The research team, led by Tetsuji Minami of the National Cancer Center Japan alongside collaborators from several Japanese institutions, broke the 8.6 percent figure into distinct categories: 4.9 percent identified as gay or lesbian, 1.1 percent as bisexual, 1.0 percent as asexual or unsure of their attraction, and 1.6 percent as gender-diverse, meaning their current gender identity did not match the sex assigned to them at birth or fell outside the binary altogether. These estimates align with the 7.0 to 16.8 percent range reported in earlier Japanese studies conducted by private companies, government agencies, and sociologists, but earlier efforts suffered from convenience sampling, inadequate statistical adjustment, and narrow cohorts that limited their generalizability. By contrast, the new study calibrated its web-based sample against the Japanese government’s 2019 Comprehensive Survey of Living Conditions using a statistically demanding technique called inverse probability weighting.

The technical machinery behind the estimates deserves attention because it addresses a well-known weakness of internet surveys. Participants were drawn from a panel of 2.3 million people managed by Rakuten Insight, with stratified multistage sampling by age and sex, and a response rate of 65.7 percent among those invited. The researchers then applied two pre-set algorithms to screen out inattentive respondents, or “satisficers,” who straight-line their answers or fail directed attention checks, removing 9 percent of the raw sample. Sampling weights were predicted from a logistic regression model comparing the web survey respondents with the census-calibrated national survey, adjusting for area of residence, marital status, education, housing tenure, self-rated health, and smoking status. The resulting inverse probability weights allowed the team to produce population-level estimates with 95 percent confidence intervals, computed with a robust variance estimator, treating the findings explicitly as weighted distributions rather than causal effects, in line with modern descriptive epidemiology frameworks.

Measurement of sexual orientation and gender identity followed the internationally recommended “two-step approach,” which asks separately about sex assigned at birth and current gender identity, supplemented by a romantic and sexual attraction item to classify sexual orientation among cisgender respondents. Gender-diverse respondents were deliberately not reclassified by sexual orientation, and the authors caution that the gender-diverse category aggregates heterogeneous subgroups, including transgender, non-binary, and questioning individuals, because the survey instrument could not capture finer self-descriptions. Similarly, respondents who selected neither or unsure on the attraction item were grouped under an inclusive “asexual cisgender or unsure” label, an operationalization the authors urge readers to interpret cautiously since it may blend true asexuality with ongoing questioning. Inattentive respondents who reported anything other than male or female for assigned sex at birth were excluded as quality controls, consistent with Japan’s family register system, and were not intended to exclude minority identities.

Beyond headline prevalence, the study mapped striking demographic and socioeconomic patterns. All sexual and gender minority groups were younger on average than heterosexual respondents, with mean ages of 44.7 years for gay and lesbian participants, 38.3 for bisexual, 40.0 for asexual, and 38.4 for gender-diverse respondents, compared with 48.8 for heterosexual participants, and prevalence was concentrated under age 30. Gay respondents were more often male, while bisexual and asexual respondents were more often female, and gender-diverse respondents were evenly split by assigned sex. Marriage and partnership rates told a more complex story: only 47.7 percent of gay and lesbian respondents and 38.1 percent of gender-diverse respondents were married or partnered, versus 65.1 percent of heterosexual respondents, and a substantial share of gay and lesbian participants reported opposite-sex marriages or partnerships, a pattern the authors link to Confucian family norms emphasizing marriage and procreation, the absence of legal same-sex marriage recognition, and structural stigma.

Socioeconomic disparities emerged with unusual clarity because the national calibration allowed income, education, employment, insurance, and housing comparisons. Lower household equivalent income was more common among minority groups, particularly male sexual minorities and female gender-diverse respondents, and women had lower incomes than men within every category. Educational attainment diverged sharply from Western patterns: whereas studies in the United States and Europe generally find gay and bisexual men more educated than heterosexual men, Japanese gay, lesbian, and bisexual male respondents showed the opposite trend, with heterosexual men most likely to hold degrees. Employment differences also inverted expectations in places, with female sexual minorities more likely to be employed than heterosexual women, plausibly because married Japanese women are often outside the labor force while minority women marry less often. Health insurance coverage was lower among minority respondents of both sexes, and housing tenure varied significantly only among men, with asexual men and lesbian women least likely to own homes.

Health indicators painted a mixed picture that partially contradicts Western literature. Psychological distress, measured with the Kessler-6 scale, was consistently more common among minority respondents of both assigned sexes, echoing minority stress theory, which holds that stigma and marginalization drive mental health disparities. Body mass index patterns were also distinctive: underweight was more common among female minority respondents, while overweight and obesity clustered among male bisexual and asexual respondents and female asexual respondents. Perhaps most surprising, current smoking and habitual drinking showed limited or reversed differences, with minority groups tending to drink less than heterosexual respondents, contrary to consistent findings from England, Canada, and the United States. Substance use other than tobacco and alcohol was higher among minority respondents but remained rare overall. Medical comorbidity did not differ significantly once results were stratified by assigned sex at birth, and self-rated health differences disappeared under stratification, prompting the authors to call for future studies with covariate adjustment and clinical data linkage.

The significance of these findings extends well beyond Japanese borders. Until now, virtually all nationally representative data on sexual and gender minority populations came from Western countries, including the United States, the Netherlands, Sweden, Portugal, Canada, and the United Kingdom, creating a geographic evidence gap the authors argue reflects both research neglect and, in parts of Asia, legal environments where same-sex acts remain criminalized. Japan presents a distinctive hybrid context: same-sex relationships were historically tolerated within certain cultural traditions, cross-national analyses suggest relatively low structural stigma and low non-disclosure, yet Japan remains the only G7 nation without comprehensive anti-discrimination legislation or marriage equality. The study’s documentation of opposite-sex marriages among gay and lesbian respondents, observed at levels between the low Western figures of 3 to 9 percent and the much higher Chinese figures of 33 to 51 percent, offers rare quantitative grounding for understanding how family norms and legal structures shape minority lives in East Asian settings.

The authors draw direct policy implications from their data. They recommend that national administrative surveys routinely incorporate sexual orientation and gender identity items and household modules that recognize diverse partnership structures, enabling ongoing surveillance of socioeconomic disparities and targeted resource allocation. They call for accessible mental health support and anti-discrimination efforts in schools and workplaces to reduce the psychological burden the Kessler-6 results document, and for longitudinal and panel designs that oversample small subgroups and analyze intersections of age and assigned sex. Acknowledging limitations, including self-reported data, potential social desirability bias, residual web-survey selection bias that weighting could reduce but not eliminate, and the coarse aggregation of gender-diverse subgroups, the team nevertheless positions the work as a foundational step. With an estimated 8.6 percent of Japan’s population identifying as a sexual or gender minority, the study transforms a population previously invisible in national statistics into a measurable, monitorable constituency whose health and socioeconomic well-being can now be tracked, compared, and protected.

Subject of Research: National estimation of the proportion and characteristics of sexual and gender minorities in Japan using a nationwide cross-sectional internet survey

Article Title: Estimation of Sexual and Gender Diversity Among People Aged 15 Years and Older in Japan: A Descriptive Epidemiological Study Using a Nationwide Cross-Sectional Internet Survey

Article References: Minami, T., Inoue, M., Matsushima, M., Yoshioka, T., & Tabuchi, T. (2026). Estimation of Sexual and Gender Diversity Among People Aged 15 Years and Older in Japan: A Descriptive Epidemiological Study Using a Nationwide Cross-Sectional Internet Survey. Archives of Sexual Behavior. https://doi.org/10.1007/s10508-026-03515-0

Image Credits: AI Generated

DOI: 10.1007/s10508-026-03515-0

Keywords: sexual orientation, gender identity, sexual and gender minorities, Japan, descriptive epidemiology, national survey, LGBTQ, health disparities, minority stress, inverse probability weighting, bisexual, transgender

The article, the product of a consensus workshop at an international meeting of the Organization for the Study of Sex Differences in May 2019 and a subsequent expert meeting in Ottawa sponsored by the Institute of Gender and Health of the Canadian Institutes of Health Research, brings together a strikingly interdisciplinary authorship. Neuroscientists, physiologists, historians of science, internists, nephrologists, nurses, social workers, epidemiologists, and implementation scientists, led by co-first authors Gillian Einstein of the University of Toronto and Louise Pilote of McGill University, along with senior author Cara Tannenbaum of the Université de Montréal, collectively propose a name and a vision for what they call Sex and Gender Science. They describe it as a transdisciplinary, integrative, bio-social-medical field that combines diverse methods to investigate how sex and gender dynamically interact to shape disease outcomes, illness experiences, and the very conduct of science itself.

The conceptual core of the proposal rests on the claim that sex and gender are interactional and deeply interwoven. Within sex, the authors situate hormonal, genetic, physiological, and morphological processes and characteristics, from chromosomal complements and gonadal steroid fluctuations to organ-level physiology and morphology. Within gender, they include roles, relations, norms, institutional imperatives, and identities, along with their downstream consequences for behavior, environment, access to resources, and exposure to stress. Crucially, the authors argue, these domains are not merely additive; they operate on each other. Gendered expectations influence hormonal and physiological responses, while biological traits shape how institutions and individuals respond to a person. In this framing, gender literally gets under the skin, while sex expresses itself inescapably through social worlds.

Concrete clinical examples illustrate the stakes. Acute coronary syndrome presents differently across patients in ways that reflect both vascular biology and gendered patterns of symptom recognition, care-seeking, and triage in emergency departments. In Alzheimer’s disease, two-thirds of affected individuals are women, and research discussed in the article points to interactions between reproductive histories, such as surgical menopause, stress physiology involving corticotropin-releasing factor, and gendered lifecourse exposures, rather than a single biological cause. In nephrology, sex differences in kidney physiology intersect with gendered differences in access to dialysis, transplantation, and medication adherence. Even occupational health reflects the interplay, as shown by analyses of personal protective equipment designed around male body norms during the COVID-19 pandemic, where ill-fitting gear compromised the safety of women in frontline roles. The authors also cite emerging concerns about automatic gender recognition technologies and gendered patterns of cannabis use disorder as domains where simplistic binary assumptions fail patients and obscure mechanisms.

Methodologically, Sex and Gender Science is defined by its refusal to choose between reductionist and constructionist approaches. The authors assume complexity, question established stereotypes and binaries, and support evolving methods that can capture interactional effects over time. That means experimental work in animal models attentive to sex as a biological variable can be paired with qualitative and quantitative human studies of gendered environments; intersectional epidemiology can be integrated with endocrine and genetic measurement; and implementation science can test whether sex- and gender-informed findings actually change clinical practice. The transdisciplinary ambition is deliberate: rather than creating another silo, the field aims to weave together the humanities, social sciences, and biomedical sciences, drawing on decades of feminist scholarship, gender studies, and basic biology that have until now developed along separate tracks.

The historical context for this synthesis is instructive. Biomedical research long treated male bodies as the default experimental subject, from clinical trials to preclinical animal studies, on the grounds that hormonal cycles made female subjects inconveniently variable. Landmark policy changes in the United States, Canada, and Europe over the past three decades required the inclusion of women in clinical research and the accounting for sex as a biological variable in grant applications. Simultaneously, scholars in gender and health demonstrated that social positions assigned by gender produce measurable health inequities, from differential exposure to violence and occupational hazards to differences in healthcare access and treatment. What was missing, the authors argue, was a systematic framework linking these two streams, so that researchers could ask not simply whether men and women differ, but how biological and social variables interact to produce particular outcomes in particular individuals.

The consensus process behind the article gives its claims unusual weight. By convening basic scientists who study sexually dimorphic neural circuits and stress pathways alongside clinicians, historians, and social scientists, the meeting produced a shared vocabulary and a shared commitment. The resulting highlights, as stated by the authors, include forging new ways of knowing about wellness, health, and disease; assuming complexity and questioning binaries; providing a more comprehensive picture of human health when sex and gender are studied together; and starting from the particularity of individuals with the ultimate goal of improving the well-being of all. That final point is significant politically as well as scientifically: the field explicitly encompasses transgender and gender-diverse populations, recognizing that gender identity itself interacts with biology in ways that mainstream medicine has historically ignored or pathologized.

For clinical practice, the implications are immediate. Diagnostic criteria, drug dosing, device design, and screening schedules built on averages derived from unrepresentative populations can be reexamined through the interactional lens that Sex and Gender Science provides. A patient is never just a sex and never just a gender; each person embodies a unique configuration of hormonal milieu, genetic background, organ physiology, gendered labor and caregiving burdens, institutional exposure, and identity. Precision medicine that ignores either domain is, on this argument, not precise at all. The authors point to the growth of national organizations, such as the Canadian Organization for Sex and Gender, and to curriculum reform in medical schools as evidence that institutional infrastructure is beginning to catch up with the science.

The article also acknowledges open questions and future directions. Measuring gender as rigorously as sex is measured remains an active methodological challenge, with validated instruments still evolving. Distinguishing interaction effects from confounding in observational data requires statistical sophistication and large, diverse cohorts. And the field must navigate political controversies surrounding sex and gender discourse without retreating from empirical evidence. The authors frame these challenges as generative rather than paralyzing, arguing that the very friction of integrating methods across disciplines produces better science, sharper questions, and more honest uncertainty. They call for funding structures, training programs, and publication venues that reward transdisciplinary work rather than penalizing it in favor of narrow, single-domain studies.

If Sex and Gender Science succeeds on its own terms, the payoff could be a medicine that finally matches the complexity of the patients it serves: one in which a heart attack, a dementia diagnosis, a kidney transplant, or a workplace injury is understood through the full entanglement of chromosomes, hormones, organs, identities, relationships, and institutions that shaped it. The article’s message to researchers is blunt in its simplicity. It is not either sex or gender; it is both, together. After decades of separation, the biological and the social are being brought back into a single scientific frame, and the authors argue that the health of everyone stands to gain from what this emerging field discovers next.

Subject of Research: Sex and Gender Science, an emerging transdisciplinary field integrating biological sex and social gender in health research

Article Title: Sex & Gender Science: integrating the social with the biological

Article References: Einstein, G., Pilote, L., De Vries, G., Richardson, S., Forger, N., Perović, M., Ahmed, S., Bauer, G., Graham, I. D., Greaves, L., Klinge, I., Logie, C. H., McKay, D., McMurtry, M. S., Oliffe, J. L., & Tannenbaum, C. (2026). Sex & Gender Science: integrating the social with the biological. Biology of Sex Differences. https://doi.org/10.1186/s13293-026-00977-8

Image Credits: AI Generated

DOI: 10.1186/s13293-026-00977-8

Keywords: sex and gender science, biological sex, gender and health, transdisciplinary research, Biology of Sex Differences, health inequities, sex differences, gender identity, precision medicine, Alzheimer's disease, cardiovascular disease, Canadian Institutes of Health Research

The hijra are neither a new phenomenon nor a Western import. Anthropological and historical scholarship, including the classic ethnographic work of Serena Nanda on the hijras of India, has documented for decades a community whose members are typically assigned male at birth but who live outside the male-female binary, often within structured guru-chela (teacher-disciple) households, performing ritual roles at weddings and births. Historical analyses of classical Indian medicine, such as the work of Sweet and Zwilling, trace taxonomies of gender and sexual variance back many centuries, demonstrating that third-gender categories existed in South Asian thought long before modern sexology or contemporary gender politics. What is new is the state’s attempt to translate this culturally embedded identity into the bureaucratic language of law, epidemiology, and public health—and it is precisely at this translation step, Hossain argues, that trouble begins.

Bangladesh took a pioneering step in 2013, when the Ministry of Social Welfare issued a gazette notification recognizing the hijra population as “Hijra Lingo,” a distinct sex/gender category. On paper, this granted formal recognition to a community that had long faced severe discrimination and social exclusion—exclusion documented in reviews published in journals such as Heliyon, which catalogued barriers to employment, housing, education, and healthcare. But the Bangladeshi recognition came with a definitional ambiguity that has haunted policy ever since. The gazette did not clearly specify whether hijra status was reserved for individuals born with specific anatomical characteristics, or whether it encompassed the broader community of masculine-to-feminine gender-diverse people, including those who might in Western frameworks be described as transgender women. In practice, Hossain notes, some hijra identified through medical screening were required to undergo physical examinations—a process widely criticized as degrading and scientifically incoherent, since it imposed a biological essentialism on what is fundamentally a social and cultural identity.

The consequences of this ambiguity are not merely symbolic. Health surveillance systems in Bangladesh have struggled to categorize the population consistently. Data from the Integrated Biological and Behavioural Surveillance (IBBS) 2020 survey, analyzed in a recent study in Discover Public Health, reveal geographic and age-related patterns in HIV-related indicators among “transgender women or Hijra” populations—a composite label that itself illustrates the category confusion. The Ministry of Health and Family Welfare issued guidelines in 2023 on standard operating procedures for sexual and reproductive health services for the “third gender population,” yet the operational definitions underlying such documents continue to waver between cultural, anatomical, and identity-based criteria. When a health worker cannot determine which category a client belongs to, or when program eligibility criteria exclude people who identify as hijra but do not fit an official anatomical definition, the result is gaps in HIV prevention, hormone-related care, and mental health services.

Pakistan pursued a different legislative route. The Transgender Persons (Protection of Rights) Act of 2018 was among the most progressive laws of its kind in the Muslim world, allowing individuals to self-identify as male, female, khwaja sira, or a combination, and to have that identity reflected on national identity cards. Crucially, the Act was grounded in self-perceived gender identity rather than anatomical verification, aligning Pakistani law more closely with international human rights frameworks. For a time, it was hailed as a model for the region.

Yet the Pakistani experience demonstrates that even self-identification laws are vulnerable to definitional backlash. In 2023, the Federal Shariat Court struck down key provisions of the Act, ruling that certain aspects were “against Islam,” a decision reported widely in Pakistani media and one that plunged the community into renewed legal uncertainty. The court’s objections centered in part on the conflation of intersex individuals—whose status in Islamic jurisprudence has long been acknowledged through the category of khuntha—with transgender women who are not intersex. Critics of the Act argued that it had blurred this line, extending protections designed for a biologically distinct group to a broader gender-diverse population, thereby provoking religious and political opposition that ultimately endangered the entire legal framework. The episode illustrates, Hossain contends, that how a law defines its protected category is not a drafting technicality but the very terrain on which legal battles are fought.

The comparison between the two countries yields what Hossain describes as a paradox of recognition, echoing the analysis of anthropologist Adnan Hossain, who wrote in Culture, Health & Sexuality about how Bangladesh’s recognition of hijra simultaneously elevated the category in official discourse while creating new hierarchies and exclusions within the community itself. Those who fit stereotypical expectations of what a hijra “looks like” gained access to recognition and its modest benefits, while others—particularly those who identify as transgender women without any claim to hijra cultural identity—found themselves in a definitional no-man’s-land, eligible for neither the protections attached to the hijra category nor any other formal recognition.

The stakes extend into education and public discourse. In 2024, Bangladesh witnessed a public controversy over a Class VII textbook chapter titled “Sharifa’s Story,” which depicted the life of a hijra individual. Media outlets reported escalating objections from conservative quarters, and the government ultimately removed the chapter. Hossain points to this episode as evidence that even carefully framed, culturally grounded narratives about the hijra community can become flashpoints when the broader public lacks a scientifically and historically accurate understanding of who hijra are and how their identity differs from, and overlaps with, contemporary transgender identities.

Against this backdrop, Hossain’s letter makes a case that will resonate far beyond South Asia: terminology in science and policy must be both culturally grounded and analytically precise. He draws on commentary in the Archives of Sexual Behavior by Paul Vasey, who examined questions of objectivity and inter-subjectivity in the study of male femininity across cultures, to argue that researchers must resist the urge to flatten culturally specific identities into universal Western categories such as “transgender women.” At the same time, he cautions against the opposite error—romanticizing cultural categories to the point of freezing them in essentialist definitions that exclude community members and invite judicial attack. The scientific literature on gender diversity, Hossain suggests, needs what might be called a bilingual approach: fluency in the local historical and cultural meanings of terms like hijra and khwaja sira, combined with rigorous attention to how those terms map onto health-relevant variables such as HIV risk, hormone use, surgical history, and access to care.

The practical implications are concrete. Survey instruments, national censuses, and HIV surveillance systems should record identity terms as respondents themselves use them, rather than forcing choices between imported or imposed categories. Legal drafters, he argues, should separate protections for intersex individuals—whose needs involve medical and bodily integrity concerns—from protections based on gender identity and expression, so that a single contested definition cannot be used to topple the entire edifice of rights. Public health programs should define eligibility by vulnerability and need rather than by anatomical screening. And educators and communicators should present the hijra community in its full historical depth, which makes both erasure and caricature harder to sustain.

What emerges from this comparative analysis is a lesson with global reach. Around the world, from South Asia to Africa to parts of Latin America, states are grappling with how to recognize, count, protect, and serve gender-diverse populations. The Bangladeshi and Pakistani experiences show that recognition without definitional clarity can produce exclusion, surveillance, and legal fragility, while recognition built on self-identification can still collapse if it fails to anticipate and address the specific religious, cultural, and anatomical fault lines in a given society. Terminology, in other words, is not the decoration on top of policy—it is the load-bearing structure. Getting it wrong does not merely confuse datasets; it determines who is seen, who is served, and who is left behind.