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NHS Choices: Behind the headlines   + / -  
last updated: Wed, 27 Jul 2016 02:07:26 GMT

 Tue, 26 Jul 2016 15:30:00 GMT 'Netflix and kill?' Binge watching box-sets linked to blood clots

"Binge watching TV can actually kill you, study finds," The Independent reports in a somewhat exaggerated manner. The Japanese study its report is based on looked at prolonged TV watching and the risk of blood clots, and only found a very weak association.

Researchers were specifically looking at deaths caused by pulmonary embolisms – blockages in the blood vessel that carries blood from the heart to the lungs.

The study included more than 80,000 adults aged between 40 and 79 from Japan. Researchers estimated that people who regularly watched more than five hours of TV a day were two and half times more likely to die of a pulmonary embolism than those who watched less than two and a half hours.

While this may sound alarming it is important to realise that deaths from pulmonary embolisms are rare. Despite the large cohort, only 59 deaths occurred. And a modest increase in a rare risk means the risk remains rare.

The small number of deaths also means that any perceived association could have been the result of chance.

Also, the study design was unable to prove any cause and effect as many other factors may have been involved. That said, there is a growing body of evidence on the risks of sedentary behaviour.

The recommendation from the authors of the study, quoted in the media, that you get up and move around for a few minutes every hour while "binge watching" is sensible. 

It is important to compensate for time spent watching your favourite box sets by exercising regularlyeating a healthy diet and trying to achieve or maintain a healthy weight.

 

Where did the story come from?

The study was carried out by researchers from Osaka University Graduate School and was funded by the Japanese Ministry of Education.

The study was published in the peer-reviewed medical journal Circulation on an open-access basis so you can read it for free online.

Much of the UK media's reporting of the study was as overblown as a season of 24 and did not mention the many limitations of the study. For example, The Independent's headline "Binge watching TV can actually kill you, study finds" is incorrect. The study found no such thing.

It was good to see advice reported in some quarters to ensure you move around for a few minutes each hour.

 

What kind of research was this?

This study used data from a large cohort study to assess the link between the number of hours spent watching the television and the risk of death from pulmonary embolism.

Pulmonary embolism is a when a blood clot gets trapped in the blood vessel that takes blood from the heart to the lungs. It usually follows a clot in one of the leg veins (deep vein thrombosis or DVT) that has travelled through the blood to the heart.

As DVT is associated with prolonged immobility the researchers wanted to know whether watching TV (or, as is increasingly the case, streaming content to a tablet) could be associated with these outcomes.

This cohort study followed participants for a long period of time to draw observations, however, due to the design and the overall rarity of the outcome, the study cannot prove that one directly causes the other.

 

What did the research involve?

The researchers collected data from the Japanese Collaboration Cohort study, which began in 1988 and included adults aged 40 to 79 from 45 regions in Japan.

Participants were excluded if they had incomplete data on time spent watching TV or those with a history of cancer, stroke, myocardial infarction (heart attack), or pulmonary embolism at study start.

Information on potential confounders was collected by a self-administered questionnaire and included:

  • body mass index
  • history of hypertension (high blood pressure) or diabetes
  • smoking status
  • perceived mental stress
  • educational level
  • walking activity
  • sports activity

Participants were categorised according to the time they spent watching television each day, these were:

  • less than two and a half hours
  • between two and a half and five hours
  • five hours or more

The death certificates of participants were examined and the number caused by pulmonary embolism was recorded up to 2009.

Statistical analyses were performed for patients with complete information and were adjusted to take into account the effects of confounding.

 

What were the basic results?

The analysis featured 86,024 participants who were followed, on average, for 19.2 years. During this time 59 deaths from pulmonary embolism were recorded. Nineteen of them occurred in the people who watched TV for less than two and half hours, 27 in the second group, and 13 in the group who watched for five or more hours.

The amount of time spend watching television was associated with increased risk of death from pulmonary embolism.
 
Compared to the first group that watched less than two and a half hours, those who watched television for between two and a half and five hours were not at significantly increased risk death (hazard ratio (HR) 1.7, 95% confidence interval (CI) 0.9 to 3.0).

However, the third group who watched TV for more than five hours a day were two and half times more likely than the lowest duration group to die from pulmonary embolism (HR 2.5, 95% CI 1.2 to 5.3). 

Overall, the data found that each additional two hours of television increased risk by 40% (HR 1.4, 95% CI 1.0 to 1.8).

 

How did the researchers interpret the results?

The researchers conclude: "our prospective cohort study suggests that prolonged television watching is a substantial risk factor for mortality from pulmonary embolism."

 

Conclusion

This study used data from a large Japanese cohort study to assess the link between the number of hours spent watching the television and the risk of death from pulmonary embolism.

The study found that a greater number of hours watching the television increased the risk of death from pulmonary embolism.

The main strength of this study is the very large sample size and long follow-up periods. However, there are a number of limitations:

  • this study design is not able to prove cause and effect, so while there appears to be a link, we cannot be sure the cause of mortality is from television watching
  • even though the researchers attempted to account for relevant health and lifestyle factors such as BMI, smoking and physical activity, this may not be entirely accurate and there is still the possibility of residual confounding from these and other factors
  • despite the large cohort size, death from pulmonary embolism is very rare. These deaths have then been further subdivided by TV category, and statistical comparisons that involve small numbers are less reliable
  • the population was a group of older adults from Japan, the findings may not relate to other age groups or geographical populations
  • mortality from pulmonary embolism was confirmed from death certificates. This is likely to be reliable, but we don't know how many people may have experienced DVT or pulmonary embolism and not died from them 
  • information on the amount of time spent watching television was only collected on one occasion, this may have changed during the follow up period. People may also not be able to estimate with much accuracy how many hours they spent watching the TV, which may vary day to day

This study does however add to the growing evidence on the risks of sedentary behaviour. While much of the research in this area focuses on the relationship between sedentary behaviour and weight, some also suggests sedentary behaviour is independently associated with all-cause mortality, type 2 diabetes and some types of cancer.

The main issue considered in this study is the amount of time an individual spends watching television. But people are also sedentary at other times, such as when travelling, sat at a computer, or reading a book. The recommendation is to make sure that you get up and move around for a few minutes every hour.

It is important to compensate for time spent watching your favourite box sets by exercising regularlyeating a healthy diet and trying to achieve or maintain a healthy weight.

Links To The Headlines

Binge watching TV can actually kill you, study finds. The Independent, July 26 2016

How binge watching your favourite box sets could be deadly: More than 2.5 hours in front of the TV raises risk of a clot by 70%. Daily Mail, July 26 2016

Why binge watching your TV box-sets could kill you. The Daily Telegraph, July 26 2016

Netflix and kill warning as watching too much telly can increase risk of dying. Daily Mirror, July 26 2016

TV addicts double risk of blood clots. The Times, July 26 2016 (subscription required)

Links To Science

Shirakawa T, Iso H, Yamagishi K, et al. Watching Television and Risk of Mortality From Pulmonary Embolism Among Japanese Men and Women. Circulation. Published online July 26 2016

 Mon, 25 Jul 2016 16:30:00 GMT Smokers who try to quit 'drink less alcohol', too

"How quitting smoking can be good for your liver: Those who have given up cigarettes 'drink less alcohol too'," the Mail Online reports.

The news follows an analysis of two ongoing studies that aimed to investigate whether people who attempt to stop smoking are more likely than other smokers to report lowering their alcohol consumption.

Those who had attempted to quit smoking within the last week had significantly lower scores on an alcohol intake questionnaire compared with non-quitters.

The same people were also more likely to report they were currently trying to reduce how much alcohol they drank. The main effect seemed to come from a reduction in binge drinking.

It is important to be aware that studies like this are unable to rule out the influence of other potential factors.

It could be the case that some people were advised by their doctor to quit smoking while also reducing their alcohol consumption for health reasons, or were simply on a health kick.

Nevertheless, the links between smoking and excessive alcohol consumption and poor health are well established.

Smoking has long been known as a risk for lung cancer and, as we discussed just last week, smoking is directly linked to seven types of cancer.

Quitting smoking and sticking to the recommended alcohol guidelines should significantly reduce your cancer risk.

Where did the story come from?

The study was carried out by researchers from a number of UK universities, including University College London, the University of Sheffield, King's College London, the University of Bristol, and Newcastle University.

It was funded by the National Institute for Health Research (NIHR) School for Public Health Research (SPHR) and Cancer Research UK.

The study was published in the peer-reviewed journal, BioMed Central (BMC) Public Health. It is available on an open-access basis, so it is free to read online.

Although the tone of the Mail Online headline made it seem like quitting smoking has potential benefits for liver health, this was not proven in this study.

You would need a much longer follow-up period to see if the reduction in alcohol consumption in ex-smokers was a long-term effect. That aside, the main body of the news story provided balanced reporting.

What kind of research was this?

This was a cross-sectional analysis of two ongoing studies: the Smoking Toolkit Study (STS) and the Alcohol Toolkit Study (ATS).

It aimed to investigate whether people who attempt to stop smoking are more likely than other smokers to lower, or at least try to reduce, their alcohol consumption.

Smoking and excessive alcohol consumption are two of the most significant factors that can lead to poor health by triggering chronic diseases such as cancer and heart disease.

The behaviours have a close and complex relationship. As such, they are important public health challenges in the UK.

Research suggests drinking lots of alcohol while also trying to quit smoking makes the quit attempt more likely to fail, one reason being that alcohol can weaken willpower, making a lapse more likely.

As a result, smokers trying to quit are often advised to cut back on alcohol as well, but it is unclear how often they follow this advice.

Cross-sectional studies like this are useful for assessing the relationship between two variables – in this case, quitting smoking and alcohol consumption.

However, the study design cannot confirm the link and say that one has caused the other. 

A longer-term cohort study that followed these people up to see how the two factors changed over time would be one of the best ways to validate these findings and see how they're related.

What did the research involve?

The researchers used data from household surveys conducted as part of two ongoing studies: the Smoking Toolkit Study (STS) and the Alcohol Toolkit Study (ATS), which collected information on smoking, alcohol consumption and related behaviours in England.

They analysed data from 6,287 participants aged 16 and over who had reported smoking tobacco from March 2014 to September 2015.

All the smokers were also asked if they had made a serious attempt to quit smoking, and were classified according to their responses.

The smokers were further classified as light or heavy drinkers. Alcohol consumption was assessed through the Alcohol Use Disorders Identification Test (AUDIT-C), which asked participants about how often they drank.

Information on various socio-demographic, possibly confounding, factors was also collected, including:

  • age
  • sex
  • socio-economic status
  • education level
  • ethnicity
  • disability

The researchers then looked for links between people who had recently attempted to stop smoking and subsequent changes in their alcohol consumption. The results were stratified by socio-demographic factors.

What were the basic results?

Those who attempted to quit smoking within the last week had significantly lower AUDIT-C alcohol scores than those who had not tried to quit. On average their scores were about -0.66 points lower (95% confidence interval [CI] -0.11 to -1.21). 

There was, however, no significant difference in their typical quantity or frequency of drinking.

But those who had attempted to quit smoking in the last week were less likely to binge drink and less likely to be classified as high-risk drinkers (AUDIT-C score of five or more).

The same people who were trying to quit were also more likely to report that they were currently trying to reduce their alcohol consumption.

These analyses were after adjustment for socio-demographic characteristics, which did not differ between quitters and non-quitters.

How did the researchers interpret the results?

The researchers concluded: "Smokers who report a recent attempt to stop are more likely to report lower-risk alcohol consumption, including less frequent binge drinking, after adjusting for socio-demographic characteristics.

"Among smokers with higher-risk alcohol consumption, those who report a last week attempt to stop are more likely to report also a current attempt to cut down on their drinking."

Conclusion

This was a cross-sectional analysis of two ongoing studies that aimed to investigate whether people who attempt to stop smoking are more likely than other smokers to lower, or at least try to reduce, their alcohol consumption.

The researchers found those who attempted to quit smoking within the last week did have lower drinking scores on the AUDIT-C survey compared with smokers who weren't quitting.

The same people were also more likely to report they were currently trying to reduce how much alcohol they drank.

There was no difference in drinking frequency, however – the main effect seemed to be coming from a reduction in binge drinking.

So some participants may have had a drink every day during the week, but still drank less overall in terms of total units consumed.

Despite these results, there are a few points to note:

  • This was an observational study, which cannot prove that the quit attempt has directly caused the reduction in alcohol. Although the researchers attempted to control for potential confounders, there could be other factors that influenced changes in alcohol consumption.
  • As the authors note, it's also not possible to rule out reverse causation – that people with lower alcohol consumption were perhaps more likely to attempt to quit smoking.
  • The self-reporting nature of the surveys could lead to misreporting as a result of possible social pressures, such as stigma attached to both smoking and high alcohol consumption.
  • The study looked at immediate changes in smoking and alcohol consumption (in the last week) but longer-term follow-up would be needed to see if these decisions stuck or whether people reverted to their previous habits.
  • People who are trying to quit smoking may be advised to cut back on alcohol by smoking cessation professionals because of the known association between the two. This study does not inform whether individuals have cut back as a result of the advice of professionals or on their own initiative.

As it stands, people are advised to follow current smoking and alcohol public health recommendations.

If you smoke, the single best thing you can do for your health is to quit smoking. Stopping drinking, or at least cutting down, would be an added bonus your body will welcome.  

Links To The Headlines

How quitting smoking can be good for your LIVER: Those who have given up cigarettes 'drink less alcohol too'. Mail Online, July 22 2016

Links To Science

Brown J, West R, Beard E, et al. Are recent attempts to quit smoking associated with reduced drinking in England? A cross-sectional population survey. BMC Public Health. Published online July 22 2016

 Fri, 22 Jul 2016 14:00:00 GMT Alcohol 'a direct cause of seven types of cancer'

"Even one glass of wine a day raises the risk of cancer: Alarming study reveals booze is linked to at least seven forms of the disease," reports the Mail Online.

The news comes from a review that aimed to summarise data from a range of previous studies to evaluate the strength of evidence that alcohol causes cancer.

The main finding was that existing evidence supports the link between alcohol consumption and cancer at seven sites, including the throat, gullet, liver, colon, rectum and female breast.

The links were said to be strongest for heavy drinking, but this study suggested that even low or moderate drinking may contribute to a significant proportion of cancer cases because of how common this level of drinking is. The study also suggests there's no evidence of a "safe" level of drinking with respect to cancer.

However, it's important to be aware that this review doesn't state how the author identified and assessed the research they've drawn upon. We don't know whether all relevant research has been considered and the conclusions must be considered largely the opinion of this single author.

Nevertheless, the main finding of the link between alcohol and these seven cancers is already well recognised. Recently updated government recommendations state there's no safe level of alcohol consumption, and men and women are advised not to regularly drink more than 14 units a week. This review further supports this advice.

Where did the story come from?

The study was carried out by one researcher from the University of Otago, New Zealand. No external funding was reported.

The study was published in the peer-reviewed scientific journal Addiction. It is available on an open-access basis and is free to read online.

Generally the media coverage of this topic was accurate, although the tone of the reporting tended to suggest this was a new discovery, when the link between alcohol and certain types of cancer is well established.

What kind of research was this?

This was a review which aimed to summarise data from published biological and epidemiological research, and meta-analyses that have pooled data, to evaluate the strength of evidence that alcohol causes cancer.

Alcoholic drinks have been considered potentially carcinogenic (cancer causing) for a while, but there are still concerns about the validity of some observational studies finding links with cancer, and uncertainty about precisely how alcohol causes cancer.

A systematic review is the best way of gathering and summarising the available research around a particular topic area. But in this case the exact methods are not described in the paper and it's not possible to say whether they were systematic.

There's a possibility that some relevant research may have been missed and that this review is giving an incomplete picture of the issue.

What did the research involve?

The author of this review reports drawing upon biological and epidemiological research as well as meta-analyses conducted in the last 10 years by a number of institutions, including the World Cancer Research Fund and American Institute for Cancer Research, the International Agency for Research on Cancer and the Global Burden of Disease Alcohol Group.

The majority of epidemiological research seemed to come from cohort and observational studies.

The research was reviewed and summarised in a narrative format which explored the evidence that alcohol causes cancer, while contrasting this with the notion that alcohol consumption may offer some form of protection from cardiovascular disease.

No methods are provided and the author does not describe how they identified the research, as you would expect from a systematic review.  For example, they do not give the literature databases searched, the search dates, search terms, study inclusion or exclusion criteria, or descriptions of how studies were quality assessed.  

What were the basic results?

There were several findings from this study, the main one being that existing evidence supports the link between alcohol consumption and cancer at seven sites: oropharynx (mouth and throat), larynx (voice box), oesophagus (gullet), liver, colon (bowel), rectum and female breast.

The strength of the association differed by the site of the cancer. It was strongest for the mouth, throat and oesophagus, with the review suggesting that someone who drinks more than 50g of alcohol a day is four to seven times more likely to develop these types of cancer compared to someone who doesn't drink. As the author says, the interaction of smoking with alcohol is also believed to contribute to the risk of these cancers.

The link was comparatively weaker for colorectal, liver and breast cancer. The review suggests someone who drinks more than 50g of alcohol a day is 1.5 times more likely to develop these types of cancer compared to someone who doesn't drink.

For all of these associations there was a dose-response relationship, where increased consumption was linked with an increase in cancer risk. This applied to all types of alcoholic drinks. The highest risks were associated with heavier drinking. There was also some suggestion that the level of risk goes down over time when alcohol consumption stops.

Recent large studies have found uncertain evidence whether low to moderate consumption has a significant effect on total cancer risk. But given that this level of consumption is common in the general population, the author considers that it could still contribute to a significant number of cases.

Furthermore, they say there is no clear threshold of what constitutes a harmful level of alcohol consumption, and therefore no safe level of drinking with respect to cancer.

The author also suggests that confounding factors may be responsible for the protective effect between alcohol consumption and cardiovascular disease that has been found in previous studies. For example, this may be due to the potential bias caused by misclassification of former drinkers as abstainers.

The research went on to report that alcohol is estimated to be responsible for approximately half a million deaths from cancer in 2012 and 5.8% of cancer deaths worldwide, deeming it to be a significant public health burden.

How did the researchers interpret the results?

The author concluded: "There is strong evidence that alcohol causes cancer at seven sites, and probably others. The measured associations exhibit gradients of effect that are biologically plausible, and there is some evidence of reversibility of risk in laryngeal, pharyngeal and liver cancers when consumption ceases."

"The highest risks are associated with the heaviest drinking, but a considerable burden is experienced by drinkers with low to moderate consumption, due to the distribution of drinking in the population."

Conclusion

This narrative review aimed to summarise data from published biological and epidemiological research to discuss the strength of evidence that alcohol causes cancer.

The author gives their main finding as a link between alcohol consumption and cancer at seven sites, and also that the highest risks seem to be associated with heavier drinking. However, they state there's no "safe" drinking threshold and that low to moderate consumption still contributes to a significant number of cancer cases.

The biggest limitation of this review is that it doesn't appear to be systematic. The author provided no methods for how they identified and appraised the research they drew on. Despite referencing a number of large studies and reviews, this study and its conclusions have to be considered largely the opinion of the author following their appraisal of the evidence.

We don't know whether the review has considered all research relevant to the topic and is able to reliably quantify the risks of cancer – overall or at specific sites – associated with alcohol consumption.

An additional limitation to keep in mind is that this data mainly appeared to be from observational studies. These cannot prove cause and effect. The individual studies will likely have varied considerably in the additional health and lifestyle factors they took account of when looking at the links with alcohol. For example, smoking, diet and physical activity are all factors likely to be associated both with level of alcohol consumption and cancer risk.

As the author notes in particular, confounding factors may be responsible for the observed protective effect between alcohol consumption and cardiovascular disease.

Another limitation is that alcohol consumption is likely to be self-reported in the studies analysed, which may be inaccurate and lead to misclassification. For example, a potential bias that the author notes is classifying former drinkers as abstainers.

The author does consider the limitations of these observational findings, saying: "The limitations of cohort studies mean that the true effects may be somewhat weaker or stronger than estimated currently, but are unlikely to be qualitatively different."

But despite the methodological limitations of this review, it does support current understanding around this topic. Cancer Research UK also reports that alcohol can increase risk of these seven cancers and that there is no "safe" alcohol limit.

While we can't give a safe limit to drink when it comes to cancer, people are advised to follow current alcohol recommendations, which are to drink no more than 14 units per week and to spread your drinking over three days or more if you drink as much as 14 units a week.

Links To The Headlines

Even one glass of wine a day raises the risk of cancer: Alarming study reveals booze is linked to at least seven forms of the disease. Mail Online, July 22 2016

Alcohol is a direct cause of seven ​​forms of cancer, finds study. The Guardian, July 22 2016

Alcohol linked to at least seven types of cancer, study says, while 'health benefits are irrelevant'. The Telegraph, July 22 2016

Alcohol raises risk of seven different cancers, experts warn – even just one glass. Daily Mirror, July 22 2016

Alcohol causes seven types of cancer – and probably others, study finds. The Independent, July 22 2016

Links To Science

Connor J. Alcohol consumption as a cause of cancer. Addiction. Published online July 21 2016


 

 
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