WHAT ARE THE HEALTH BENEFITS OF SEX?

We don't need rigorous scientific testing to accept that when done well, sex is generally pleasurable. There is also plenty of evidence that it helps you get to sleep, and can exercise a woman’s pelvic floor muscles, providing a range of benefits from enhanced sensation to the prevention of ‘leakage and incontinence’ and ‘post-menopausal vaginal atrophy’ in older women. Women have also found that sex can provide pain relief, although it might be difficult to separate psychological from hormonal effects. Writing in Sex by Numbers: What Statistics Can Tell Us About Sexual Behaviour, author David Spiegelhalter points out that these same claims – including that sex may help us live longer – get trotted out time and time again. So what's the science to sex? Can sex help you live longer? A much-cited study of men in Caerphilly (Sex in America: A Definitive Survey) carried out by a respectable team, estimated that an extra 100 orgasms a year was associated with a one-third reduction in the risk of dying each year – this would translate to about three years’ extra life. A later re-analysis of the same data suggested that more sex was associated with fewer heart attacks but possibly more strokes over 20 years. Of course, correlation is not causation, and we’ve already seen that healthy people have more sex, so maybe the causation is in the other direction. The authors tried to allow for this, but clearly we need to look at some more specific potential benefits of sex. How many calories do you burn during sex? A recurrent media obsession is the benefits of sex as an exercise regime, although some estimates have put the energy expenditure at a paltry 21 Kcal, or about the same as in a satsuma. So what is the truth? Laboratory studies of sexual activity can be rather clinical, but researchers in Montreal solved this by instructing 21 volunteer couples to have sex once a week for a month in their own homes. The only condition was that they both needed to wear a portable SenseWear armband during sex, which measured their energy expenditure, and to compare their sexual activity with a 30-minute treadmill test. The sex sessions lasted an average of 25 minutes, and the average energy use was 101 Kcal for men and 69 Kcal for women, but the values varied between 13 to 306 for men, and 12 to 164 for women, showing a range from extreme mellowness to athletic exuberance among the participants. For calibration, 85 Kcal is about what you get in a very small glass of wine, a chocolate biscuit, or a bag of cheesy Wotsits. How effective is sex as a form of exercise? The average intensity of sexual activity was around 6 METS (1 MET is about the intensity of watching television), which is the borderline of moderate/vigorous, roughly between cycling and jogging. But some went up to 9 METS – higher than doing push-ups. Overall, as a source of exercise, sex came in at about half as effective as 30 minutes on a treadmill, although the participants (with one notable exception) rated it as considerably more enjoyable. These were healthy young couples with an average age of 23, but for older people, could those METS be all you need to bring on a heart attack? Can sex cause heart attacks? A review of 14 studies concluded that the risk of a heart attack did go up by nearly three times in the hours after sex for older people, but it was still only the same as any other form of similar exercise, such as shovelling snow, and the risk depended on fitness. A plausible estimate is that if 1,000 middle-aged people had sex for an hour a week for ten years, then there would be around one sudden death and two to three extra heart attacks. This may seem a risk worth taking, and it is interesting to note that the majority of the case reports of sudden death in the past have been men engaged in ‘extramarital sexual activity, in most cases with a younger partner in an unfamiliar setting and/or after excessive food and alcohol consumption’. I think we get the picture. How beneficial are the hormones in semen? Considerably less dramatic than the possible risk of death is the suggestion that exposure to semen can lighten a woman’s mood, based on the theory that it’s got lots of great hormones, which could create a positive mental state. But how can you test this? How can you expose some women to semen and others not, while controlling for the amount of sex going on? The researchers who tested this had a brainwave, realising that condom use provides a sort of natural experiment: women who use condoms during sex are deprived of this (possibly) physically beneficial substance. A study analysed the condom use of 293 college females; non-users scored an average 8 on a standard scale of depression, while those who usually or always used a condom scored around 12, where a score of 10 or more indicates ‘mild depression’. So there is a correlation, but not a very conclusive one: think of all the ways this apparent anti-depressant property of semen could be explained by some other factor. Was the benefit really coming from oral contraceptives? Or because non-condom users were having more sex, or in more committed relationships? The authors tried to allow for all of these, but were forced to admit that the data were ‘only suggestive’. Orgasms: a cure for hiccups? There is one possible benefit that never seems to get mentioned in all these lists. Two doctors reported on one of their patients who had hiccups continuously for four days after a steroid injection, preventing him from working or sleeping. Perhaps surprisingly, he did finally manage to have sex, during which the hiccups ‘continued throughout the sexual interlude’ (there is no mention of how his partner felt about this). This went on ‘up until the moment of ejaculation when they suddenly and completely ceased’, presumably to both parties’ considerable relief. The medical conclusion is that masturbation might be tried when trying to stop intractable hiccups: an inexpensive treatment with few side effects.