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. 2014 Feb 18;9(2):e88378.
doi: 10.1371/journal.pone.0088378. eCollection 2014.

The distribution of sex acts and condom use within partnerships in a rural sub-Saharan African population

Jennifer Smith  1 , Constance Nyamukapa  2 , Simon Gregson  2 , James Lewis  3 , Sitholubuhle Magutshwa  4 , Christina Schumacher  5 , Phyllis Mushati  4 , Tim Hallett  1 , Geoff Garnett  6
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The distribution of sex acts and condom use within partnerships in a rural sub-Saharan African population

Jennifer Smith et al. PLoS One. .

Abstract

Introduction: In an HIV/AIDS epidemic driven primarily by heterosexual transmission, it is important to have an understanding of the human sexual behaviour patterns that influence transmission. We analysed the distribution and predictors of within-partnership sexual behaviour and condom use in rural Zimbabwe and generated parameters for use in future modelling analyses.

Methods: A population-based cohort was recruited from a household census in 12 communities. A baseline survey was carried out in 1998-2000 with follow-up surveys after 3 and 5 years. Statistical distributions were fitted to reported within-partnership numbers of total, unprotected and protected sex acts in the past two weeks. Multilevel linear and logistic regression models were constructed to assess predictors of the frequency of unprotected sex and consistent condom use.

Results: A normal distribution of ln(sex acts+1) provided the best fit for total and unprotected sex acts for men and women. A negative binomial distribution applied to the untransformed data provided the best fit for protected sex acts. Condom use within partnerships was predominantly bimodal with at least 88% reporting zero or 100% use. Both men and women reported fewer unprotected sex acts with non-regular compared to regular partners (men: 0.26 fewer every two weeks (95% confidence interval 0.18-0.34); women: 0.16 (0.07-0.23)). Never and previously married individuals reported fewer unprotected sex acts than currently married individuals (never married men: 0.64 (0.60-0.67); previously married men: 0.59 (0.50-0.67); never married women: 0.51 (0.45-0.57); previously married women: 0.42 (0.37-0.47)). These variables were also associated with more consistent condom use.

Discussion: We generated parameters that will be useful for defining transmission models of HIV and other STIs, which rely on a valid representation of the underlying sexual network that determines spread of an infection. This will enable a better understanding of the spread of HIV and other STDs in this rural sub-Saharan population.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Overlaid histograms showing the distributions of the numbers of sex acts (total, unprotected and protected) with a specified partner within the last two weeks for (A) men and (B) women.
Note that the line for total sex acts is lower than that for either unprotected or protected sex acts at zero because individuals reporting either zero unprotected or protected sex acts did not often report zero sex acts in total (due to the observed bimodal pattern of condom use described later).
Figure 2
Figure 2. Observed and fitted distributions of the number of sex acts in the last two weeks.
Panels A, C and E represent the numbers of sex acts (total, unprotected and protected) reported by men and B, D and F represent the same for women. A normal approximation of ln(sex acts+1) is used for A–D, and a negative binomial approximation of the untransformed data is used for E and F.
Figure 3
Figure 3. Partnership characteristics.
A and B. Boxplots showing the total number of sex acts in the past two weeks by age for (A) men and (B) women. The heavy solid line marks the median and the box edges show the lower and upper quartiles. Whiskers show the minimum and maximum results which are no more than 1.5 multiplied by the interquartile range (IQR) from the box and outliers are not shown. C and D. Scatterplots showing the relationship between respondent age and age difference with partner reported by (C) men and (D) women. Solid lines mark the linear regression of respondent-partner age difference on respondent; these are in the form y = mx+c, where x is the respondent age and y is the respondent-partner age difference. For men (C), m = 0.30 (95% confidence interval [CI95] −0.31 to −0.29) and c = 3.4 (2.9–3.9). For women (D), m = −0.013 (−0.033–0.0065) and c = 7.0 (6.3–7.6).
Figure 4
Figure 4. Histograms showing the proportion of sex acts in the last two weeks within a partnership in which a condom has been used throughout for men and women with regular and non-regular partners.
See this image and copyright information in PMC

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