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Why rising sex infection figures may be good news

Mark Easton | 17:34 UK time, Wednesday, 25 August 2010

Reading much of the press coverage of today's figures on sexually transmitted infections and the message is clear: the irresponsibility of our hedonistic teenagers is to blame for record levels of STIs. Some of the papers even have a photo of obviously promiscuous youngsters leering at the camera in case we don't get it.

But what the articles fail to stress is that the rise in diagnoses can be almost entirely explained by a massive increase in young people coming forward to be tested for chlamydia. And the proportion testing positive is actually going down.

Graph showing testing volumes and proportion of positive index cases by sex in England: April 2003 - March 2010

It is hardly a surprise that the NHS is finding more cases when its National Chlamydia Screening Programme (NCSP) [540.15KB PDF] has seen the number of tests rise from around a million in 2008 to 1.5m in 2009. An extra 500,000 young people are asked to pee in a pot and doctors discover an additional 14,000 cases of chlamydia and a handful of other infections.

The findings don't mean there is more sexual infection but that we have identified more of what there is. It could be that STIs are falling. We don't know.

When I was a teenager virtually no-one got tested for chlamydia. The number of people diagnosed was close to zero. That didn't mean chlamydia wasn't a problem. We simply hadn't looked to see how big it was. Chlamydia, after all, is an infection that can display few obvious symptoms.

When I asked the Health Protection Agency why their press release today does not mention the fact that the proportion of people testing positive for STIs is going down they gave me some complicated explanation about how the data comes from different parts of the organisation.

"It just happens not to be the way we calculate the data because we were combining GUM (STI) clinic and NCSP data," an official told me.


The release does quote Dr Gwenda Hughes who runs the Agency's STI section conceding that her people are "doing more testing, such as through the National Chlamydia Screening Programme, and some of the tests we are using for gonorrhoea and herpes are more sensitive, so as a result we are now picking up more infections."

But she then goes on to say that "the rise in STIs is also due in part to unsafe sexual behaviour". Well, of course it is. What we don't know, though, is whether there is more 'unsafe sexual behaviour' or less. Too high? Certainly. Getting worse? The evidence is far from compelling.

On the other hand, it is quite possible that the fall in the proportion of people testing positive for STIs is simply a factor of an expanding programme.

Indeed it does seem that the proportion of tests conducted through education establishments (where infection rates are around 4%) has risen a little while the proportion done in sexual health advice clinics (where rates are about 11%) has fallen. The programme has a target of screening 35% of all 16-24-year-olds in England so I suppose it is inevitable they will have to work harder to find willing recruits.

It is not, though, necessarily a justification for national hand-wringing.

That the chlamydia screening programme puts the level of sexual infection among 16-24-year-olds at around 7-8% is useful information. One might regard it as shocking, but without comparable data from other years or other similar countries it simply shows us the size of the challenge not the direction of travel.

The fact, though, that more than a million and a half young people agreed to have their sexual health checked out last year must be a positive sign. It is, arguably, evidence of a generation which has been persuaded to take its responsibilities in this regard much more seriously than its forebears who only went to the clap clinic when it was much too late.


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  • 1. At 5:50pm on 25 Aug 2010, dennisjunior1 wrote:


    To the opening statement how is STI figures (may be good news) for what side? For the public health authorities or for medical specialists.....


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  • 2. At 6:07pm on 25 Aug 2010, Peter Bolt wrote:

    I accept the idea behind the headline.
    Nonetheless promiscuous or not is not really the point. Where on earth do
    these highly infectious diseases come from ?

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  • 3. At 6:13pm on 25 Aug 2010, Don Dealgan wrote:

    Great blog Mark...illustrating that the effective analysis of statistics demands careful consideration of context.

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  • 4. At 6:28pm on 25 Aug 2010, Spindoctor wrote:

    Obviously if you increase the number of people tested by a factor of 3 then you will get more positives.

    The GOOD is that MORE people are being tested, therefore more people are being treated and we have a clearer picture of how big the issue is, rather than guess work based on a very low base line.

    Hopefully the publicity of this will encourage more people to take care and practice safe sex, or at least be tested when they do not.

    Chlamydia whilst not life threatening, does cause major fertility problems for young women, it is expensive and time consuming for the NHS to treat people for fertility issues.

    Much quicker and safer to treat the Chlamydia early than wait for it to do it's damage.

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  • 5. At 6:38pm on 25 Aug 2010, Michael Finney wrote:

    I don't see how Mark Easton is coming to any conclusion but that there is a plague of STI's occuring. If he looks at the charts properly for males in 2003/4 then 20% of nothing is nothing. In 2009/10 6% of 250,000 is 15,000 cases. How is that "nothing" to be worried about? For femails it's even worse. I think that somewhere the public is being hoodwinked again.

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  • 6. At 6:38pm on 25 Aug 2010, Maria13 wrote:

    Apart from the cost to the NHS, the cost to their health has to be far greater. Women who have unprotected sex with different partners or with men who have slept around are more likely to contract cervical cancer.

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  • 7. At 6:47pm on 25 Aug 2010, ExpatKS wrote:

    If everyone read a report about HIV and STI's etc before engaging in you know what, the whole world would be a cleaner place!

    The practicalities however, will need further research!

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  • 8. At 7:15pm on 25 Aug 2010, Andy wrote:

    This comment was removed because the moderators found it broke the House Rules.

  • 9. At 7:26pm on 25 Aug 2010, jr4412 wrote:

    Mark Easton.

    interestingly, on Channel 4 News earlier one teenager implicated alcohol drunk at parties.

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  • 10. At 7:28pm on 25 Aug 2010, Shivari wrote:

    #2 "Where on earth do these highly infectious diseases come from?"

    Ummm... I think you'll find it's 'other people'?


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  • 11. At 8:06pm on 25 Aug 2010, John Ellis wrote:

    Just a shame we cant have the same effect on the stigma of drug use.

    Another good piece though none the less. My kids were lucky they had good sexual health centre 'Brook Advisory' I think its such places that has contributed to the openness with the current generation.

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  • 12. At 8:17pm on 25 Aug 2010, tarquin wrote:

    See, honest, objective data analysis from someone without an axe to grind

    cheers, Mark

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  • 13. At 8:22pm on 25 Aug 2010, DXC wrote:

    It's great to see the BBC checking the facts and statistics before broadcasting the message the spindoctors want us to hear. I wish it happened more often.

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  • 14. At 10:12pm on 25 Aug 2010, Matthew Slyman wrote:

    These results are clearly open to interpretation (on that point I can agree.) However, unless I am mistaken, you failed to review the possible _reasons_ why more people might be getting tested for sexually transmitted diseases now than ever before. These reasons might include:
    1. Being tested is becoming more socially acceptable. (Sex education is probably helping with this.)
    2. The tests are becoming more efficacious (more accurate and worthwhile), less invasive or embarrassing (increasing willingness to participate), and easier and cheaper to perform (increasing a doctor's readiness to recommend and/or perform testing.)
    3. More people have reason to believe they might have contracted a sexually transmitted disease.

    Obviously the first two reasons are a cause to be celebrated. The last reason (point 3) would only confirm the conclusions that you are apparently criticising... I would not be surprised if Point 3 was a significant factor, given this country's emphasis on encouraging "safe sex" rather than encouraging abstinence and loyalty. And teachers/ health visitors handing out free condoms and teaching children about contraceptives generally minimises the potential risks of sex in the minds of the children being taught. The emphasis is wrong. The human immune system is evidently not equipped to handle the consequences of promiscuity, and neither is our medical science; with or without contraceptives. "Safe sex" is a misnomer, in the context of a promiscuous culture.

    My own reasons for never being tested for a sexually transmitted disease in my life? I was a virgin before I got married, and so was my wife. We are monogamous now. Why get tested? Abstain from sex before marriage, and be loyal after you get married, and you won't have to worry. Perhaps that was one of the several reasons fewer people got tested in the past. Maybe I had tests as part of routine urine analysis, and didn't even know about it - if so, the lack of summons only confirms what I already knew.

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  • 15. At 10:48pm on 25 Aug 2010, Wiseman wrote:

    Mark, Congratulations on a well researched, well prepared and well presented article. I've actually paused something I was working on and created a BBC id just to say that.

    As a statistician, it's refreshing to see someone perform some basic checks to let the data give us the story, rather than fit an analysis to an agenda. You rescued a bit of faith I had lost in my generation.

    Being in my 20s, it's wonderful to see one of the so called 'grown-ups' put aside their prejudices towards young people, not get on the bandwagon, and take the time to look a bit deeper for the truth. I'm not trying to justify things that our generation does, just saying that I get the impression that older generations will happily take any reason to launch an attack at us, irrespective of the strength of foundation of that reason. I'm not going to blame the media, it only gives people what they want.

    Regarding Michael Finney's point: I don't have the dataset, but that looks like a classic case of an axis scaling issue where the size of the axis dwarfs a column into looking like zero. I strongly doubt there were no Chlamydia tests in 03/04.

    Once again, kudos Mark. I'd certainly rather see my license fees go to you than Chris Moyles.

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  • 16. At 11:06pm on 25 Aug 2010, GeoffWard wrote:

    A good article, Mark.
    Let's hope that the authorities reporting their findings in future have this simple graph in front of them as a reminder before they go public again on these and other matters.
    We don't ask just for statistics - we demand authoritative interpretation. Any erroneous interpretations, especially those intentionally so, should be cause for sackings of the statisticians and their managers.

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  • 17. At 11:51pm on 25 Aug 2010, Matthew Slyman wrote:

    To the person who wrote this:
    "...we demand authoritative interpretation. Any erroneous interpretations, especially those intentionally so, should be cause for sackings..."

    You obviously never studied statistics, and particularly not, biological or medical science (the fields most relevant to these data.) Interpretation is inherent to the study itself - interpretation of epidemiological data cannot be turned into an exact science.

    The truth obviously lies somewhere in-between the extreme viewpoints presented:
    1. The original suggestion that STD infections are newly reaching epidemic proportions, which might threaten the fertility and future demographic trends of our society on a macro scale;
    2. The proportion of test results returned positive is decreasing, and the proportion of people willing to be tested and treated is increasing. This is good news for our society. (Nobody has even examined whether or not we're looking at the same kind of test - i.e., whether or not the rate of false positives/ false negatives has changed.)

    As justified in my first post, I suspect the truth lies somewhere in-between these two positions. I think, in large degree, the very reason more tests are being done now than previously is because more people have reason to suspect they have contracted a sexually transmitted disease. Seriously, as far as I understand, with most STD's, you can't very well ignore them for longer than a decade or two, without getting some kind of discomfort and/or attention from the medical profession. It's unreasonable to assume that the comparatively low rate of testing in previous generations was mainly due to more people ignoring their symptoms and living in denial, in fear of stigmatisation.

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  • 18. At 00:26am on 26 Aug 2010, Reaper_of_Souls wrote:

    Its always good to question statistics and often agenda drive "analysis".

    However, the conclusion that the proportion of those tested showing infection has fallen being a good thing isn't necessarily so, it all depends on who was tested; was it previously more likely to be those who considered themselves at higher risk?
    More people being tested certainly seems like a positive, although of course it could be in part due to more people engaging in riskier behaviour.
    ..but much of this is just speculation, statistics don't tend to show causality (just correlations), but despite this they're used to back up claims of cause and effect time and time again.

    As the saying goes, lies, damn lies and statistics; you can often interpret the same data in numerous ways and pick whatever angle happens to suit the agenda you're pushing.

    Cynical, yep; but also realistic.

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  • 19. At 00:59am on 26 Aug 2010, AndieRae wrote:

    Someone scoffed at the question of where the infections originate, but do they not originate from relations between different 'generations'? I mean to say, between a 'generation' which embraces testing and one that did not? What Mark writes is indeed noteworthy, because as more young people are tested and treated, as they become the next (in every sense) 'slightly more mature generation', should we not expect the percentage to continue to fall, in fact should we not expect that decline to accelerate as the programme progresses? Given the diversity of society, surely there must be a tipping point of significance in the numbers tested and conversely, ultimate limits of effectiveness?

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  • 20. At 01:07am on 26 Aug 2010, Simon wrote:

    Here's the real question, why do we need analyses like this (well thought out and balanced) when the reporter(including the BBCs own) on the leading articles should have done the sums properly themselves and cut out the scaremongering?

    Maybe we need a better "reporter education programme" more than we need to fiddle with our Sex Ed system?

    Any volunteers for giving a statistics class to reporters...... reminds me of this

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  • 21. At 01:53am on 26 Aug 2010, U14594484 wrote:

    There is a famous quote: "There are lies, damned lies, and there are statistics." Any statistics can be reported in such a way as to support the reseatch, or disprove the research, as needed. An example is that when a woman reaches 40 yrs her chances of giving birth to a child affected by Downs rises to 1 in 90. However, the age group having the highest number of babies affected by Downs is the 20 year olds, as they are the age group having the most children and they aren't screened in same way as women over 35years. This is how STI figures can be used to show whatever outcome is desirable for that particular research- in this case, those promiscious teens are riddled with sexually transmitted diseases. Allowing the Government to come up with 'appropriate' policy. As we all know, the Government are masters of massaging figures to suit, so why so surprised?

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  • 22. At 08:13am on 26 Aug 2010, Framer wrote:

    Mark probably never got tested for chlamydia because in his day it largely went under another name - NSU.

    I also take the point above as to why we pay for one part of the BBC to go with the scare aspect of these statistics while another, seemingly unconnected, takes a deeper look at the HPA's statistics. If he is Home Editor, Mark Easton should surely have some power of direction over mere news reporters.

    What Mark however does not do in his analysis is to check out the cost effectiveness of running a chlamydia programme when the results of the disease are rarely significant. Some public health research suggests such screening is a waste of money and effort.

    It may only exist because the HPA and the health authorities have a budget and must spend it on something, anything, or risk losing it.

    At least we are not being patronised by being told lack of sex education is the problem.

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  • 23. At 08:26am on 26 Aug 2010, Daisy Chained wrote:

    Well done Mr Eaton. A great explanation as to why statistics often tell us plenty if only we are open to what they do not say. And, of course, the explanation for every STI is a story of its own.

    The most important plus point would appear to be the numbers prepared to be screened for STIs; does this mean, at the very least, that sexual taboos are being eroded? Makes a positive, if not altogether pleasant, change from the 'dirty' days of VD etc.

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  • 24. At 11:16am on 26 Aug 2010, Shivari wrote:


    Yes, the figures should decline, but only up to a point, as inter-generational sexual relationships are not the only source of infection. You need to allow for infections caused by sex between someone living in the UK and someone who comes from another country that may not have such a programme. This may be as a result of holiday liaisons, sex tourism or foreign prostitutes working in the UK. If a country's sexual demographic was completely self-contained, HIV would never have left Africa.

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  • 25. At 2:05pm on 26 Aug 2010, GeoffWard wrote:

    For Matthew Slyman @ 14:
    Thank you for your comments.
    It seems that the bias in the report came from the Health Protection Agency management, not the various media reporters.
    The statisticians would have been very well aware of the interpretations possible - especially the position Mark took in his article.
    The Health manager chose to bias his Release in the opposite direction in order to make the point he wanted to fix in the nation's consciousness.
    So, sack the Machaevellian Health manager and leave the statisticians to reflect on whether they have a higher order responsibility to ensure that the message accords with their best professional interpretations. When the message belies the facts the statistician should consider his position. The manager is not named Goebbels and you can walk away without being shot.

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  • 26. At 1:25pm on 27 Aug 2010, Dr Colm O Mahony wrote:

    Whilst Marks interpretation is largely correct it has to be pointed out that no sophisticated tests are required to diagnose genital warts! You just look down one morning and there thay are (see if you dare). New cases of genital warts are still at the horrendous levels of previous years so the ongoing STI epidemic is still as bad as ever. The last government don't seem to think this is an issue however as they ignored the vaccine that could have eradicated genital warts from the UK and instead chose a cheaper vaccine that ensures the UK remains the warts capital of the developled world.

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  • 27. At 2:54pm on 03 Sep 2010, Peter Greenhouse wrote:

    This excellent piece prompted me to send the following note to my colleagues on the media committee of BASHH (British Association for Sexual Health & HIV):
    "Well worth checking out the BBC's (incisive & probably correct) analysis of the HPA data, and the subsequent critical commentary. A salutary lesson for those of us preparing our next public 'splash'."
    Picking up on comment 15, there have been wide variations in rates of STI between different generations over the last century, which are best demonstrated by the rise & fall in gonorrhoea, which acts as a barometer of sexual mores. People of Wiseman's generation (20s) have an intermediate risk of STIs between those born in the '50s & '60s (the post-pill, pre-AIDS generation) who have very high lifetime risk, and those born in the '70s (now aged 30-40)who got the full blast of the AIDS education campaigns and consequently had far fewer STIs due to lower rates of partner change & higher levels of paranoia triggering meticulous condom use.
    Chlamydia appears to have highest prevalence in teenagers because of frequency of partner change AND the fact that older people clear the infection faster. Youngsters are nowadays guaranteed a sympathetic, non-judgemental approach from their sexual health doctors because most of us have "been there" - a very different experience from that of older generations.

    Thanks, Mark. Any more news about sexual health & we'll come to you first.

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  • 28. At 9:29pm on 04 Sep 2010, PJohnston wrote:

    A major source of heterosexual HIV infection in the UK is immigration from sub Saharan Africa. Seventy percent of all heterosexual cases diagnosed in the UK are among those born in Africa.

    Not that you will read or hear discussion of this problem on this particular blog.

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  • 29. At 11:49pm on 09 Sep 2010, Rob_Hampshire wrote:

    I fully agree with Matthew Slyman @14

    There is a simple technique that is effective against all sexually-transmitted infections. It also prevents unwanted pregnancies, and a lot of emotional harm. It does not rely on medicines or physical barriers, is completely free and can be practiced by anyone.

    It's called not having sex. Do you think it might catch on?

    Sex isn't the be-all and end-all of life, whatever the magazines say. You can still be happy without it. But for some reason this option seeme to largely get ignored. Why?

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  • 30. At 12:13pm on 02 Jun 2011, U14890913 wrote:

    This comment was removed because the moderators found it broke the House Rules.

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