Table 2

Determinants of any incident asymptomatic chlamydia, gonorrhoea or syphilis among PrEP users, AMPrEP cohort study, August 2015–February 2020, Amsterdam, the Netherlands

	# events	Person-years	Univariable Poisson model			Multivariable Poisson model
	# events	Person-years	IRR	95% CI	P value	aIRR	95% CI	P value
Years since PrEP initiation
1	199	359	Ref		0.763	Ref
2	169	338	0.90	0.73 to 1.11		0.94	0.76 to 1.15	0.532
3	171	320	0.97	0.79 to 1.19		1.08	0.87 to 1.33	0.491
4	132	259	0.92	0.74 to 1.15		1.09	0.84 to 1.41	0.517
Age, per 10-year increase*			0.87	0.81 to 0.93	<0.001	0.86	0.80 to 0.92	<0.001
Age*
<35 years	191	308	Ref		<0.001
35–44 years	246	413	0.96	0.79 to 1.16
≥45 years	256	582	0.71	0.59 to 0.86
Self-declared ethnicity†
White	595	1117	Ref		0.932
Non-white	98	186	0.99	0.80 to 1.23
Highest education level†
No college/university	129	286	Ref		0.029
College/university	564	1016	1.23	1.02 to 1.49
Employment†
Unemployed	142	279	Ref		0.507
Employed	544	1006	1.06	0.88 to 1.28
Sexual preference†
Exclusively homosexual	564	1029	Ref		0.165
Not exclusively homosexual	129	269	0.87	0.72 to 1.06
CAS with a steady partner*
No	413	748	Ref		0.360
Yes	259	504	0.93	0.80 to 1.09
CAS with a known casual partner*
No	125	347	Ref		<0.001	Ref		0.004
Yes	547	906	1.67	1.38 to 2.03		1.36	1.10 to 1.68
CAS with an unknown casual partner*
No	105	331	Ref		<0.001	Ref		<0.001
Yes	567	922	1.94	1.57 to 2.39		1.86	1.48 to 2.34
Chemsex*‡
No	283	690	Ref		<0.001	Ref		<0.001
Yes	339	477	1.73	1.48 to 2.03		1.51	1.28 to 1.78
Alcohol Use Disorder Identification Test*§
Score <8	493	884	Ref		0.049
Score ≥8	129	280	0.83	0.68 to 1.00
Drug Use Disorder Identification Test*§
Score <8	395	802	Ref		0.004
Score ≥8	227	362	1.28	1.08 to 1.50
MHI-5*¶
Score ≥60	504	939	Ref		0.842
Score <60	117	222	0.98	0.80 to 1.20
Sexual Compulsivity Scale score***
Score <24	535	1021	Ref		0.180
Score ≥24	86	140	1.17	0.93 to 1.47

*Time updated.
†As reported at baseline.
‡Defined as any gamma-hydroxybutyrate/gamma-butyrolactone, crystallised methamphetamine or mephedrone use during sex.
§A score of 8 or higher indicates possible presence of alcohol or drug use disorder.
¶A score lower than 60 indicates possible mood or depressive mood disorder.
**A score or 24 or higher indicates a greater impact of sexual thoughts on daily functioning and an inability to control sexual thoughts or behaviour.
aIRR, adjusted incidence rate ratio; AMPrEP, Amsterdam PrEP demonstration project; CAS, condomless anal sex; IRR, incidence rate ratio; MHI-5, Mental Health Inventory screening test; PrEP, pre-exposure prophylaxis.