This forum is about wrong numbers in science, politics and the media. It respects good science and good English.
Has anyone seen this little clip?
"Brushing your teeth isn't only good for your dental health - it could also save you from a heart attack, reports the Daily Mail. A new study, based on 11,000 people in Scotland, has found that those who rarely or never brush their teeth are 70% more likely to suffer heart disease than those who brush twice a day, even after factors such as smoking and obesity are taken into account. The report, published in the British Medical Journal, concedes that more work is needed to confirm that poor oral hygiene causes heart disease, rather than being merely a risk marker; however, it is known that gum infections cause inflammation, which is in turn strongly associated with a higher risk of cardiovascular disease."
I wonder what other risk factors there are between people who care about oral hygiene and those that don't?
This is a typical Junk Science story. In any study there will always be a large number of confounding factors, that is factors that can significantly affect what is being seen. When these are not accounted for or acknowledged in any way they muddy the waters between any cause and effect that is going on.
It would appear obvious to most thinking people that those who neglect one part of their anatomy, i.e. their teeth, are probably most likely to ignore other aspects of their health as well. Bad teeth can therefore often be an effect rather than a cause. If the researchers haven’t acknowledged or considered this then I would suggest they are responsible for poor research.
The real key phrase here is “… more work is needed”, or just plain old “… gimmee more money”! It is amazing how often this phrase creeps into stories like this and always triggers my suspicions. More work will always be needed by those who do research for a living. When did you ever read one that said no further benefit could be achieved from following this line of research.
Yep, the old "More research is needed" meme. Amply covered in our bending guru's works, this aspect gets a specific hammering in Ben Goldacre's "Bad Science", which I've just finished reading and can strongly recommend. Rather sadly, he doesn't refer to "S,WN" at all. As he is a Guardian columnist I should be very interested to see his views on CAGW, as most of his criticisms directed at health matters (he is an NHS doctor) apply equally to the Global Warming scam.
In this case, quite clearly we are looking at correlation if not a data dredge. Let's face it, for centuries people didn't brush their teeth (yes, I know they're all dead now!) so it would be astonishing if failing to do so was fatal.
Actually this theme is not complete junk (though the report might be).
Oral hygiene can affect the heart through infective endocarditis. Of the internal organs the heart is particularly vulnerable to infection because, somewhat ironically, it is rather poorly supplied with blood (this is also the reason that it's the most common target for infarction), and as a result the immune response to an infection of the heart is weak. Most typically the mitral valves are affected.
Any infection reaching the heart has to enter through the bloodstream, thus endocarditis is common in hospitalised patients needing drips, central lines and the like. But the most common place for infections to enter the bloodstream is the mouth, because that's where you have the highest concentration of pathogenic bacteria alongside the greatest probability of injury which allows said bacteria to enter the bloodstream. For the same reason, tooth abscesses are treated aggressively, because septicaemia can result otherwise.
This is not to say that there would be any increased risk of a "heart attack" (coronary artery thrombosis) following endocarditis or stenosis that would in turn increase risk - this is about one specific form of heart disease, but it is very easy for the media to confuse the issue as they have done here.