THE DETAILS: The authors used data from 2,392 people enrolled in an asthma study in Rochester, Minnesota, half of whom had asthma and the other half did not. They compared the incidence of irritable bowel disease, rheumatoid arthritis, diabetes, and coronary artery disease among those with asthma and those without, and found that with each disease, people with asthma had higher rates. The relationship was strongest with coronary artery disease, in which people with asthma had a 59 percent higher incidence, and with diabetes, in which people with diabetes had a 68 percent higher incidence. Rates of irritable bowel disease and rheumatoid arthritis also increased in asthma patients, but, says lead author Young J. Juhn, MD, pediatrician at the Mayo Clinic in Rochester, the associations weren't as strong.
WHAT IT MEANS: Though it may seem logical to think that an inflammatory condition like asthma would be accompanied by other inflammatory conditions, such as diabetes and cardiovascular disease, Dr. Juhn says his results came as somewhat of a surprise, based on the way our immune systems work. "Our immune systems have something called T-helper cells. T-helper 1 cells determine pro-inflammatory conditions, such as coronary artery disease, irritable bowel disease, rheumatoid arthritis, and diabetes, while T-helper 2 cells are considered to play a very important role in determining allergic disorders, such as asthma," he says. Because our immune systems work to maintain a balance between the two types, he adds, it would stand to reason that people with asthma would actually have lower rates of those diseases. But that's not what his study found. "At this point, we think there may be some common immune mechanisms underlying this association," he says, most likely something genetic or environmental.
Dr. Juhn's study is one of very few analyzing the relationship between asthma and other inflammatory diseases, so he says that doctors are still in the early stages of understanding what all this means, especially when it comes to solving the problem. "If we find that the association isn't genetic, then, potentially, controlling your asthma may be helpful in reducing your risk of these other pro-inflammatory conditions," Dr. Juhn says. "But if it the underlying mechanism is genetic, the association may be independent from asthma control."
The most important thing to remember, Dr. Juhn says, is that if you do have asthma, pay attention to any out-of-the-ordinary symptoms you may experience. "This study could be very important for early detection," he says. "If patients experience nonspecific chest pain, their doctors may think it's just their asthma, but it could be the beginning of heart disease."
To help you out, here's a list of some common symptoms associated with each condition.
• Coronary artery disease: Chest pain and shortness of breath are the two primary signs of coronary artery disease, which, unfortunately, makes it easy to confuse with asthma. However, pay attention to where you feel pain. Coronary heart pain may be felt under your breastbone, or in your neck, arms, stomach, or upper back. The condition is also accompanied by weakness and fatigue. The most serious symptom is, of course, having a heart attack. And check out these other six unusual signs of heart disease, such as excessive snoring and sexual dysfunction.
• Diabetes: People with type 2 (adult-onset) diabetes typically exhibit very few symptoms, but those who do may notice things like unusual thirst or hunger, blurred vision, frequent infections, and tingling or numbness in your hands or feet. A blood-glucose test will tell your doctor whether you have diabetes, and recently, doctors developed an easy online test that will allow you to assess your diabetes risk based on things like family history and weight. It doesn't include asthma as a potential risk factor, but the test should help you figure out if you're already at an increased risk.
• Rheumatoid arthritis: This is a disease that's stumped a lot of doctors, as the causes of RA remain unknown and symptoms can be vague and sporadic. But you might have rheumatoid arthritis if your joints ache or swell or are tender to the touch (it usually begins in the smaller joints, such as those in your hands and feet), you feel firm bumps of tissue under the skin on your arms, or have morning stiffness that lasts longer than the morning.
• Irritable bowel disease: If you experience a lot of abdominal discomfort, cramping, or bloating, you could be suffering from irritable bowel disease or the less-severe irritable bowel syndrome, or IBS. As with rheumatoid arthritis, there isn't a known cause, but it is an autoimmune condition that seems to be exacerbated by environmental causes, including stressful jobs.