Chronic inflammation linked to host of ailments, but it can go unnoticed
Inflammation can be a visible part of how your body fights illness or injury. If you’ve ever sprained your ankle, you know this. But it also can be much less obvious, and researchers are still unraveling its mysteries. Some of what they’ve learned has intriguing potential for treating heart disease and other illnesses.
“Inflammation is a complex reaction triggered by your immune system when it fights off invaders such as a virus or what it thinks are invaders,” said Dr. Jun Li, a research scientist in the departments of nutrition and epidemiology at the Harvard T.H. Chan School of Public Health in Boston.
Inflammation is considered either acute or chronic.
When it’s responding to an injury or intruder — such as bacteria, viruses or a splinter — it’s acute. The immune system releases chemicals that cause small blood vessels to expand, allowing more blood to reach injured tissue. Chemicals released there attract immune system cells, where they help healing.
Dr. Paul Ridker, director of the Center for Cardiovascular Disease Prevention at Brigham and Women’s Hospital in Boston, said flu is an example of acute inflammation.
“Your muscles ache, your joints ache, you feel cruddy,” Ridker said. “That’s because all the immune cells in your body are talking to each other, saying, ‘Hey, there’s a foreign invader here. We’ve got to attack, and we’ve got to get rid of it.’ That’s a massive immunologic response, driven by these things called cytokines.”
Cytokines are messages immune cells use to speak to one another and coordinate an immune response.
Acute inflammation might be treated with an over-the-counter painkiller like ibuprofen or with steroids.
If inflammation keeps simmering at a low level, it’s chronic. This can be triggered by smoking, obesity and chronic stress. Chronic inflammation has been linked to cancer, arthritis, diabetes and heart disease.
“What we’re talking about is a very, very low-grade inflammatory response that people don’t notice,” Ridker said.
In the 1990s, Ridker led studies that associated this chronic inflammation with the risk of heart attack and stroke. He’s also led trials that show lowering such inflammation could protect against heart problems at levels similar to what’s provided by statins, the cholesterol-lowering drugs.
Only two anti-inflammatory drugs have been shown to provide this heart-protecting benefit.
One of them, canakinumab, was studied for heart disease and now is being developed as a lung cancer drug. The other is colchicine, an inexpensive drug used to treat gout. In a 2019 trial, low-dose colchicine reduced the risk of serious cardiovascular complications after a heart attack by 23%.
Ridker said cardiologists have been prescribing colchicine to people whose heart disease keeps progressing despite aggressive cholesterol-lowering treatment and healthy lifestyles.
Screening for an inflammation marker called C-reactive protein, CRP, can spot people who might benefit from such treatment.
“Some people have a more active, underlying cytokine immune system,” Ridker said. “They don’t know it. They can’t feel it. Their doctors don’t know it. And if you’re not measuring CRP the same way your doctor measures LDL cholesterol, you just don’t know if you’re one of those people who has this advanced immune response.”
Ridker expects such screenings to become standard practice. For now, he said, “Most doctors are not measuring the inflammation at all. So patients have to ask for it.”
Li said COVID-19, which can trigger a massive inflammatory response, has focused more attention on inflammation. Studies are investigating links between inflammation and the severity and prognosis of coronavirus infection as well as other chronic illnesses.
She also has looked at how what you eat affects low-level inflammation. In November, Li published a study in the Journal of the American College of Cardiology linking high-inflammatory diets to heart disease and stroke risk. Studying more than 210,000 people for up to 32 years, Li’s team found those who ate pro-inflammatory diets had a 46% greater risk of heart disease and a 28% greater risk of stroke than those who ate anti-inflammatory diets.
Inflammation-fighting foods include leafy green vegetables, yellow vegetables, whole grains, coffee, tea and wine. Refined grains, sugary drinks and processed, red and organ meats are associated with higher inflammation. A typical healthy diet that’s also antiinflammatory is the Mediterranean diet.
Fruits, vegetables and tea contain antioxidants and phytochemicals that can fight certain chemicals that cause inflammation. Dietary fiber can be metabolized by gut bacteria into chemicals researchers have associated with a lower risk of some chronic diseases.
Chronic stress and lack of sleep can promote inflammation. Exercise fights it, partly by reducing fat.
Ridker’s advice? “Go to the gym, throw out the cigarettes, eat a more healthy diet — and then control their blood pressure and their cholesterol.”
“INFLAMMATION IS A COMPLEX REACTION TRIGGERED BY YOUR IMMUNE SYSTEM WHEN IT FIGHTS OFF INVADERS SUCH AS A VIRUS OR WHAT IT THINKS ARE INVADERS.”
DR. JUN LI, Harvard T.H. Chan School of Public Health in Boston