Sexual behaviour and STI testing among Dutch swingers: A cross-sectional internet based survey performed in 2011 and 2018

Carolina J G Kampman; Jeannine L A Hautvast; Femke D H Koedijk; Marieke E M Bijen; Christian J P A Hoebe

doi:10.1371/journal.pone.0239750

. 2020 Oct 1;15(10):e0239750. doi: 10.1371/journal.pone.0239750

Sexual behaviour and STI testing among Dutch swingers: A cross-sectional internet based survey performed in 2011 and 2018

Carolina J G Kampman ^1,^2,^*, Jeannine L A Hautvast ², Femke D H Koedijk ¹, Marieke E M Bijen ¹, Christian J P A Hoebe ^3,⁴

Editor: Henry F Raymond⁵

PMCID: PMC7529206 PMID: 33002013

Abstract

Background

Swingers, heterosexuals who, as couples, practice mate swapping or group sex with other couples or heterosexual singles, are at risk for sexually transmitted infections (STIs). Therefore, the aim of this study was to assess changes in sexual behaviour and STI testing behaviour, as well as predictors of STI testing.

Methods

Two cross-sectional studies were performed, using the same internet survey in 2011 and 2018. For trend analysis, sexual behaviour and STI testing behaviour were used. Socio-demographics, swinger characteristics, sexual behaviour, and psycho-social variables were used to assess predictors of STI testing in the past year, using multivariable regression analysis.

Results

A total of 1173 participants completed the survey in 2011, and 1005 in 2018. Condom use decreased for vaginal (73% vs. 60%), oral (5% vs. 2%), and anal sex (85% vs. 75%). STI positivity was reported in 23% and 30% of the participants, respectively, although testing for STI was comparable between both years (~65%).

The following predictors of STI testing were significant: being female (OR = 1.9, 95%CI: 1.2–2.9), having a high swinging frequency (>12 times a year, OR = 3.7, 95%CI: 1.9–7.3), swinging at home (OR = 1.6, 95%CI: 1.0–2.7), receiving a partner notification (OR = 1.7, 95%CI: 1.2–2.6), considering STI testing important (OR = 4.3, 95%CI: 2.2–8.5), experiencing no pressure from a partner to test (OR = 0.6, 95%CI: 0.3–0.9), partners test for STI regularly (OR = 10.0, 95%CI: 6.2–15.9), perceiving STI testing as an obligation (OR = 2.1, 95%CI: 1.3–3.5), experiencing no barriers such as being afraid of testing (OR = 1.9, 95%CI: 1.2–3.1), limited opening hours (OR = 1.6, 95%CI: 1.0–2.4), and forgetting to plan appointments (OR = 3.0, 95%CI: 2.0–4.6).

Conclusions

Swingers exhibit self-selection for STI testing based on their sexual behaviour. However, STI prevention efforts are still important considering the increasing numbers of reported STIs, the decreased use of condom use, and the one-third of swingers who were not tested in the previous year.

Introduction

Swingers are heterosexuals who, as couples, practice mate swapping or group sex with other couples or heterosexual singles. Although swingers self-identify as heterosexual, they frequently engage in same-sex sexual activities. Swingers are at risk for sexually transmitted infections (STIs), as they engage in unprotected sex with multiple sexual partners and substance misuse [1–3]. Swingers can transmit STIs within their own sexual network and to other sex partners outside their network through overlapping sexual partnerships. These concurrent sexual partnerships and potential bridging make them a target population of public health importance [1,4].

Only a few studies have estimated STI positivity rates among swingers. A Dutch study by Dukers et al found a Chlamydia trachomatis (CT) positivity rate of 8% and a Neisseria gonorrhoea (NG) positivity rate of 4% among swingers, which was lower than the STI positivity rate among all heterosexuals attending the STI clinic [5]. In the Dutch surveillance data, the overall STI positivity rate among swinger men was 16%, and 11% among swinger women [6]. A Belgian study by Platteau et al found that 81 out of 313 swingers who reported ever being tested for STI had ever had an STI diagnosis [7].

A Dutch study by Dukers et al showed that swingers take an STI test more often than men who have sex with men (MSM), or heterosexual men and women [5]. Another Dutch study by Spauwen et al showed that, overall, 72%, 62%, and 56% of swingers who consulted the STI clinic, reported that regular STI testing, partner notification, and condom use when engaging in sex, respectively, is the norm in the swinger community [8].

Before 2015, swingers were eligible for free and anonymous consultations at Dutch STI clinics. However, since 2015, based on the relatively low STI incidence, they were no longer eligible at STI clinics and have therefore been advised to consult a general practitioner (GP) for STI testing. This change in health policy since 2015 might hamper proper STI control in swingers, because STI testing at GPs is not free and anonymous, and swingers might refrain from identifying themselves as a swinger.

Lack of testing in swingers might implicate a potential rise in STI prevalence, and therefore testing behaviour among swingers is relevant as this might have a public health impact. To our knowledge, no studies have been conducted on to determine whether STI testing behaviour in swingers changes over time. Therefore, we performed cross-sectional studies in 2011 and 2018, using an internet survey, to compare sexual behaviour and STI testing behaviour, and to assess the influence of possible socio-demographic, behavioural, and psycho-social predictors of testing behaviour. The study outcomes can be used to evaluate current STI testing policy for swingers and provide information about the optimal STI clinic accessing policy and optimal STI test advice.

Methods

Study design, population, and data collection

Two cross-sectional studies were performed using an internet survey with the same questions in 2011 and in 2018. The content of the internet survey was developed based on information gathered in semi-structured interviews with swingers. The psycho-social variables were developed based on these interviews combined with the theory of planned behaviour [9–11]. The survey consisted of questions on socio-demography, swinger characteristics, sexual behaviour, STI test behaviour, and psycho-social determinants.

To recruit a broad sample of swingers in the Netherlands, both internet surveys were advertised at national websites that are frequently visited by swingers, including swinger websites, swinger club websites, and swinger dating websites. A banner with a link to the survey was published on the participating websites. Participants were requested to fill in the survey alone (not together as a couple) and were asked to only participate in the survey once per study. Participants who did not meet the definition of swinging (being part of a heterosexual couple and having sex with others, or being single and having sex with heterosexual couples), participants who were younger than 18 years, and those who did not swing in the past year were excluded from the analysis.

The incentive to participate in the study was the chance to win one of five dinner cheques with a value of 50 euros at the end of both study periods. Both internet surveys remained online for two months.

The survey software program Survey Monkey was used to embed the questions and provide the data for the analysis. Surveys that were not fully completed were excluded from analysis.

Variables

Data on the following socio-demographic variables were collected: age at time of filling in survey, highest reported level of education (low educational level is pre-primary education; primary education or first stage of basic education; intermediate educational level is lower secondary education or second stage of basic education and high educational level is upper secondary education or tertiary education), gender, sexual preference, and relationship status (single or in a relationship). We combined the variables gender and sexual preference, as we expected sexual preference in men to be of greater public health importance than sexual preference in women.

Furthermore, the following swinger characteristics were analysed: swinging years (how many years engaged in swinging), swinging frequency (swinging how many times in the past year), and swinging location (at home, sexclub, hotel, party or holiday, answered by ‘yes’ or ‘no’).

The following sexual behaviour variables were collected: mean number of partners during swinging, ever received a partner notification for an STI during swinging period, having had condomless sex during vaginal, oral, and/or anal sex and when changing partners, ever had an STI during swinging period (chlamydia, gonorrhoea, syphilis, HIV, hepatitis B, genital warts, Herpes genitalis, Trichomonas vaginalis, and scabies were considered STIs), and drug and alcohol use during swinging.

Additionally, the following STI testing behaviour variables were collected: STI testing in the past year, STI testing location, and reasons for STI testing.

Lastly, psycho-social variables were collected as part of the following domains: STI risk perception, attitudes towards STI testing, social norm regarding STI testing, and self-efficacy and barriers regarding STI testing.

Data analysis

We included only fully completed surveys in our data analysis. Descriptive analyses were performed for all variables, separately for both years. The χ² test was used for testing differences in proportions between outcomes from 2011 and 2018. A p-value of <0.01 was considered to be statistically significant.

Univariable and multivariable logistic regression analyses were performed to identify predictors for the outcome measure ‘STI testing in the past year’, separately for both years. The results of the univariable and multivariable regression analysis were comparable between both years, except for the following predictors from the univariable regression analysis: gender, number of partners while swinging, condom change when changing partners, drug use, and the STI risk perception predictors ‘Swinging partners don’t have many STIs’ and ‘STI consequences are not severe’. Since most variables in the regression analyses for both years separately were comparable, a combined logistic regression analysis was performed to identify predictors for the outcome measure ‘STI testing in the past year’ for 2011 and 2018 together. As the demographic variables age and education were significantly different between 2011 and 2018, all predictors were adjusted for these demographics, as well as study year, in the combined logistic regression analyses. Backward logistic regression was used in multivariable analysis to further analyse the influence of predictors on STI testing. All variables with a p-value < 0.01 in univariable analyses were included. Predictors with p<0.01 were considered statistically significant in the multivariable analysis. Odds Ratios (ORs) and 99% Confidence Intervals (CIs) were presented to show the associations between the predictors and the outcomes in Table 2.

Table 2. Predictors of STI testing in the past year among swingers in The Netherlands (2011 and 2018, n = 2178), adjusted for year, age and education.

	Univariable analysis aOR(99%CI)	Multivariable analysis aOR(99%CI)
Socio-demographic variables
Gender and sexual preference (men)
Bisexual men	1.3 (1.0–1.7)	1.2 (0.8–1.9)
Heterosexual men	ref 1.7 (1.2–2.2)	ref 1.9 (1.2–2.9)
Women
Relationship status
Relationship	ref	nt
Single	1.1 (0.8–1.6)
Swinger characteristics
Swinging years
0–5 years	ref	nt
6–10 years	1.1 (0.8–1.4)
11–20 years	1.1 (0.7–1.5)
≥21 years	1.0 (0.5–2.0)
Swinging frequency
1–2 times a year	ref	ref
3–12 times a year	2.9 (2.0–4.1)	2.0 (1.1–3.5)
>12 times a year	6.3 (4.1–9.6)	3.7 (1.9–7.3)
Swinging location (ref = no)^*
At home	2.8 (2.1–3.7)	1.6 (1.0–2.7)
Sexclub	0.8 (0.6–1.0)	nt
Hotel	1.3 (1.0–1.7)	nt
Party	1.6 (1.1–2.3)	ns
Holidays	1.3 (0.9–1.9)	nt
Sexual behaviour variables
No. partners during swinging
1–2	ref	ns
3 or more	1.5 (1.1–2.1)
Ever received partner notification during swing period
Yes	3.8 (2.9–4.9)	1.7 (1.2–2.6)
No	ref	ref
Vaginal sex with condom during swinging
Always	ref	nt
Not always	1.0 (0.8–1.4)
Oral sex with condom during swinging
Always	ref	nt
Not always	1.2 (0.6–2.3)
Anal sex with condom during swinging
Always	ref	nt
Not always	0.9 (0.6–1.3)
Condom change when changing partners
Always	ref	nt
Not always	0.6 (0.4–0.9)
Drug use during swinging
Yes	2.9 (2.2–3.7)	1.3 (0.9–2.0)
No	ref	ref
Alcohol use during swinging
Yes	0.7 (0.5–0.9)	nt
No	ref
Ever had an STI during swinging-period
Yes	3.5 (2.5–4.8)	1.4 (0.9–2.3)
No	ref	ref
Psycho-social variables
STI risk perception (ref = agree/neutral)^*
Risk of getting an STI is small	1.9 (1.5–2.5)	ns
Swing partners don’t have many STI	1.2 (0.8–1.9)	nt
Swingers are a risk group for STI	0.8 (0.5–1.2)	nt
STI consequences are not severe	1.4 (1.0–1.8)	ns
Attitudes towards STI testing (ref = disagree/neutral)^*
STI testing is important for me	15.4 (10.1–23.5)	4.3 (2.2–8.5)
STI tests are unpleasant	0.6 (0.4–0.8)	ns
Testing as prevention	0.6 (0.4–1.0)	ns
Social norm regarding STI testing (ref = disagree/neutral)^*
Partners consider testing important	10.8 (7.2–16.2)	ns
Peer pressure to test	2.9 (2.3–3.7)	ns
Partner pressure to test	5.2 (4.0–6.6)	0.6 (0.3–0.9)
Most swingers test for STI	4.0 (3.1–5.1)	ns
Partner tests for STI regularly	16.5 (12.3–22.1)	10.0 (6.2–15.9)
STI testing is an obligation	8.1 (6.0–10.9)	2.1 (1.3–3.5)
Self-efficacy and barriers regarding STI testing (ref = agree/neutral)^*
Make time	3.6 (2.8–4.6)	ns
Afraid of needles	2.8 (2.1–3.7)	ns
Afraid of test result	2.1 (1.6–2.8)	ns
Afraid of test procedure	5.4 (4.1–7.2)	1.9 (1.2–3.1)
Coming out as swinger	3.8 (2.9–4.9)	ns
Testing is expensive	2.4 (1.8–3.1)	ns
Afraid to see acquaintances	2.6 (1.9–3.3)	ns
Limited opening hours	2.8 (2.2–3.5)	1.6 (1.0–2.4)
Secrecy steady partner	3.5 (2.5–5.0)	ns
Forget to make appointment	5.4 (4.1–7.0)	3.0 (2.0–4.6)

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ref, reference.

*for these variables the indicated options were each tested separately with a yes/no or agree/disagree/neutral categorization, the reference being shown in the title of the variable.

In bold: Significant (p<0.01 in univariable and p<0.01 in multivariable analysis).

Analyses were conducted using SPSS for Windows, version 25.0 (IBM Inc., Somers, New York, United States).

Medical ethical approval

The study was formally exempted from full medical ethical approval, as stated by the medical ethical committee of the Radboudumc Nijmegen (nr: 2018–4217) and according to Dutch Law. Data were obtained using the online survey tool ‘Survey Monkey’ and were registered in a fully anonymized and de-identified manner. To enter the prize pool for random allotment of dinner cheques, respondents were directed to a separate survey where they could enter their email address (only used for sending the incentive when applicable).

Results

Study population

In 2011, a total of 2152 participants started the survey, of which 1173 completed it (54.5%). In 2018, a total of 1478 participants started the survey, of which 1005 completed it (68.0%). Between both surveys, there were slight differences in the participating study population of swingers. In 2018, participating swingers were slightly older (mean age 43.4 years in 2011 vs. 46.5 years in 2018), had a higher educational level (59% vs. 50%), had slightly higher numbers of swinging years (mean 6.5 vs. 7.9 years), and had small differences in swinging locations (e.g. in 2011 84% were swinging at home vs. 79% in 2011). Gender, sexual preference, swinging frequency, relationship status, number of swinging partners and drug and alcohol use while swinging were equally distributed in both years; see Table 1.

Table 1. Socio-demographic, sexual behaviour, STI testing behaviour and psycho-social variables of swingers in The Netherlands (2011, 2018).

	2011 (n = 1173)	2018 (n = 1005)	Total (n = 2178)	p value
	N(%)	N(%)	N(%)
Socio-demographic variables
Age^*				<0.001
18–30	109 (9.3)	74 (7.4)	183 (8.4)
31–40	290 (24.8)	208 (20.7)	498 (22.9)
41–50	542 (46.3)	347 (34.6)	889 (40.9)
51–60	203 (17.3)	308 (30.7)	511 (23.5)
≥61	27 (2.3)	66 (6.6)	93 (4.3)
Education				<0.001
Low educational level	135 (11.5)	66 (6.6)	201 (9.3)
Intermediate educational level	452 (38.7)	347 (34.7)	799 (36.8)
High educational level	582 (49.8)	588 (58.7)	1170 (53.9)
Gender and sexual preference (men)				0.019
Bisexual men	324 (27.6)	311 (30.9)	635 (29.9)
Heterosexual men	443 (37.8)	402 (40.0)	845 (38.8)
Women	406 (34.6)	292 (29.1)	698 (32.0)
Relationship status				0.013
Relationship	1036 (88.3)	851 (84.7)	1887 (86.6)
Single	137 (11.7)	154 (15.3)	291 (13.4)
Swinger characteristics
Swinging years^*				<0.001
0–5 years	658 (56.3)	488 (48.6)	1146 (52.7)
6–10 years	326 (27.9)	282 (28.1)	608 (28.0)
11–20 years	160 (13.7)	187 (18.6)	347 (16.0)
≥21 years	25 (2.2)	47 (4.7)	72 (3.3)
Swinging frequency				0.030
1–2 times a year	161 (13.8)	119 (11.9)	280 (12.9)
3–12 times a year	692 (59.0)	635 (63.1)	1327 (61.0)
>12 times a year	320 (27.2)	251 (25.0)	571 (26.2)
Swinging location^#
At home	927 (79.0)	847 (84.3)	1774 (81.5)	0.002
Sexclub	728 (62.1)	561 (55.8)	1289 (59.2)	0.003
Hotel	194 (16.5)	283 (28.1)	477 (21.9)	<0.001
Party	158 (13.5)	144 (14.3)	302 (13.9)	0.563
Holidays	147 (12.5)	115 (11.4)	262 (12.0)	0.436
Sexual behaviour variables
No. partners during swinging^{^}				0.766
1–2	900 (76.7)	643 (64.0)	1543 (70.8)
3 or more	252 (21.5)	186 (18.5)	438 (20.1)
Ever received partner notification for an STI during swing period				0.289
Yes	508 (43.3)	458 (45.6)	966 (44.4)
No	665 (56.7)	547 (54.4)	1212 (55.6)
Vaginal sex with condom during swinging				<0.001
Always	813 (72.7)	589 (58.9)	1402 (66.7)
Not always	306 (27.3)	393 (40.0)	699 (33.3)
Oral sex with condom during swinging				<0.001
Always	55 (4.9)	18 (1.8)	73 (3.5)
Not always	1072 (95.1)	964 (98.2)	2036 (96.5)
Anal sex with condom during swinging				<0.001
Always	630 (84.6)	499 (74.6)	1129 (79.8)
Not always	115 (15.4)	170 (25.4)	258 (20.2)
Condom change when changing partners				0.005
Always	987 (91.9)	796 (88.2)	1783 (90.2))
Not always	87 (8.1)	107 (11.8)	194 (9.8)
Drug use during swinging^*				0.258
Yes	572 (48.8)	513 (51.2)	1085 (49.9)
No	601 (51.2)	489 (48.8)	1090 (50.1)
Alcohol use during swinging				0.364
Yes	911 (77.7)	764 (76.0)	1675 (76.9)
No	262 (22.3)	241 (24.0)	503 (23.1)
Ever had an STI during swing period				<0.001
Yes	266 (22.7)	298 (29.7)	564 (25.9)
No	907 (77.3)	707 (70.3)	1614 (74.1)
STI testing variables
STI testing past year				0.291
Yes	777 (66.2)	644 (64.1)	1421 (65.2)
No	396 (33.8)	361 (35.9)	757 (34.8)
STI testing location				<0.001
STI clinic	496 (63.8)	291 (45.3)	787 (55.5)
General practitioner	196 (25.2)	260 (40.5)	456 (32.1)
Hospital	76 (9.8)	33 (5.1)	109 (7.7)
Home-test	3 (0.4)	47 (7.3)	50 (3.3)
Multiple test locations	4 (0.5)	6 (0.9)	10 (0.7)
Other	2 (0.3)	5 (0.8)	7 (0.5)
Reasons for STI testing				0.064
Routine screening	610 (78.5)	476 (73.8)	1086 (76.4)
Partner notification	47 (6.0)	60 (9.3)	107 (7.5)
Unprotected sex	46 (5.9)	52 (8.1)	98 (6.9)
STI related symptoms	31 (4.0)	27 (4.2)	58 (4.1)
Other	43 (5.5)	30 (4.7)	73 (5.1)
Psycho-social variables
STI risk perception (%agree)^$
Risk of getting an STI is really small	438 (53.9)	327 (32.5)	765 (35.1)	0.019
Swing partners don’t have many STI	632 (37.7)	509 (50.6)	1141 (52.4)	0.132
Swingers are a risk group for STI	896 (76.4)	814 (81.0)	1710 (78.5)	0.009
STI consequences are not severe	68 (5.8)	42 (4.2)	110 (5.1)	0.086
Attitudes towards STI testing (%agree)$
STI testing is important for me	999 (85.2)	854 (85.0)	1853 (85.1)	0.901
STI tests are unpleasant	251 (21.4)	222 (22.1)	473 (21.7)	0.696
Testing as prevention	71 (6.1)	86 (8.6)	157 (7.2)	<0.024
Social norm regarding STI testing (%agree)^$
Partners consider testing important	1005 (85.7)	879 (87.5)	1884 (86.5)	0.224
Peer pressure to test	704 (60.0)	590 (58.7)	1294 (59.4)	0.535
Partner pressure to test	724 (61.7)	606 (60.3)	1330 (61.1)	0.497
Most swingers test for STI	736 (62.7)	561 (55.8)	1297 (59.6)	0.001
Partner tests for STI regularly	739 (63.0)	592 (58.9)	1331 (61.1)	0.051
STI testing is an obligation	890 (75.9)	768 (76.4)	1658 (76.1)	0.767
Self-efficacy and barriers regarding STI testing (%agree)^$
Make time	285 (24.3)	217 (21.6)	502 (23.0)	0.135
Afraid of needles	132 (11.3)	99 (9.9)	431 (10.6)	0.289
Afraid of test result	89 (7.6)	62 (6.2)	151 (6.9)	0.194
Afraid of test procedure	92 (7.8)	88 (8.8)	180 (8.3)	0.440
Coming out as a swinger	165 (14.1)	209 (20.8)	374 (17.2)	<0.001
Expensive	148 (12.6)	451 (44.9)	599 (27.5)	<0.001
Afraid to see acquaintances	126 (10.7)	126 (12.5)	252 (11.6)	0.192
Limited opening hours for STI testing	272 (23.2)	260 (25.9)	532 (24.4)	0.146
Secrecy for steady partner	46 (3.9)	40 (4.0)	86 (3.9)	0.944
Forget to make an appointment	148 (12.6)	151 (15.0)	299 (13.7)	0.104

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percentages may not precisely add up to 100% due to rounding.

* Missings are not displayed.

# category ‘other’ swinging location was filled in by 42 participants in 2011 and 44 participants in 2018.

^ in 2018 169 participants had sex only with others and 30 participants had sex with own partner only in 2011 and 2018.

$ for these variables the indicated options were tested separately with a agree/disagree/neutral categorization, the selected % is shown in the title of the variable.

In bold: A p-value of <0.01 was considered to be statistically significant.

STI and sexual behaviour

Swingers who participated in 2018 reported having had an STI more often than swingers who participated in 2011 (23% vs. 30%). Furthermore, in 2018, participating swingers reported using a condom less often than participating swingers in 2011 (for example, 73% used a condom during vaginal sex vs. 59%); see Table 1.

Predictors of STI testing in the past year

The predictors of the outcome measure ‘STI testing in the past year’ are shown in Table 2. In multivariable analysis, women tested more often for STIs in the past year than men (OR = 1.9, 95% CI 1.2 to 2.9). Furthermore, swingers who had a higher swinging frequency tested more often than swingers with a lower swinging frequency (OR = 3.7, 95% CI 1.9 to 7.3). Swingers who swing at home tested more often than swingers who do not swing at home (OR = 1.6, 95% CI 1.0 to 2.7). Furthermore, swingers who were notified of an STI by a partner during the swinging period tested more often than swingers who had not received a notification by a partner for an STI during the swinging period (OR = 1.7, 95% CI 1.2 to 2.6).

Concerning psycho-social variables related to STI testing, variables of the domains of attitude, social norm, and self-efficacy and barriers were significant predictors, whereas no variables of the risk perception domain were significant predictors. Important significant variables were that swingers who perceive STI testing to be important (OR = 4.3, 95% CI 2.2 to 8.5), who indicate that their partner tests for STIs regularly (OR = 10.0, 95% CI 6.2 to 15.9), and who perceive STI testing to be an obligation (OR = 2.1, 95% CI 1.3–3.5), tested more often for STIs than swingers who perceived differently. Otherwise, swingers who felt partner pressure to test had tested less often for STIs in the past year (OR = 0.6, 95% CI 0.3 to 0.9) than swingers who did not.

Furthermore, swingers who indicated not being afraid of the test procedure (OR = 1.9, 95% 1.2 to 3.1), did not perceive limited opening hours for STI testing (OR = 1.6, 95%CI 1.0 to 2.4), and who indicated not forgetting to make an appointment (OR = 3.0, 95%CI 2.0 to 4.6) tested more often for STIs than swingers who indicated having opposite opinions regarding these issues.

Discussion

Statement of principal findings

Our study of two cross-sectional Dutch surveys showed that swingers reported reduced use of condoms in 2018 (for example, in 2011, 73% used a condom during vaginal sex, compared to 59% in 2018) and reported having had an STI more often (23% versus 30%) than swingers who participated in 2011. However, a similar majority of swingers reported testing for STIs in both years (66% in 2011 and 64% in 2018) and regarded testing for STIs as important (85% in 2011 and 85.0% in 2018). We thus recognize an increased STI positivity rate and increase in sexual risk behaviour between 2011 and 2018 in swingers, although testing behaviour remained the same.

The following predictors for STI testing in swingers were assessed and appeared to be positive: swingers with a higher swinging frequency (>12 times a year OR = 3.7), swingers who were notified of an STI by a partner (OR = 1.7), swingers who swing at home (OR = 1.6), swingers who feel that STI testing is an obligation (OR = 2.1), swingers whose partners test for STIs regularly (OR = 10.0), and swingers who state that STI testing is important (OR = 4.3) tested for STI more often.

Strengths and weaknesses

A strength of this study was that a large number of swingers participated in the survey in both years (55% and 68%). Due to changed public health policy, it has become more difficult for swingers to be tested at STI clinics after 2015, and swingers are therefore harder to reach for studies through STI clinics. Posting the advertisement online has proven to be effective in reaching swingers and has shown the willingness among swingers to participate in research and voice their opinions.

Another strength of this study is the measurement of psycho-social variables, such as STI risk perception, attitudes, social norms, and self-efficacy regarding STI testing besides the more often measured sexual behaviour variables. With the use of these variables, clearer insight has been obtained into reasons and beliefs of swingers possibly influencing STI testing behaviours. Addressing these reasons in public health messages might lower existing barriers for swingers who are still hesitant to undergo testing, even though almost two-thirds are already regularly tested.

However, a general limitation of our study is a possible sampling bias. First, only swingers who visit a swinger dating website were invited to participate. As a consequence, generalizability to the entire population of swingers in the Netherlands might be affected, although we know from field work and other studies that most swingers are registered at these websites.

Though we did perform semi-structured interviews with swingers and used the theory of planned behaviour as input for our survey, we did not validate our survey. Therefore, we do not know for sure if our survey is measuring what we intended to measure. Our results should be read bearing this in mind.

Third, STI diagnosis was self-reported over their period of swinging years, though self reported STI history may not be an appropriate proxy for true STI history. Therefore, self-reported STI diagnosis mighthamper translation into the prevalence or incidence of STI [12].

Lastly, in this study, no identifying information was available, and therefore we do not know if the same swingers participated in both surveys. Study findings show that participants in 2018 were older and reported more swinging years than those in 2011. This might indicate that some swingers participated in both years, which might have led to overestimation of some outcomes.

Comparison to other studies

This study shows that the majority of participating swingers tested for STIs in the past year (66.2% in 2011 and 64.1% in 2018). A Canadian study, however, stated that swingers ‘rarely’ access STI health services (< 40.8% visited STI health services) [13]. Since public health policy changed in 2015, it is more difficult for swingers to access STI clinics in the Netherlands. This change in policy is reflected in our study findings, which shows that instead of testing at an STI clinic, swingers report visiting their general practitioner or ordering a home test more often than in 2011. This is in line with national data on declining STI clinic attendance of swingers [6].

Furthermore, this study shows a substantial percentage of self-reported STI diagnosis during swinging years (22.7% in 2011 and 29.7% in 2018). This finding is in line with a Belgian study performed by Platteau et al, which reported that 26% of the swingers have had an STI [7]. Several other studies have reported about STI positivity rates among swingers, but they reported lower STI incidences ranging from 8 to 13%, because of a shorter time span in which the STI was diagnosed or reported [1,5,7]. Our study shows that swingers who have a higher swinging frequency and those who were notified by a partner during a swinging period, tested more often for STI. There are no other studies that have found a similar relationship. There are, however, studies that have shown associations between a high STI positivity rate among swingers who have received a partner notification, swingers who had STI related symptoms, swingers with a previous STI, and swingers who had unprotected sex [5,8,13].

Our study also assessed psycho-social variables as predictors for STI testing in the past year. There are no other studies on psycho-social predictors of STI testing among swingers. There are, however, studies among students on predictors of STI testing. These studies show that attitude was positively associated with STI testing among students, as were perceived social norms towards STI testing, high STI risk perception, and the absence of perceived STI test barriers. These findings are in line with our study, except for high STI risk perception, as, in our multivariable analysis, we did not have significant results in this domain [14,15].

Our study also shows that within the domain of self-efficacy and barriers, swingers who are not afraid of the test procedure, who do not experience limited opening hours, and who do not forget to make an appointment test for STIs, tested more often than those swingers experiencing the opposite. There are no studies that have assessed self-efficacy and barriers towards STI testing among swingers, but there are studies performed on self-efficacy and test barriers among MSM. One Canadian study among MSM reported that perceived lack of health knowledge among testing providers and limited clinical capacity were two major barriers towards STI testing [16]. A Dutch study among MSM found that burdensome testing procedures, among others, was a barrier towards STI testing [17].

Significance of the study

Our study findings show that swingers in the Netherlands test for STIs regularly, even after the change in public health policy that made swingers no longer eligible at STI clinics for free and anonymous STI testing. Therefore, reconsidering this changed public health policy on swingers has proven to be of lesser need.

Although swingers test for STIs regularly, the location of STI testing has changed, when comparing study results of 2011 and 2018. Participating swingers in 2018 reported visiting a GP more than participating swingers in 2011. However, as studies show that GPs may omit testing for all STIs and all body locations, especially when swingers do not identify themselves as such and being MSM while swinging, which means that education is needed for GPs [18–23].

Participating swingers in 2018 reported making use of a home-based STI test more often than participating swingers in 2011. Home-based testing has advantages, such as a wider reach, being anonymous, and no need to travel for an STI test. However, there are also downsides to home-based testing, such as poor quality of the STI test and lack of opportunity to obtain sexual health counselling [24–26]. Fortunately, a list of test facilities proven to be of good quality is already present in the Netherlands. Monitoring these online and home-based test facilities will continue to be needed in the future.

It is of concern that swingers did report a higher STI positivity rate during their swinging years, when comparing results from 2011 with 2018. However, participants in 2018 were older and had more swinging years than participants in 2011. Therefore, participating swingers in 2018 had a greater time period to report having had an STI than participating swingers in 2011. However, condom use with any kind of sex had decreased when comparing 2011 to 2018. These findings indicate that primary prevention targeting swingers to prevent them from getting STIs is still needed.

Conclusion

This study shows that two-third of swingers tested for STIs in the past year. STI testing is perceived as important, and barriers for testing such as fear or logistical challenges are infrequently reported. Swingers show a self-selection for STI testing based on their sexual risk behaviour, such as swingers who receive a partner notification and swingers with a high swinging frequency undergoing more testing for STIs. Taking swingers into account as a target group for STI prevention efforts is still important considering the high reported STI positivity rate, the decreased use of condoms, and the one-third of swingers who were not tested in the previous year.

Supporting information

S1 File. Survey 2011.

(PDF)

Click here for additional data file.^{(1.2MB, pdf)}

S2 File. Survey 2018.

(PDF)

Click here for additional data file.^{(803.3KB, pdf)}

S3 File. Swingers data 20112018 minimal deidentified dataset.

(SAV)

Click here for additional data file.^{(344.2KB, sav)}

S4 File. Swingers data 20112018 minimal deidentified dataset.

(XLSX)

Click here for additional data file.^{(908.2KB, xlsx)}

Acknowledgments

We would like to acknowledge the participating swinger websites during our 2011 and 2018 survey. Furthermore, we would like to thank Editage (www.editage.com) for English language editing.

Data Availability

All relevant data are within the manuscript and its Supporting Information files.

Funding Statement

The author(s) received no specific funding for this work.

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PLoS One. doi: 10.1371/journal.pone.0239750.r001

Decision Letter 0

Henry F Raymond

27 May 2020

PONE-D-20-05060

Trends and predictors of STI testing behaviour among Dutch swingers; a cross-sectional internet based survey performed in 2011 and 2018

PLOS ONE

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Reviewer #1: This paper takes on an interesting topic – sexually transmitted infection testing among swingers – and provides online survey results from two time points in the Netherlands. There are a few areas where clarifying language and expanding analyses can improve the paper, as described below. Additionally, more information is needed about how the data can be accessed beyond just instructions to contact the corresponding author, unless more detail is added to the data availability statement.

Major:

The title and introduction reference trends, but a formal trend analysis (e.g. Cochran-Armitrage test for trend) does not seem to have been included. Adding one to the existing chi-square tests (or clarifying if the described chi-square tests are tests for trend) should be a priority in the revision.

Provide confidence intervals for estimates.

Please clarify whether the multivariable model includes year. If not, please justify, as it seems that year would be an important factor to adjust for if interested in changes over time.

How were the questions for the survey written and chosen? More details about development of the survey would be helpful. Were any of the questions validated? If not, this needs to be mentioned in the limitations.

Why is gender and sexual orientation combined into one variable? It would make sense to consider these separately, and the rationale for combining them is not clear.

To the degree it is possible, it would be helpful to assess for missingness not at random. Did the people who started but did not complete the survey systematically differ from those who did? If so, predictors of missingness need to be included in the multivariable model (e.g., if younger people were less likely to complete the survey, then having age in the multivariable model will decrease bias in estimator).

Pay attention to terminology. I have highlighted a few examples, but it would be worthwhile to review the whole paper to ensure use of consistent, updated terminology. E.g., Line 5: Rephrase sentence to avoid stigmatizing term “risky sexual behavior” (and tautology of risky behavior leading to risk) and instead focus on describing what the behaviors are and stating whether the literature suggests swingers engage in the behaviors more often than non-swingers. Additionally, replace the term “substance abuse” with the more precise/less stigmatizing “substance misuse” (behavior) or “substance use disorder” (diagnosis) as appropriate. Review the rest of the paper for this kind of terminology and update.

Was “protected” defined for participants? Does it include only condoms or also contraception (or in 2018, HIV pre-exposure prophylaxis)? It would be more precise to use the term “condomless” than “unprotected” but this should be balanced with preserving the language from the survey itself.

Similarly, how was a “swing period” defined?

It would be helpful to provide the full text of the survey itself as an appendix to answer these and previous questions noted.

The limitations section should potentially note a few other limitations based on the wording of questions described above. It would be worthwhile to cite a reference about discrepancies between reported vs. laboratory confirmed STI results there.

Would remove “rational” from describing decision making – it is non-specific and implies a value judgment – calls to question, what would “irrational self-selection” be? A better term could be something like risk-based, or risk-informed.

Minor:

Throughout, use verb “tested” instead of “performed testing” to refer to the action taken by people. As in: Swingers surveyed in 2018 tested for STIs more frequently than swingers surveyed seven years earlier.

In the intro, since same studies are referenced a few times, it would be helpful to identify them by first author’s last name.

Line 112: State what the higher education level is.

Line 114: Clarify what is meant by proportion at home (e.g., “Significantly more swingers reported swinging at home in 2018 (84%) compared to 2011 (79%).”

Table 1: Clarify “partner notification” refers to STI diagnosis and if applicable, specify if this includes partner-partner notification as well as third-party notification (e.g., via health dept). If this is in the questionnaire, providing the questionnaire is sufficient.

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PLoS One. 2020 Oct 1;15(10):e0239750. doi: 10.1371/journal.pone.0239750.r002

Author response to Decision Letter 0

8 Jul 2020

Editor comments

Thank you for reading our paper and giving us a chance to improve our manuscript. We will address each point below.

We have ensured that our manuscript meets PLOS ONE’s requirements.

2. Please address the following:

a. Please refrain from stating p values as 0.00, either report the exact value or employ the format p<0.001.

We have replaced p values 0.00 with p<0.001 throughout our manuscript. We have reported all our p-values in the same manner.

b. Please refer to any post-hoc corrections to correct for multiple comparisons during your statistical analyses. If these were not performed please justify the reasons. Please refer to our statistical reporting guidelines for assistance (https://journals.plos.org/plosone/s/submission-guidelines.#loc-statistical-reporting).

We did not perform any post-hoc correction, due to the reason that we already lowered our p value to <0.01 instead of <0.05 to correct for multiple comparisons.

c. Please include additional information regarding the survey or questionnaire used in the study and ensure that you have provided sufficient details that others could replicate the analyses. For instance, if you developed a questionnaire as part of this study and it is not under a copyright more restrictive than CC-BY, please include a copy, in both the original language and English, as Supporting Information.

We will include a copy of the questionnaire in the original language as ‘Supporting Information’. Unfortunately, we do not have an English translation. Therefore, we elaborated on the topics in our ‘methods’ section by describing variables more extensively, on page 4, as follows:

“Data on the following socio-demographic variables were collected: age at time of filling in survey, highest reported level of education (low educational level is pre-primary education, primary education or first stage of basic education, intermediate educational level is lower secondary education or second stage of basic education and high educational level is upper secondary education or tertiary education), gender, sexual preference, and relationship status (single or in a relationship). We combined the variables gender and sexual preference, because of an already large list of variables and because sexual preference in men is possibly of greater public health importance than sexual preference in women.

The following sexual behaviour variables were collected: mean number of partners during swinging, ever received a partner notification for an STI during swinging period, having had condomless sex during vaginal, oral, and/or anal sex and when changing partners, ever had an STI during swinging period (chlamydia, gonorrhoea, syphilis, HIV, hepatitis B, genital warts, Herpes genitalis, Trichomonas vaginalis, and scabies were considered STIs), and drug and alcohol use during swinging.

Additionally, the following STI testing behaviour variables were collected: STI testing in the past year, STI testing location, and reasons for STI testing.

d. We note that you have indicated that data from this study are available upon request. PLOS only allows data to be available upon request if there are no legal or ethical restrictions on sharing data publicly. For information on unacceptable data access restrictions, please see http://journals.plos.org/plosone/s/data-availability#loc-unacceptable-data-access-restrictions

In your revised cover letter, please address the following prompts:

We will update your Data Availability statement on your behalf to reflect the information you provide.

There are no restrictions on sharing a minimal de-identified data set. We will upload our a minimal de-identified data set as Supporting Information.

We reason that publication of the minimal de-identified dataset is a negligible risk to participant confidentiality, because only 2 demographic variables were included in our dataset; age group and gender and sexual preference. Other demographic variables of the participants were not included in the minimal de-identified dataset.

We have added the following paragraph in our ‘data availability statement’ section on page 16;

“Data availability statement

Consent for publication of raw data is not obtained, but the dataset is fully anonymous in a manner that can easily be verified by any user of the dataset. Publication of the dataset clearly and obviously presents minimal risk to confidentiality of study participants.”

We have also addressed this altered data availability statement in our revised cover letter.

The ‘data not shown’ phrase concerns the subheading under table 1, page 7. What we meant is that this data is not shown in our table, but we do show the data in the subheading. Therefore, ‘data not shown’ is redundant and deleted from our manuscript.

Reviewer comments

1. Is the manuscript technically sound, and do the data support the conclusions?

Reviewer #1: Partly

2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes __

3. Have the authors made all data underlying the findings in their manuscript fully available?

Reviewer #1: No

4. Is the manuscript presented in an intelligible fashion and written in standard English?

Reviewer #1: Yes

5. Review Comments to the Author

Thank you very much for carefully reading our manuscript and for providing us with your useful comments. We will address your comments point by point below.

Major:

a. The title and introduction reference trends, but a formal trend analysis (e.g. Cochran-Armitrage test for trend) does not seem to have been included. Adding one to the existing chi-square tests (or clarifying if the described chi-square tests are tests for trend) should be a priority in the revision.

In our data analysis we used Pearson chi-square tests to test for differences in proportions between demographic outcomes from 2011 and 2018. We did not use the chi-square test for trends, because there were only two measure points (year 2011 and year 2018). This does however (which we realised in hindsight after reading your comments) not fully qualify as a ‘trend’ and does not justify using the chi-square for trends. Therefore, we adjusted our title on page 1, as follows:

“STI testing and sexual behaviour among Dutch swingers; a cross-sectional internet based survey performed in 2011 and 2018”

Also, we have improved our ‘introduction’ section on page 3 as follows:

“Lack of testing in swingers might implicate a potential rise in STI prevalence, and therefore testing behaviour among swingers is relevant as this might have a public health impact. To our knowledge, no studies have been conducted on to determine whether STI testing behaviour in swingers changes over time. Therefore, we performed cross-sectional studies in 2011 and 2018, using an internet survey, to compare sexual behaviour and STI testing behaviour, and to assess the influence of possible socio-demographic, behavioural, and psycho-social predictors of testing behaviour. The study outcomes can be used to evaluate current STI testing policy for swingers and provide information about the optimal STI clinic accessing policy and optimal STI test advice.”

b. Provide confidence intervals for estimates.

We have already provided confidence intervals for the estimates in our ‘results’ section on page 9 and in table 2 on page 10. We have added confidence intervals in our ‘results’ section of our abstract on page 2.

c. Please clarify whether the multivariable model includes year. If not, please justify, as it seems that year would be an important factor to adjust for if interested in changes over time.

We did adjust our multivariable model for year (2011/2018), as stated in the heading in table 2, page 9:

“Table 2. Predictors of STI testing in the past year among swingers in The Netherlands (2011 and 2018, n=2178), adjusted for year, age and education”

d. How were the questions for the survey written and chosen? More details about development of the survey would be helpful. Were any of the questions validated? If not, this needs to be mentioned in the limitations.

We elaborated about the development in our ‘methods’ section on page 4 as follows:

“The content of the internet survey was developed based on information gathered in semi-structured interviews with swingers. The psycho-social variables were developed based on these interviews combined with the theory of planned behaviour [9,10,11]. The survey consisted of questions on socio-demography, swinger characteristics, sexual behaviour, STI test behaviour, and psycho-social determinants. ”

The questions were not validated, we have added a limitation in our ‘discussion’ section on page 12 as follows:

“Though we did perform semi-structured interviews with swingers and used the theory of planned behaviour as input for our survey, we did not validate our survey. Therefore, we do not know for sure if our survey is measuring what we intend to measure. Our results should be read bearing this in mind.”

e. Why is gender and sexual orientation combined into one variable? It would make sense to consider these separately, and the rationale for combining them is not clear.

It is a common in the Netherlands to pair these two variables, we have added a section on this in our ‘methods’ section on page 4 as follows:

“We combined the variables gender and sexual preference, as we expected sexual preference in men to be of greater public health importance than sexual preference in women.”

f. To the degree it is possible, it would be helpful to assess for missingness not at random. Did the people who started but did not complete the survey systematically differ from those who did? If so, predictors of missingness need to be included in the multivariable model (e.g., if younger people were less likely to complete the survey, then having age in the multivariable model will decrease bias in estimator).

We only included fully completed surveys in our data analysis. We have added this sentence in our ‘methods’ section on page 5 as follows to clarify this:

“We included only fully completed surveys in our data analysis.”

The missings that are present in table 1 are participants who did not fill in a question, because the question was not applicable to them.

g. Pay attention to terminology. I have highlighted a few examples, but it would be worthwhile to review the whole paper to ensure use of consistent, updated terminology. E.g., Line 5: Rephrase sentence to avoid stigmatizing term “risky sexual behavior” (and tautology of risky behavior leading to risk) and instead focus on describing what the behaviors are and stating whether the literature suggests swingers engage in the behaviors more often than non-swingers. Additionally, replace the term “substance abuse” with the more precise/less stigmatizing “substance misuse” (behavior) or “substance use disorder” (diagnosis) as appropriate. Review the rest of the paper for this kind of terminology and update.

We have reviewed our paper and we have replaced stigmatizing sentences with less stigmatizing sentences in our manuscript, including your examples, as follows:

Page 3: “Swingers are at risk for sexually transmitted infections (STIs), as they engage in unprotected sex with multiple sexual partners and substance misuse.”

Page 15: “Swingers show a self-selection for STI testing based on sexual risk behaviour , such as swingers who receive a partner notification and swingers with a high swinging frequency undergoing more testing for STIs.”

h. Was “protected” defined for participants? Does it include only condoms or also contraception (or in 2018, HIV pre-exposure prophylaxis)? It would be more precise to use the term “condomless” than “unprotected” but this should be balanced with preserving the language from the survey itself.

In our survey the participants were asked if they used a condom with various sexual behaviours. We have replaced ‘protected’ with ‘condom use’ throughout our manuscript as well as in our tables.

i. Similarly, how was a “swing period” defined?

Swinging period was defined as how many years one engaged in swinging. We have added this to our ‘methods’ section on page as follows:

“Furthermore, the following swinger characteristics were analysed: swinging years (how many years engaged in swinging), swinging frequency (swinging how many times in the past year), and swinging location.”

j. It would be helpful to provide the full text of the survey itself as an appendix to answer these and previous questions noted.

We will upload a copy of our survey as a supplementary file. As our survey is only available in Dutch language, we have elaborated more on the variables used in our ‘methods’ section on page 5, as follows:

“Data on the following socio-demographic variables were collected: age at time of filling in survey, highest reported level of education (low educational level is pre-primary education, primary education or first stage of basic education; intermediate educational level is lower secondary education or second stage of basic education; and high educational level is upper secondary education or tertiary education), gender, sexual preference, and relationship status (single or in a relationship). We combined the variables gender and sexual preference, because of an already large list of variables and because sexual preference in men is possibly of greater public health importance than sexual preference in women.

The following sexual behaviour variables were collected: mean number of partners during swinging, ever received a partner notification for an STI during swinging period, having had condomless sex during vaginal, oral, and/or anal sex and when changing partners, ever had an STI during swinging period (chlamydia, gonorrhoea, syphilis, HIV, hepatitis B, genital warts, Herpes genitalis, Trichomonas vaginalis, and scabies were considered STIs), and drug and alcohol use during swinging.”

k. The limitations section should potentially note a few other limitations based on the wording of questions described above. It would be worthwhile to cite a reference about discrepancies between reported vs. laboratory confirmed STI results there.

We have added 2 limitations in our ‘discussion’ section on page 12 based on previous questions of the reviewer (see text below). And we have provided the limitation addressing self-reported versus laboratory confirmed STI results with a reference, as follows:

“ Though we did perform semi-structured interviews with swingers and used the theory of planned behaviour as input for our survey, we did not validate our survey. Therefore, we do not know if our survey is measuring what we were meaning to measure. Our results should be read bearing this in mind.

Third, STI diagnosis was self-reported over their period of swinging years, though self-reported STI history may not be an appropriate proxy for true STI history. Therefore, self-reported STI diagnosis might hamper translation into the prevalence or incidence of STI [12].”

l. Would remove “rational” from describing decision making – it is non-specific and implies a value judgment – calls to question, what would “irrational self-selection” be? A better term could be something like risk-based, or risk-informed.

We have deleted the word ‘rational’ in our abstract on page 2 and in our conclusion on page 15. By deleting the word ‘rational’ we remove a value whether or not it is a good self-selection. Our conclusion on page 15 is as follows:

“Swingers show a self-selection for STI testing based on their sexual risk behaviour, such as swingers who receive a partner notification and swingers with a high swinging frequency undergoing more testing for STIs.”

Minor:

a. Throughout, use verb “tested” instead of “performed testing” to refer to the action taken by people. As in: Swingers surveyed in 2018 tested for STIs more frequently than swingers surveyed seven years earlier.

We have removed the word “performed testing’ with “tested” throughout our manuscript.

b. In the intro, since same studies are referenced a few times, it would be helpful to identify them by first author’s last name.

We identified the authors of Dukers (ref. 5), Platteau (ref. 7) and Spauwen (ref. 8) in our introduction on page 3 and in our discussion on page 13.

c. Line 112: State what the higher education level is.

We have explained the definition of the education levels in our ‘methods’ section on page 4, as follows:

d. Line 114: Clarify what is meant by proportion at home (e.g., “Significantly more swingers reported swinging at home in 2018 (84%) compared to 2011 (79%).”

We have elaborated on swinging location in our ‘methods’ section on page 5, as follows:

Also, we have explained the example we gave on swinging location in our ‘results’ section on page 6 better, as follows:

“In 2018, participating swingers were slightly older (mean age 43.4 years in 2011 vs. 46.5 years in 2018), had a higher educational level (59% vs. 50%), were more often single (15% vs. 12%), had slightly higher numbers of swinging years (mean 6.5 vs. 7.9 years), and had small differences in swinging locations (e.g. in 2011 84% were swinging at home vs. 79% in 2011).”

e. Table 1: Clarify “partner notification” refers to STI diagnosis and if applicable, specify if this includes partner-partner notification as well as third-party notification (e.g., via health dept). If this is in the questionnaire, providing the questionnaire is sufficient.

In table 1 on page 7 we have referred to receiving a partner notification for STI, as follows:

“Ever received partner notification for an STI during swing period”

Furthermore, we elaborated on the partner notification variable in our ‘methods’ section on page 5, as follows:

“ever received a partner notification for an STI during swinging period”

Unfortunately we did not specify the partner notification in partner-partner notification and third party notifications.

________________________________________

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Reviewer #1: No

Attachment

Submitted filename: Response to reviewers.docx

Click here for additional data file.^{(37KB, docx)}

PLoS One. doi: 10.1371/journal.pone.0239750.r003

Decision Letter 1

Henry F Raymond

14 Sep 2020

STI testing and sexual behaviour among Dutch swingers; a cross-sectional internet based survey performed in 2011 and 2018

PONE-D-20-05060R1

Dear Dr. Kampman,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

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Kind regards,

Henry F. Raymond

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments:

PLoS One. doi: 10.1371/journal.pone.0239750.r004

Acceptance letter

Henry F Raymond

22 Sep 2020

PONE-D-20-05060R1

Sexual behaviour and STI testing among Dutch swingers; a cross-sectional internet based survey performed in 2011 and 2018

Dear Dr. Kampman:

I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department.

If your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information please contact onepress@plos.org.

If we can help with anything else, please email us at plosone@plos.org.

Thank you for submitting your work to PLOS ONE and supporting open access.

Kind regards,

PLOS ONE Editorial Office Staff

on behalf of

Dr. Henry F. Raymond

Academic Editor

PLOS ONE

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

S1 File. Survey 2011.

(PDF)

Click here for additional data file.^{(1.2MB, pdf)}

S2 File. Survey 2018.

(PDF)

Click here for additional data file.^{(803.3KB, pdf)}

S3 File. Swingers data 20112018 minimal deidentified dataset.

(SAV)

Click here for additional data file.^{(344.2KB, sav)}

S4 File. Swingers data 20112018 minimal deidentified dataset.

(XLSX)

Click here for additional data file.^{(908.2KB, xlsx)}

Attachment

Submitted filename: Response to reviewers.docx

Click here for additional data file.^{(37KB, docx)}

Data Availability Statement

All relevant data are within the manuscript and its Supporting Information files.

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PERMALINK

Sexual behaviour and STI testing among Dutch swingers: A cross-sectional internet based survey performed in 2011 and 2018

Carolina J G Kampman

Jeannine L A Hautvast

Femke D H Koedijk

Marieke E M Bijen

Christian J P A Hoebe

Roles

Abstract

Background

Methods

Results

Conclusions

Introduction

Methods

Study design, population, and data collection

Variables

Data analysis

Table 2. Predictors of STI testing in the past year among swingers in The Netherlands (2011 and 2018, n = 2178), adjusted for year, age and education.

Medical ethical approval

Results

Study population

Table 1. Socio-demographic, sexual behaviour, STI testing behaviour and psycho-social variables of swingers in The Netherlands (2011, 2018).

STI and sexual behaviour

Predictors of STI testing in the past year

Discussion

Statement of principal findings

Strengths and weaknesses

Comparison to other studies

Significance of the study

Conclusion

Supporting information

Acknowledgments

Data Availability

Funding Statement

References

Decision Letter 0

Henry F Raymond

Roles

Author response to Decision Letter 0

Decision Letter 1

Henry F Raymond

Roles

Acceptance letter

Henry F Raymond

Roles

Associated Data

Supplementary Materials

Data Availability Statement

ACTIONS

PERMALINK

RESOURCES

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