Table 1

Factors associated with the composite indicator of unprotected sex* between M+F− and M−F+ couples, univariable and multivariable analyses

M+F− couplesM−F+ couples
Multivariate Model†Multivariate Model†
Total cohort (N interval, % or mean, SD)Any unprotected sex (N interval, % or mean, SD)Unadjusted p Value (2-tail)aHR95% CIp Value (two-tail)Total cohort (N interval, % or mean, SD)Any unprotected sex (N interval, % or mean, SD)Unadjusted p value (two-tail)aHR95% CIp Value (two-tail)
 Man age (per year increase)‡35.27.634.07.4<0.00010.980.98 to 0.99<0.000135.28.634.38.3<0.00010.990.98 to 0.99<0.0001
 Woman age (per year increase) ‡28.46.827.46.6<0.000128.66.727.96.5<0.0001
 Years cohabiting (per year increase) ‡<0.00016.<0.001
Woman alcohol use last year
 Yes254917%105718%0.0221.151.01 to 1.310.033360624%155023%0.729
 No12 58283%472782%Ref11 58576%511977%
Man alcohol use last year
 Yes10 15267%396468%0.0331.110.99 to 1.240.08811 18173%497974%0.166
Family planning and sexual behaviour
 Contraceptive method (time-varying)
  Condoms alone955362%370163%Ref10 31867%469869%
  OCPs212814%96916%<0.00011.371.22 to 1.54<0.0001206113%91013%0.368
  Injectables201113%79413%0.0021.431.25 to 1.64<0.0001197513%80812%0.271
  Permanent method, IUD, implant171111%4377%0.5081.140.90 to 1.440.29311577%4056%0.716
 Pregnancy status (time-varying)
  Not pregnant11 92287%442780%Ref12 16789%531585%Ref
  Pregnant (not incident)134610%93817%<0.00011.851.71 to 2.01<0.000111408%85714%<0.00011.561.46 to 1.66<0.0001
  Post-partum (up to 6 months)5104%1362%0.0040.830.70 to 0.990.0383412%1082%0.0050.810.68 to 0.950.0107
  Number of previous pregnancies (per pregnancy increase)‡
 Fertility intentions of woman
   Yes, next year105118%41821%0.045164223%69324%0.372
  Yes, but not next year121721%47224%0.005177025%77227%0.063
  Do not know/no361061%107655%375052%143549%
 Fertility intentions of man
  Yes, next year67113%25915%0.126114518%51120%0.023
  Yes, but not next year165232%57334%0.160255639%107342%0.016
  Do not know/No288055%86951%282943%99439%
 Woman self-reporting sex with outside partner (time-varying)
  Yes2051%1152%<0.0011.301.09 to 1.550.0032362%1312%0.241
  No14 84899%572098%Ref14 15098%640898%
 Circumcised male partner
  Yes150810%61911% to 1.460.021258717%108416%0.249
  No13 87690%526689%Ref12 96383%574584%
  • Fertility intentions collected from 2002 to 2011; viral load collected from 1999.

  • p Values are two-tailed.

  • *Composite of: any self-reported unprotected sex with the study partner in the past 3 months, incident pregnancy, sperm present on a vaginal swab wet prep and incident linked HIV seroconversion.

  • Log viral load of positive partner (per log10 copies/mL increase), Nyanja literacy and man self-reporting sex with outside partner were not associated (p>0.05).

  • †Controlling for time since enrolment (>0–3 months vs later, p<0.005).

  • ‡Indicates a continuous variable, mean and standard deviation reported.

  • Nyanja: Commonly spoken language in Lusaka, Zambia.

  • Stage of HIV, income and man’s literacy were not significant.

  • IUD, copper intrauterine device; OCP, oral contraceptive pill.