Are allergies associated with heart disease?

Common allergies that bring on wheezing, sneezing and watery eyes could be next to join the list of factors linked to heart disease, suggests a large new study.

However, the researchers stress that the findings do not prove that allergies actually cause heart disease, the leading cause of death in the US.

To look for ties between common allergic symptoms and heart disease, Dr Jongoh Kim of Albert Einstein Medical Center in Philadelphia, Pennsylvania and colleagues analysed data on more than 8,600 adults aged 20 or older who participated in the National Health and Nutrition Examination Survey conducted between 1988 and 1994.

They found that common allergies and heart disease frequently paired up.

Rhinoconjunctivitis

18% of the adults reported wheezing and 46% suffered bouts of a stuffy nose or itchy and watery eyes, a combination of allergic symptoms known as rhino conjunctivitis.

Heart disease was present in 6% of the adults overall. It was found in 13% of wheezing cases, 5%of rhino conjunctivitis cases and 4% of people without any allergic symptoms.

After adjusting for other related factors, such as age and asthma, there was a 2.6-fold increased risk of heart disease with wheezing and a 40% increased risk with rhino conjunctivitis, compared to no allergies. The association was mainly seen in women younger than age of 50.

Kim suggests that the intermittent inflammation that comes with allergies may lead to the thickening of artery walls, and eventually heart disease. It could also be that some people simply carry genes that are linked to the development of both allergies and heart disease, Kim added.

Allergies may lead to heart disease

But given the nature of the study, the researchers are not yet able to say if allergies truly have a role to play in the development of heart disease.

Much more study is needed to "clearly see" whether there is a cause and effect relationship, Kim said. "And even if there is a cause and effect, it is not clear whether treating allergic disease can reduce the risk," Kim noted.

Dr Carlos Iribarren, a research scientist at Kaiser Permanente in Oakland, California, who was not involved in the study, said: "Because common allergic symptoms are highly prevalent in asthma, these findings are consistent with prior research conducted at Kaiser Permanente showing a significant association between self-report of asthma and future risk of coronary disease, particularly among women."

Caution against jumping to conclusions

But he cautioned against jumping to any "premature conclusion, consumer-level advice or public health recommendation based on these findings."

Iribarren also noted that study subjects with allergy (particularly wheezing) had a greater burden of heart disease risk factors (for example, smoking, obesity, high blood pressure), compared with allergy-free subjects. Therefore, "allergists, internists and cardiologists should be made aware of this link and intensify cardiovascular risk profile assessment and modification among patients presenting with allergy."

Dr Viola Vaccarino, of the Rollins School of Public Health at Emory University School of Medicine in Atlanta, told Reuters Health that the current findings also fit with studies she and her colleagues have done, "finding of an association of chronic inflammatory conditions such as asthma and other allergic conditions with coronary disease in women but not in men."

Women may have a stronger inflammatory response

"Young women may have a stronger inflammatory response due to allergic conditions than men, perhaps due to oestrogens," explained Vaccarino, who was also not involved in the current study.

It's also possible, she said, that "people with history of coronary heart disease are sicker with respiratory symptoms just because they have coronary heart disease and not vice-versa."

"I really wouldn't draw any strong message from this study," said Vaccarino. "I would not alarm the public with the news that common allergic symptoms (other than asthma) increase the risk of coronary heart disease in women, based on this study." (Reuters Health/ August 2010)

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