Table 2

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

# eventsPerson-yearsUnivariable Poisson modelMultivariable Poisson model
IRR95% CIP valueaIRR95% CIP value
Years since PrEP initiation
 1199359Ref0.763Ref
 21693380.900.73 to 1.110.940.76 to 1.150.532
 31713200.970.79 to 1.191.080.87 to 1.330.491
 41322590.920.74 to 1.151.090.84 to 1.410.517
Age, per 10-year increase*0.870.81 to 0.93<0.0010.860.80 to 0.92<0.001
Age*
 <35 years191308Ref<0.001
 35–44 years2464130.960.79 to 1.16
 ≥45 years2565820.710.59 to 0.86
Self-declared ethnicity†
 White5951117Ref0.932
 Non-white981860.990.80 to 1.23
Highest education level†
 No college/university129286Ref0.029
 College/university56410161.231.02 to 1.49
Employment†
 Unemployed142279Ref0.507
 Employed54410061.060.88 to 1.28
Sexual preference†
 Exclusively homosexual5641029Ref0.165
 Not exclusively homosexual1292690.870.72 to 1.06
CAS with a steady partner*
 No413748Ref0.360
 Yes2595040.930.80 to 1.09
CAS with a known casual partner*
 No125347Ref<0.001Ref0.004
 Yes5479061.671.38 to 2.031.361.10 to 1.68
CAS with an unknown casual partner*
 No105331Ref<0.001Ref<0.001
 Yes5679221.941.57 to 2.391.861.48 to 2.34
Chemsex*‡
 No283690Ref<0.001Ref<0.001
 Yes3394771.731.48 to 2.031.511.28 to 1.78
Alcohol Use Disorder Identification Test*§
 Score <8493884Ref0.049
 Score ≥81292800.830.68 to 1.00
Drug Use Disorder Identification Test*§
 Score <8395802Ref0.004
 Score ≥82273621.281.08 to 1.50
MHI-5*¶
 Score ≥60504939Ref0.842
 Score <601172220.980.80 to 1.20
Sexual Compulsivity Scale score***
 Score <245351021Ref0.180
 Score ≥24861401.170.93 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.