Table 1

Characteristics of 4727 partnerships in which inconsistent condom use was practised and 1674 partnerships in which consistent condom use was practised, by partnership type, reported by 2144 heterosexual individuals who visited the sexually transmitted infections outpatient clinic in Amsterdam in 2010

 Steady partnershipsCasual partnerships
Total (n=2387)Inconsistent condom use (n=2056)Consistent condom use (n=331)Total (N=4014)Inconsistent condom use (n=2671)Consistent condom use (n=1343)
Participant characteristics
Female gender1293 (54.2%)1114 (54.2%)179 (54.1%)2016 (50.2%)1380 (51.7%)636 (47.4%)
Ethnicity
 Dutch1875 (78.6%)1618 (78.7%)257 (77.6%)3297 (82.1%)2224 (83.3%)1073 (79.9%)
 Surinamese/Antillean241 (10.1%)211 (10.3%)30 (9.1%)296 (7.4%)181 (6.8%)115 (8.6%)
 Other271 (11.4%)227 (11.0%)44 (13.3%)420 (10.5%)265 (9.9%)155 (11.5%)
Median age in years (IQR)25 (22–30)25 (22–30)25 (23–30)25 (22–29)25 (22–29)25 (23–31)
Low educational level796 (33.3%)712 (34.6%)84 (25.4%)1221 (30.4%)826 (30.9%)395 (29.4%)
Median no. of partners in the preceding year (IQR)4 (2–6)4 (2–6)4 (3–7)5 (4–8)5 (4–8)5 (4–8)
Characteristics of the partnership
Median age difference in years (IQR)*0 (−3–3)0 (−3–3)0 (−2–3)0 (−2–3)0 (−2–3)0 (−3–4)
Discordant ethnic mixing788 (33.0%)655 (31.9%)133 (40.2%)1478 (36.8%)890 (33.3%)588 (43.8%)
Median duration of a partnership in days (IQR)†182 (60–660)207 (62–712)72 (31–197)1 (1–92)23 (1–121)1 (1–60)
Number of sex acts within a partnership in the preceding year†
 1–4364 (15.3%)280 (13.6%)84 (25.4%)2953 (73.6%)1824 (68.3%)1129 (84.1%)
 5–19671 (28.1%)543 (26.4%)128 (38.7%)790 (19.7%)620 (23.2%)170 (12.7%)
 20–39475 (19.9%)409 (19.9%)66 (19.9%)166 (4.1%)137 (5.1%)29 (2.2%)
 ≥40876 (36.7%)823 (40.1%)53 (16.0%)103 (2.6%)88 (3.3%)15 (1.1%)
Anal sex†455 (19.1%)425 (20.7%)30 (9.1%)249 (6.2%)204 (7.7%)45 (3.4%)
Sex-related drug use†,‡1463 (61.4%)1299 (63.3%)164 (49.6%)2490 (62.1%)1760 (66.0%)730 (54.4%)
Partnership ongoing at the time of inclusion†1184 (49.6%)1035 (50.4%)149 (45.0%)523 (13.0%)403 (15.1%)120 (8.9%)
Concurrency of partnership§
 Definitely non-concurrent804 (33.7%)663 (32.2%)141 (42.6%)1326 (33.0%)905 (33.9%)421 (31.3%)
 Unknown198 (8, 3%)174 (8.5%)24 (7.3%)602 (15.0%)383 (14.3%)219 (16.3%)
Definitely concurrent1385 (58.0%)1219 (59.3%)166 (50.2%)2086 (52.0%)1383 (51.8%)703 (52.3%)
  • *Age of the partner subtracted from age of the participant.

  • †The number of missings per variable were 1539 for duration, 3 for number of sex acts, 5 for anal sex, 7 for recreational drug use and 2 for ongoing partnership.

  • ‡Recreational use of XTC (3,4-methyleendioxymethamfetamine), GHB (γ-hydroxybutyric acid), amphetamines, cocaine, poppers or sildefanil prior to or during sex.

  • §For people reporting >4 eligible partners, concurrency could not be established for the first of four reported partners; for these, concurrency data were estimated after multiple imputation. For details, see online appendix.