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NHS Choices: Behind the headlines   + / -  
last updated: Sun, 04 Oct 2015 04:08:07 GMT

 Fri, 02 Oct 2015 14:00:00 GMT Too soon to say being tall increases cancer risk

"Higher risk of cancer if you are tall," says the Daily Mirror. Most media outlets provided a similar spin on the seemingly big news that the risk of developing cancer increases with every 10cm of height.

Tall people shouldn't lose any sleep over this news: let's face it, there's nothing you can do about your height (although there are plenty of things you can do to reduce your risk of cancer). What's more, the research these stories are based on does not provide proof being tall means you will get cancer.

Currently, only preliminary results have been presented in the form of a conference abstract, and the research hasn't had the kind of independent rigorous scrutiny you'd hope for in published science.

That's not to say this was bad research: the study was large, involving 5.5 million adults, which is usually a good thing. However, it did not take into account many known risk factors for cancer, such as smoking. 

Neither the study nor any of the papers covering the story suggested adult height directly causes cancer. Theories presented in the media about why being taller would increase cancer risk are simply speculation – no matter how well informed they are.

Where did the story come from?

The study was carried out by researchers from Karolinska Institute in Stockholm and was funded by HKH Kronprinsessan Lovisas förening för Barnasjukvård and Stiftelsen Samariten.

It was summarised briefly ahead of the European Society for Paediatric Endocrinology conference in a very short article called a conference abstract. This means there is little detail on the methods and results presented, and its strengths and weaknesses can't be appraised in any depth.

It has not yet been published in a peer reviewed journal, so the research hasn't been scrutinised by experts for scientific accuracy or rigour.

Generally, the media reported the story accurately. It was made clear that no-one was saying being tall causes cancer directly. However, because the actual science was not presented in great detail, most padded out their copy with speculation about what could cause the link between being tall and cancer. Fortunately, the media outlets that did this tended to use independent and informed commentators. 

What kind of research was this?

This was a cohort study of a very large group of mostly Swedish adults over several decades. The researchers were looking for a link between height and risk of cancer.

Previous studies have linked being taller with a higher risk of developing cancer overall – breast cancer and skin cancer in particular – and this was also the focus of the new study.

According to media reports, the research team don't believe increased height directly causes cancer. Instead, height is thought to be a marker of other factors that raise the risk of cancer.

One theory presented in the media is that taller people have more cells in their body growing and dividing, with more potential to undergo cancerous change. The higher food intake needed to maintain a larger body size may also play a part.

For this particular study, the researchers were less interested in explaining exactly how height might be linked to cancer risk – they first wanted to establish whether height was linked to cancer.

Apparently, the topic hadn't been studied on a large scale before. Using a large group of people, as they did, increases the chances of finding a true link if one exists, and also increases the accuracy of any calculations of the risk.  

What did the research involve?

The researchers tracked 5.5 million Swedish adults aged over 20 over several decades, although the average time was not reported in the brief summary available.

Sweden has very complete information on its residents. This meant it was relatively simple for the researchers to get height measurements from a combination of military conscription records and passports. These heights ranged from 3 feet 3 inches (100cm) to 7 feet 5 inches (225cm).

The researchers were also able to easily link the height data to medical records showing when a person was diagnosed with cancer and the cancer type.

The team then calculated the risk of people getting cancer for every 10cm increase in height. They worked this out for men and women separately, working out the risk for cancer overall and separately for breast cancer and skin cancer.

Adjustments were made for education level and income, which are known to influence both height and cancer risk. There was no adjustment for smoking, alcohol intake, sun exposure or other factors known to affect cancer risk. 

What were the basic results?

The results presented showed that:

  • Both taller men and taller women had a higher risk of developing cancer overall. For every extra 10cm of height as an adult, the risk of cancer rose by 11% in men and 18% in women.
  • For breast cancer, a 10cm increase in height raised the risk of breast cancer in women by 20%. As breast cancer is much rarer in men, their risk was not calculated.
  • A 10cm increase in height raised the risk of skin cancer by 32% in men and 27% in women.  

How did the researchers interpret the results?

Dr Emelie Benyi, who led the study, said the results could help identify risk factors that could lead to the development of treatments.

She added: "As the cause of cancer is multi-factorial, it is difficult to predict what impact our results have on cancer risk at the individual level." 


This large, long-term cohort study was able to give precise estimates of the risk increase of cancer for taller adults.

Currently, this information has only been presented as a conference abstract and accompanying press release. It is not possible to fully assess the study's methods, strengths and limitations from this, but some potential limitations are apparent.

While the study clearly showed a link between height and cancer, it did not take into account a range of confounding factors known to affect cancer risk – things like smoking, alcohol intake and sun exposure.

The problem is cancer risk may be influenced by these factors – and potentially others – and may explain some or all of the risk increases linked to height here. This study really doesn't provide much in the way of an explanation of how height might be linked to cancer, although media reports mentioned a number of theories.

These theories were largely speculative. The study did not look at whether taller people were more likely to die of cancer, but this is something they plan to do in the future.

Tall people shouldn't be worried by this study. There is not much you can do as an adult to change your height. But the good news is there are many simple things you can do that may help reduce your risk of cancer – for example, eating a balanced, healthy diet, taking regular exercise, not smoking, and drinking alcohol in moderation.

Read more about how a healthy lifestyle can help reduce your chances of developing cancer.

Links To The Headlines

Being tall can increase your risk of cancer, say researchers. The Guardian, October 2 2015

The taller you are, the higher your risk of getting cancer. The Times, October 2 2015

The taller you stand the higher your risk of cancer, scientists calculate. The Daily Telegraph, October 2 2015

Tall people exposed to greater risk of many forms of cancer, say scientists. The Independent, October 1 2015

If you're tall, your risk of cancer could be up to 30% higher. Daily Mail, October 1 2015

Higher risk of cancer if you are tall. Daily Mirror, October 1 2015

Cancer risk linked to your height. Daily Express, October 2 2015

Study supports cancer link with height. BBC News, October 2 2015

Taller people are more likely to develop cancer, says study. Metro Online, October 2 2015


Links To Science

Conference abstract

Benyi E. et al. Positive Association between Height and Cancer in the Swedish Population. ESPE Abstracts. 2015. 84 FC4.6

 Thu, 01 Oct 2015 13:30:00 GMT High blood pressure: does it lead to diabetes?

"Study gives strongest link yet between blood pressure and diabetes," says The Guardian. At first glance these might be considered two unconnected conditions, but research over the years has led to diabetes being classified as a risk factor for cardiovascular disease.

Researchers looked at data on more than 4 million people in the UK who were free of any vascular disease or diabetes. They then analysed these people's medical records for around seven years and recorded new cases of diabetes and changes in blood pressure.

People with high blood pressure were found to have around a 50% increased risk of developing type 2 diabetes. The researchers then backed up their findings by looking at previous research and found a risk of more than 70%.

While these types of studies can't prove increased blood pressure causes diabetes, they lend weight to the advice to take steps to lower your blood pressure if it's high to reduce your risk of diabetes.

Read our advice on how to look after your heart and circulation

Where did the story come from?

The study was carried out by researchers from the University of Oxford and was funded by the UK National Institute for Health Research.

It was published in the peer-reviewed Journal of the American College of Cardiology.

This story has been reported widely in the media. Both The Guardian and The Independent have responsibly provided quotes from one of the researchers, who explained the findings tell us a link exists, but we don't know whether high blood pressure is a cause of diabetes or whether it's a risk factor. 

What kind of research was this?

This was a large cohort study and systematic review with meta-analysis to determine whether there is an association between blood pressure and type 2 diabetes.

While the cohort study cannot prove causation, it does provide a link to be investigated further. Combined with a meta-analysis of previously reported studies, we can see if the findings are in agreement. 

What did the research involve?

Researchers collected data from the UK Clinical Practice Research Datalink (CPRD) of 4.1 million people who had a blood pressure measurement recorded in the previous year.

The researchers included people who were aged between 30 and 90 years and were free of any form of vascular disease or diabetes.

Baseline measurements were recorded for:

  • body mass index (BMI)
  • cholesterol (total and high-density lipoprotein)
  • smoking status

The main outcome measures were a diagnosis of diabetes or the prescription of diabetic medication.

A meta-analysis was carried out using prospective observational studies assessing the link between blood pressure and risk of diabetes. The medical database Medline was searched to identify relevant reports.

Studies were only included if they had:

  • at last one year of follow-up
  • looked at the risk associated with a higher systolic blood pressure of 20mmHg 
  • adjusted the findings for sex, age and BMI

Data was combined to assess the risk of diabetes, with separate analyses performed to investigate differences because of gender, BMI and age. 

What were the basic results?

The cohort study included 4.1 million adults (median age 46) who were free of diabetes and cardiovascular disease at the start of the study.

These adults were an average of 46 years old (median), had a BMI slightly above the healthy range (median 25.7), and were followed up for around seven years. There were 186,698 new cases of diabetes during the study period.

Analysis of the data found raised systolic blood pressure of 20mmHg increased the risk of diabetes by 58% (hazard ratio (HR) 1.58; 95% confidence interval (CI) 1.56 to 1.59) and a higher diastolic blood pressure of 10mmHg was associated with a 52% higher risk of diabetes (HR 1.52; 95% CI 1.51 to 1.54). There was a weaker association between blood pressure and diabetes observed with increased age and BMI.

The literature search identified 30 relevant studies, including 285,664 participants and 17,388 new cases of diabetes. Pooling and analysis of the data found a 77% increased risk of diabetes for a 20mmHg higher usual systolic blood pressure (relative risk (RR) 1.77, 95% CI 1.53 to 2.05). 

How did the researchers interpret the results?

The researchers concluded that, "People with elevated [blood pressure] are at increased risk of diabetes. The strength of the association declined with increasing body mass index and age. Further research should determine if the observed risk is modifiable." 


A large-scale cohort study and meta-analysis has assessed the link between increased blood pressure and risk of type 2 diabetes, and found an increase of 20mmHg systolic blood pressure raised the risk of type 2 diabetes by 58%. It also found a higher diastolic blood pressure of 10mmHg was associated with a 52% increased risk of type 2 diabetes.

These findings were confirmed by the results of the meta-analysis, which found a 77% increased risk of diabetes for a 20mmHg higher than usual systolic blood pressure. This study was very large and followed the patients for a fairly long period of time, so we can be more certain of the links it makes.

However, as the authors say, there is a risk the electronic health records misclassified people's blood pressure. An interesting addition to the study would have been to analyse risk according to ethnic group.

Reducing your risk of diabetes and increased blood pressure can be done in similar ways, such as by:

  • maintaining a healthy weight
  • taking regular exercise
  • stopping smoking 
  • eating a healthy diet

Links To The Headlines

Study gives strongest link yet between blood pressure and diabetes. The Guardian, September 29 2015

High blood pressure is linked to greater risk of developing diabetes. The Times, September 29 2015

People with high blood pressure 'more likely to suffer diabetes' - new study finds. Mirror, September 29 2015

High blood pressure 'increases risk of diabetes by 60%'. The Independent, September 29 2015

Links To Science

Emdin CA, et al. Usual Blood Pressure and Risk of New-Onset Diabetes: Evidence From 4.1 Million Adults and a Meta-Analysis of Prospective Studies. Journal of the American College of Cardiology. 2015. 66:1552-62

 Thu, 01 Oct 2015 10:23:00 GMT Probiotic friendly bacteria may play role in stopping asthma

"'Good bacteria' key to stopping asthma," says BBC News.

Before you go out and buy a year's supply of probiotic yoghurt drinks, it's worth noting a few points that burst the hype bubble.

The news is based on research that found that the lack of some types of bacteria in babies' guts affected their later chances of asthma. However, this was only the case for three-month-olds so the effect, if it exists, is likely to be time-limited.

The researchers did an experiment to demonstrate the concept – by feeding poo from these babies with the relevant bacteria added in to mice that had an asthma-like condition. The offspring of these mice were less likely to have the disease, but this is not the same as a real-life (and potentially unpalatable) experiment in humans.

Asthma has been linked to the "hygiene hypothesis", a theory that says asthma happens when the immune system does not develop properly. Some believe this can happen if a growing baby is not exposed to enough varied bacteria, with antibiotics and caesarean births implicated.

While this new study has provided evidence in support of this theory, it is too early to say the case is proven. We don't know for sure that the levels of these bacteria directly affect risk of asthma in the way suggested.


Where did the story come from?

The study was carried out by researchers in Canada, from the University of British Columbia, the Child Research Institute and British Columbia Children’s Hospital, McMaster University, the University of Toronto, Hospital for Sick Children Toronto, University of Alberta and University of Manitoba. It was funded by the Canadian Institutes of Health Research. The study was published in the peer-reviewed journal Science Translational Medicine.

The story was not widely covered in the media. BBC News published an accurate account of the research, although the headline that these bacteria are "key to stopping asthma" probably overstates the results.


What kind of research was this?

This research included two separate studies. The first was a nested case-control study of children, who were taking part in the bigger, ongoing Canadian Healthy Infant Longitudinal Development study, a prospective cohort study. The second study was a laboratory experiment using mice.

Case-control and longitudinal studies can highlight links between two factors – in this case between the type of bacteria in the gut and the chances of having asthma – but cannot prove by itself that one causes the other. The mouse study shows what happens when you do something to mice, and although it does provide support for the hypothesis, we don't know for certain if the results are directly applicable to humans.


What did the research involve?

For the study in children, researchers selected groups of children at different levels of asthma risk, and analysed samples of their poo (stools), which had been taken at three months and one year of age. They looked for differences between the composition of the gut bacteria in the children at different asthma risk levels.

They later carried out tests to see whether they could find differences in how the children's digestion worked, and whether these could be linked to specific bacteria.

Researchers selected 319 children with relevant samples. They chose all those who fitted the criteria at age one of having both allergic reactions (tested by skin-prick tests) and wheezing, wheeze only or allergic reactions only. They also looked at a sample of children with neither allergy or wheeze, to act as a comparison group. Children with allergic reactions and wheeze have a much higher chance than those without these conditions of being diagnosed with asthma by age five.

The researchers used DNA analysis to identify bacteria in the stool samples and looked for differences in the bacteria present between the groups at highest and lowest risk of asthma. After analysing the bacteria in the gut, researchers looked for differences in products of digestion, including certain short-chain fatty acids. They wanted to see whether the differences in bacteria were linked to differences in the way the children's digestion worked.

In a separate experiment, researchers took mice bred to be free from bacteria and introduced either a stool sample from a child at high risk of asthma, or the same sample with additional bacteria. They allowed these mice to breed, and showed that their offspring carried the bacteria their parents had been given in their guts. The researchers then provoked an asthma-like condition in these offspring, and later provoked an immune response in the lungs of these animals and looked at the resulting levels of inflammation.


What were the basic results?

The 22 children who had both allergic reactions and wheeze at age one, had similar overall amounts and range of different types of bacteria in their stool samples, compared with other children. However, the researchers found that their levels of four particular types of bacteria were much lower, compared to children at the lowest asthma risk.

These bacteria were Faecalibacterium, Lachnospira, Rothia and Veillonella. Babies who had both allergic reactions and wheeze at age one were also more likely by the age of three to either have been diagnosed with asthma or meet criteria for being at high risk, including having had recurrent wheezing episodes.

Importantly, the researchers only found differences between the groups' stool samples when the children were three months old. By one year, the differences had gone.

The researchers also found that children at higher asthma risk had some differences in the way their body digested food, shown by the fact that they had lower levels of a type of short-chain fatty acid called acetate in their stool.

In the mouse experiment, the offspring of mice given the stool sample with additional samples of the four missing bacteria had a lower level of inflammation in the lung, compared to those mice that did not get the additional bacteria. The stool sample with no added bacteria did not have this effect.


How did the researchers interpret the results?

The researchers say their research shows that changes in the gut bacteria in the first few months of life may be "an important factor influencing asthma development", and that the four bacteria they identify may have a "protective role" against the disease.

They went on to say that the findings "enhance the potential for using rationally designed microbe-based therapies to prevent the development of asthma and other allergic diseases that begin in childhood". By this they mean scientists may be able to design a "friendly bacteria" cocktail to be given to children at high risk of asthma, which could reduce their chances of getting allergies and asthma.



This complicated and interesting study sheds light on one potential cause of asthma in children, and points towards areas where research might lead to a treatment to prevent it or reduce its severity. However, this exciting prospect depends on much more work to confirm the results of this study and find out whether what seems to work in laboratory mice can also work in people.

The idea that reduced exposure to bacteria in childhood might increase the chances of getting allergies and asthma has been around for some time. This theory suggests that, for a child's immune system to develop well, it needs to be exposed to a wide variety of bacteria and viruses. If this doesn't happen, the immune system might become oversensitive and react to things that it shouldn't, like certain types of food, or pollen in the atmosphere.

This study suggests that particular types of gut bacteria in the first few months of life might be important for the development of a healthy immune system. However, the study has limitations. While 319 babies were studied, only 22 had wheeze and allergic reactions at age one, and only 19 of these were in the group classified as having, or being at highest risk of, asthma at age three. 

We need to see these results replicated in bigger studies to be sure that all or most babies at risk of asthma have low levels of these specific bacteria. Also, this type of study alone cannot prove that the differences in gut bacteria actually cause asthma. There may be other factors that are important but have not been considered in this study.

We should also be wary of animal studies. While there are a lot of biological similarities between different species, there are differences. In this study, the mice had an asthma-like condition, but the authors acknowledge that this is not exactly the same as human asthma. Also, the bacteria in the guts of the mice in this study and humans are likely to be different. The effect of adding certain bacteria to a mouse gut may be very different if tried in a human. We need to see carefully controlled studies in humans to know whether this treatment could work.

However, the study suggests lots of future research pathways that could increase our understanding of how asthma develops and how it might best be treated, or eventually prevented. For now, we still don't fully understand what causes asthma. 

Links To The Headlines

'Good bacteria' key to stopping asthma. BBC News, October 1 2015

Links To Science

Arrieta M-C, et al. Early infancy microbial and metabolic alterations affect risk of childhood asthma. Science Translational Medicine. September 30 2015


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