Sexualized drug use and STD and HIV incidence among men who have sex with men in Amsterdam,the Netherlands

Abstract

Background

We assessed the association between sexualized drug use (SDU), and incident sexually transmitted diseases (STDs) and human immunodeficiency virus (HIV) infections among men who have sex with men (MSM).

Methods

We used data from the MS2 cohort study, conducted at the STI Outpatient Clinic of the Public Health Service of Amsterdam, the Netherlands, in 2014–2019. Eligible participants were adult HIV-negative MSM with ≥2 STDs in the preceding year and MSM living with HIV and ≥1 STD. Participation encompassed 3-monthly visits including STD screening and questionnaires on drug use. Primary outcomes were incident HIV, anal chlamydia/gonorrhoea, and syphilis. We studied the association between SDU of individual drugs and incident HIV and STDs, using Poisson regression. Analyses were adjusted for age and HIV-status.

Results

131 HIV-negative MSM and 173 MSM living with HIV were included for analysis. SDU with GHB/GBL (aIRR = 7.2, 95% CI = 1.4–35.5) in the 3 months before testing was associated with incident HIV. SDU with GHB/GBL (aIRR = 1.2, 95% CI = 1.0–1.4), ketamine (aIRR = 1.3, 95% CI = 1.0–1.6) or methamphetamine (aIRR = 1.3, 95% CI = 1.0–1.6) was associated with incident anal chlamydia/gonorrhoea. We found no association between SDU with specific drug types and syphilis incidence.

Conclusions

SDU with GHB/GBL, ketamine and methamphetamine among MSM was associated with incident HIV and anal chlamydia/gonorrhoea. HIV-negative MSM engaging in SDU should be advised to use HIV pre-exposure prophylaxis, and all MSM engaging in SDU should be advised to have STD screening regularly. We suggest counselling on STDs among MSM engaging in SDU.

Keywords

MSM sexualized drug use HIV chlamydia gonorrhoea syphilis sexually transmitted diseases

Introduction

Drug use in general and during sexual activity has increased between 2008 and 2018 among men who have sex with men (MSM).^1–3 Sexualized drug use (SDU) among MSM is highest in the Netherlands (15%) compared to other EU countries (2–11%).⁴ SDU is defined as the use of any drug before or during sex,¹ while chemsex is defined as the use of gamma-hydroxybutyrate (GHB)/gamma-hydroxybutylactone (GBL), methamphetamine or mephedrone to enhance or facilitate sex.^1–3,5 Studies show an association between both SDU and chemsex and the occurrence of sexually transmitted diseases (STDs), including HIV.^1–3,6 The reasons for MSM to engage in SDU and chemsex may include disinhibition, enhanced performance, increased sexual arousal, but also social reasons such as a sense of belonging (within a community of other chemsex users) and coping with everyday problems.^3,7

Although most MSM who engage in SDU may experience SDU as enjoyable and may not struggle with managing their drug use,⁸ the co-occurrence of drug use, STDs and mental health conditions among MSM is common.^9,10 In a previous study, we showed a high prevalence (80%) of mental health conditions and substance use among MSM at risk for STDs.⁹ SDU has also been associated with condomless anal sex (CAS) and an increased number of sexual partners,^1,11 which may result in an increased risk for STDs.^1,12,13 A cross-sectional study among participants of four cohorts of MSM in Amsterdam found that the use of multiple drugs during sex was associated with a higher risk of STDs.² Moreover, while the use of alcohol is generally accepted, it is nevertheless one of the main predictors of CAS and STIs.^14,15 Nonetheless, much remains unknown about the actual impact of SDU and alcohol use on sexual health.

More knowledge about the risk of STD acquisition when engaging in SDU can provide guidance in clinical care of MSM presenting to STD clinics. Therefore, we aimed to assess the impact of SDU on the incidence of HIV and other STDs (chlamydia, gonorrhoea, syphilis, and lymphogranuloma venereum (LGV)) among MSM in Amsterdam participating in the MS2 cohort study.

Methods

Study design and participants

The MS2 cohort was a longitudinal cohort study at the STI Outpatient Clinic of the Public Health Service of Amsterdam, the Netherlands, with recruitment between January 2014 and October 2018, and follow-up until October 2019. The aim of MS2 was to improve care and detect recurring STDs at an early stage by switching from “case finding” (screening on the initiative of a client) to “case holding” (systematic and recurrent screening among a subpopulation to detect cases). The inclusion criteria were MSM with a minimum age of 18 years. HIV-negative MSM were eligible if they had at least two STD diagnoses in the 12 months prior to enrolment, or received HIV post-exposure prophylaxis (PEP). MSM living with HIV were eligible if they were diagnosed with at least one STD in the 12 months prior to enrolment.

Procedures

Participants were invited for follow-up visits four times a year. During these 3 monthly visits participants had face-to-face consultations with a study nurse or physician, and were screened for syphilis and oropharyngeal, anal, and urogenital chlamydia and gonorrhoea. HIV-negative MSM were also screened for HIV. Detailed information on the screening procedures has been provided elsewhere.¹⁶ Participants could visit the STI Outpatient Clinic for additional STD testing between study visits at own initiative. Results from STD and HIV tests performed during these additional visits were included in these analyses.

Participants also completed self-administered questionnaires on drug use and sexual behaviour in the 3 months prior to a study visit. The drug use questionnaire was divided in drug use in general and drug use during sex with steady, known casual, or unknown casual partners, and during group sex.

Statistical analyses

Participants with at least two study visits (i.e. baseline and one other study visit) were included in the analyses.

Baseline characteristics were reported separately for HIV-negative MSM and MSM living with HIV and compared using Pearson’s Chi-squared test and Fisher’s exact test for categorical variables, and Wilcoxon rank-sum test for continuous variables.

Among those included in the analyses, we assessed the number of participants who were lost-to-follow-up. Loss-to-follow-up was defined as not having a visit within 9 months of the end-of-study date. Moreover, we assessed determinants for being lost-to-follow-up using Poisson regression. Determinants with p < 0.2 from a Wald χ² test in univariable analysis were included in an initial multivariable model. Backwards variable selection was performed to obtain the final multivariable model; variables that did not significantly improve the model (p > 0.05) based on the likelihood-ratio test were removed from the multivariable model.

Incidence rates (IRs) per 100 person-years for HIV, syphilis, chlamydia, gonorrhoea, and LGV were estimated by dividing the number of incident infections by the total amount of person-years. For bacterial STDs, the total amount of person-time was calculated as the sum of individual person-years of all participants (i.e. the amount of years that each participant has been under observation). For HIV, person-time was calculated as the sum of individual person-years of HIV-negative MSM until HIV diagnosis. For HIV, person-time stopped at the midpoint between the date of the last negative HIV test and the date of the first positive HIV test. Repeated infections for syphilis, chlamydia, gonorrhoea and LGV were included and all follow-up time was considered time at risk. If a participant had missed three or more consecutive scheduled study visits (i.e. no study visit within 274 days of the last visit), person-time was stopped at the last attended study visit. Participants could re-enter the analysis if they later resumed attendance and had at least two more study visits; person-time then re-started from the moment of re-entry.

Incidence rate ratios (IRRs) comparing MSM who engaged in SDU with MSM who did not, were assessed using Poisson regression analysis, and were assessed for alcohol and each drug separately. IRRs for HIV were adjusted for age; IRRs for all bacterial STDs were adjusted for age and HIV-status. We did not adjust for sexual behaviour (e.g., CAS), since sexual behaviour lies on the causal pathway from SDU to incident STD (i.e., SDU indirectly effects the incidence of STDs through its effects on sexual behaviour). Analyses were done for alcohol and each individual drug, whereby we did not adjust for concurrent use of other substances, because of collinearity.

All analyses were done using STATA (version 15.1; StataCorp, College Station, Texas, USA).

Ethical approval

Ethical approval for the MS2 cohort was not required (W12_252 # 12.17.0286). All participants provided written informed consent before participating in the study.

Results

Between January 2014 and October 2018, 324 participants were included in the MS2 cohort. 20 of 324 (6.2%) participants only attended the baseline visit and did not contribute person-years. Therefore, they were excluded from analyses. Of the 304 included participants, 131 (43.1%) were HIV-negative at baseline and 173 (56.9%) were living with HIV (Table 1). MSM living with HIV were older (median 46 years [interquartile range (IQR) 38–51]) than HIV-negative MSM (median 33 [IQR 28–44], p < 0.001). MSM living with HIV more often engaged in SDU with any type of drug (94.8%) than HIV-negative MSM (85.5%, p = 0.005) and in chemsex (i.e. the sexualized use of GHB/GBL, methamphetamine and/or mephedrone, 58.4% versus 45.8%, p = 0.030). Drugs most often used during sex were nitrites (66.8%), erectile dysfunction drugs (63.5%), XTC/MDMA (50.3%), and GHB/GBL (49.7%). Erectile dysfunction drugs (p < 0.001), methamphetamine (p < 0.001) and nitrites (p = 0.005) were more often used during sex by MSM living with HIV. Fifty-six (18.4%) participants had gonorrhoea at baseline, 35 (11.5%) chlamydia and 13 (4.3%) syphilis. Seven (2.3%) participants had LGV at baseline, all of whom were living with HIV.

Table 1.

Baseline characteristics of the 304 participants (131 HIV-negative MSM and 173 MSM living with HIV) of the MS2 observational cohort study, January 2014 to October 2019, Amsterdam, the Netherlands.

	Total (n = 304)		HIV-negative MSM (n = 131)		MSM living with HIV (n = 173)		p-value^b
	n ^a	% ^a	n ^a	% ^a	n ^a	% ^a	p-value^b
Sociodemographic characteristics
Age in years							<0.001
Median [IQR]	41	(32–50)	33	(28–44)	46	(38–51)
Country of origin							0.273
Netherlands	232	(76.3%)	104	(79.4%)	128	(74.0%)
Other	72	(23.7%)	27	(20.6%)	45	(26.0%)
Highest educational level							0.959
None/primary/secondary	60	(19.7%)	25	(19.1%)	35	(20.2%)
College/university	224	(73.7%)	97	(74.1%)	127	(73.4%)
Other	20	(6.6%)	9	(6.9%)	11	(6.4%)
Sexual behaviour
Sexual orientation^c							0.508
Not exclusively homosexual	2	(0.7%)	0	(0.0%)	2	(1.2%)
Exclusively homosexual	302	(99.3%)	131	(100%)	171	(98.8%)
Number of sex partners^c
Median [IQR]	10	(5–25)	10	(5–25)	10	(5–25)	0.305
Alcohol and drug use – grouped
Any drug use^d	284	(93.4%)	116	(88.6%)	168	(97.1%)	0.003
Any sexualized drug use^e	276	(90.8%)	112	(85.5%)	164	(94.8%)	0.005
Any chemsex^f	161	(53.0%)	60	(45.8%)	101	(58.4%)	0.030
Slamming^g	14	(5.2%)	2	(2.0%)	12	(7.2%)	0.061
Sexualized alcohol and drug use – individual substances
Alcohol	196	(64.5%)	88	(67.2%)	108	(62.4%)	0.392
Amphetamine	58	(19.1%)	25	(19.1%)	33	(19.1%)	0.998
Cannabis	116	(38.2%)	42	(32.1%)	74	(42.8%)	0.057
Cocaine	94	(30.9%)	44	(33.6%)	50	(28.9%)	0.381
Erectile dysfunction drugs	193	(63.5%)	66	(50.4%)	127	(73.4%)	<0.001
GHB/GBL	151	(49.7%)	58	(44.3%)	93	(53.8%)	0.102
Ketamine	73	(24.1%)	33	(25.2%)	40	(23.1%)	0.676
Methamphetamine	43	(14.1%)	8	(6.1%)	35	(20.2%)	<0.001
Mephedrone	38	(12.5%)	13	(9.9%)	25	(14.5%)	0.237
Nitrites/poppers	203	(66.8%)	76	(58.0%)	127	(73.4%)	0.005
XTC/MDMA	153	(50.3%)	61	(46.6%)	92	(53.2%)	0.253
Sexually transmitted diseases
Syphilis	13	(4.3%)	5	(3.8%)	8	(4.6%)	0.730
Chlamydia	35	(11.5%)	13	(9.9%)	22	(12.7%)	0.450
LGV	7	(2.3%)	0	(0.0%)	7	(4.1%)	0.021
Gonorrhoea	56	(18.4%)	23	(17.6%)	33	(19.1%)	0.735

Abbreviations: GBL, γ-butyrolactone; GHB, γ-hydroxybutyrate; HIV, human immunodeficiency virus; IQR, interquartile range; LGV, lymphogranuloma venereum; MDMA, methylenedioxymethamphetamine; MSM, men who have sex with men; XTC, ecstasy.

Data were missing for: number of sex partners (n = 1), slamming (n = 35).

^aUnless stated otherwise.

^bp-values were estimated using Wilcoxon’s ranksum-sum test for continuous variables and Pearson’s Chi-square test and Fisher’s exact test for categorical variables.

^cIn the 6 months before baseline.

^dIn the 3 months before baseline.

^eIncluding amphetamine, cannabis, cocaine, erectile dysfunction drugs, GHB/GBL, ketamine, methamphetamine, mephedrone, nitrites, and/or XTC/MDMA. Excluding alcohol.

^fIncluding GHB/GBL, methamphetamine and/or mephedrone.

^gDefined as the intravenous use of drugs in a sexualized setting.

STDs and sexualized drug use during follow-up

The follow-up period was from January 2014 to October 2019. For the 304 participants that were included for analysis, the total follow-up time was 774.6 person-years with a median of 2.5 [IQR 1.4–4.1] years per participant. The median number of study visits was 9 [IQR 5–15] and the median number of study visits including additional STD visits was 11 [IQR 7–18]. Participants attended a median of one [IQR 0–3, range 0–10] additional STD visit.

113 (37.2%) of 304 participants that were included in the analysis were lost-to-follow-up. Participants living with HIV were less likely to be lost-to-follow-up (adjusted incidence rate ratio (aIRR) = 0.39, 95% confidence interval (95%CI) = 0.27–0.57, p < 0.001) (Supplementary Table 1).

HIV

Among 131 participants who were HIV-negative at baseline, eight incident HIV infections were diagnosed over 270.1 person-years (IR = 3.0 per 100 person-years, 95%CI = 1.5–5.9) (Supplementary Table 2). The incidence rate of HIV was higher among MSM who used GHB/GBL (aIRR = 7.2, 95%CI = 1.4–35.5, p = 0.016) in a sexualized setting than those who did not (Figure 1, Supplementary Table 3).

Any bacterial STD

807 incident bacterial STDs were diagnosed among 304 participants during 774.6 person-years (IR = 104.2 per 100 person-years, 95%CI = 97.2–111.6) (Supplementary Table 2). MSM who used GHB/GBL (aIRR = 1.2, 95%CI = 1.0–1.3, p = 0.047), ketamine (aIRR = 1.2, 95%CI = 1.0–1.5, p = 0.019) or methamphetamine (aIRR = 1.2, 95%CI = 1.0–1.5, p = 0.031) in a sexualized setting had a higher risk of acquiring any incident STD than those who did not (Table 2). The risk of acquiring any incident STD was lower for MSM who used alcohol (aIRR = 0.6, 95%CI = 0.5–0.7, p < 0.001) or nitrites (aIRR = 0.7, 95%CI = 0.6–0.9, p < 0.001).

Table 2.

Incidence rate of syphilis, chlamydia and/or gonorrhoea by drug used in a sexualized setting among 304 participants of the MS2 observational cohort study, January 2014 to October 2019, Amsterdam, the Netherlands.

	Substance used			Substance not used			IRR (95%CI)	aIRR (95%CI) ^b
	Events	Person-years	IR (95% CI) ^a	Events	Person-years	IR (95% CI) ^a	IRR (95%CI)	aIRR (95%CI) ^b
Alcohol	454	526.3	86.3 (78.7–94.6)	353	248.2	142.2 (128.1–157.8)	0.61 (0.53–0.70)	0.62 (0.54–0.71)
Amphetamine	120	110.7	108.4 (90.7–129.7)	687	663.9	103.5 (96.0–111.5)	1.05 (0.86–1.27)	1.03 (0.85–1.25)
Cannabis	238	233.5	102.0 (89.8–115.8)	569	541.1	105.2 (96.9–114.2)	0.97 (0.83–1.13)	0.95 (0.81–1.10)
Cocaine	186	180.5	103.1 (89.3–119.0)	621	594.1	104.5 (96.6–113.1)	0.99 (0.84–1.16)	0.95 (0.80–1.12)
Erectile dysfunction drugs	433	425.9	101.7 (92.5–111.7)	374	348.7	107.3 (96.9–118.7)	0.95 (0.83–1.09)	0.95 (0.83–1.10)
GHB/GBL	334	290.8	114.8 (103.2–127.8)	473	483.7	97.8 (89.4–107.0)	1.17 (1.02–1.35)	1.15 (1.00–1.33)
Ketamine	156	121.5	128.4 (109.7–150.2)	651	653.0	99.7 (92.3–107.6)	1.29 (1.08–1.53)	1.23 (1.04–1.47)
Methamphetamine	126	99.5	126.7 (106.4–150.8)	681	675.1	100.9 (93.6–108.7)	1.26 (1.04–1.52)	1.24 (1.02–1.50)
Mephedrone	59	53.8	109.7 (85.0–141.6)	748	720.8	103.8 (96.6–111.5)	1.06 (0.81–1.38)	1.05 (0.81–1.37)
Nitrites	393	436.1	90.1 (81.6–99.5)	414	338.4	122.3 (111.1–134.7)	0.74 (0.64–0.85)	0.74 (0.64–0.85)
XTC/MDMA	324	304.7	106.3 (95.4–118.6)	483	469.8	102.8 (94.0–112.4)	1.03 (0.90–1.19)	1.02 (0.89–1.18)

Abbreviations: aIRR, adjusted incidence rate ratio; CI, confidence interval; GBL, γ-butyrolactone; GHB, γ-hydroxybutyrate; HIV, human immunodeficiency virus; IR, incidence rate; IRR, incidence rate ratio; MDMA, methylenedioxymethamphetamine; NA, not applicable; XTC, ecstasy.

^aPer 100 person-years.

^bAdjusted for age and HIV status, but not for use of other substances in table.

Syphilis

116 incident syphilis were diagnosed among 304 participants over 774.6 person-years (IR = 15.0 per 100 person-years, 95%CI = 12.5–18.0) (Supplementary Table 2). Twenty-three (7.6%) participants were diagnosed with infectious syphilis multiple times during follow-up: 18 participants were diagnosed twice and five three times. We found no association between SDU with specific drug types and syphilis incidence (Figure 1, Supplementary Table 4).

Anal chlamydia or gonorrhoea

549 anal chlamydia or gonorrhoea were diagnosed among 304 participants during 774.6 person-years (IR = 70.9 per 100 person-years, 95%CI = 65.2–77.1) (Supplementary Table 2). Participants who engaged in SDU with GHB/GBL (aIRR = 1.2, 95%CI = 1.0–1.4, p = 0.027), ketamine (aIRR = 1.3, 95%CI = 1.0–1.6, p = 0.029), or methamphetamine (aIRR = 1.3, 95%CI = 1.0–1.6, p = 0.035) were at higher risk of acquiring an incident anal chlamydia or gonorrhoea (Table 3). The risk of acquiring anal chlamydia or gonorrhoea was lower among MSM reporting alcohol (aIRR = 0.6, 95%CI = 0.5–0.7, p < 0.001) or nitrites use (aIRR = 0.7, 95%CI = 0.6–0.9, p < 0.001) during or around sex.

Table 3.

Incidence rate of anal chlamydia and/or gonorrhoea by drug used in a sexualized setting among 304 participants of the MS2 observational cohort study, January 2014 to October 2019, Amsterdam, the Netherlands.

	Substance used			Substance not used			IRR (95%CI)	aIRR (95%CI) ^b
	Events	Person-years	IR (95% CI) ^a	Events	Person-years	IR (95% CI) ^a	IRR (95%CI)	aIRR (95%CI) ^b
Alcohol	300	526.3	57.0 (50.9–63.8)	249	248.2	100.3 (88.6–113.6)	0.57 (0.48–0.67)	0.58 (0.49–0.69)
Amphetamine	87	110.7	78.6 (63.7–97.0)	462	663.9	69.6 (63.5–76.2)	1.13 (0.90–1.42)	1.09 (0.87–1.38)
Cannabis	151	233.5	64.7 (55.1–75.9)	398	541.1	73.6 (66.7–81.1)	0.88 (0.73–1.06)	0.86 (0.71–1.03)
Cocaine	122	180.5	67.6 (56.6–80.7)	427	594.1	71.9 (65.4–79.0)	0.94 (0.77–1.15)	0.89 (0.73–1.10)
Erectile dysfunction drugs	291	425.9	68.3 (60.9–76.7)	258	348.7	74.0 (65.5–83.6)	0.92 (0.78–1.09)	0.94 (0.79–1.12)
GHB/GBL	234	290.8	80.5 (70.8–91.5)	315	483.7	65.1 (58.3–72.7)	1.24 (1.04–1.46)	1.21 (1.02–1.44)
Ketamine	109	121.5	89.7 (74.3–108.2)	440	653.0	67.4 (61.4–74.0)	1.33 (1.08–1.64)	1.26 (1.02–1.56)
Methamphetamine	88	99.5	88.5 (71.8–109.0)	461	675.1	68.3 (62.3–74.8)	1.30 (1.03–1.63)	1.28 (1.02–1.62)
Mephedrone	45	53.8	83.7 (62.5–112.0)	504	720.8	69.9 (64.1–76.3)	1.20 (0.88–1.62)	1.18 (0.87–1.61)
Nitrites	263	436.1	60.3 (53.4–68.0)	286	338.4	84.5 (75.3–94.9)	0.71 (0.60–0.84)	0.72 (0.61–0.85)
XTC/MDMA	225	304.7	73.8 (64.8–84.1)	324	469.8	69.0 (61.8–76.9)	1.07 (0.90–1.27)	1.06 (0.89–1.25)

^aPer 100 person-years.

^bAdjusted for age and HIV status, but not for use of other substances in table.

Chlamydia

361 incident chlamydia were diagnosed among 304 participants during 774.6 person-years (IR = 46.6 per 100 person-years, 95%CI = 42.0–51.7), of which 264 were anal infections, 114 urogenital, and 27 pharyngeal (Supplementary Table 2). Ninety-two (30.3%) participants were diagnosed with chlamydia multiple times during follow-up; median number of diagnoses was 1 [IQR 0–2, range 0–8]. The risk of chlamydia was higher among MSM who used GHB/GBL (aIRR = 1.4, 95%CI = 1.2–1.8, p = 0.001), ketamine (aIRR = 1.5, 95%CI = 1.1–1.9, p = 0.004), or methamphetamine (aIRR = 1.3, 95%CI = 1.0–1.8, p = 0.047) during sex (Figure 1, Supplementary Table 5). The use of XTC/MDMA during sex was non-significant (aIRR = 1.23, 95%CI = 1.0–1.5, p = 0.055). The use of alcohol was associated with a lower risk of acquiring chlamydia (aIRR = 0.7, 95%CI = 0.6–0.9, p < 0.001).

37 incident anal LGV were diagnosed (IR = 4.8 per 100 person-years, 95%CI = 3.5–6.6) (Supplementary Table 2). The sexualized use of ketamine (aIRR = 2.1, 95%CI = 1.1–4.4, p = 0.037), methamphetamine (aIRR = 2.2, 95%CI = 1.0–4.5, p = 0.039) and mephedrone (aIRR = 3.6, 95%CI = 1.7–8.0, p = 0.001) were associated with a higher risk of incident LGV (Supplementary Table 6). The use of nitrites was associated with a lower risk of LGV (aIRR = 0.4, 95%CI = 0.2–0.9, p = 0.017).

Gonorrhoea

436 incident gonorrhoea were diagnosed among 304 participants during 774.6 person-years (IR = 56.3 per 100 person-years, 95%CI = 51.2–61.8), of which 336 were anal infections, 102 urogenital and 157 pharyngeal (Supplementary Table 2). 113 participants (37.2%) were diagnosed with gonorrhoea multiple times; median number of diagnoses was 1 [IQR 0–2, range 0–8]. The sexualized use of alcohol (aIRR = 0.5, 95%CI = 0.4–0.7, p < 0.001), cannabis (aIRR = 0.8, 95%CI = 0.6–1.0, p = 0.046) and nitrites (aIRR = 0.7, 95%CI = 0.6–0.9, p < 0.001) were associated with a lower risk of acquiring gonorrhoea (Figure 1, Supplementary Table 7).

Discussion

Our study shows that the incidence of HIV and bacterial STDs was high among MSM included in the MS2 cohort study. Moreover, the use of drugs during sex was high in this population. We found that MSM who engaged in SDU had a higher risk of acquiring incident HIV and bacterial STDs, specifically those using GHB/GBL, ketamine, methamphetamine, or mephedrone. In contrast, MSM reporting use of alcohol, nitrites, or cannabis in a sexualized setting had a lower risk of acquiring bacterial STDs.

The incidence of HIV was high in this cohort (IR 2.9 per 100 person-years). We found that MSM who used GHB/GBL during sex had a seven times higher risk of acquiring HIV. A prospective cohort study performed among MSM attending STI clinics in England found that chemsex (which commonly includes the use of GHB/GBL) was associated with a 6-fold higher risk of acquiring HIV.¹⁷ Whereas the association between GHB/GBL and HIV prevalence among MSM has been reported before, the association with incident HIV has not.¹⁸ If SDU with GHB/GBL is a risk factor for incident HIV, this could be of practical use for STD clinic physicians, who should consider offering PrEP to HIV-negative MSM who engage in SDU with GHB/GBL, and likely chemsex in general. Our findings are in line with the PrEP guideline of the European AIDS Clinical Society, which mentions chemsex as possible marker of increased risk for HIV.¹⁹ The ASTRA study showed that drug use among MSM living with HIV is associated with CAS with partners with a different HIV-status.²⁰ This finding underscores the importance of PrEP among HIV-negative MSM who engage in SDU, assuming that most MSM who use drugs during a sexual act have sex with partner(s) that also use drugs during that sexual act.

Our findings imply that sexualized use of GHB/GBL, ketamine, methamphetamine and mephedrone are associated with higher risk of incident bacterial STD. Several studies found an association between SDU or chemsex and incident or prevalent bacterial STDs, but these studies did not stratify for specific drug types.^{1–3,6,21,22} Our results imply that the risk of incident STD differs between different types of drugs and that not all drugs are associated with a higher risk. Moreover, we found that sexualized use of a specific drug did not necessarily increase the risk for all incident STDs. For example, use of GHB/GBL was associated with an increased risk of chlamydia, but not with syphilis or gonorrhoea. The difference in effect of sexualized use of specific substances on incident STDs might be due to different scenes of SDU. A study among MSM in the UK suggested that there may be multiple chemsex scenes which are based on different sets of norms and in which different MSM engaging in SDU participate.²³ Their findings suggested that MSM may engage in a chemsex scene based on their own HIV status and that of the other participants, which drugs are used, course of administration of drugs, and frequency and intensity of SDU.²³ Some STDs might therefore be more prevalent in specific scenes, which may result in a difference in STD risk between different scenes. Research investigating the risk of specific STDs MSM contract when engaging in a specific scene or when using a specific drug could contribute to better and personalized care by optimizing screening on STDs.

Furthermore, we found that the sexualized use of alcohol, cannabis and nitrites (poppers) was associated with lower risk of incident bacterial STD. This result was not expected, since previous studies found that the use of alcohol or nitrites during sex was associated with higher risk of prevalent bacterial STDs.^11,15,18 Although the negative association between nitrites and bacterial STDs is found in some studies, other studies had contradictory findings.^11,18,22 An explanation for our findings could be that SDU of a specific drug was compared to no sexualized use of this specific drug; non-use of that specific drug did not exclude use of other drugs. For example, we compared MSM who used alcohol during sex with MSM who did not, but who may have used other drugs during sex, such as GHB/GBL. Due to the high frequency of drug use, we were unable to compare use of specific drugs to no drug use at all. Moreover, alcohol is legal in the Netherlands, and cannabis and nitrites are openly tolerated, which may result in less risky behaviour when using these drugs. We were not able to assess the effect of alcohol use on STD incidence for moderate alcohol use and binge drinking; a previous study only found that binge drinking was positively associated with CAS.¹⁴ Further research could compare SDU of individual drugs with no SDU of any drug, and could investigate the exact role of nitrites, moderate alcohol use and binge drinking on sexual risk behaviour and STD incidence.

A strength of this study is that we were able to estimate incidence rates of STDs per use of individual drug. This study also has limitations. First, participants in the MS2 cohort do not represent the general MSM population, since participants were included based on HIV and STD risk. Moreover, participants may have had STD screening outside of our STI Outpatient Clinic without our knowledge. This may have resulted in an underestimation of the number of incidence events. Moreover, approximately one third of our study population was lost-to-follow-up before study end. This led to reduced power to assess possible associations. Finally, drug use was self-reported, which may have led to underreporting of (sexualized) drug use.

In conclusion, the use of GHB/GBL, ketamine, methamphetamine, and mephedrone in a sexualized setting were associated with an increased risk of incident HIV and bacterial STDs among MSM at high risk of STD, while the use of other drugs, such as alcohol and nitrites, was associated with a lower risk of incident bacterial STDs. The increased risk of HIV when engaging in SDU with GHB/GBL emphasizes the importance of PrEP for MSM who engage in SDU. Since SDU of GHB/GBL, ketamine, methamphetamine, and mephedrone was associated with a higher risk of incident bacterial STDs, there should be attention for SDU when MSM present with recurring STDs. Moreover, MSM who engage in SDU should be advised to get regularly screening on STDs. More research is needed to unravel the co-occurrence of STDs and HIV, drug use and mental health among MSM, for example into the role of drug use dependency and which factors make SDU problematic, with the aim to give appropriate care and improve sexual health and pleasure among MSM.

Supplemental Material

Supplemental Material - Sexualized drug use and STD and HIV incidence among men who have sex with men in Amsterdam, the Netherlands

Supplemental Material for Sexualized drug use and STD and HIV incidence among men who have sex with men in Amsterdam, the Netherlands by Carien M Blomaard, Vita W Jongen, Roel CH Achterbergh, Maarten F Schim van der Loeff and Henry JC de Vries in International Journal of STD & AIDS

Footnotes

Acknowledgements

We would like to thank all study participants and the following individuals: Kees de Jong, Ilya Peters, Princella Felipa and Myra van Leeuwen, Wim van den Brink, Udi Davidovich, Arjan Hogewoning, Amy Matser, Elske Hoornenborg, Gerben Rienk Visser, Marieke Been and Hent van Elsen.

Author contributions

RCHA and HJCdV conceptualized the MS2 cohort. CB, VJ, MFSvdL and HJCdV contributed to study design of the current study. All authors were involved in data collection, data analysis, or interpretation of the data. CB and VJ drafted the manuscript. All authors critically revised the manuscript.

Ethics approval

Ethical approval for the MS2 cohort was not required (W12_252 # 12.17.0286).

ORCID iD

Carien M Blomaard

Supplemental Material

Supplemental material for this article is available online.

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