The science of desire

It's a biological riddle. We think of our libidos as a force of nature beyond our control; yet we also complain, increasingly, that they are too weak. Cathy Holding investigates the enigma of sexual response

Human sexual response is a complex combination of social, hormonal, physiological and psychological factors, most of which are poorly understood. Society plays a role in what is considered to be acceptable in sexual desire: religious beliefs, family values and upbringing all affect one's attitude to one's own feelings of sexual desire. Hormones play a role the massive surges in testosterone and oestrogen in adolescents that precedes sexual activity are overwhelming in the changes they bring about in the transition from youth to adult. Sexual desire is the first of three behvioural repertoires associated with reproduction: sex drive (to find a mate), attraction (to find the best mate) and attachment or love (to allow time successfully to reproduce).

It is possibly one of the strongest drives in man (and animals) and it can bring out the best and the worst in people. In excess it can lead to hypersexuality and hyperstimulation of the genital region, sex crime, sexual addiction and persistent use of pornography. When repressed it can result in depression and neurosis or conversely it can be channelled into great creativity. When ignored, within stable relationships, it can lead good men and women to stray outside these relationships and threaten the happiness and stability of their families. It can be entirely suppressed, as in elective celibacy, and the energies re-routed to the greater spiritual good of the person and those around them. It can be denied and used to form the basis of lifelong friendships between people based on emotions much stronger than mere affection. It can be unfulfilled producing some of the most beautiful prose, poetry, music and art. It can change lives following chance meetings. It can lead to shotgun weddings... or it can just end up in total frustration after a boozy night and lead to the writing of songs such as "All Revved Up and Nowhere to Go".

The term "sexual desire" can mean one of two things: it can refer to the need for sexual intercourse itself, or it can mean something closer to sexual attraction for a specific person. This can lead to confusion in how sexual dysfunction is interpreted: it is possible that failure of the partner of the first part in their desire for the partner of the second part has nothing to do with the partner of the first part's true capability for sexual desire. This dimension to sexual desire/dysfunction is not addressed at all in the scientific literature.

The sexual response comprises three phases: desire, arousal and orgasm. Desire is the anticipation through imaginary processes of a pleasure hoped for in reality. It both precedes and accompanies the rise of excitation or arousal. The phases are, however, not independent of each other: for example, problems with orgasm can be related to problems with arousal that in turn can stem from a lack of desire. Conversely, erectile dysfunction is associated with lowered sexual desire. Sexual dysfunction of female sexual desire, arousal, or orgasm affects approximately one in three (30 per cent) of women. Sexual desire decreases with increasing age, and social, psychological or physical distress lowers levels of sexual desire in both genders. Few studies are aimed at examining sexual desire in the normal population but most focus on sexual dysfunction, particularly in the older generation.

(Most) people like sex

Having an orgasm is a powerful demonstration of a person's health. It is also very good for you. In a Welsh study on 918 men between the ages of 45 and 59, death from heart attacks or heart disease were 50 per cent lower in men with high orgasmic frequency than in those with low orgasmic frequency sex actually has a protective effect on men. Most men enjoy sex with their partners; more than two thirds of men (75 per cent) always achieve orgasm with their partner. A third of women always climax with their partners, but according to one feminist this may be because the rest simply choose to limit the number of climaxes they award to their mates. Higher orgasm rates are recorded in older people.

Losing one's mojo

Reduction in sexual desire can, in fact, be perfectly normal, particularly with increasing age. It only becomes a problem when it causes pain or distress to oneself or a partner and hence conflict. Differences in desire can be linked to hormone differences and men seem to be provided with more of the hormone of desire, so to speak, (ie, testosterone) than women. In addition, on a psychosexual level, men have a greater need actively to express their sexuality to prove their masculinity to themselves. Some women may only need to experience their man's desire to be reassured of their femininity.

Sexual desire and age

From an evolutionary point of view, female sexual desire must contribute to the success of reproduction, and hence a link exists between levels of desire and levels of fertility. Positive emotional responsiveness to erotic stimuli is found to be increased during the follicular phase of the menstrual cycle, when women are at their most fertile, and this could mean an increase in the probability of sexual activity at that time; in general it is known that female sexual desire fluctuates with the menstrual cycle. However, sexuality is completely dissociated from reproduction in older women, and usually so in older men. Nevertheless sex is a need that improves quality of life, promotes feelings of well-being and undoubtedly a person's health whatever the age. Most (younger) people are repulsed by the idea that older folks should be sexually active and this can reflect back on the older person who may feel that they should not be behaving in this manner at their age. It is the responsibility of health workers and those professionally in charge of older people to help them better understand that their desires are perfectly normal. Older people seem to enjoy sex more. A study in 904 men with an average age of 60 years (and mild to severe erectile dysfunction) found that older men are not quite so anxious about sexual performance as are younger men, which may reflect different levels of expectation between age groups. Older men reported more sexual satisfaction than younger men no matter how severe their erectile dysfunction. Older men reported slightly less sexual desire than younger men but lower sexual desire was related to higher levels of erectile dysfunction. In this day and age, medications such as sildenafil (Viagra(R)) are available to assist in overcoming the physical limitations of the elderly population (ie, erectile dysfunction), but others such as testosterone have been found to increase sexual desire in older men without improving any of the other parameters of sexual function.

It's a man thing...

A recent Danish study, in which 8,868 adults responded to a questionnaire, examined the prevalence of self-reported sexual desire and the decrease in sexual desire over a five-year period in both men and women across different age ranges. Results showed that men have a significantly higher level of sexual desire than women. Investigations into the sexual activity of an elderly population with an average age of 81 years, who were mostly (56 per cent of them) women, found that only 18 per cent of women, compared with 41 per cent of the men, were sexually active. The most common sexual activity was intercourse for men and masturbation for women. Among the women, "no desire" was the most common reason for sexual inactivity. Sexual function scores for women were low across all categories which included lubrication, desire, orgasm, arousal, pain, and satisfaction. For men, the main reason for sexual inactivity was erectile dysfunction, and sexual function scores were also low for the categories of orgasm, and overall satisfaction but not for desire. For older men at least, it seems that the spirit is willing, even if the flesh is weak. For the majority of older women, the desire for sex appears mostly to be lost.

Desire and the menopause

The Menopause Epidemiology Study, a cross-sectional, population-based study of 1,480 sexually active postmenopausal women aged 40 to 65 in the United States, attempted to define female sexual dysfunction. It found that sexual dysfunction, in terms of desire, arousal and orgasm difficulties, was due mainly to vulvovaginal atrophy defined as vaginal dryness, itching and irritation, pain on urination, or pain or bleeding on intercourse. Estimates of the prevalence of low sexual desire and hypoactive sexual desire disorder (HSDD) in the US were calculated in 755 premenopausal women and 552 naturally and 637 surgically menopausal women. Low sexual desire is more common among surgically and naturally menopausal women compared to premenopausal women. However, the women who were surgically menopausal were distressed about their low desire. Low levels of sex hormones, particularly oestradiol, physical and mental well-being and, importantly, feelings for partner are all relevant to a woman's sexuality in natural menopause.

Working at it

In a questionnaire study in 219 Brazilian-born women, the sexuality of women in midlife was found to be adversely affected by such factors as living with a sexual partner and being in the menopausal transition or being postmenopausal. Living with a sexual partner might be viewed as an unusual reason for an adverse effect on sexual desire, but maintaining sexual desire in long-term relationships can be a problem. A "goal-oriented" strategy is one psychological approach to such a problem. Studies tested whether adopting strong "approach goals" (ie, goals focused on the pursuit of positive experiences in a relationship such as fun, growth, and development) result in greater sexual desire in relationships. They found that individuals with strong approach goals experience even greater desire on days where partners are getting along, and less of a decrease in desire on days when things aren't going too well between partners. This kind of goal-oriented "working-at-the-relationship" approach works better with women than with men, but men surely must benefit from their partner's increased sexual desire. How a woman sees herself, in terms of positive imagery of the female body, affects a woman's sexual desire and what she does with it. Signs and symptoms of depression are significantly associated with loss of libido in older women and the odds of losing libido increases as the number of depressive symptoms increases. Women who do not have concerns over their level of sexual desire say that they feel loved and safe with their partner, that he tells her she's sexy, and that he is romantic. It makes no difference in this case whether or not the woman is in menopause, but interestingly, postmenopausal women prefer more love and emotional bonding cues from their partner, with these resulting in feelings of sexual desire in the woman, compared with premenopausal women.

In conclusion

Overall, knowledge about human sexual desire is somewhat limited, mainly because it is such a complex issue revolving around hormones, feelings and health. Generally speaking, desire decreases with age, but this may simply be because older people are more likely to suffer illness and loss of loved ones, as well as lower hormone levels. Whether loss of desire causes distress ultimately depends on the individual, although it may have repercussions in partner relationships for example, because more men experience sexual desire than women, which can continue right into old age.

Treatment therapies: for hypoactive sexual desire disorder

Exogenous testosterone treatment has been suggested as a rational therapeutic alternative for women whose low libido negatively affects their quality of life. Despite a recent (anonymous) publication suggesting that the disorder HSDD has been cynically created by drug companies to coincide with the market release of testosterone patches, HSDD is a recognised disorder and testosterone therapy is known to improve HSDD.

Testosterone patches are licensed in the UK for women with surgically induced menopause who are taking concomitant oestrogen therapy.

Testosterone patches are not recommended for naturally menopausal women or for those taking conjugated oestrogens. Safety and efficacy of testosterone patches have not been established beyond one year of treatment. In the meantime, hormone replacement therapy (HRT) has been shown to provide significant improvement in sexual function compared to women receiving no treatment although harmful effects have been found in some clinical trials: certain health authorities now consider that risk-benefit considerations do not favour the use of HRT. However, most experts agree that if HRT is used on a short-term basis (taken for no more than five years) then the benefits of HRT outweigh any associated risk.

As with all aspects of partner relationships, the most important aspects in dealing with problems are communication and a will to make the relationship succeed.

It is also important that people should practise healthy lifestyles – not drink too much or smoke, and take more exercise for overall health and fitness. Women should strengthen pelvic floor muscles (preferably with those little Japanese balls that you get from Ann Summers).

Couples should seek counselling if necessary – and, for men, psychosexual therapy significantly can deal with erectile dysfunction, caused by mental problems, more than sildenafil on its own.