Tad Davison asked:
I suffer from hayfever. I was once told that my allergy would in time give way to a cardiovascular disorder, as those who experience allergies in early life, are more susceptible to coronary artery disease.
I didn't dismiss the assertion out of hand, I just kept it in mind, but it didn't seem feasible in my case as I didn't smoke, and at that time, wasn't carrying a lot of extra weight.
But, alas, as I got into my 30s, I started to gain weight, and my arteries clogged up, so my question is this, is it a proven medical fact that allergies do indeed give way to coronary artery disease, or is there no correlation whatsoever?
Chris - This is an interesting question. You have to be very careful how you phrase the statement because there's a difference between association and causation. Does having an allergy cause heart disease or does one go hand in hand with the other?
At the moment, we can't say.
One study that was done and it was done by a guy called Jongoh Kim. Heís at the Albert Einstein Medical Centre in Philadelphia and what he did was to look at some data that are being collected for a nutritional study and they'd asked people whether they have allergies and rhinitis Ė that means runny nose, itchy eyes. They'd also looked at whether people had cardiovascular disease, but they haven't actually looked at the correlation between the two and that's what he did.
It turned out that people who had reported symptoms of allergy like hay fever or wheezing, had a 2Ĺ times greater chance of also having or developing heart disease.
Now, that may suggest there is an association between the two; it doesnít tell us that allergies cause heart disease.
But it might be linked by inflammation because we know that heart disease is an inflammatory condition of arteries and we also know that diseases or conditions that increase the overall inflammation in the body accelerate cardiovascular disease.
Gum disease is strongly linked as a risk factor for heart disease, probably because if you have inflammation going on in your gums, you secrete into the bloodstream various inflammatory stimuli and inflammatory mediators, and this triggers the process of inflammation in the walls of arteries and accelerates arterial disease.
It may be that the periodic inflammatory bursts you get with things like wheezing, asthma, hay fever, also increase the general inflammatory tone in your body. And therefore, if there is atherosclerosis - arterial damage - going on, this is going to accelerate a bit in people with those symptoms who also have a risk of heart disease; therefore, you see that association.
But, itís one study and no one has yet got quite to the bottom of it.
Dominic - I guess itís very difficult to distinguish causation from correlation.
Chris - Well thatís exactly right. This is an association. To prove causation, youíve got to show there's a dose-dependent effect, for starters. So, you'd have to show that people who had worse allergies had worse heart disease and I donít think thatís very easy to do...