Sexual Behaviors among Individuals Aged 20-49 in Japan: Initial Findings from a Quasi-Representative National Survey, 2022

ABSTRACT

Nationally representative data on sexual health and behaviors in Japan are scarce. We conducted an online survey, including questions about a range of topics related to sexual behaviors and outcomes. The sample, including 8000 men and women aged 20–49 years in Japan, was stratified by sex and weighted with respect to age, marital status, and region of residence to reflect the population of Japan. Of the women, 82.9% and 10.0% reported that they were heterosexual and asexual, respectively; corresponding proportions for men were 87.4% and 6.9%. 15.3% of women and 19.8% of men reported never having had any partners with whom they engaged in vaginal, anal, or oral sex. 45.3% of women and 44.5% of men reported not having had any sexual partners during the past year; this proportion was highest among women aged 40–49 years (51.7%) and men aged 20–29 years (55.1%). The proportion of those reporting satisfaction with their sex life was 27.8% for women and 23.1% for men; 17.6% of women and 27.1% of men reported dissatisfaction. Pornography use of ≥3 times per week was most common among those aged 20–29 years (6.5% of women; 34.8% of men), and the frequency of pornography use decreased slightly with age. 4.0% of women and 48.3% of men reported ever having used commercial sex worker services in their lifetime. This survey-based study provides data on sexual behaviors and health outcomes in Japan. Compared to other high-income countries, levels of sexual inexperience and inactivity seem to be high in Japan.

The improvement of sexual and reproductive health remains a priority on the public health agenda in Japan, as it is elsewhere around the world (Starrs et al., 2018; World Health Organization, 2006). National surveys on sexual health and behavior play an important role in informing the design and assessment of interventions to improve sexual health and increase the understanding of human sexual behaviors among clinicians, educators, and the general public.

The early sexual health surveys, such as the first National Survey of Sexual Attitudes and Lifestyles (Natsal-1; Wellings et al., 2001) in Britain or The National Health and Social Life Survey (NHSLS; Laumann et al., 1994) in the US, both conducted in the 1990s, tended to focus on the negative outcomes of sexual activity, including sexually transmitted infections (STIs) and unintended pregnancy. In recent years, however, other aspects of sexual health, such as sexual freedom, satisfaction, and wellbeing, have been increasingly recognized as important components of sexual and reproductive health (Starrs et al., 2018; Wellings & Johnson, 2013; World Health Organization, 2006), with this broadened scope in sexual health research being reflected in the content of national surveys in many Western countries (Bajos et al., 2010; Hansen et al., 2020; Herbenick et al., 2017; Hogben et al., 2017; Matthiesen et al., 2021; Mercer et al., 2013; New Zealand Ministry of Health, 2019; Public Health Agency of Sweden, 2019; Rissel et al., 2014; Rotermann & McKay, 2020; Slaymaker et al., 2020). Over the past decades, there have been many developments that have affected sexual behaviors: for example, dating apps have become widely used (Rosenfeld et al., 2019) and pornography is now free and easily available online (Malki et al., 2021; Miller et al., 2020; Regnerus et al., 2016; Rissel et al., 2017). Concurrently, it has been reported that the frequency of sexual activity may have declined among adults in many countries (Beutel et al., 2018; Burghardt et al., 2020; Twenge et al., 2017; Ueda et al., 2020; Wellings et al., 2019), including Japan (Ghaznavi et al., 2020), and it has been suggested that the COVID-19 pandemic has accelerated this trend (Mercer et al., 2021).

There is a dearth of research concerning sexual health and behavior in East Asia, including Japan (Slaymaker et al., 2020). Previous Japanese studies on sexual health outcomes have been small and used limited samples (Hayashi et al., 1999), been based on limited age groups (Kawamura, 2012; Saotome, 2010), or been restricted to questions included in surveys focusing on heterosexual marriage and factors associated with fertility (Ghaznavi et al., 2019).

Here, we present the data collected from the first round of the National Inventory of Japanese Sexual Behavior (NInJaS), a quasi-representative national survey of Japanese adults aged 20–49 conducted in 2022. We use NInJaS to present a descriptive overview of socioeconomic/demographic variables, sexual orientation, sexual partners and frequency, satisfaction, and other sexual behaviors among Japanese adults.

Method

Study population

The survey was administered online between July 5 and 6, 2022 via Cross Marketing Inc. (https://www.cross-m.co.jp/en/), an online survey company. As of January 2022, Cross Marketing Inc. had access to a total of approximately 5.41 million panel members with diverse demographic, socioeconomic, and geographic characteristics. The survey panel for the current study consisted of those aged 20 to 49 years who were able to respond to surveys in Japanese. In return for responding to surveys on a voluntary basis, respondents receive “points” (calculated based on question volume answered) which could be used to purchase goods/services from partner companies.

The target sample size was set at 8000, divided equally across men and women and 10-year age groups (20–29, 30–39, and 40–49 years). Once the survey was made available, respondents participated on a first-come first-served basis, and the survey period ended once predetermined quotas for each sex-and-age group were reached.

Survey participants were required to pledge they would respond honestly before answering the remaining survey questions. Prior research has found that this method improves response quality, as evidenced by decreased straight-line and midpoint responses (Masuda et al., 2019). Respondents were required to answer every question, so no missing values were generated.

The study was approved by the Regional Ethics Committee at the University of Tokyo, Japan. Respondents were required to provide consent before beginning the survey.

Measures

The survey was designed based on a review of previous sexual health surveys, such as those conducted in the US (Herbenick et al., 2017), the UK (Mercer et al., 2013), and Sweden (Public Health Agency of Sweden, 2019). Some questions were taken directly from the British Natsal survey; these questions were translated by investigators who were proficient in both Japanese and English.

An English translation of the full survey is provided in the Supplementary Material. In brief, the survey included questions about sociodemographic variables and relationship status, sexual orientation, self-rated attractiveness and anthropometric data, lifetime experience of sexual intercourse, number of sexual partners including and excluding commercial sex workers, age at first sexual intercourse, as well as questions regarding sexual behaviors and the perception of one’s sex life during the past year: frequency of masturbation and pornography use, frequency of sexual intercourse, satisfaction with one’s sex life, satisfaction with one’s sexual frequency, and the importance of sexual activity. “Sexual intercourse” was defined within the survey as consisting of vaginal, anal, and/or oral intercourse, as in previous surveys (Mercer et al., 2013). Questions regarding sexual partners referred to the number of individuals with which one has had sexual intercourse. Here, we present the results of all survey questions with the exception of one which was found to have questionable internal validity (see Supplementary Material).

Sample weights

Sample weights were calculated to reflect the 2020 Population Census of Japan, stratified by 5-year age groups (20–24, 25–29, 30–34, 35–39, 40–44, 45–49), marital status (married and unmarried), and region (Hokkaido/Tohoku, Kanto, Chubu, Kansai, Chugoku/Shikoku, and Kyushu/Okinawa). Analyses were performed separately for women and men. After weighting, the sample closely reflected the Population Census of Japan (eTables 1–3).

In order to assess the representativeness of the sample after the application of sample weights, we compared the educational status and income of the NInJaS sample to that of the National Fertility Survey, a nationally representative survey conducted in Japan in 2015 (National Institute of Population and Social Security Research, 2016). Details of the survey are presented elsewhere (National Institute of Population and Social Security Research, 2016) and have been used in prior studies of sexual health and behavior in Japan (Ghaznavi et al., 2019, 2020).

Statistical analyses

All analyses were conducted in R version 4.1.1 and Stata version 17.0. We describe the results of the survey by sex, using the full age range, and by 10-year age groups. All results are presented using sample weights such that results were representative of the national population with respect to age, marital status, and region of residence.

Results

Demographic Characteristics

The weighted demographic characteristics of NInJaS respondents, stratified by sex and ten-year age groups, are shown in Table 1. The mean (SD) age was 36.3 (8.7) years for women and 36.4 (8.6) years for men. Among women, 56.5% were married, 2.7% were unmarried and cohabiting, 8.7% were unmarried, not cohabiting, and in a romantic relationship, and 32.0% were single. The corresponding numbers for men were 50.0, 1.8, 6.7, and 41.5%.

Table 1. Weighted demographic characteristics of NInJaS respondents, stratified by sex and ten-year age groups.

		Women					Men
		20–29 (N = 1333)	30–39 (N = 1333)	40–49 (N = 1334)	p	20–49 (N = 4000)	20–29 (N = 1333)	30–39 (N = 1333)	40–49 (N = 1334)	p	20–49 (N = 4000)
Age	Mean (SD)	24.6 (3.2)	34.7 (2.9)	44.8 (2.5)	<.0001	36.3 (8.7)	24.8 (3.2)	34.9 (3.0)	44.9 (2.5)	<.0001	36.4 (8.6)
Marital status	Married	21.1	65.5	72.0	<.0001	56.5	15.2	56.6	66.9	<.0001	50.0
	Never married	73.0	30.5	20.8		37.6	80.2	40.3	29.5		46.3
	Previously married	5.9	4.1	7.2		5.9	4.6	3.1	3.5		3.7
Relationship status	Married	21.1	65.5	72.0	<.0001	56.5	15.2	56.6	66.9	<.0001	50.0
	Cohabiting	6.6	1.8	1.0		2.7	3.3	2.0	0.8		1.8
	In a relationship	17.8	5.9	5.1		8.7	12.3	5.3	4.1		6.7
	Not in a relationship	54.5	26.8	21.9		32.0	69.2	36.2	28.2		41.5
Sexual orientation	Heterosexual	75.7	83.8	86.8	<.0001	82.9	80.4	87.4	91.7	<.0001	87.4
	Bisexual	7.1	6.2	3.9		5.5	5.2	3.4	2.2		3.4
	Homosexual	1.5	0.7	0.6		0.9	2.9	2.1	1.4		2.0
	Asexual	14.7	8.6	8.2		10.0	11.2	6.6	4.5		6.9
	Other	1.1	0.7	0.5		0.7	0.4	0.6	0.2		0.3
Occupational status	Full-time	43.7	35.0	32.5	<.0001	36.2	53.1	76.9	80.8	<.0001	72.3
	Part-time	18.9	27.0	28.2		25.4	11.0	7.6	4.2		7.1
	Self-employed	2.7	4.2	4.6		4.0	3.1	5.9	8.7		6.3
	Student	17.4	0.0	0.0		4.6	19.6	0.1	0.0		5.2
	Housewife/husband	8.0	26.9	28.8		22.7	0.3	1.0	0.8		0.7
	Unemployed	9.3	6.9	6.0		7.1	12.9	8.6	5.6		8.4
Income	<100	38.3	40.8	45.1	<.0001	41.9	35.6	10.8	7.7	<.0001	16.0
(in ¥10,000s)	100–299	35.7	29.8	29.0		31.0	26.1	16.7	12.1		17.2
	300–499	19.9	18.8	15.4		17.6	27.7	35.2	30.4		31.2
	500–799	4.2	7.3	7.3		6.5	8.5	29.7	32.4		25.2
	>800	2.0	3.3	3.2		2.9	2.2	7.6	17.4		10.3
Education	High school or less	32.0	29.2	28.1	<.0001	29.5	30.6	27.4	24.8	<.0001	27.2
	Trade/vocational school or short college	19.0	27.5	36.4		29.0	11.2	15.5	15.9		14.5
	Undergraduate studies	47.5	40.6	33.1		39.3	52.2	50.4	47.3		49.6
	Graduate studies	1.5	2.7	2.4		2.3	6.0	6.7	12.0		8.7
Region of residence	Hokkaido & Tohoku	9.7	10.7	10.6	.9903	10.4	10.1	10.7	10.7	.9996	10.5
	Kanto	37.4	35.9	35.5		36.1	37.1	36.3	36.2		36.5
	Chubu	16.1	16.2	16.6		16.4	17.1	17.2	17.3		17.2
	Kansai	18.3	17.3	18.0		17.8	17.5	16.6	17.1		17.0
	Chugoku & Shikoku	7.8	8.2	8.4		8.2	7.9	8.3	8.4		8.2
	Kyushu & Okinawa	10.8	11.7	10.9		11.1	10.3	11.1	10.4		10.6
Urbanity of residence	Within Tokyo’s 23 wards or prefectural capital	30.1	29.6	31.6	.0699	30.6	31.9	30.1	31.4	.0531	31.1
	In Tokyo but outside of the 23 wards	4.5	4.2	3.8		4.1	4.0	5.4	4.3		4.6
	Cities other than prefectural capitals (population >500,000)	15.5	14.6	14.8		14.9	14.3	13.3	12.7		13.3
	Cities other than prefectural capitals (population 300,000–499,999)	15.1	13.1	13.2		13.7	13.3	12.3	11.0		12.0
	Cities other than prefectural capitals (population <300,000)	22.4	27.5	27.5		26.2	25.7	27.9	31.8		28.9
	Village or town	12.4	11.2	9.1		10.6	10.8	11.1	8.8		10.1
Height	Mean (SD)	158.0 (7.3)	158.2 (6.3)	158.4 (5.1)	.4274	158.2 (6.1)	170.3 (8.5)	170.7 (7.0)	171.3 (5.9)	.0044	170.8 (6.9)
Weight	Mean (SD)	50.6 (10.1)	51.8 (9.4)	52.7 (8.6)	<0.0001	51.8 (9.4)	63.4 (14.8)	65.8 (12.2)	68.9 (11.1)	<0.0001	66.5 (12.6)
How would you describe your attractiveness?	Above average	9.5	9.3	8.6	.0607	9.0	9.8	8.6	8.9	.6593	9.0
	About average	53.9	54.8	59.4		56.5	53.4	55.9	56.3		55.4
	Below average	36.6	35.9	32.0		34.4	36.8	35.5	34.8		35.5

With respect to sexual orientation, 82.9% of women and 87.4% of men responded that they were heterosexual; these proportions were lowest among those aged 20–29 years (women: 75.7%; men 80.4%). Among women, 5.5% and 0.9% responded that they were bisexual and homosexual, respectively; corresponding numbers for men were 3.4 and 2.0%. The proportion who responded that they were asexual was 10.0% for women and 6.9% for men, with these proportions being the highest among those aged 20–29 (women: 14.7%; men 11.2%) and decreasing with age.

The application of sample weights successfully made the NInJaS sample representative of the national population with respect to age, region, and marital status (Supplement eTables 1–3). The weighted NInJaS sample was more educated and had slightly higher income than that of the 2015 National Fertility Survey (Supplement eTables 4 & 5).

Sexual Experience, Partners, and Debut

The weighted proportions of NInJaS respondents reporting certain sexual behaviors, stratified by sex and ten-year age groups, are shown in Table 2 for women and Table 3 for men. In total, 15.3% of women reported never having had any sexual partners with whom they engaged in vaginal, anal, or oral sex; this proportion was 29.7% among women aged 20–29 years and 7.3% among women aged 40–49 years. Among men, 19.8% reported never having had any sexual partners with whom they engaged in vaginal, anal, or oral sex; this proportion was 43.0% among men aged 20–29 years and 7.4% among men aged 40–49 years.

Table 2. Weighted proportions of female NInJaS respondents reporting certain sexual behaviors, stratified by sex and ten-year age groups.

		20–29 (N = 1333)	30–39 (N = 1333)	40–49 (N = 1334)	p	20–49 (N = 4000)
With whom have you had sexual experiences so far?	Only with the opposite sex; never with the same sex	64.6	81.0	87.1	<.0001	79.3
	Mostly with the opposite sex; occasionally with the same sex	5.0	3.4	2.5		3.5
	Both with the opposite and same sexes in roughly equal amounts	1.6	1.0	0.9		1.1
	Mostly with the same sex; occasionally with the opposite sex	0.7	0.3	0.5		0.5
	Only with the same sex; never with the opposite sex	1.2	0.8	0.8		0.9
	I have never had any sexual experiences	26.9	13.5	8.2		14.8
Have you ever had sexual partners (vaginal sex, anal sex, and/or oral sex only)?	No	29.7	14.0	7.3		15.3
	Yes	70.3	86.0	92.7		84.7
Number of lifetime sexual partners (including CSW)	0	29.7	14.0	7.3	<.0001	15.3
	1	20.5	17.2	16.7		17.9
	2	10.3	11.2	13.1		11.8
	3–4	15.2	19.7	18.7		18.1
	5–9	11.0	18.7	21.8		18.0
	10 or more	13.2	19.3	22.4		19.0
Number of lifetime sexual partners (including CSW) [median (IQR)]		1 (0–4)	3 (1–6)	4 (2–8)		3 (1–6)
Number of lifetime sexual partners (excluding CSW)	0	31.7	15.7	8.2	<.0001	16.8
	1	20.4	17.2	16.9		17.9
	2	10.3	11.2	12.9		11.6
	3–4	14.7	19.2	18.6		17.8
	5–9	10.5	19.3	22.8		18.5
	10 or more	12.4	17.5	20.6		17.5
Number of lifetime sexual partners (excluding CSW) [median (IQR)]		1 (0–4)	3 (1–6)	4 (1–7)		3 (1–6)
Age at first volitional sexual intercourse [median (IQR)]		20 (18-)*	20 (17–24)	20 (18–22)		20 (18–24)
First sexual intercourse before age 16 years		9.7	9.2	6.2	.0018	8.0
Number of sexual partners in past year (including CSW)	0	41.7	39.7	51.7	<.0001	45.3
	1	45.2	52.6	43.8		46.9
	2 or more	13.1	7.8	4.6		7.8
Number of sexual partners in past year (including CSW) [median (IQR)]		1 (0–1)	1 (0–1)	0 (0–1)		1 (0–1)
Number of sexual partners in past year (excluding CSW)	0	42.6	41.1	52.5	<.0001	46.3
	1	45.4	52.8	44.2		47.2
	2 or more	12.0	6.1	3.3		6.5
Number of sexual partners in past year (excluding CSW) [median (IQR)]		1 (0–1)	1 (0–1)	0 (0–1)		1 (0–1)
Sexual intercourse frequency in past year (including CSW)	Daily or almost daily	1.0	1.1	0.5	<.0001	0.8
	3–5 times per week	4.9	1.9	1.0		2.3
	1–2 times per week	13.8	10.9	6.6		9.9
	2–3 times per month	17.4	17.6	11.4		15.0
	Once per month or less	21.2	28.9	28.8		26.8
	Never	41.7	39.7	51.7		45.3
Sexual intercourse frequency in past year (excluding CSW)	Daily or almost daily	0.8	0.6	0.3	<.0001	0.5
	3–5 times per week	4.1	2.2	1.0		2.2
	1–2 times per week	13.2	10.3	6.5		9.5
	2–3 times per month	17.7	17.5	11.4		14.9
	Once per month or less	21.7	28.4	28.3		26.6
	Never	42.6	41.1	52.5		46.3
Masturbation frequency	Daily or almost daily	3.0	2.1	0.9	<.0001	1.8
	3–5 times per week	4.7	3.7	2.7		3.5
	1–2 times per week	14.4	11.6	6.7		10.2
	2–3 times per month	11.7	14.1	10.2		11.8
	Once per month or less	13.8	20.1	25.3		20.6
	Never or almost never	52.4	48.4	54.3		51.9
Pornography viewing frequency	Daily or almost daily	2.1	2.0	0.7	<.0001	1.5
	3–5 times per week	4.3	2.3	1.3		2.4
	1–2 times per week	10.1	7.0	2.8		6.1
	2–3 times per month	10.2	9.0	5.5		7.8
	Once per month or less	17.5	19.1	17.0		17.8
	Never or almost never	55.8	60.6	72.8		64.5
Does your pornography viewing (or your partner’s) exert an effect on your sex life?	No effect	29.7	26.8	20.5	<.0001	24.9
	Good effect	11.7	11.2	7.1		9.6
	Bad effect	3.8	2.6	1.8		2.6
	Unsure	30.9	37.1	40.1		36.7
	Neither I nor my partner use pornography	24.0	22.3	30.5		26.2
“I am satisfied with my sex life”	Strongly agree	7.4	7.6	6.1	.0001	6.9
	Agree	25.9	20.1	18.5		20.9
	Neither agree nor disagree	51.5	52.9	57.8		54.6
	Disagree	8.9	10.5	11.0		10.3
	Strongly disagree	6.4	9.0	6.6		7.3
Would you like to change your frequency of sexual intercourse?	Yes, I would like to increase it a lot	6.0	6.5	4.6	<.0001	5.6
	Yes, I would like to increase it a little	24.3	21.9	17.0		20.5
	No	58.3	56.6	65.1		60.6
	Yes, I would like to decrease it a little	3.7	5.4	3.4		4.1
	Yes, I would like to decrease it a lot	7.8	9.7	9.9		9.3
How important is sex to you?	Very important	10.8	10.2	6.8	<.0001	8.9
	Somewhat important	32.4	31.2	23.9		28.5
	Neither important nor unimportant	28.0	26.2	31.3		28.8
	Not very important	15.3	14.6	19.7		16.9
	Not important at all	13.5	17.8	18.3		16.9
Have you ever used CSWs?	No	94.7	95.6	97.2	.0054	96.0
	Yes	5.3	4.4	2.8		4.0
Have you ever used/received:**
Soapland (soopu)		1.4	2.0	1.1	.1516	1.5
Erotic massage (seikan massaaji)		1.3	1.3	0.7	.2309	1.0
Call services (fasshon herusu/deribarii herusu)		1.1	1.9	1.2	.184	1.4
Image club (imeeji kurabu)		1.0	1.1	0.4	.0765	0.8
Pink salon (pinku saron)		1.0	1.1	0.6	.2905	0.8
Male sex worker (urisen)		0.6	0.7	0.3	.269	0.5
Sexy cabaret (sekushii kyabakura)		1.1	1.4	0.3	.0085	0.8
Other		0.3	0.5	0.6	.5835	0.5
Yes, but unsure of what type of establishment		0.5	0.3	0.4	.8986	0.4
Never used CSW		94.7	95.6	97.2	.0054	96.0

*No 75^th percentile is presented as less than 75% of those in the 20–29 years category have had sexual intercourse.

**Soaplands refer to a commercial sex establishment that offers erotic massages using personal lubricant often paired with penetrative intercourse. Call services are split into two types: “fashion health” refers to commercial sex work establishments that typically offer erotic massages and oral sex, but penetrative intercourse may incur an extra charge; “delivery health” refers to a service in which commercial sex workers meet clients at their homes or hotels and offer the same services as “fashion health.” Image clubs are commercial sex establishments in which staff dress in costumes (e.g., schoolgirls or nurses). Pink salons are commercial sex establishments that primarily offer oral sex. Urisen generally refers to male sex workers who primarily cater to homosexual men. Sexy cabaret are hostess clubs (e.g., bars with female staff that cater to men) where sexual conduct may be included among their services.

Table 3. Weighted proportions of male NInJaS respondents reporting certain sexual behaviors, stratified by sex and ten-year age groups.

		20–29 (N = 1333)	30–39 (N = 1333)	40–49 (N = 1334)	p	20–49 (N = 4000)
With whom have you had sexual experiences so far?	Only with the opposite sex; never with the same sex	54.9	76.7	86.9	<.0001	75.2
	Mostly with the opposite sex; occasionally with the same sex	2.4	1.6	2.4		2.1
	Both with the opposite and same sexes in roughly equal amounts	1.6	1.2	0.5		1.0
	Mostly with the same sex; occasionally with the opposite sex	1.2	0.9	0.7		0.9
	Only with the same sex; never with the opposite sex	1.4	1.4	0.8		1.1
	I have never had any sexual experiences	38.5	18.2	8.9		19.6
Have you ever had sexual partners (vaginal sex, anal sex, and/or oral sex only)?	No	43.0	17.1	7.4		19.8
	Yes	57.0	82.9	92.6		80.2
Number of lifetime sexual partners (including CSW)	0	43.0	17.1	7.4	<.0001	19.8
	1	14.3	10.7	11.3		11.9
	2	7.2	9.0	7.2		7.8
	3–4	9.2	11.6	12.5		11.3
	5–9	11.5	17.0	16.5		15.3
	10 or more	14.9	34.7	45.3		33.9
Number of lifetime sexual partners (including CSW) [median (IQR)]		1 (0–5)	5 (1–10)	6 (2–20)		4 (1–10)
Number of lifetime sexual partners (excluding CSW)	0	46.9	19.8	9.2	<.0001	22.5
	1	15.7	15.3	14.5		15.1
	2	8.5	11.0	11.2		10.4
	3–4	9.1	14.6	17.0		14.2
	5–9	9.3	18.9	19.9		16.8
	10 or more	10.6	20.6	28.1		21.1
Number of lifetime sexual partners (excluding CSW) [median (IQR)]		1 (0–3)	3 (1–6)	4 (2–10)		3 (1–6)
Age at first volitional sexual intercourse [median (IQR)]		22 (18-)*	20 (17–26)	20 (18–23)		20 (18–27)
First sexual intercourse before age 16 years		7.9	11.3	6.4	.0001	8.4
Number of sexual partners in past year (including CSW)	0	55.1	39.2	41.8	<.0001	44.5
	1	27.3	43.0	42.0		38.4
	2 or more	17.7	17.8	16.2		17.1
Number of sexual partners in past year (including CSW) [median (IQR)]		0 (0–1)	1 (0–1)	1 (0–1)		1 (0–1)
Number of sexual partners in past year (excluding CSW)	0	57.9	43.2	46.1	<.0001	48.3
	1	28.8	44.7	43.7		40.1
	2 or more	13.3	12.1	10.2		11.6
Number of sexual partners in past year (excluding CSW) [median (IQR)]		0 (0–1)	1 (0–1)	1 (0–1)		1 (0–1)
Sexual intercourse frequency in past year (including CSW)	Daily or almost daily	2.8	1.4	0.8	<.0001	1.5
	3–5 times per week	3.7	3.4	1.1		2.5
	1–2 times per week	9.5	11.5	7.3		9.2
	2–3 times per month	11.1	14.5	15.4		14.0
	Once per month or less	17.9	30.0	33.6		28.3
	Never	55.1	39.2	41.8		44.5
Sexual intercourse frequency in past year (excluding CSW)	Daily or almost daily	2.0	1.0	0.8	<.0001	1.2
	3–5 times per week	3.3	3.5	1.1		2.4
	1–2 times per week	10.0	11.2	7.0		9.1
	2–3 times per month	11.2	14.0	14.9		13.6
	Once per month or less	15.6	27.1	30.1		25.3
	Never	57.9	43.2	46.1		48.3
Masturbation frequency	Daily or almost daily	19.5	13.4	8.8	<.0001	13.0
	3–5 times per week	22.0	21.0	18.4		20.2
	1–2 times per week	25.5	35.4	36.8		33.3
	2–3 times per month	6.6	10.7	16.5		12.1
	Once per month or less	7.3	8.8	11.8		9.7
	Never or almost never	19.2	10.8	7.7		11.7
Pornography viewing frequency	Daily or almost daily	15.1	11.8	7.8	<.0001	11.0
	3–5 times per week	19.7	18.9	17.3		18.4
	1–2 times per week	24.2	30.7	33.0		30.0
	2–3 times per month	8.0	12.0	14.9		12.2
	Once per month or less	9.6	11.1	15.6		12.6
	Never or almost never	23.4	15.5	11.5		15.9
Does your pornography viewing (or your partner’s) exert an effect on your sex life?	No effect	34.5	33.7	36.7	<.0001	35.2
	Good effect	18.5	20.2	19.1		19.3
	Bad effect	5.5	4.9	2.6		4.1
	Unsure	26.9	31.8	34.3		31.5
	Neither I nor my partner use pornography	14.8	9.4	7.3		9.9
“I am satisfied with my sex life”	Strongly agree	6.8	5.1	3.0	<.0001	4.7
	Agree	20.7	20.0	15.9		18.5
	Neither agree nor disagree	48.8	47.8	51.8		49.8
	Disagree	13.4	14.7	15.8		14.8
	Strongly disagree	10.2	12.5	13.4		12.3
Would you like to change your frequency of sexual intercourse?	Yes, I would like to increase it a lot	16.1	17.2	19.2	.0001	17.7
	Yes, I would like to increase it a little	26.6	28.4	30.1		28.6
	No	48.8	47.7	47.3		47.8
	Yes, I would like to decrease it a little	2.4	2.3	1.0		1.8
	Yes, I would like to decrease it a lot	6.1	4.5	2.5		4.1
How important is sex to you?	Very important	16.1	18.8	19.5	<.0001	18.4
	Somewhat important	30.1	37.4	38.3		35.9
	Neither important nor unimportant	33.9	28.3	28.1		29.7
	Not very important	8.9	8.0	9.4		8.9
	Not important at all	11.0	7.5	4.7		7.2
Have you ever used CSWs?	No	71.4	50.3	40.4	<.0001	51.7
	Yes	28.6	49.7	59.6		48.3
Have you ever used/received:**
Soapland (soopu)		16.2	32.0	38.5	<.0001	30.6
Erotic massage (seikan massaaji)		5.5	13.0	17.5	<.0001	12.9
Call services (fasshon herusu/deribarii herusu)		12.5	27.9	35.6	<.0001	27.1
Image club (imeeji kurabu)		2.1	5.0	9.3	<.0001	6.0
Pink salon (pinku saron)		8.3	20.2	26.0	<.0001	19.5
Male sex worker (urisen)		1.3	2.2	3.2	.0146	2.4
Sexy cabaret (sekushii kyabakura)		5.7	17.8	19.3	<.0001	15.2
Other		1.6	2.8	2.7	.1401	2.5
Yes, but unsure of what type of establishment		1.2	1.5	2.6	.0462	1.9
Never used CSW		71.4	50.3	40.4	<.0001	51.7

*No 75th percentile is presented as less than 75% of those in the 20–29 years category have had sexual intercourse.

**Soaplands refer to a commercial sex establishment that offers erotic massages using personal lubricant often paired with penetrative intercourse. Call services are split into two types: “fashion health” refers to commercial sex work establishments that typically offer erotic massages and oral sex, but penetrative intercourse may incur an extra charge; “delivery health” refers to a service in which commercial sex workers meet clients at their homes or hotels and offer the same services as “fashion health.” Image clubs are commercial sex establishments in which staff dress in costumes (e.g., schoolgirls or nurses). Pink salons are commercial sex establishments that primarily offer oral sex. Urisen generally refers to male sex workers who primarily cater to homosexual men. Sexy cabaret are hostess clubs (e.g., bars with female staff that cater to men) where sexual conduct may be included among their services.

The median (IQR) number of lifetime sexual partners (including commercial sex workers) was 3 (1–6) for women and 4 (1–10) for men. The median (IQR) age at first sexual intercourse was 20 (18–24) for women and 20 (18–27) for men. The proportion reporting first sexual intercourse before the age of 16 years was roughly similar among women and men (8.0% vs 8.4%).

Frequency of Sexual Intercourse in the Past Year

13.0% of women and 13.2% of men reported a sexual frequency (including sexual activity with commercial sex workers) of at least once per week during the past year. For women, this proportion was highest among those aged 20–29 years and decreased monotonically with age. For men, the proportion reporting a sexual frequency of weekly or more was highest among those aged 30–39 years. 45.3% of women and 44.5% of men reported not having had any sexual partners (including commercial sex workers) during the past year. The proportion with no sexual partners in the last year was highest among women aged 40–49 years (51.7%) and men aged 20–29 years (55.1%).

Satisfaction with Sex Life, Sexual Frequency, and the Importance of Sex

The proportion of those reporting agreement with the statement, “I am satisfied with my sex life” was 27.8% for women and 23.1% for men. These proportions were highest among women aged 20–29 (33.2%) and men aged 20–29 (27.5%). The corresponding proportions for those who disagreed were 17.6% for women and 27.1% for men. These proportions were highest among women aged 30–39 (19.5%) and men aged 40–49 (29.2%).

The proportion of those reporting that they would like to increase their frequency of sexual intercourse was 26.0% for women and 46.4% for men. These proportions were highest among women aged 20–29 (30.3%) and men aged 40–49 (49.3%). The proportion of those reporting that they would like to decrease their frequency of sexual intercourse was 13.4% for women and 5.8% for men. These proportions were highest among women aged 30–39 (15.0%) and men aged 20–29 (8.5%).

The proportion of those describing sex as being “very important” or “somewhat important” was 37.4% among women and 54.2% among men. These proportions were highest among women aged 20–29 (43.3%) and men aged 40–49 (57.8%). The proportion of those describing sex as being “not very important” or “not at all important” was 33.8% among women and 16.1% among men. These proportions were highest among women aged 40–49 (38.0%) and men aged 20–29 (19.9%).

Masturbation and Pornography Use

In total, 48.1% of women and 88.3% of men reported that they engaged in masturbation. Masturbation frequency of at least three times per week was most common among those aged 20–29 years (7.7% of women; 41.5% of men). Frequency of masturbation decreased slightly with age. In total, 35.5% of women and 84.1% of men used pornography. Pornography use of at least three times per week was most common among those aged 20–29 years (6.5% of women; 34.8% of men), and frequency of pornography use decreased slightly with age. 2.6% of women and 4.1% of men reported that their or a sexual partner’s pornography use affected their sex life negatively while 9.6% of women and 19.3% of men reported that their sex life was affected positively.

Use of Commercial Sex Workers

In total, 4.0% of women and 48.3% of men reported ever having used commercial sex worker services in their lifetime. These proportions were highest among women aged 20–29 (5.3%) and men aged 40–49 (59.6%). The three most commonly used services among men included soaplands (30.6%) [a type of commercial sex work establishment that offers erotic massages using personal lubricant often paired with penetrative intercourse], call services (27.1%) [split into two types: “fashion health” refers to commercial sex work establishments that typically offer erotic massages and oral sex, but penetrative intercourse may incur an extra charge; “delivery health” refers to a service in which commercial sex workers meet clients at their homes or hotels and offer the same services as “fashion health”], and pink salons (19.5%) [a type of commercial sex work establishment in which clients receive oral sex].

Discussion

This quasi-representative national survey including women and men aged 20–49 years in Japan aimed to address the scarcity of data available on sexual health outcomes, behaviors, and wellbeing in the country. Below we describe our main findings.

Sexual Inexperience

We found that a large proportion of Japanese women and men report that they have never had sexual intercourse. The proportion reporting that they had zero lifetime sexual intercourse partners was around 30% for women and 43% for men aged 20–29 years, 14% for women and 17% for men aged 30–39 years, and 7% for both women and men aged 40–49 years. These proportions were higher than those previously reported using data from the National Fertility Survey in Japan conducted in 2015 (Ghaznavi et al., 2019), in which 12% of women and 13% of men aged 30–34 years and 9% of women and 10% of men aged 35–39 years reported no experience of heterosexual intercourse (data on non-heterosexual experience were not available). The findings of the two studies are compatible with the hypothesis that sexual inexperience has increased between 2015 and 2022, consistent with an increasing trend in sexual inexperience observed among women and men in their 30s in six rounds of the National Fertility Survey from 1992 to 2015 (Ghaznavi et al., 2019). Sexual inexperience across age groups may have been accelerated by the COVID-19 pandemic and associated social distancing measures. In fact, a decrease in the frequency of sexual intercourse during the pandemic in Japan has been previously reported (Kitamura et al., 2021). However, the differences between these studies could also be explained by how study participants were recruited: the National Fertility Survey was carried out by the Japanese Ministry of Health, Labor and Welfare and used a population-based sample of participants who were actively recruited by the investigators while we aimed to recruit a nationally representative sample from individuals who had volunteered to answer survey questions online. There may also have been differences in how participants reported their sexual experience, and the questions regarding sexual experience were differently phrased in the two surveys. Nonetheless, these findings lend further support to the notion that levels of sexual inexperience could be higher in Japan as compared to many Western countries (Jorgensen et al., 2015; Mercer et al., 2021; New Zealand Ministry of Health, 2019; Rissel et al., 2014). However, most studies on sexual inexperience in Western countries were conducted several years ago and it is possible that levels of sexual inexperience among adults in the US and Europe are catching up with those of Japan. For example, the nationally representative online survey Natsal-COVID, conducted in 2020, found indications of an increase in sexual inexperience in Britain as compared with the previous Natsal-3 study from 2010–2011: in Natsal-COVID, 27% of women and 28% of men aged 18–24, 10% of women and 7% of men aged 25–34, and 11% of women and 8% of men aged 35–44 years reported never having had partnered sex (Mercer et al., 2021), although it should be noted that some of these numbers are incompatible with the lower levels of sexual inexperience reported by the same birth cohorts when sampled 10 years earlier in the Natsal-3 study. Moreover, differences in sampling methods and response rates (the Japanese National Fertility Survey has a response rate of 70.0–92.5% as compared to 30–40% in many Western surveys; Mercer et al., 2013; Public Health Agency of Sweden, 2019; Ueda et al., 2020), how questions regarding sexual inexperience are phrased and perceived, and whether the data were gathered through interviews or questionnaires, may also partially explain the differences. Furthermore, sexual inexperience and inactivity is widely discussed in the public sphere and considered to be common in Japan (Ghaznavi et al., 2020; Kitamura, 2011). It is possible that social desirability bias is less pronounced among study participants without sexual experience in Japan.

While nationally representative data are not available, it is possible that other East Asian countries have rates of sexual inexperience comparable to those of Japan. For example, in a survey of undergraduates aged 15–24 years (mean 20 years) conducted in China in 2019, 86% of women and 73% of men reported having no experience of sexual intercourse (Lyu et al., 2020), and the median age of sexual debut in our Japanese sample (20 years) was similar to values reported by limited surveys from South Korea and China (Park et al., 2021; Zhang, 2020). Furthermore, in a national survey in India from 2019–2021, 3% of women and 11% of men aged 30–34 and 1% of women and 4% of men aged 35–39 reported having no experience of sexual intercourse (Ministry of Health and Family Welfare, 2021).

Sexual Inactivity

We found that 42% of women and 55% of men aged 20–29 years reported having had no sexual partners during the past year. These proportions are higher than those reported in comparable studies from other countries before the pandemic. For example, in nationally representative US data from 2016–2018, the proportion reporting no partnered sexual activity in the past year was around 20% for women and 30% for men aged 18–24 years and 14% for men and 13% for women aged 25–34 years (Ueda et al., 2020). In a national survey in Germany from 2016, around 20% of both men and women aged 18–30 years reported no sexual activity in the past year (Beutel et al., 2018; Burghardt et al., 2020). A Danish study from 2012 found that among those aged 15–29, around 4% of women and 8% of men reported zero sexual partners in the past year (Jorgensen et al., 2015), and in a British study from the same year, around 10% of men and women aged 20–29 years were sexually inactive (Ueda & Mercer, 2019). However, comparisons with our findings should be done with caution due to differences between surveys in sampling methods, response rates, the phrasing of questions, and potential cultural differences affecting self-reported sexual activity. Importantly, the data from these previous studies were collected before the COVID-19 pandemic. In the British Natsal-COVID study, over 40% of women and men aged 18–24 and around 25% of women and men aged 25–34 reported no partnered sexual activity during the up to 4 months that had passed between society going into “lockdown” and study participation (Mercer et al., 2021).

Sexual Orientation, Including Asexuality, Importance of Sex and Sexual Satisfaction

A substantial proportion of women (15%) and men (11%) aged 20–29 years responded that they were asexual. While this proportion decreased slightly with age, it is manyfold higher than the prevalence of asexuality (<1%) reported in countries such as Britain (Aicken et al., 2013) and Sweden (Public Health Agency of Sweden, 2019). Moreover, 37% of women and 54% of men in our study responded that they considered sex to be important; these proportions are lower than those reported in countries such as Sweden (Public Health Agency of Sweden, 2019), Britain (Field et al., 2013), and France (Bajos et al., 2010). In a previous study using data from a national survey in 2015, around half of Japanese singles (21% of the women and 25% of men in the total population aged 18–39 years) reported that they had no interest in heterosexual romantic relationships (Ghaznavi et al., 2020). The proportion reporting no interest in heterosexual relationships was largest among those aged 18–24 years and decreased with higher age. Questions regarding sexual orientation, the perceived importance of sex, and interest in sexual relationships address different aspects of sexual interest/desire; findings from the current and previous studies indicate that sexual relationships might play a less prominent role in Japan at the individual, cultural, and societal level as compared with many Western countries, although potential differences across study populations in how the survey questions were perceived and interpreted warrant caution when making cross-cultural comparisons.

While 28% of women and 23% of men indicated that they were satisfied with their sex life, 18% of women and 27% of men indicated that they were dissatisfied. In addition, 26% of women and 46% of men indicated that they wanted to increase their sexual frequency. While the higher levels of sexual dissatisfaction and desire to increase sexual frequency among men than women have been observed across many cultures and countries (Hakim, 2015; Mitchell et al., 2013), our findings indicate that a large proportion of women and men in Japan are dissatisfied with their sex lives and wish to increase their level of sexual activity.

Pornography Use

We found that approximately 36% of women and 84% of men used pornography. Among those aged 20–29 years, 17% of women and 59% of men reported a frequency of pornography use of weekly or more and 2% of women and 15% of men reported daily or almost daily use. While detailed data on the frequency of pornography use in national populations are scarce (Miller et al., 2020; Regnerus et al., 2016; Rissel et al., 2017), the values reported in this study were similar to those observed in analyses of nationally representative survey data collected in Sweden where 13% of women and 66% of men aged 16–24 years reported at least weekly pornography use and 1% of women and 17% men reported daily or almost daily use (Malki et al., 2021). In accordance with findings from Australia and Sweden, reporting negative effects of pornography use on one’s sex life was rare and less common than reporting positive effects (Malki et al., 2021; Rissel et al., 2017).

Use of Commercial Sex Worker Services

We found that 4% of women and 48% of men reported ever having used commercial sex worker services in their lifetime. These proportions are higher than those reported in surveys from other countries. For example, in a national survey from Sweden, around 10% of men and less than 1% of women aged 16–84 years reported that they had given money or other types of compensation for sex in their lifetime (Public Health Agency of Sweden, 2019). In the British Natsal-3 survey, the proportion of men who reported having paid for sex during the past 5 years ranged between 3 and 5% across age groups, while this proportion was close to zero for women (Mercer et al., 2013). In a Danish survey among those aged 15–29 years, around 10% of men had paid for sex during their lifetime, while this proportion was nearly zero for women (Jorgensen et al., 2015). In Germany, 27% of men participating in a national survey reported having paid for sex in their lifetime (Doring et al., 2022). It could be hypothesized that the rate of commercial sex service use is high in Japan due to easy accessibility and visibility of such services in metropolitan areas (e.g., the famous red light district in Kabukicho, Tokyo), many types of sexual services being legal in Japan (although services including vaginal intercourse are not technically legal, these laws are not strictly enforced), the diversity in the types of services offered (including many services that do not include penetrative sex), and the relatively low stigma concerning the use of commercial sex services, among men but also women, as compared with Western nations (Fu, 2011; Koch, 2021; Takeyama, 2021).

Implications for Future Research

The findings presented here engender additional opportunities for future research. First, given the increasing socioeconomic disparities in Japan, which may also correlate with sexual inactivity and prospects for finding sexual partners (Ghaznavi, Sakamoto et al., 2022; Ghaznavi et al., 2019), it would be informative to assess the sociodemographic characteristics of those who have responded that they are sexually inexperienced, sexually inactive, and asexual. Assessment of the association of sexual inexperience, sexual inactivity, and asexuality with variables related to sexual health and wellbeing may shed light on potential reasons for and experiences of sexual inexperience and inactivity. For example, whether individuals who have responded that they are asexual are sexually inactive and whether sexually inactive individuals tend to report satisfaction with their sex lives or consider sex as unimportant would be of interest to explore (Andresen et al., 2022; Ueda & Mercer, 2019). Another venue for future research is to assess the association of frequent pornography use with sexual health outcomes and with self-reported positive or negative effects of pornography use on individuals’ sex lives (Hald & Malamuth, 2008; Malki et al., 2021; McKee, 2007; Miller et al., 2020; Rissel et al., 2017). Moreover, sociodemographic characterization of individuals who use commercial sex work services and assessment of the association between use of commercial sex work services and sexual health outcomes and sexual behaviors, including other risk behaviors, are warranted (Doring et al., 2022).

Limitations

Our study had limitations. First, the survey used in the current analysis was conducted via an online platform. Similar to other quasi-representative national surveys (Herbenick et al., 2017; Mercer et al., 2021), it is uncertain to what extent the study participants are representative of the national population (Ross et al., 2005). Although we weighted the sample based on age, region, and marital status to ensure that the survey was nationally representative with respect to these variables, the weighted NInJaS sample was more educated and had slightly higher income across all age and sex groups, as compared to the National Fertility Survey; the slight overrepresentation of highly educated and higher income individuals has been reported in previous literature using the same survey platform (Nomura et al., 2021). Second, questions pertaining to sexual health are sensitive and thus susceptible to response bias, especially social desirability bias. However, the anonymous nature of the self-administered online survey may have mitigated the risk of response bias (Gribble et al., 1999). Third, our survey was conducted in July 2022, during the late stages of the COVID-19 pandemic in Japan. During the course of the pandemic, between one and four state of emergency declarations (SoEs) were implemented in each of Japan’s 47 prefectures, with the final SoE ending after the Tokyo Olympic Games in late 2021. During SoEs, residents of Japan were encouraged to minimize social interactions outside the home by limiting nonessential outings, restaurants and bars instituted shortened business hours or halted services entirely, and many businesses switched to remote work. Notably, SoE compliance was voluntary, but even still considerable declines in mobility were recorded, especially during earlier SoEs (Ghaznavi, Yoneoka et al., 2022). Previous research has found that the frequency of sexual activity decreased in Japan during the pandemic (Kitamura et al., 2021), possibly due to the nationwide social distancing policies and SoEs. Thus, future iterations of this survey will be needed to assess sexual behavior during non-pandemic periods. Fourth, we were limited in the number of items we could include in our questionnaire, and thus the first iteration of NInJaS was not as comprehensive as many other, long-established sexual health surveys from Western nations. As we expected few participants to identify as transsexual, we did not include questions that encompass trans experiences. Finally, the self-administered nature of the survey precluded respondents from asking clarifying questions and may have led to misunderstandings regarding the intent of specific questions. For example, terms such as sexual orientation are not yet widely used in Japanese. In these instances, we added explanations next to terms that may be unfamiliar to the average Japanese resident in order to minimize any misunderstandings.

Contributors

Conception/design of the work: CG, HS, and PU; survey preparation: CG, HS, PU; survey coordination: HS; analysis of data: CG; data curation: CG and HS; interpretation of findings: all authors; drafting of the work: CG and PU; funding acquisition: HS; substantially revised the work: all authors. All authors approved the final version of the manuscript.

Data Availability

The survey data used in the current study are not publicly available due to the formulation of the ethical approval but may be made available by the corresponding author on reasonable request. Population census data are openly available online (https://www.e-stat.go.jp/stat-search/database?page=1&layout=datalist&toukei=00200521&tstat=000001136464&cycle=0&tclass1=000001136466&result_page=1&tclass2val=0).

Ethics Statement

The study was approved by the Regional Ethics Committee at the University of Tokyo, Japan. Respondents were required to provide consent before beginning the survey.

Acknowledgments

The funding source of this study had no role in the study design, data collection, data analysis, data interpretation, or writing of the report. The views expressed in this paper are solely those of the authors.

Disclosure Statement

No potential conflict of interest was reported by the authors.

Supplementary Material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/00224499.2023.2178614

Additional information

Funding

The present work was supported in part by grants from the Ministry of Education, Culture, Sports, Science and Technology of Japan (21H03203). The funding source of this study had no role in the study design, data analysis, data interpretation, or writing of the report.