Laird Harrison

March 01, 2014

SAN DIEGO — Their runny noses might drive them crazy, but people with allergic rhinitis are likely to outlive the rest of us, a new study suggests.

"We found that allergic rhinitis patients had a decreased risk of heart attack, a decreased risk of stroke and, most strikingly, a decreased risk of all-cause mortality," said lead investigator Angelina Crans Yoon, MD, from the Department of Allergy and Clinical Immunology at the Kaiser Permanente Los Angeles Medical Center.

"They were basically half as likely to die during the study period," she told Medscape Medical News.

Dr. Crans Yoon presented the results during a news conference here at the American Academy of Allergy, Asthma & Immunology 2014.

Previous research has suggested a complex relation between allergies and asthma and other aspects of health in general, and cardiovascular disease in particular. Inflammation plays a role in the disease, but not all immunologic responses are detrimental, said Dr. Crans Yoon.

Experiments in mice have suggested that type 1 T-helper lymphocytes (Th1) increase the risk for cardiovascular disease, whereas type 2 T-helper lymphocytes (Th2) decrease the risk.

Researchers looking at Kaiser patients in Northern California previously found an association between asthma and cardiovascular disease and an association between cardiovascular disease and allergies, but they used a broader category of allergies than we did, Dr. Crans Yoon explained.

 
They were basically half as likely to die during the study period.
 

Researchers studying data from the National Health and Nutrition Examination Survey (NHANES) found that people who tested positive for allergies were less likely to suffer cardiovascular events.

To explore the issue further, Dr. Crans Yoon and her team looked at a database of Southern California patients.

The cohort consisted of 109,229 patients with allergic rhinitis and 109,229 people without allergic rhinitis who were matched for age, sex, and ethnicity. It also consisted of 92,775 patients with asthma who were matched with a similar group without asthma.

The researchers examined ICD-9 codes in the Kaiser Permanente Southern California regional database to determine the incidence of cardiovascular and cerebrovascular events and all-cause mortality from January 1, 1995 to December 31, 2012.

They adjusted for diabetes, hypertension, cancer, autoimmune disease, renal disease, dyslipidemia, smoking, HIV status, and obesity.

Risk for acute myocardial infarction was 25% lower in patients with allergic rhinitis than in those without, risk for a cerebrovascular event was 19% lower, and risk for all-cause mortality was 49% lower. Risk for all cardiovascular events was similar in the allergic rhinitis and control groups.

In contrast, risk for all cardiovascular events was 36% higher in patients with asthma than in those without, whereas risk for cerebrovascular disease and all-cause mortality were similar.

This could be the result of a difference in phenotypes in asthma patients, said Dr. Crans Yoon. People whose asthma is caused by allergies could be at less risk for cardiovascular events than people whose asthma has other causes.

Table. Hazard Ratio for Each Condition, Compared With Control Groups

Outcome Allergic Rhinitis Group (95% Confidence Interval) Asthma Group (95% Confidence Interval)
Acute myocardial infarction 0.75 (0.71–0.80) 1.27 (1.19–1.35)
Cerebrovascular events 0.81 (0.77–0.84) 1.03 (0.99–1.08)
Cardiovascular events 0.97 (0.94–1.00) 1.36 (1.32–1.40)
All-cause mortality 0.51 (0.49–0.53) 1.00 (0.97–1.03)

 

In a secondary analysis, Dr. Crans Yoon and her team looked at the use of allergy and asthma medications. Patients who used more drugs were more likely to have a decreased risk for cardiovascular events, although it was difficult to account for over-the-counter medications purchased outside the Kaiser system.

"It's unlikely to be a specific effect of the drug," said Dr. Crans Yoon. "Patients are more likely to take the drugs because they have allergies, and they have decreased risk because they have allergies."

Why should allergic rhinitis decrease someone's risk for death? It could be that sufferers are more likely to have a Th2 than a Th1 response, "but I think it's more complicated than that," said Dr. Crans Yoon.

Another explanation could be that the immune systems of patients with allergic rhinitis are hyperalert, aggressively fighting off disease, as well as causing symptoms, when it is not necessary. More work is needed to evaluate that.

This research could lead to drugs that target specific immune responses, although such an approach is far in the future, said Dr. Crans Yoon. "There are investigational trials looking at certain cytokines that block Th1, especially in autoimmune diseases, but they have so many side effects and risks that I don't think it's something that will be widely used."

"It is too early to draw conclusions from the research," Todd Rambasek, MD, associate professor of allergy and immunology at the Ohio University Heritage College of Osteopathic Medicine in Athens, told Medscape Medical News.

"You wonder if it's association, not causation," he said. "I would guess that there's some selection bias going on. I would bet that people who present to the allergy clinic are of higher socioeconomic status than people who present with other problems."

Dr. Crans Yoon and Dr. Rambasek have disclosed no relevant financial relationships.

American Academy of Allergy, Asthma & Immunology (AAAAI) 2014: Abstract 811. Presented March 1, 2014.

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