|Measuring changes in sexual behaviour is essential in the monitoring and evaluation of national HIV/AIDS and STI control programmes. In fact, indicators of sexual behaviour and condom use are probably the most important of all indicators in monitoring HIV prevention programmes and evaluating their success.
More has been done to measure sexual behaviour than was dreamed possible a decade ago, when it was believed that people would never tell the truth about their sex lives. In country after country, it has now been demonstrated that people do answer questions about sex, and that the trends derived from their answers match other forms of evidence such as condom sales and STI prevalence. However, there is still room for improvement. Women, especially, continue to underreport sex outside of marriage in standardised surveys. Qualitative data collection gives rather better results, but is rarely practical on a large scale and does not lend itself to the construction of indicators necessary for monitoring and evaluation.
Perhaps the trickiest issue in measuring sexual behaviour is how to filter relationships to get an idea of levels of risk involved. This question becomes more vexing as prevalence in the general population rises and the lines between "high-risk" partners such as sex workers and "low-risk" partners such as husbands become blurred. The matter of central interest is not numbers of partners but patterns of sexual networking, and this is all but impossible to analyse with simple indicators.
To date, the most common way of dividing relationships into high and low risk has been using a simple measure of time: any (non-marital) relationship that has lasted or is expected to last for more than a year is classified as "regular", while any other relationship is classified as "non-regular".
There is a growing feeling that a time-based definition of "non-regular" does not adequately capture the level of risk inherent in the partnership. For example, many men may consider a sex worker they visit frequently to be a "regular partner" under the time-based definition, although she clearly represents higher risk than a faithful wife.
It is therefore proposed that relationships be divided on the basis of cohabitation and marriage. Sex with any non-cohabiting, non-marital partner is considered to be higher risk than sex with a cohabiting partner, regardless of the duration of the relationship. This definition has the advantage that it is equally valid for all age groups.
Sexual behaviour data are one of the central pillars of a monitoring and evaluation system. They should be used to inform and explain trends observed in HIV and STI surveillance data as much as possible. With this in mind, sampling for major surveys of sexual behaviour should be carried out in relation to the catchment areas for HIV sentinel sites.
Thought must also be given to the frequency of surveys of sexual behaviour. In the absence of a major and radically new programme effort, sexual behaviour is unlikely to change significantly in a single year, or even two, in the general adult population. Among young people, however, new behavioural trends may emerge more rapidly, especially if more programme resources are aimed at establishing safe behaviour in this group.