Table 1.

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

	M+F− couples								M−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)	aHR	95% CI	p Value (two-tail)	Total cohort (N interval, % or mean, SD)		Any unprotected sex (N interval, % or mean, SD)		Unadjusted p value (two-tail)	aHR	95% CI	p Value (two-tail)
Demographics
Man age (per year increase)‡	35.2	7.6	34.0	7.4	<0.0001	0.98	0.98 to 0.99	<0.0001	35.2	8.6	34.3	8.3	<0.0001	0.99	0.98 to 0.99	<0.0001
Woman age (per year increase) ‡	28.4	6.8	27.4	6.6	<0.0001				28.6	6.7	27.9	6.5	<0.0001
Years cohabiting (per year increase) ‡	8.1	6.5	7.3	6.0	<0.0001				6.1	5.8	5.6	5.4	<0.001
Woman alcohol use last year
Yes	2549	17%	1057	18%	0.022	1.15	1.01 to 1.31	0.033	3606	24%	1550	23%	0.729
No	12 582	83%	4727	82%		Ref			11 585	76%	5119	77%
Man alcohol use last year
Yes	10 152	67%	3964	68%	0.033	1.11	0.99 to 1.24	0.088	11 181	73%	4979	74%	0.166
No	5034	33%	1825	32%		Ref			4034	27%	1722	26%
Family planning and sexual behaviour
Contraceptive method (time-varying)
Condoms alone	9553	62%	3701	63%		Ref			10 318	67%	4698	69%
OCPs	2128	14%	969	16%	<0.0001	1.37	1.22 to 1.54	<0.0001	2061	13%	910	13%	0.368
Injectables	2011	13%	794	13%	0.002	1.43	1.25 to 1.64	<0.0001	1975	13%	808	12%	0.271
Permanent method, IUD, implant	1711	11%	437	7%	0.508	1.14	0.90 to 1.44	0.293	1157	7%	405	6%	0.716
Pregnancy status (time-varying)
Not pregnant	11 922	87%	4427	80%		Ref			12 167	89%	5315	85%		Ref
Pregnant (not incident)	1346	10%	938	17%	<0.0001	1.85	1.71 to 2.01	<0.0001	1140	8%	857	14%	<0.0001	1.56	1.46 to 1.66	<0.0001
Post-partum (up to 6 months)	510	4%	136	2%	0.004	0.83	0.70 to 0.99	0.038	341	2%	108	2%	0.005	0.81	0.68 to 0.95	0.0107
Number of previous pregnancies (per pregnancy increase)‡	3.7	2.5	3.5	2.3	0.001				3.4	2.3	3.3	2.1	0.032
Fertility intentions of woman
Yes, next year	1051	18%	418	21%	0.045				1642	23%	693	24%	0.372
Yes, but not next year	1217	21%	472	24%	0.005				1770	25%	772	27%	0.063
Do not know/no	3610	61%	1076	55%					3750	52%	1435	49%
Fertility intentions of man
Yes, next year	671	13%	259	15%	0.126				1145	18%	511	20%	0.023
Yes, but not next year	1652	32%	573	34%	0.160				2556	39%	1073	42%	0.016
Do not know/No	2880	55%	869	51%					2829	43%	994	39%
Woman self-reporting sex with outside partner (time-varying)
Yes	205	1%	115	2%	<0.001	1.30	1.09 to 1.55	0.003	236	2%	131	2%	0.241
No	14 848	99%	5720	98%		Ref			14 150	98%	6408	98%
Clinical
Circumcised male partner
Yes	1508	10%	619	11%	0.05	1.23	1.03 to 1.46	0.021	2587	17%	1084	16%	0.249
No	13 876	90%	5266	89%		Ref			12 963	83%	5745	84%

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.