CANCER, HEART DISEASE, dementia, diabetes: In the lexicon of ageing and disease, these are some worrisome words. But researchers have suspected for years that all of these health issues, and more, have at their heart one common trigger: chronic low-grade inflammation. And now they may finally have proof.
In 2017, researchers in Boston reported on a clinical trial with more than 10,000 patients (mean age: 61) in 39 countries that tested whether an anti-inflammatory drug, canakinumab, could lower rates of heart disease. They discovered that it could, but they also found that it reduced lung cancer mortality more than 67 per cent, and reports of gout and arthritis (conditions linked to inflammation) also fell.
“Inflammation plays a role in everyone’s health,” says Dr Dana DiRenzo, a rheumatologist and instructor of medicine at Johns Hopkins University School of Medicine in Baltimore, USA. When inflammation levels increase, so does the risk of disease. But understanding inflammation can be tricky because, when you get a disease, inflammation levels naturally increase as your body fights the condition. Inflammation, in other words, is both good and bad.
When is inflammation a problem?
When you catch the flu and your body temperature rises to fight the virus, that’s a form of acute inflammation. So is the redness and swelling that occur when you sprain your ankle. The process is a temporary, helpful response to an injury or illness. It provides the healing chemicals and nutrients your body needs to repair the damage. Once the danger goes away, so does the inflammation.
Chronic low-grade inflammation, on the other hand, is a slow, creeping condition sustained by a misfiring of the immune system that keeps your body in a constant, long-term state of alert, says Dr Robert H. Shmerling, teaching clinician in the department of rheumatology at Beth Israel Deaconess Medical Center in Boston, USA.
Over time, inflammation damages healthy cells. Here’s why: When cells are in distress, they release chemicals that alert the immune system. White blood cells then flood the scene, where they work to eat up bacteria, viruses, damaged cells and debris from an infection or injury. If the damage is too great, they call in backup cells known as neutrophils, which are the hand grenades of the immune system—they blow up everything in sight, healthy or not. Each neutrophil has a short lifespan, but in chronic inflammation, they continue to be sent in long after the real threat is gone, causing damage to the healthy tissue that remains. The inflammation can start attacking the linings of your arteries or intestines, the cells in your liver and brain or the tissues of your muscles and joints.
This inflammation-caused cellular damage can trigger diseases like diabetes, cancer, dementia, heart disease, arthritis and depression. And because it’s low grade, “its slow and secret nature makes it hard to diagnose in day-to-day life,” says Roma Pahwa, a researcher for the National Institutes of Health who specializes in the inflammatory response. “You have no idea it’s even happening until those conditions show symptoms.”
Causes of chronic inflammation
When you contract a chronic infection like hepatitis C or Lyme disease, your body responds with inflammation that also lingers for a long time. In fact, it’s often the chronic inflammation, not the viruses themselves, that causes much of the long-term damage related to these diseases.
Genetics can be a factor. In some cases, the genes related to these health issues can be turned on by inflammation: Diabetes and cancer are two genetically related diseases that can be triggered by it. In other cases, the gene itself leads to a misfiring of the immune system that causes the inflammation in rheumatoid arthritis, multiple sclerosis, lupus and other diseases.
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