9.2 Sexual behaviour 1597

9.2 Sexual behaviour 1597

ESSENTIALS Discussion of sexual lifestyle and the ability to take a sexual history are relevant to many types of clinical practice. Most of the popula- tion is attracted to, and has sex, exclusively with people of the op- posite sex. The age at which people first have sex has decreased and the age at which people start cohabiting has become later in recent decades, increasing the time available to accumulate sexual part- ners and thus be at risk of sexually transmitted infections, including human immunodeficiency virus. While many people have few part- ners, a small proportion of the population has many. People with many partners are most at risk of sexually transmitted infections, but there are many other influences including the gender, age, and ethnicity of their partners and the type of sexual practice. Strategies to reduce the adverse consequences of sexual behaviour (including sexually transmitted infections and unintended preg- nancy) encourage reducing partner numbers, using condoms and effective contraception, and engaging in less risky practices. Issues with sexual function are relatively common and need to be considered in a range of clinical consultations. Introduction Most men and women are sexually active for a large part of their adult life and sexual fulfilment is important in enhancing the quality of many people’s lives. Patterns of sexual behaviour in populations are a key determinant of fertility and transmission of sexually transmitted infections (STIs). Discussion of sexual lifestyle and ability to take a sexual his- tory are relevant to many types of clinical consultations. Common topics include management of genitourinary symptoms, contra- ceptive advice, sexual dysfunction, and resumption of sexual ac- tivity following childbirth, major illnesses, or surgery. Sexual orientation Surveys of sexual behaviour in representative population samples show that most men and women are predominantly attracted to, and have experience with, members of the opposite sex throughout their lives. However, sexual orientation is not a simple dichotomy between ‘homosexual’ and ‘heterosexual’, but varies from ex- perience exclusively with people of the opposite-sex experience through various shades of attraction to, and experience with, both genders, to having exclusively same-​sex experience. Indeed, gender is increasingly recognized as being a more fluid concept, as more and more people identify as neither nor male nor female. In a large British study of adults aged 16–​74 years undertaken 2010–2012, 8.0% of men and 11.5% of women reported having sexual experience with someone of the same sex at some time. For some, this was a fleeting adolescent experience, followed in many cases by partnerships exclusively with people of the opposite-sex. A smaller proportion of the British population report same-sex partnerships involving some form of genital contact (5.5% of men and 6.1% of women). Similar findings are reported from France and the United States of America. Most of those with same-​sex partners have had experience of intercourse with someone of the opposite- sex at some time. Exclusively same-sex experience throughout life is thus relatively unusual. Age of first intercourse with someone of the opposite-sex The age of first intercourse with someone of the opposite-sex has been gradually decreasing over recent decades. The proportion of people having sexual intercourse before marriage has rapidly in- creased, so that sex before marriage has become almost universal in Britain. For men born in the years between 1935 and 1945, the median age of first intercourse was 18, and for women 19. For men and women born between 1985 and 1995, the median age at first intercourse is 16. Similar trends have been observed in other European countries and in the United States of America. English law gives the age of consent for intercourse with someone of the opposite-sex as 16, and it is illegal for a man to have sex with a woman under 16 in England (and other parts of the United Kingdom). The proportion of men and women in Britain reporting first intercourse before the age of 16 has risen rapidly over recent decades to 34.1% of men and 30.9% of women aged 16–​19 in 2010–​ 12. This has important implications for the provision of sex educa- tion and the timing of human papilloma virus (HPV) vaccination programmes. Those just embarking on their sexual careers may 9.2 Sexual behaviour Catherine H. Mercer and Anne M. Johnson

Section 9   Sexually transmitted diseases 1598 be most vulnerable to the unwanted consequences of unprotected sexual intercourse: STIs and termination of pregnancy are more common in 16-​ to 24-​year-​olds than in older men and women. Numbers of sexual partners The number of opposite-sex partners is highly variable. While many people have few partners, a small proportion has many. Among men aged 16–​74 in Britain, 67.0% reported zero or one opposite-sex partners in the last five years; 5.6% reported at least 10; and a small proportion reported hundreds or even thousands of partners during their lives. The risk of acquiring or transmitting an STI increases with the number of sexual partners. For example, in the British survey, 1.1% of men and women reporting one partner in the five years prior to the survey reported STI diagnoses, compared to 23.8% of those with at least 10 partners. Those with high numbers of part- ners may account for a relatively high proportion of STI transmis- sion in a community and for sustaining endemic STI transmission. The choice of partner also influences STI transmission in popu- lations. Age, gender, and ethnic mixing are important, as well as the extent to which people choose partners with lifestyles similar to their own (assortative mixing) or different (disassortative mixing), and whether they have serially monogamous or concur- rent partnerships. Commercial sex workers and their clients remain at high risk of HIV and STIs in some parts of the developing world where condom use is infrequent. In some countries, such as Thailand, public health campaigns have succeeded in increasing the use of condoms in commercial sex contacts. In many developed countries, although sex workers are at increased risk of STIs, there is evidence that high levels of condom use may protect both them and their clients. The proportion of men who have commercial sex contacts varies widely between countries. In the British survey, 11.0% of men aged 16–​74 years reported paying money for sex at some time in their lives, but considerably more frequent exposure is reported in other countries. Multiple partnerships with people of the opposite-sex are most common among young people, and among those who are not mar- ried or cohabiting. More than 1 in 10 men aged 16–​24 in Britain re- ported more than 10 partners during the previous five years, even though this group included many individuals who had not yet be- come sexually active. Age is not the only influence on sexual be- haviour. Whatever their age, those who are separated, divorced, or widowed are more likely than married people of a similar age to have multiple partners, illustrating the effects of the life course on pat- terns of partnership. Since the HIV epidemic emerged, public health campaigns have emphasized behaviour change for sexual health promotion. Some evidence suggests that, in the developed world in the late 1980s, there was a reduction in numbers of partners and in- creased use of condoms resulting in declining rates of STIs. However, since the late 1990s, these trends have been reversed with a return to risky sexual behaviour. In some parts of the developing world, such as Uganda and Thailand, the incidence of HIV has decreased, mainly due to changes in behaviour but also the epidemic stage. Sexual practices with people of the opposite-sex The repertoire and frequency of sexual practices varies between individuals. Vaginal intercourse is the most common practice in opposite-sex partnerships, but most couples include other prac- tices, particularly mutual masturbation and orogenital contact, in their repertoire. The frequency of sexual contact varies with age, life stage, and availability of a sexual partner. Among sexually active people, the median frequency of sexual intercourse is about three times per month, but this is highly variable. Frequency declines with age, depending partly on the duration of the relationship, but also the tendency for people to experience greater poor health as they age. Among men and women aged 16–​74 in Britain, around two-​ thirds reported orogenital contact during the previous year, both cunnilingus and fellatio. In contrast, anal intercourse is a relatively infrequent activity in opposite-sex partnerships. In the British survey, 34.9% of men and 28.3% of women reported having experienced anal intercourse with a partner of the op- posite sex at some time, but only around 11.9% had experienced it in the previous year. Anal intercourse was more commonly re- ported by younger people with 17.8% of 16-​ to 24-​year-​olds doing so, although these data provide no indication of the frequency with which people engage in this sexual practice; some people may experiment with anal sex, while others may make it part of their regular sexual repertoire. Engaging in sexual practices with a partner increases the risk of the transmission of STIs. Anal intercourse, in addition to vaginal intercourse, may increase the risk of transmission of HIV between people of opposite-sex, but since anal intercourse is practised relatively infrequently world- wide, most HIV transmission people of the opposite-sex is attrib- utable to vaginal intercourse. Same-sex behaviour The lifestyles of gay, bisexual and other men who have sex with men have been more intensively studied than those of lesbian and bisexual women. Studies of volunteer samples of men who have sex with men (MSM) in the United States of America in the 1970s identified a distinctive lifestyle characterized by multiple casual sexual partners, often encountered at gay meeting places such as bars, clubs, and ‘bathhouses’. These men were at high risk of STIs and were among the first to experience high rates of HIV infection. Research in Britain identified a group of MSM with similar life- styles. However, studies of MSM recruited from places other than sexual health clinics and gay-​orientated venues show smaller num- bers of sexual partners, less frequent changes of partner, and lower prevalence of sexually acquired pathogens. MSM are at increased risk of HIV infection and other STIs, including hepatitis B and syphilis. The sexual practices engaged in by women who have sex with women (WSW) carry a low risk of STI transmission. However, WSW may be at risk of STIs and HIV as a result of their partnerships with men, since a high proportion of these women also have male partners.

9.2  Sexual behaviour 1599 Many same-sex partnerships are restricted to mutual mastur- bation or orogenital contact and do not involve penetrative anal intercourse. It is anal intercourse that carries the highest risk of transmission of sexually acquired organisms between MSM. Many MSM practise both receptive and insertive anal intercourse. Receptive anal intercourse carries the highest risk of HIV trans- mission. After the HIV epidemic emerged, there was evidence of a reduction in high-​risk behaviour among gay men. Increased use of condoms and reduced partner numbers reduced exposure to unprotected anal intercourse. However, since the late 1990s, risky behaviour has increased and new HIV infections continue to be a significant public health challenge. Data from surveys of MSM in London have shown that over the last decade the proportion re- porting unprotected anal intercourse has increased, although a higher proportion also report ‘serosorting’ (i.e. choosing partners with the same reported HIV status). While uptake of HIV testing has increased greatly, as has the number of men in treatment, overall this has not reduced the incidence of HIV infection due to continuing high-​risk behaviours. Risk reduction strategies and sexual health Increasing attention is being paid to promoting sexual health and reducing the adverse consequences of sexual behaviour. Extensive discussion of population strategies is outside the scope of this chapter. However, individuals can reduce their risk of STIs and unintended pregnancy by reducing the numbers of partners with whom they have unprotected intercourse, using condoms, using ef- fective contraception, and enjoying sexual practices with less risk of transmission. Negotiating sexual fulfilment is a more difficult matter, but a greater focus on communication between partners, and on sexual technique, is important. Difficulties with sexual function are relatively common. Around 40% of the men and 50% of the women in the British survey reported some kind of issue with sexual function lasting at least three months during the previous year. The most common difficulty experienced by both sexes is a lack of interest in having sex. Although issues with sexual function are common, few people report being dissatisfied or distressed with their sex lives, and few avoid sex because of their own or their partner’s sexual dif- ficulties. However, among those who believe that their health af- fects their sex life, only a minority—​23.5% of men and 18.4% of women—​had sought clinical help. Most who do consult their gen- eral practitioner. Health professionals can help by being capable of taking a tactful sexual history, having the necessary clinical skills, and being informed about sexual health and the need for health promotion. FURTHER READING Field N, et al. (2013). Associations between health and sexual life- styles in Britain: findings from the third National Survey of Sexual Attitudes and Lifestyles (Natsal-​3). Lancet, 382, 1830–​44. Johnson AM, et al. (1992). Sexual behaviour and HIV risk. Nature, 360, 410–​12. Johnson AM, et al. (1993). Sexual attitudes and lifestyles. Blackwell Scientific, Oxford. Mercer CH, et al. (2013). Changes in sexual attitudes and lifestyles in Britain through the life course and over time: findings from the National Surveys of Sexual Attitudes and Lifestyles (Natsal). Lancet, 382, 1780–​94. Mitchell K, et al. (2013). Sexual function in Britain: findings from the third National Survey of Sexual Attitudes and Lifestyles (Natsal). Lancet, 382, 1817–​29. Sonnenberg P, et al. (2013). Prevalence, risk factors, and uptake of interventions for sexually transmitted infections in Britain: find- ings from the National Surveys of Sexual Attitudes and Lifestyles (Natsal). Lancet, 382, 1795–​806. Wellings K, et al. (2006). Sexual behaviour in context: a global per- spective. Lancet, 368, 1706–​28.