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NHS Choices: Behind the headlines   + / -  
last updated: Fri, 23 Jun 2017 22:50:22 GMT

 Fri, 23 Jun 2017 00:00:00 GMT Does paracetamol taken in pregnancy affect masculinity?

"Taking paracetamol when pregnant 'makes boys less manly, less aggressive and lowers their sex drive'," reports The Sun.

But the alarming headline doesn't explain that the research was in mice, not humans.

Researchers gave daily doses of paracetamol to pregnant mice, and looked into the effect on their male offspring.

They measured an area of the brain linked to male behaviours. They also carried out experiments to test how typically masculine their behaviour was, such as how much they urinated around their cages, bit other male mice, and copulated with female mice.

Importantly, the study only found that paracetamol had any effects at the equivalent of doses three times higher than the recommended maximum for human adults.

When mice were given the equivalent of the maximum daily dose for humans, paracetamol had no discernible effect in their offspring.

Paracetamol is commonly recommended for pain and fever relief for pregnant women, as it's thought to have fewer risks for the baby than other drugs.

Most women would only take paracetamol for a day or two as needed during pregnancy – not every day, as in this study.

This study doesn't provide evidence that standard-dose paracetamol, used from time to time as needed during pregnancy, carries any risk to a developing male baby.

Get more information on taking paracetamol in pregnancy

Where did the story come from?

The study was carried out by researchers from the University of Copenhagen, Universidade Federal do Paraná in Brazil, Icahn School of Medicine in the US, and INSERM in France, and was funded by the Danish Council for Independent Research. 

It was published in the peer-reviewed journal Reproduction and is free to read online.

Several UK media headlines were incorrect and scaremongering, not making it clear that the study was carried out in mice – for example, The Sun claimed that paracetamol "makes boys less manly".

Headlines aside, the media coverage did go on to explain that the study had been carried out in mice, and gave a reasonably accurate overview.

But most of the coverage stated that the mice had been given doses of paracetamol "comparable" to doses recommended for humans, including pregnant women. The Mail Online says: "Taking paracetamol at recommended doses could harm the masculinity" of an unborn boy.

The statement that mice were given "comparable" doses came from the study's press release. 

In fact, the study found no significant effects in mice given the equivalent of the recommended dose in humans, and only those given three times the recommended amount for humans showed brain and behavioural changes.

What kind of research was this?

This animal experimental study carried out in mice aimed to see whether taking paracetamol during pregnancy could affect the development of the male foetus' brain and male behaviour in later life.

Animal studies like this can give an indication of the possible biological effects of a drug, but results in animals don't always translate into the same effect in humans. 

What did the research involve?

Researchers fed pregnant laboratory mice daily with either plain water, water laced with standard-dose paracetamol, or water laced with high-dose paracetamol from the fifth day of pregnancy till they gave birth.

They then tested the behaviour of the male offspring when they were eight weeks old. They carried out experiments to assess typical masculine behaviour in mice, such as:

  • urinating to mark territory
  • aggressive behaviour towards other males
  • sexual activity with females on heat

After death, the brains of the male mice were also examined to calculate the size of an area called the sexually dimorphic nucleus (SND), which is typically larger in male animals than females.

Researchers looked for differences between mice given plain water and water laced with different doses of paracetamol.

The doses were designed to be "comparable" to those taken by humans. The standard dose of 50mg per kg of body weight is in line with the maximum dose recommended for adult humans.

The higher dose of 150mg per kg body weight, although three times higher than the maximum recommended dose, was still "in the range of human exposure", the researchers said.

The behavioural tests were carried out only on mice whose mothers had taken high-dose paracetamol.

The tests included:

  • recording the distribution, size and number of urine spots left around a cage
  • introducing an "intruder" male mouse into the cage of a study male mouse and counting how often the study mouse sniffed, attacked, rattled his tail at, and bit the intruder mouse
  • introducing a female mouse in heat into the cage of a study male mouse and counting how often the study mouse sniffed, mounted and copulated with the female mouse

As well as paracetamol, the researchers tested the effects of aniline, a pollutant used in industrial processes thought to have similar effects to paracetamol.

What were the basic results?

Researchers found no difference in the size of the brain SND between mice whose mothers had been fed standard-dose paracetamol and those who'd had plain water.

But mice whose mothers had the high-dose paracetamol had 50% fewer cells in the SND area. Aniline produced the same effect.

Mice whose mothers had been fed high-dose paracetamol and control mice whose mothers had plain water were tested in behavioural experiments. 

In these tests:

  • paracetamol-exposed mice urinated fewer, but bigger, drops when scent-marking their cages
  • paracetamol-exposed mice sniffed and rattled their tails at intruder mice less, and didn't bite them
  • paracetamol-exposed mice copulated with female mice less often and didn't ejaculate

How did the researchers interpret the results?

The researchers say paracetamol has an "anti-androgenic effect" that "could also include an effect on the masculinisation processes of the brain". They say this may cause "reduction in male sexual behaviour and lack of ejaculation", as well as "differences in aggression".

They say that, depending on the method used to compare human doses with mouse doses, "these exploratory experiments have relevance for human health".


Headlines like those in the media about this study are likely to alarm pregnant women who have taken or may need to take paracetamol in pregnancy.

While the study's results can't be dismissed altogether, there are three important things to bear in mind:

  • Studies in mice don't always translate into results in humans.
  • The doses of paracetamol that produced the effects in mice were the equivalent of three times higher than the maximum daily dose for adult humans.
  • The pregnant mice were fed paracetamol every day throughout the last two-thirds of their pregnancy.

Most pregnant women take paracetamol at the recommended dose, and for only a short time to manage pain or fever, when they need it. Nothing in this study suggests that women should stop doing that.

Pregnant women have few options when it comes to managing pain or fever, and it's important that they can take medicines they need that are unlikely to harm their baby.

Not treating pain or fever could be distressing for the pregnant woman, and carry greater risk to the overall health and wellbeing of the mother and pregnancy than not using short-term pain relief.

Current UK advice is that pregnant women can take paracetamol. But as with any medicine taken during pregnancy, it should be used at the lowest effective dose for the shortest possible time.

How much you can take depends on your age, your weight, the type of paracetamol you're taking, and how strong it is.

Adults can usually take one or two 500mg tablets every 4-6 hours, but shouldn't take more than 4g (eight 500mg tablets) in the space of 24 hours.

For more information, see Can I take paracetamol in pregnancy? and paracetamol.

Links To The Headlines

Paracetamol could be a risk to unborn boys. The Daily Mail, June 23 2017.

Sons less manly if mum on pain pill. The Sun, June 23 2017.

Paracetamol 'makes sons less masculine'. The Times, June 23 2017.

Taking paracetamol during pregnancy could make male child less masculine. inews, June 22 2017.

Links To Science

Hay-Schmidt A, Ejlstrup Finkielman OT, Jensen BAH, et al. Prenatal exposure to paracetamol/acetaminophen and precursor aniline impairs masculinisation of male brain and behaviour. Reproduction. Published online May 30 2017.

 Thu, 22 Jun 2017 18:30:00 GMT Sex link to older people's brain power, says study

"Sex is the key to staying sharp in old age," reports the Mail Online after researchers found older people who have regular sex scored better on two of five brain tests.

Participants who had sex at least once a week scored higher on tests that measured their verbal fluency and spatial awareness compared with those who had no sex at all.

The verbal fluency test involved asking participants to say as many words beginning with a letter – in this case "f" – in a minute, and also name as many animals as they can.

In the spatial awareness test, participants had to draw an image, such as a square, triangle, cube or pyramid, and draw a clock face from memory.

These tests are part of the Addenbrookes Cognitive Examination III (ACE-III) test, a standard test to measure brain function.

The study involved 73 people aged between 50 and 83, and was conducted by researchers at the universities of Coventry and Oxford.

Researchers say their results "demonstrate that older men and women who engage in regular sexual activity have better cognitive functioning than those who do not … or do so infrequently".

But it's not clear why.

Previous studies have shown that older people who have active social lives and keep physically active are likely to have better cognitive function.

It's possible the social or physical elements of sexual activity are simply another aspect of this previous finding.

Researchers speculated it could also be caused by the release of dopamine, a chemical that transmits information in the brain during activities like sex.

We can't draw any conclusions from this study about whether sex keeps the brain functioning well, or whether people with better cognitive function are more likely to continue to have sex – or if the link is caused by something else entirely.  

Where did the story come from?

The study was carried out by researchers from Coventry University and the University of Oxford.

It was funded by the Coventry University Pump-Prime Research Grant Scheme. 

The study was published in the peer-reviewed Journals of Gerontology and is free to read online.

The Mail Online's story was mostly accurate, although the reporting assumed that increased sexual activity was the cause of better cognitive function, which may not be the case.

Most of the media coverage made the same error. The i newspaper stated that, "Having more sex can boost brain power", while The Sun incorrectly informed readers that, "Testers aged up to 83 were asked to keep a bonking diary".

What kind of research was this?

This was a cross-sectional observational study. This type of study can show an association between different things, but can't tell whether one thing (in this case sexual activity) causes the other (cognitive function), or whether other factors are at play.

What did the research involve?

Researchers recruited 73 volunteers over the age of 50: 45 women and 28 men.

They were asked to say how often they'd had sex over the past year:

  • never
  • once a month
  • once a week

They then filled out a general health questionnaire and took a range of tests designed to assess their mental abilities.

Researchers then looked at whether people who said they'd had sex never or monthly did better or worse on the tests than people who said they'd had sex weekly.

The researchers used the Addenbrookes Cognitive Examination III (ACE-III) test, which includes brief measures to assess people's abilities in attention, memory, fluency, language, and visual-spatial fields (how well people can visualise things in relation to those around them).

They adjusted their figures to account for people's age, years in education, gender, and cardiovascular health, as these factors might affect both how often they had sex and their cognitive abilities.

What were the basic results?

Frequency of sexual activity didn't vary significantly by age, education level, cardiovascular health, or other factors measured.

People who said they'd not had sex in the past year had on average lower scores for overall cognitive function and fluency compared with those who said they'd had sex weekly.

People who reported having sex monthly had on average lower scores for fluency and spatial awareness, although the difference here was small and may just have been down to chance.

More people in the group of 73 said they'd had sex weekly than monthly or never. All 10 of the respondents who said they never had sex were women.

More women than men said they'd had sex monthly (65% women and 35% men), and about equal numbers of men and women said they'd had sex weekly.

How did the researchers interpret the results?

The researchers say their results "demonstrate that older men and women who engage in regular sexual activity have better cognitive functioning than those who do not … or do so infrequently".

They suggest this might be because of the biological effect of dopamine, a chemical that transmits information in the brain, and is linked to pleasure and reward pathways.

They say that, "We can only speculate that continued engagement in regular sexual activity may have a positive influence on cognitive function", but add "the findings have important implications for the maintenance of intimate relationships in later life".


This study got widespread and enthusiastic coverage in the media, as many studies about sex do. But the findings are limited and it's difficult to draw conclusions from them.

As the researchers point out, we already know that a healthy social life and staying physically active seem to help keep people's cognitive abilities sharper as they age.

It's not a surprise that sexual activity, which has elements of both social and physical activity, is also linked to better cognitive function.

But this small observational study only provides a snapshot in time of how sexual activity may link to brain function.

We can't draw any firm conclusions about whether sexual activity keeps the brain functioning well, or whether people with better cognitive function are more likely to continue to have sex.

The results of the study are quite limited. Although overall scores of cognitive function were better for people who reported having sex weekly, this seems to have been driven by only two of the five types of mental ability, and the relationships weren't consistent.

And it's hard to explain how having sex monthly could give you worse spatial awareness than either having sex weekly or not at all, for example.

While continued sexual activity may be pleasurable and generally healthy into older age, this study doesn't mean it's a panacea for keeping the brain sharp.

If you're older and don't want to engage in sexual activity, the results of this study don't mean there's any reason to worry about it.

Links To The Headlines

Sex is the key to staying sharp in old age! Regularly getting intimate improves vocabulary and visual awareness. Mail Online, June 22 2017

Over 50s 'should have more sex to boost their IQ'. iNews, June 22 2017

Hump away brain decay: Over-50s who have more sex have better memory and visual awareness, says study. The Sun, June 22 2017

Frequent sex is officially good for your health and it can boost your brain performance. Daily Express, June 22 2017


Links To Science

Wright H, Jenks RA, Demeyere N. Frequent Sexual Activity Predicts Specific Cognitive Abilities in Older Adults. Journals of Gerontology: Psychological Sciences. Published online June 21 2017

 Wed, 21 Jun 2017 00:00:00 GMT 'Contaminated air' on planes linked to health problems

"Toxic fumes in aircraft cabins could cause serious health problems, scientists warn," reports The Sun. This is based on a UK study investigating air contamination on aircraft and its possible effects on the health of pilots and cabin crew.

The researchers say the air supply on planes can become contaminated by leaks of oil or other chemicals from the engines and they wanted to find out if this was associated with any health problems.

The study, published in the World Health Organization journal, found there is a link between exposure to contaminated air and short-term problems such as drowsiness, loss of consciousness, headache and tremors, and longer-term issues such as problems with memory or concentration and fatigue.

This is mainly worrying for pilots and staff on aircrafts, but could also be a concern for passengers if exposure to highly contaminated air causes a pilot to feel drowsy or pass out. However, only a few case studies of serious air contamination were investigated in this study, suggesting these events are rare.

The study didn't look in detail at whether exposure to contaminated air on planes was harmful to passengers, so it's not possible to draw firm conclusions about whether there's a health risk for people who fly regularly or only occasionally.

Where did the story come from?

The study was carried out by researchers from the University of Stirling and the University of Ulster in the UK, as well as a consultant respiratory physician from Melbourne in Australia. It received no sources of funding.

The study was published in the peer-reviewed journal Public Health Panorama, a journal of the World Health Organization. It is open access, meaning you can read it online for free (PDF, 314kb).

The UK media generally reported the story accurately, although the Sun's message of "Flying should 'come with a health warning' as toxic fumes contaminate air in cabins leading to serious health problems, research suggests" is fairly misleading as it suggests the research was done on passengers, when it was actually only carried out on aircraft staff.

What kind of research was this?

This was a combination of two studies, one involving a survey of pilots from the UK and the second an analysis of 15 case reports of potential cabin air quality incidents. They both aimed to look at the circumstances and symptoms of aircrew working in the pressurised air environment of aircraft. 

There have been concerns over the years regarding the health effects of exposure to aircraft contaminated air for aircrew. Unfiltered breathing air is provided to the cabin by the engine compressor. If oil leaks over the engine oil seals, chemicals can enter the air being supplied to the cabin. This might mean those on board may be exposed to some potentially harmful substances.

By combining these two types of studies, the authors aimed to carry out a more in-depth investigation of aircrew involved in suspected aircraft contaminated events by seeing if the reported symptoms were consistent with exposure to pyrolysed (heated) jet engine oil and other chemicals.

What did the research involve?

Researchers carried out two independent studies to investigate the circumstances and symptoms of aircrew who worked in the pressurised air environment of aircraft.

The first was a survey of UK British Airways pilots between 2005 and 2009 who agreed to a telephone interview or responded to a written questionnaire.

The pilots were asked:

  • whether they were aware of exposure to contaminated air
  • how they thought the contaminated air affected them
  • about any medical diagnoses they had

Of all the pilots who were contacted, 274 (14%) agreed to participate.

The second study involved 15 case reports from Australia, the US, Germany and the UK, of potential cabin air quality incidents. These particular cases were chosen because the health problems reported were suggestive of exposure to contaminated air.

Data sources included: the airlines, crew and maintenance reports, incident investigation and regulator reports, health effects and medical records, as well as media, union and legal reports.

Symptoms for both studies were recorded. 

The substances found in the engine oils and other chemicals were then measured against European standards to see if they were at hazardous levels or not.

What were the basic results?

From the survey:

  • Of the 274 pilots surveyed, 88% reported exposure to aircraft contaminated air, mostly in the form of fumes, and 34% reported frequent exposure.
  • 142 pilots reported specific symptoms and diagnoses, 30 reported health problems but gave no specific details, 77 reported no health effects and 25 failed to respond either way.
  • Acute adverse effects most commonly reported were: breathing problems, exhaustion or fatigue, dizziness and reduction in performance level.
  • Long-term effects most commonly reported were: breathing problems, poorer levels of performance, memory impairment and chronic fatigue.

Among the case studies:

  • In 33% of the incidents both pilots ability to fly the plane was affected during the air contamination.
  • 53% of events included long-term adverse effects for one or more crew members.
  • Chronic health problems diagnosed at some point after the exposure event included asthma, post-traumatic stress disorder (PTSD), problems with memory or concentration, seizures (fits) and cancer.
  • Nine pilots either became unfit to fly or died.
  • 80% of incidents occurred during take off or landing and 87% were linked to positive maintenance findings of oil leakage.

How did the researchers interpret the results?

The authors concluded that "aircraft air supplies contaminated by pyrolysed [heated] engine oil and other aircraft fluids can reasonably be linked to acute and chronic symptoms, findings and diagnoses, thus establishing causation".

They further add that "there is an obvious need for a clearly defined internationally recognised medical protocol, occupational syndrome and disease recognition, and health and environmental data collection".


These findings indicate that on rare occasions, pilots have not been able to perform as usual due to poor air quality in the cabin. Also poor air quality has been linked to health problems in the long term.

However, there are some limitations of the study that need to be considered:

  • The authors claim they have demonstrated a cause-and-effect relationship based on certain criteria. But with the exception of the acute air toxicity incident investigation reports in the second study, these types of study cannot prove causality. While it is likely that exposure to chemicals is toxic, this study did not link many of the symptoms with on-board air samples. There is still a possibility that the acute symptoms experienced by the pilots and crew were brought on by other things too, not just the contaminated air. With regard to the potential chronic effects, it is even harder to eliminate other factors that may have played a role.
  • The data in the pilot survey was self-reported, which might be subject to bias as people might not remember accurately or might exaggerate health outcomes. There was also a high risk of selection bias as only a small proportion of pilots invited to participate agreed. It is likely that those who didn’t participate hadn’t experienced any obvious health problems.
  • The data from the case studies comes from multiple sources that might not have consistent ways of reporting things, so analysing them as a group might lead to inaccuracies.
  • We do not know if frequency of exposure affects the health outcomes (if the symptoms get worse the more times staff are exposed to contaminated air). This might have some consequence for frequent flyers, so it’s important to know.

Links To The Headlines

Contaminated air on flights can lead to long-term sickness and airlines are ignoring the problem, study claims. The Independent, June 19 2017

Toxic fumes in aircraft cabins could cause serious health problems, scientists warn. The Sun, June 19 2017

Contaminated air on planes linked to crew ill-health, study finds. The Guardian, June 19 2017

Air in a plane cabin can damage your health, say scientists. Mail Online, June 19 2017

Flight safety 'degraded' by contaminated air. BBC, June 19 2017

Links To Science

Michaelis S, Burdon J, Vyvyan Howard C. Aerotoxic syndrome: a new occupational disease? (PDF, 314kb). Public Health Panorama. Published online June 2017


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