors (Table II): male first authors weremore likely to publish papers in journals with impact factors >6; more likely to write reviews and other types of
papers such as letters, commentaries, and editorials; and wrote more articles on disaster-related topics than female
first authors. In particular, 553 of 596 (92.8%) review papers and 91 of 96 (94.8%) disaster-related papers were
written by male first authors. Female first authors were more likely to belong to preclinical departments. Consistent
with previous studies (20, 28), first authors were more likely to be women for articles with female corresponding
authors and last authors.
Table II. Factors associated with female first authorship on biomedical articles published by three medical universities

Journal impact factor
0–3
3–6
>6
Type of article
Original article
Case report
Review
Othersa
Disaster-related topicb
Yes
No
First author’s department
Clinical department
Preclinical department
Corresponding author’s gender
Male
FemaleLast author’s gender
Male
FemaleNumber of author(s)First author’s affiliation type
Public university
Private university

All (n = 5,873)

Male first author(n = 4,896)

Female first author(n = 977)

P

3,261 (55.5)
1,997 (34.0)615 (10.5)

2,729 (55.7)
1,632 (33.3)*
535 (10.9)**532 (54.5)
365 (37.4)**
80 (8.2)*

0.007<0.001
4,340 (73.9)818 (13.9)
596 (10.1)
119 (2.0)

3,564 (72.8)*
668 (13.6)
553 (11.3)**
111 (2.3)**

776 (79.4)**
150 (15.4)
43 (4.4)*
8 (0.8)*96 (1.6)
5,777 (98.4)

91 (1.9)
4,805 (98.1)

5 (0.5)972 (99.5)

1,697 (28.9)
4,176 (71.1)

1,287 (26.3)
3,609 (73.7)

410 (42.0)
567 (58.0)

4,896 (83.4)
977 (16.6)

4,785 (97.7)
111 (2.3)

494 (50.6)
483 (49.4)

5,678 (96.7)
195 (3.3)
7 (4–10)

4,760 (97.2)
136 (2.8)
7 (4–10)918 (94.0)
59 (6.0)
7 (4–9)4,712 (80.2)
1,161 (19.8)

3,919 (80.0)
977 (20.0)

793 (81.2)
184 (18.8)

0.002<0.001<0.001<0.001

0.275
0.421

Data are expressed as n (%) or median (interquartile range). aLetter, commentary, editorial, etc. bPapers on the Great East
Japan Earthquake and related topics. Identified by a set of keywords (e.g., Great East Japan Earthquake, tsunamis, nuclear
power plant accident) that appeared in their titles or abstracts. **Adjusted standardized residual >1.96. *Adjusted
standardized residual ≤1.96.

Regarding JSPS KAKEN grants obtained, the Great East Japan Earthquake seems not to have widened the existing
gender gap (Figure 4).

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Figure 4. Gender disparities in the number and amount of public grants obtained at three medical universities ina disaster-affected area: before versus after the Great East Japan Earthquake(a) Comparison of the median JSPS KAKEN grant between male and female researchers. Solid line inside thebox represents the median, x represents the mean, the box represents the 25th and 75th percentiles, the whiskers
represent the lower and upper extremes. ***p < 0.001, *p < 0.05. P-values were derived from Mann-Whitney U
test.
(b) Comparison of the sum of JSPS KAKEN grant between male and female researchers.
(c) Comparison of the annual amount of JSPS KAKEN grant between male and female researchers.
(d) Gender proportion in total amount of JSPS KAKEN grant. aDuring the 4 years before the Great East Japan
Earthquake (March 11, 2007, to March 10, 2011). bDuring the 4 years after the Great East Japan Earthquake(March 11, 2011, to March 11, 2015). JSPS: Japan Society for the Promotion of Science.

Reference dataset
As a reference, we obtained all types of biomedical articles published by Kobe University School of Medicine
and Hyogo Medical University, Japanese medical universities minimally affected by the disaster (Figure 5 andTable III).

Figure 5. Study flow diagram (reference dataset)

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Y. ONO et al.
Table III. Differences in biomedical articles published from two medical universities minimally affectedby the disaster: before versus after the Great East Japan Earthquake

Journal impact factor
0–3
3–6
>6
Type of article
Original article
Case report
Review
OtherscDisaster–related topicd
Yes
No
First author’s department
Clinical department
Preclinical department
Number of authors
First author’s affiliation type
Public university
Private university

All (n = 3,988)

Before disaster(n = 1,614)a

After disaster(n = 2,374)b

1,953 (49.0)
1,589 (39.8)
446 (11.2)

761 (47.1)
644 (39.9)
209 (12.9)**

1,192 (50.2)
945 (39.8)
237 (10.0)*

3,012 (75.5)588 (14.7)
345 (8.7)
43 (1.1)

1,181 (73.2)*
250 (15.5)
171 (10.6)**
12 (0.7)

1,831 (77.1)**
338 (14.2)
174 (7.3)*
31 (1.3)

0 (0)
0 (0)

0 (0)
0 (0)

0 (0)
0 (0)

3,151 (79.0)
837 (21.0)
6 (3–9)1,217 (75.4)
397 (24.6)
5 (3–8)1,934 (81.5)
440 (18.5)
7 (5–10)

2,523 (63.2)
1,465 (36.7)

1,040 (64.4)
574 (35.6)

1,483 (62.5)
891 (37.5)

P
0.009

0.001

<0.001<0.001
0.206

Data are expressed as n (%) or median (interquartile range). aBiomedical articles published during the 4
years before the Great East Japan Earthquake (March 11, 2007, to March 10, 2011). bBiomedical articles
published during the 4 years after the Great East Japan Earthquake (March 11, 2011, to March 11, 2015).
cLetter, commentary, editorial, etc. dPapers on the Great East Japan Earthquake and related topics.
Identified by a set of keywords (e.g., Great East Japan Earthquake, tsunamis, nuclear power plant accident)
that appeared in their titles or abstracts. **Adjusted standardized residual >1.96. *Adjusted standardized
residual ≤1.96.

In contrast with the primary analysis, the proportion of female first authorship increased over time (Figure 6a). As
shown in Figure 6b, the ORs for female first authorships; corresponding authorships; and last authorships all
increased after the Great East Japan Earthquake (First author: OR 2.19; 95% CI 1.82–2.65; corresponding author:
OR 2.11; 95% CI 1.56–2.86; and last author: OR 2.04; 95% CI 1.36–3.06).

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GENDER AND FIRST AUTHORSHIP AFTER THE GREAT EARTHQUAKE

Figure 6. Female authorship at two medical universities minimally affected by the disaster: before versus after
the Great East Japan Earthquake(a) Percentage of female first authorship over 6 months. Orange points represent the percentage of female firstauthors; vertical lines represent 95% CI; the dotted line represents the simple moving average (2 consecutive
points to average).
(b) ORs for female first, corresponding, and last authorships: before versus after the Great East Japan Earthquake.
aBiomedical articles published during the 4 years before the Great East Japan Earthquake (March 11, 2007, to
March 10, 2011). This group is the reference set. bBiomedical articles published during the 4 years after theGreat East Japan Earthquake (March 11, 2011, to March 11, 2015). CI, confidence interval; OR, odds ratio.

As shown in Figure 7, there was a similar trend for the subgroups of clinical department (OR 2.35; 95% CI 1.86–
2.97); original article (OR 1.98; 95% CI 1.62–2.43); public medical university (OR 1.44; 95% CI 1.16–1.78); andprestigious journal with impact factor >6 (OR 2.16; 95% CI 1.25–3.72). Both these results and those of the primary
analysis described above demonstrate an effect of the Great East Japan Earthquake on female first authorship in
the biomedical field.

Figure 7. Subgroup analysis of female first authorship at two medical universities minimally affected by thedisaster: before versus after the Great East Japan Earthquake
aBiomedical articles published during the 4 years before the occurrence of the Great East Japan Earthquake (March
11, 2007, to March 10, 2011). This group is the reference set. bBiomedical articles published during the 4 years
after the occurrence of the Great East Japan Earthquake (March 11, 2011, to March 11, 2015). CI, confidence
interval; OR, odds ratio.

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Y. ONO et al.
DISCUSSION
This study showed that the proportion of publications by women after the Great East Japan Earthquake declined
significantly, and this trend was apparent in all predetermined subgroups (clinical department, original article,
public medical university, and journal impact factor >6). The most significant reduction in the proportion of female
first authors occurred in the first 2 years after the disaster. Female researchers also produced fewer publications
related to the Great East Japan Earthquake than their male counterparts. The reference data from two medical
universities minimally affected by the Great East Japan Earthquake showed the opposite trend. Collectively, theseresults suggest that large natural disasters enforce the existing disparities in academic productivity between maleand female researchers. Advancements in academic medicine are largely contingent on publication in medical
journals (17). Therefore, the worrying trend identified by this study may increase the existing gender gap inacademic promotion. Our results should be used to encourage the scientific community, institutional administrators,
funding bodies, and policymakers to address these problems.
For the last few decades, there has been increased participation by women in various scientific disciplines,
including medicine (22, 34–36). The representation of women among first authors of articles in biomedical
journals has also substantially increased, suggesting that the gender gap is shrinking (17–21). Consistent with theseobservations, the presents findings show that the proportion of female first authorship increased over time at two
Japanese medical universities that were minimally affected by the Great East Japan Earthquake. A recent study inJapan also identified a consistent increase in the proportion of female faculty in medicine since 1995 (36). Thus,
a sudden reduction in female biomedical research output after the Great East Japan Earthquake is an unusual
reverse trend. There are several plausible explanations for the observed findings.
First, female healthcare professionals working at the study sites may have had less time to spend on researchin the aftermath of the Great East Japan Earthquake. In this study, the decline in female first authorship wasparticularly pronounced in the first 2 years after the disaster. In the acute phase of a large natural disaster, there isincreasing need to care for children or other family members. Women often actively care for the family and spend
more time per day on unpaid domestic work than men, roles they are expected to fulfil during disaster situations(37–39). As healthcare professionals and researchers working at the three study sites, the authors have direct
experience of how workloads substantially increased following the disaster to address disaster-related healthcare
problems and meet increasing educational needs. Following disasters, women tend to be “doubly burdened” (39,40); they may struggle more with integrating work and family life, which reduces their academic productivity.
Greater attention should be paid to this pattern, and future policies should address this problem appropriately.
Second, most research related to the Great East Japan Earthquake, which comprised approximately 3% of allacademic output from the three study sites, was conducted by male researchers. The Great East Japan Earthquakeand subsequent nuclear power plant accident is a high-profile dynamic research topic. There is a general trend forthis type of research to be conducted by those in research leadership positions (12, 37), who are more often men.
A relatively large number of review papers were commissioned articles, which are generally written by researchersin leadership positions. We found that 553 of 596 (92.8%) review articles were written by male researchers. In theaftermath of a major disaster, masculine traits (e.g., being aggressive, competitive, and dominant) tend to be valued
more, and men are expected to adopt leadership and decision-making roles (12, 37, 38). Previous studies indicatethat women are praised when they followed traditional norms (e.g., assisting men in relief and recovery efforts,
caring for family members and disaster victims, and taking care of people’s emotional and mental health) but are
denigrated when they perform what are viewed as male-oriented tasks (12, 39). These social norms may prevent
women from adopting leadership roles, which in turn may prevent them from conducting disaster-related research.
We must be aware of the existence of such bias (39), particularly in the aftermath of major natural disasters.
Our findings are consistent with those of previous related studies. Stay-at-home orders, lockdowns, and school
closures during the COVID-19 pandemic have also disproportionately affected scientists in the biomedical field(23–26). Female scientists, particularly those caring for children or other family members during the pandemic,
have reported a substantial reduction in the time they have available for research (41–43). Consequently, theacademic productivity of female scientists has declined (23–26). These results, together with our own findings,
collectively suggest that major disasters reinforce existing disparities in academic productivity between male andfemale researchers.
Science and innovation benefit greatly from gender diversity (44). Therefore, we need to identify ways toreduce gender inequalities and support women in academia during and after disasters. Both organizational efforts
and political commitment are needed to address disaster-related gender disparities (45, 46). The academic
promotion process places high value on publication in medical journals (16–22). When assessing team members
for promotion, institutional administrators and academic departments should recognize that disasters canexacerbate the gender gap in academic productivity. Formal disaster response agencies and funding bodies may
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GENDER AND FIRST AUTHORSHIP AFTER THE GREAT EARTHQUAKE
need to consider gender quotas, as these can help to rectify the underrepresentation of women in prominent
positions (e.g., in political, economic, and academic systems) (23, 47). We believe that concerted organizational
and political efforts could help to prevent the loss of women’s scientific expertise from the scientific publication
realm in the aftermath of disasters.
This study had several limitations. First, as with any observational study, the observed associations between
the occurrence of the Great East Japan Earthquake and gender disparities in first authorship may have been
confounded by other unmeasured factors. For example, authors’ job titles, academic degrees, marital status, andnumber and age of children may have affected the publication rate. During the COVID-19 pandemic, female
scientists with young children have reported a greater reduction in research time than their male colleagues (41–43). Further analyses that include such in-depth personal information are required to further clarify how the Great
East Japan Earthquake affected gender disparities in scientific output, and to identify vulnerable individuals within
academia who may need assistance. Another important variable that was not measured was the change in the
proportion of male and female researchers after the Great East Japan Earthquake compared with before. Consistent
with a recent study in Japan (36), the proportion of female faculty and researchers at Tohoku University
consistently increased rather than decreased during the study period (48). In addition, the proportion of female
faculty at Iwate Medical University during 2011–2015 (part of the study period) also increased (49). This may
have biased our results toward the null hypothesis. Data on the proportion of male and female researchers in theother study facilities during the study period were not available.
Second, as with previous studies that similarly assessed female first authorship (17–21, 23–26), somemisclassification may have occurred when determining the gender of a publication’s author or grant winner.
However, in addition to using previously applied gender-detection methods (17, 18), we tried to minimize thispotential error by consulting scientists who belong to the study sites during the gender determination process, andby excluding low-confidence results. We believe that our data are the best available, and that the proportion of
authors whose gender was categorized incorrectly was small and would not have altered the main conclusions of
this study.
Third, because we searched for published articles in a single database (MEDLINE) using a single search engine(PubMed®), some peer-reviewed papers may have been overlooked. However, we believe that our search strategy
was appropriate and clinically relevant because most biomedical researchers use MEDLINE as the first and mostreliable source of medical information. It is also unlikely that the results would have substantially differed if otherdatabases (e.g., Embase® and Google Scholar®) had been included. For example, Berry et al. (50) found their
MEDLINE search for articles included in systematic reviews of medical imaging identified 94% of target
references.
Fourth, the use of biomedical articles published by Kobe University School of Medicine and Hyogo Medical
University may be insufficient. These two medical universities were chosen as a reference because several of thepresent coauthors (YO, SI, and JK) belong to or used to belong to these institutions and thus were able to confirm
the gender of the researchers. The use of other medical universities as a reference would have made it more difficult
to determine the gender of the authors of publications because Asian names (particularly Japanese names) can be
ambiguous and are not gender specific (22, 24). In this study, we prioritized the accuracy of the data. Our reference
data were consistent with previous observations suggesting that the gender gap in academic research is shrinking
over time (17–21, 36).
Finally, we did not use an a priori estimate of sample size. As described in the Methods, the retrospective
nature of the study predetermined the sample size. However, a posthoc power calculation demonstrated that the
study had sufficient power (>0.80) for all primary outcomes examined.
Despite these limitations, to the best of our knowledge this is the first study to document increased genderdisparities in academic productivity following a major natural disaster. In addition to examining the proportion of
female first authors, we assessed the number and amount of grants obtained by female researchers before and after
the Great East Japan Earthquake. We also obtained reference data from a university minimally affected by theearthquake to improve our understanding of this phenomenon. This is the first study to conduct this type ofmultifaceted analysis. Major earthquakes and tsunamis occur repeatedly (51), and disasters like the Great East
Japan Earthquake can happen at any time and in many locations. It is therefore important that the scientificcommunity, institutional administrators, funding bodies, and policymakers take into consideration the present
findings that major natural disasters may disproportionately disadvantage some groups of scientists and worsen
existing disparities. Further research should be informed by our findings and seek to identify objective ways toassist female researchers in the aftermath of major disasters.
In conclusion, at three medical universities severely affected by the Great East Japan Earthquake, therepresentation of women among first authors of biomedical research articles significantly declined in the aftermathof the disaster. This effect was particularly evident in the first 2 years following the disaster and for papers related
to the Great East Japan Earthquake. Data from two medical universities minimally affected by the Great East JapanE75

Y. ONO et al.
Earthquake showed the opposite trend. Taken together, these findings suggest that major natural disasters reinforce
existing disparities in academic productivity between male and female researchers. This may have important shortand longer-term effects on the academic careers of women, which policymakers, institution leaders, and research
funders need to address appropriately.
ACKNOWLEDGEMENTS
This work was supported by grants from Academic collaboration grant between Tohoku University and Kobe
University for earthquake disaster reconstruction and disaster science (2022 grant to YO). The funders had no rolein the study design, data collection and analysis, or preparation of the manuscript. The authors thank the following
persons: Ms. Mariko Jyukei (a librarian, Library for Medical Sciences, Kobe University School of Medicine) for
her pertinent advice in determining the search strategy using PubMed®; Nozomi Ono, M.D. (Department of
Psychiatry, Hoshigaoka Hospital, Koriyama, Japan) for her assistance in reviewing the manuscript, and Diane
Williams, Ph.D., from Edanz (https://jp.edanz.com/ac) for editing a draft of this manuscript.

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