“Brushing your teeth twice a day could save you from a heart attack”, the Daily Mail has reported.

Its story is based on a study from Scotland, which looked at the potential association between how often people brushed their teeth and their risk of cardiovascular disease. It found that people who never or rarely brushed their teeth were 70% more likely to get cardiovascular disease than those who brushed their teeth twice a day. People with poor oral hygiene also had higher blood levels of specific chemical marker of inflammation, which is thought to increase the risk of developing heart disease.

This type of research cannot prove that poor oral hygiene causes cardiovascular disease as it may simply be that people who follow a healthy lifestyle also brush their teeth more. Equally, the results of this analysis were adjusted to account for this likelihood. The study is in line with other research suggesting a link between periodontal (gum) disease, inflammation and cardiovascular disease. Overall, this study does suggest that brushing may reduce the risk of cardiovascular disease in addition to the clear benefits of preventing tooth decay and keeping gums healthy.

 

Where did the story come from?

The study was carried out by researchers from the Department of Epidemiology and Public Health, University College London. It did not receive any specific grants from any funding agencies. The study was published in the peer-reviewed British Medical Journal.

Newspaper reporting of this research was generally fair, with most stories reporting the main result accurately – that people who reported poor oral hygiene had a 70% increased risk of cardiovascular disease, compared to those who brushed their teeth twice a day. The BBC correctly reported that poor oral had not been proved as a cause of heart attacks, as this study has found only an association between the two. The Daily Mail’s headline, “Clean your teeth twice a day to keep a heart attack at bay” ignored other established risk factors for cardiovascular disease, such as obesity and smoking.

 

What kind of research was this?

This study was based on data from the Scottish Health Survey, a cross-sectional survey undertaken every three to five years, of a nationally representative sample of the general population in Scotland.  Over the past two decades there has been increasing interest in a possible link between periodontal disease (i.e. gum disease and inflammation tissue surrounding teeth) and cardiovascular disease.  Most periodontal disease is associated with inflammation. It is now thought that inflammation in the body (including mouth and gums) is also associated with damage to arteries, which can in turn lead to heart disease.

While some smaller studies have looked at the possible association between confirmed periodontal disease and cardiovascular disease, this is the first large population study to look at self-reported oral hygiene and the risk of both inflammation and heart disease. Although this type of study on its own cannot prove cause and effect, the size of the study and the fact that the participants were followed for more than eight years on average makes the findings notable.

 

What did the research involve?

Researchers combined data from three of the Scottish surveys undertaken between 1995 and 2003, involving 11,869 men and women with an average age of 50 years. Survey interviewers and nurses  had visited Scottish households and collected data on demographics and lifestyle. This includes risk factors for cardiovascular disease, such as smoking, physical exercise, blood pressure and medical family history. People taking part were also asked how often they visited the dentist and how often they brushed their teeth – twice, once or less than once a day.

To find out what happened to participants over time, each survey was linked to a database of hospital admissions and deaths, which was followed up until December 2007. The study researchers used the database to look at the underlying causes at both the fatal and non-fatal cases of cardiovascular disease, heart attacks and admissions for bypass surgery. Blood samples were collected from 4,830 people who consented, and they were laboratory tested for two proteins called C reactive protein and fibrinogen, both of which are markers for inflammation.

The researchers then used established statistical techniques to analyse this body of information. They calculated the risk of heart disease and death in relation to frequency of toothbrushing, plus the association between oral hygiene and levels of inflammatory markers. Their modelling made adjustments to account for the influence of major factors that might contribute to people’s risk, such as smoking, obesity and family history. The figures were also adjusted for age, sex and socioeconomic group.

 

What were the basic results?

The researchers followed-up participants for an average of about eight years. Among the 11,869 people followed there were 555 (4.7%) cases of cardiovascular disease, of which 170 were fatal.  Most of these people were diagnosed as having coronary heart disease.

Importantly, the researchers found that:

• When all other possible influences had been taken into account, people who reported poor oral hygiene (who never or rarely brushed their teeth) had a 70% greater risk of cardiovascular disease, compared with those who brushed their teeth twice a day. (Hazard ratio (HR) 1.7 (95% confidence interval[CI] 1.3 to 2.3)
• By modelling the link between toothbrushing and inflammatory markers, the researchers say that the fully adjusted model shows a reduced rate of brushing is linked to higher levels of the two markers for inflammation - C reactive protein (ß 0.04, 95% CI 0.01 to 0.08) and fibrinogen (ß 0.08,95% CI  –0.01 to 0.18). This suggests a significant association.

The study also found that other known risk factors for cardiovascular disease, such as smoking and diabetes, had a stronger association than poor oral hygiene. For example, people who smoke had more than double the risk of cardiovascular disease than non-smokers.

Encouragingly, the researchers found oral hygiene to be generally good, with about 62% of participants reporting regular (at least every six months) visits to a dentist and 71%  reporting good oral hygiene (brushing teeth twice a day). Participants who brushed their teeth less often than twice a day were slightly older, more likely to be men, and of lower social status. They also had a high prevalence of risk factors including smoking, physical inactivity, obesity, hypertension and diabetes.

How did the researchers interpret the results?

The researchers conclude that poor oral hygiene is associated with a higher risk level of cardiovascular disease, and also with low grade inflammation. However, they point out that cause and effect is not yet proven. The results confirm previous findings that have found a link between gum disease (known to be mainly caused by poor oral hygiene) and cardiovascular disease. Experimental studies, they say, are now needed to confirm whether poor oral hygiene is a cause of cardiovascular disease or a marker for other risk factors, such as smoking.

Doctors, say the researchers, should be alert to the possibility that oral hygiene causes inflammation, and patients should be told that improving oral hygiene is beneficial, regardless of any relation to heart disease.

 

Conclusion

This is the first large study to look at a possible association between self-reported toothbrushing habits and the risk of cardiovascular disease. Its findings are in line with other studies showing a link between gum disease, inflammation and heart disease, although, as the researchers point out, it cannot prove cause and effect. Its analysis used data gathered from a large, rigorously-designed population survey that was linked to patient databases and followed people for a reasonably long period of time. It has also used recognised statistical methods.

However it should be noted that:

• although the study took account of other things that might influence whether people developed cardiovascular disease (such as smoking), it is possible that the results may have still been influenced by factors that were not measured or incompletely measured.
• Toothbrushing habits were self-reported, which could increase the chance of obtaining inaccurate data. The study did not look at clinical data on gum disease, although, as the researchers point out, previous research has shown a correlation between self-reported gum disease and clinical evaluations of the condition.

Another key point is that a 70% increased risk may sound quite large, but that it may be more useful to consider risk in terms of absolute rates, i.e. the actual numbers of people who might have been affected. Using the unadjusted figures:

• 59 people out of 538 (10.9%) who brushed their teeth less than once a day developed cardiovascular disease over about eight years
• 188 people out of 2,850 (6.6%) who brushed their teeth once a day developed cardiovascular disease over about eight years, and
• 308 people out of 8,481 (3.6%) who brushed their teeth twice a day developed cardiovascular disease over about eight years

This study did not establish a cause-and-effect relationship between oral health and cardiovascular disease. However, in theory these figures would equate to about 73 cardiovascular events in every 1,000 (10.9% minus 3.6%) being prevented by brushing teeth twice a day for eight years instead of brushing less than once a day (unadjusted). Expressed another way, only 14 people would need to do this for eight years to prevent one event (Number needed to treat =14). The analysis suggests that these people would probably have other healthy habits.

It is important to remember that good oral hygiene is important to help prevent gum disease and tooth decay, regardless of its effect on cardiovascular risk. Equally, following a healthy diet and doing regular physical activity are all important, proven ways to prevent the risk of cardiovascular disease.

Links To The Headlines

Brushing teeth 'halts' heart disease. BBC News, May 28 2010

Clean your teeth twice a day to keep a heart attack at bay. Daily Mirror, May 28 2010

Cleaning teeth boosts heart. Daily Mirror, May 28 2010

Links To Science

de Oliveira C, Watt R, Hamer M. Toothbrushing, inflammation, and risk of cardiovascular disease: results from Scottish Health Survey. BMJ 2010;340:c2451

“Eating lots of nuts and olive oil may be harmful for some people,” reported the Daily Mirror. The Daily Telegraph said that some heart attack patients may have genetic mutations that mean “the diet increases their risk of suffering further cardiac problems”.

The newspapers’ emphasis on the relevance of the Mediterranean diet here is misleading. The study did not look at diet and HDL levels, but attempted to define groups of people who are at higher risk of having a heart attack.

Researchers analysed the risk of heart-attack patients having a second heart attack. Those most at risk had higher overall levels of high-density lipoprotein (HDL) cholesterol and inflammatory proteins, and that they also had particularly large HDL particles and some associated genetic differences.

Many previous studies have found a Mediterranean-style diet to be associated with a reduced risk of heart attack. Claiming that the opposite may be true for some people could be confusing. 

 

Where did the story come from?

The study was carried out by researchers, pathologists and cardiologists from the University of Rochester School of Medicine and Dentistry, and geneticists from the Southwest Foundation for Biomedical Research in Texas.

The study was supported by grants from the National Institutes of Health. It was published online in the medical journals Arteriosclerosis, Thrombosis, and Vascular Biology.

Neither the Mirror nor the Telegraph’s headlines reflect the findings of the research. The study did not look at diet, but at defining groups of people who are at higher risk of having a heart attack.

 

What kind of research was this?

This cross-sectional study in people who had already experienced a heart attack investigated how high levels of high-density lipoprotein (HDL), C-reactive protein (CRP) and other inflammatory proteins affected the risk of having a recurrent (second) heart attack.

HDL carries cholesterol away from the cells and back to the liver, where it is either broken down or passed from the body as a waste product. For this reason, it is referred to as 'good cholesterol' and, in tests, higher levels are usually considered to be better.

CRP is produced by the liver. If there is more CRP than usual, there is inflammation in your body. A CRP test can indicate inflammation in the blood stream.

The researchers also investigated the roles of other inflammatory proteins and, specifically, a protein called cholesteryl ester transfer protein (CETP) and its associated gene. This protein is involved in the regulation of cholesterol transport in and out of the proteins that carry fats around the body. The researchers say that previous research has found that some people with higher HDL cholesterol levels may actually be at higher risk of a second heart attack. This research was aimed at investigating whether CETP could be responsible for this.

The study was well conducted and designed to answer the questions the researchers set. However, its relevance to the diets of a general population without known heart disease and most people after a heart attack has been overstated by the press.

 

What did the research involve?

The researchers had data on 767 people without diabetes who had enrolled in another study of heart attacks called the THROMBO post-infarction study. Patients were enrolled after their first heart attack and followed up for recurrence for over two years.

The researchers followed these people and recorded the next coronary event, such as cardiac death, heart attack or unstable angina (worsening angina pain that needed a hospital admission).

They tested the patients’ blood markers two months after the first heart attack, looking for a wide range of protein types attached to cholesterol or involved in clotting and inflammation. These included ApoB, total cholesterol, lipoprotein-associated phospholipase A2, apolipoprotein A-I, HDL-C, triglyceride, glucose, insulin, lipoprotein(a), plasminogen activator inhibitor- 1, CRP, von Willebrand factor antigen, fibrinogen, D-dimer, factor VII, factor VIIa and serum amyloid A.

The researchers also separated the HDL particles according to size and sequenced the CETP gene so that they could identify which patients had one of three genotypes: B1B1, B1B2 or B2B2. CETP as a protein is involved in the regulation of cholesterol transport in and out of the proteins that carry fats around the body.

The researchers used statistical modelling techniques to test the links between the two main blood tests, HDL and CRP, the different sized HDL molecules and the chance of carrying the CETP gene variants.

 

What were the basic results?

Clinical and laboratory results, including the genotyping, were available for 680 (88.7%) of the 767 patients in the study population. Average age was 58 years, 77% were men and 79% were white. In general, patients were overweight, with high triglycerides and slightly low HDL-C levels.

The researchers found they could define a subgroup of patients who had high HDL and CRP levels and who also had larger HDL particles and a higher risk of recurrence of heart attack.

In this high-risk subgroup, there was over twice the assumed risk of recurrent heart attack for those who showed less CETP activity compared with those with greater activity of this protein (hazard ratio 2.41, 95% confidence interval 1.04 to 5.60).

 

How did the researchers interpret the results?

The researchers say that patients with high HDL-C and C-reactive protein levels after a heart attack show increased risk for recurrent events. They say they have shown that CETP genotypic differences may potentially be related to this increase in risk.

They call for future studies to characterise the altered HDL particles from such patients and untangle the complex physiology related to inflammation and HDL particle remodelling.

 

Conclusion

This study was designed for a different purpose to that suggested by the controversial headlines.

The researchers used a new type of data modelling to see if heart attack patients at high risk of recurrence, defined by high levels of modified HDL and CRP, could be better identified by other tests. They investigated whether a genetic test for a protein known to be involved in lipid transport could be useful in identifying high-risk patients and found that it could.

The study had a few limitations including the fact that additional risk-factor data, including diet, physical activity, alcohol consumption, blood pressure, smoking status, mental status and social support, were lacking and were not adjusted for in the results.

The main mistake in the news reporting has been the misplaced emphasis on the relevance of the Mediterranean diet to this study. The research did not look at diet or for links between food intake and HDL levels. Many previous studies have found a Mediterranean-style diet to be associated with a reduced risk of heart attack. Claiming that the opposite is now true could be misleading confusing.

Links To The Headlines

Mediterranean diet 'could raise risk of heart attacks'. The Daily Telegraph, May 27 2010

When good fats go bad. Daily Mirror, May 27 2010

Links To Science

A lack of exercise is “worse for health than being obese”, The Daily Telegraph has reported. It quotes an expert as saying that lack of fitness is the root cause of more illness than excess body fat.

The Telegraph’s story is based on one of a pair of opinion pieces by medical experts with opposing views about how to improve public health and reduce the risk of major health problems, such as diabetes and stroke. One article argues that health policy should focus purely on increasing people’s physical activity rather than worrying about weight loss. The other article maintains that treatment to prevent and reduce obesity is crucial, and that radical changes to diet and lifestyle are needed.

The Telegraph’s story emphasises the view that physical activity needs to be encouraged, but the newspaper only gives a cursory mention to the other viewpoint, that reducing  obesity should be given priority. Together, these arguments illustrate the dilemma behind forming public health policy, but they do not diminish the fact that staying active and eating healthily are both important health goals for individuals to pursue.

 

Where did the story come from?

The news comes from a pair of opinion-based pieces debating the priorities for public health policies:

• The first is by Dr Richard Weiler, a specialist registrar in sport and exercise medicine at Charing Cross Hospital, London, and colleagues. He argues that health policy should focus on fitness rather than fatness.
• The second is by Associate Professor Timothy Gill, principal research fellow at the Boden Institute of Obesity, Nutrition and Exercise, University of Sydney, and colleagues. He argues that health policy should focus on fatness rather than fitness.

The opinion pieces were both published in the same issue of the peer-reviewed British Medical Journal.

 

What kind of research was this?

The two papers were a ‘head to head’ feature, in which two experts in the field put forward their opposing opinions about a topical issue. In this case, the issue was whether health policy should focus purely on reducing physical inactivity or target the prevention and treatment of obesity.

Both sets of experts discussed their professional opinions and experiences, supporting these views by referencing relevant medical literature.

 

What evidence was presented?

In the first paper, Dr Weiler argues that improving physical activity is associated with improvements in health, even if no weight is lost. A lack of physical activity presents “one of the greatest health threats facing developed nations today”, he believes, particularly given that 95% of the UK population does not achieve recommended amounts.

To support his view, he cites several large cohort studies, which found that physical inactivity, rather than obesity, is the cause of many major life-threatening disorders, including cardiovascular disease, diabetes, dementia, stroke, mental health problems and cancer. He draws particular attention to one synthesis of systematic reviews, which has found that physically active people have a reduced risk of many of these disorders.

Dr Weiler goes on to cite evidence that cardiovascular fitness, which is developed and maintained by regular physical activity, is a better predictor of mortality than obesity. He also cites a Scottish Health Survey, which found that even when body mass index is taken into account, all types of physical activity are linked to reduced mortality.

He also argues that drugs and bariatric surgery for obesity, which are now becoming more commonly used, have serious risks and do not have the same health benefits as physical activity. Dr Weiler also cites a report suggesting that since the 1980s we have become less active because of our environment. Policy makers, he argues, should look at changing our built environment, patterns of land use and transport infrastructure in order to encourage greater physical activity.

In the second paper, Professor Gill argues that although the promotion of physical activity is important, ignoring the problem of obesity and poor diet is unlikely to bring overall improvements in health. To that end, he argues that physical inactivity is just one marker of a society’s overall “obesogenic lifestyle”. He cites a report from the World Health Organization in 2003, which he says examined a wide range of evidence and identified poor-quality nutrition as a major contributor to obesity and other health problems, such as tooth decay, high blood pressure and various cancers.

He also cites evidence that the health risks of obesity are associated with more severe chronic disease and early death. He believes that physical activity alone, while able to reverse some of these negative health consequences, is not enough to counteract all of them.

Professor Gill says that people who are obese need access to high-quality treatment and well-trained professionals, but that obesity services and management are often under-resourced. He says that although previous programmes on obesity have had limited success, there is now evidence, including systematic reviews, that small group- and community-based lifestyle programmes can be effective.

Professor Gill also further emphasises the need for improved urban planning – for example, more cycle lanes, improved public transport and increased access to green space. But he also advocates changes in local food production and food pricing strategies as a way of encouraging healthier eating.

 

What conclusions did the authors make?

Dr Weiler concludes that for health policy to focus on weight loss is “largely misleading” and that undesirable health risks can be greatly reduced by increasing physical activity, which leads to improved fitness, even in the absence of weight loss.

Professor Gill says that a focus on reducing obesity through a broad range of actions, including diet and behavioural issues, is likely to be more effective than focusing solely on physical inactivity.

Interestingly, both specialists agree that there is a need for wider programmes to improve the environment and encourage changes in behaviour.

 

Conclusion

The issue of physical inactivity and obesity are both major public health problems, which policymakers and professionals must work hard to address. This pair of “head to head” articles is a valuable contribution to the debate over how best to tackle the overlapping problems of obesity and inactivity. Both authors write convincingly about the subject, and both cite good evidence to support their opinions as to how the problems should be addressed. This debate highlights the difficulty in agreeing on the best approach to public health problems, particularly when there is good evidence for different policies.

Both authors agree that reducing the risk factors for major illnesses such as cardiovascular disease, cancer and diabetes is crucial to public health, although they disagree about whether the emphasis should be on physical activity alone or whether it should include the prevention and treatment of obesity. They both agree that the wider environment needs to change in order to encourage individual behavioural change.

It is also important to note that this debate is about the merits of different health policies and how to best allocate finite health resources. The articles are not intended to offer advice on individual behaviour or to decide whether a person’s inactivity poses a greater or lesser risk than their obesity. Indeed, there is no reason why individuals cannot tackle both problems by adopting a healthy diet, maintaining a healthy weight and getting 30 minutes of moderate-intensity physical activity every day.

Links To The Headlines

Lack of exercise 'worse for health than being obese'. The Daily Telegraph, May 26 2010

Links To Science

Weiler R, Stamatakis E, Blair S et al. Should health policy focus on physical activity rather than obesity? Yes. BMJ 2010;340:c2603