[Table of Contents]

Volume: 23S6 - November 1997

National Goals for the Prevention and Control of Sexually Transmitted Diseases in Canada
November 1997

Goals

High-risk Sexual Behaviour

Dr. Eleanor Maticka-Tyndale

Three behaviours which correlate with STD rates have been noted: number of sexual partners, age of first sexual intercourse (most typically vaginal intercourse), and condom use. There is a dearth of Canadian data to permit clear conclusions about the extent and relationships among these and other factors. The data we do have come from a few national studies that, unfortunately, contain few in-depth questions on sexual behaviour, and a small number of local studies that attempt to identify the social and behavioural factors that may affect STD rates.

This position paper is based on the assumption that two factors are directly related to STD rates: the probability of sexual contact between infected and susceptible individuals and the probability of infection of the susceptible individual once such contact has been made. Existing data are reviewed to identify where future efforts should be placed to decrease both of these probabilities in light of the three sexual behaviours correlated with STDs.

Three national health surveys conducted by Health Canada, the 1995 National Population Health Survey (NPHS) and the Canada Health Monitors of 1994 and 1995 (CHM94 and CHM95) provide the most recent national data on sexual behaviours. The Canada Youth and AIDS study (CYA) of 1988 provides more detailed information on sexual behaviours and STD profiles from the late 80s. Several other studies funded under the National AIDS Strategy provide information for specific population subgroups such as the Men Who Have Sex With Men (MSM) study in 1992, the Ethnocultural Communities Facing AIDS (ECFA) study (1994) and the First Nations (FN) study (1991).

Probability of exposure to STDs

The two predictive factors of STDs related to the probability of sexual contact between infected and susceptible individuals are the number of sexual partners and the age of first intercourse. Although these two factors may be closely related (i.e. earlier age of first intercourse likely predicts a greater number of sexual partners), data related to them will be considered separately.

Number of sexual partners

Recent research suggests that the contemporary normative pattern for sexual relationships in Canada is one of serial monogamy, particularly among young women. Such a pattern typically results in a population modal number of one partner in any one-year period but more than one lifetime partner. The impact of this behaviour is shown in the NPHS data (Table 8).

TABLE 8 National Population Health Survey of Canadians Reporting Number of Sexual Partners in the Past Year, by Age and Gender (percentages are weighted to show Canadian population percent prevalence)

In the NPHS study the proportions of men and women who reported more than one partner in the past year peaked in the 20 to 24-year-old group, then decreased with age. For people aged 15 and 19 years who had been sexually active in the past year, about 20% of men and 13% of women had more than one partner. This compares to 27% of men and 16% of women between 20 and 24 years, and 6% or less for those 30 years and older. The same general trend was found in CHM94.

In the CYA study, of those with sexual intercourse experience, 27% of males and 15% of females reported six or more lifetime partners. The proportion was highest for school drop-outs (48% of males and 30% of females) and street youth (65% of males and 58% of females).

Age of first intercourse

The age of first intercourse is often considered a salient behaviour to target in order to reduce STDs. From an examination of studies conducted between 1974 and 1995 in Canada (Table 9), it appears that the proportion of young men who report sexual intercourse by Grade 9 (approximately 15 years of age) has remained relatively stable. For women this proportion decreased in recent years. This pattern is repeated for women in Grade 11 (approximately 17 years of age); however, the proportions of young men reporting sexual intercourse by this age has been increasing.

What is apparent from the most recent data is that the majority of Canadian men and women initiate sexual intercourse between 16 and 19 years of age. Unfortunately, the use of broad age categories (i.e. 15 to 19 years) or of indirect questions in the national studies make it difficult to be more precise about the age of first intercourse.

TABLE 9 Percent of Grade 9 and 11 Students Reporting Previous Sexual Intercourse: 1974-1995

Research from small-scale studies and studies in other countries suggests that the very youngest ages of first intercourse (i.e. under 15 years, and in particular 13 years and younger) are related to sexual coercion, `street' involvement, low socioeconomic status, specific racial and ethnic groups, survival sex, and alcohol use.

Probability of infection

There are both biologic and behavioural aspects to the probability that infection will occur after sexual contact between a susceptible and infected partner. It is known, for example, that different STDs have different degrees of infectivity and women are biologically more susceptible to infection than men. Behaviourally, different sexual acts carry different degrees of risk for infection (e.g. penetrative vs. non-penetrative activity). In terms of modifiable risk factors, however, condom use is the most important.

Condom use

While condom use is less likely in first intercourse when the partners are younger, those who are younger report higher rates of condom use overall (see Table 10) or during the last sexual encounter. The data on condom use and the factors influencing the very youngest age of first intercourse suggest that it is not age per se which carries heightened risk for STDs, but rather the full social context within which the very youngest intercourse often occurs. Targeting age in itself would not necessarily have the desired effect of decreasing STDs.

TABLE 10 NPHS on Reported Condom Use in Canada by Age and Sex for Those with ³ 1 Partner in Last 2 Years (percentages are weighted to show Canadian population percent prevalences)

With the introduction of oral contraception, condom use began to decline in Canada. This trend quickly reversed in the late 1980s, likely due to AIDS prevention programs. However, there is a concern in more recent studies that there may be a normative bias. Condom use has become a socially responsible norm, placing a great deal of pressure on survey respondents to endorse and claim condom use.

NPHS and CHM94 data demonstrate that condom use is most frequent for those who have more than one partner (from a low of 32% of women 25 to 29 years of age to a high of 66% of males 15 to 19 years of age), in sex with `non-regular' partners (e.g. 85% of males 15 to 19 years of age reported they used a condom always or most of the time with their non-regular partner compared with 41% with their regular partner, and for those who are younger (for those with more than one partner in the past 2 years, 66% of males 15 to 19 years compared with 48% of 20 to 24 years, 46% of 25 to 29 years and 44% of 30 to 49 years used a condom each time). This pattern was replicated in all communities participating in the ECFA study. Smaller studies have noted that condom use appears to vary with factors other than age and gender, such as socioeconomic status, race and ethnicity, education, as well as marital and relationship status.

Control strategies

Of the three behaviours suggested for targeting, number of partners, age of first intercourse and condom use, only one - condom use - appears efficacious for broad-scale, population-wide targeting. The social and behavioural dynamics associating number of partners and age of first intercourse with STD rates have not been adequately elaborated and therefore population-wide targets set in these areas may not be effective in reducing STDs. Promoting condom use has the added advantage of being congruent with AIDS; therefore, programs to realize a target of increased condom use can be collaborative with those on HIV/AIDS prevention.

The need to promote condom use is only the beginning of a behavioural approach to decreasing the incidence of STDs. A second salient target is encouraging health-seeking behaviours in high-risk groups. The goal here is to decrease duration of infectivity and thereby decrease the likelihood of contact between infected and susceptible people. Little research has been done on the factors that influence individuals to seek out diagnosis and treatment. The following are some factors that have been suggested: age, gender, socioeconomic status, ethnicity, presence, type and persistence of symptoms, sex education that normalizes STDs as an appropriate concern for all who are sexually active and not just certain `types' of people, prior experience with STDs, vicarious experience through friends or partners who have had STDs, and perception of vulnerability.

Education that promotes healthy sexuality is also an important behavioural approach. The use of sex education in the schools has received mixed reviews. School-based sex education programs have been associated with postponement of first intercourse for in-school populations. However, many of those at risk leave school before sexual health education occurs. Research shows that most parents are supportive of sexual health education but teens prefer receiving sexual health information from friends and the mass media. Use of peer educators may be a valuable alternative. The focus of these programs should be healthy sexual practices including condom use, non-penetrative activities and sexual health screening.

Improving our surveillance capacity is critical to any public health approach. Surveys should include specific questions on the number of partners (lifetime and recent), context of partnerships, age at first intercourse, condom use, life circumstance factors and geographic region. All national surveys should include questions to obtain a sexual history.

Research needs

Before we can begin to have an impact on the other two behavioural predictors of STDs - young age at first intercourse and multiple sexual partners - we need to understand more about sexual networks. Networks can be defined either by behaviour or by disease; we need to establish which is more appropriate. While sexual networks drive transmission, social networks drive prevention. We need to understand the relationship between sexual and social networks. And we know little about the effectiveness of some of the proposed prevention strategies, such as outer-course, or sexual intimacy without penetration. Behavioural scientists should be able to address these questions.

In the absence of more detailed analyses, it is impossible to identify any patterns or targeted population subgroups beyond the very broad age group of those under 30. The three recent studies of specific population subgroups (ECFA, FN and MSM), as well as many smaller-scale studies all support the conclusion that there are pronounced variations in the number of sexual partners across different population subgroups, which may or may not coincide with STD rates. More detailed analyses to examine the relationship of number of partners and marital status and years since first sexual intercourse, the shape and dynamics of the association between number of partners and STD rates, and these factors for specific population subgroups are important if salient behavioural targets are to be set. Research on sexual networks, particularly among and between population subgroups or communities with different rates of infection, would also make a substantial contribution to efficacious behaviour targeting.

Ultimately, all public health strategies using a behaviour-based model should be evaluated. Specifically, we need to look at the populations targeted, the program content and delivery, and reliable outcome measures. Only then will the real value of a behaviourally-based approach become apparent.

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