NEW YORK, March 5: Why do our ankles swell when sprained, or our skin turn red or inflamed when scraped? The quick response we see is inflammation, and it plays a critical role in protecting our bodies.

At its core, inflammation is the body’s natural response to injury or illness, aimed at restoring health. Dr. Robert Shmerling, a rheumatologist and faculty member at Harvard Medical School, explained that inflammation helps the body heal and fight off infections. “It’s the response of the body to an illness or injury to try to restore health,” he said.

While inflammation is essential for survival, it has recently come under scrutiny due to its links to chronic diseases like diabetes, heart disease, and allergies. Reducing chronic inflammation is also seen as crucial for healthier aging. “It’s a classic double-edged sword,” said Dr. David Hafler, a neurologist at Yale School of Medicine. While necessary for survival, inflammation, when unchecked, can cause long-term harm.

Inflammation is crucial in fighting infections. For example, when you have a sore throat, it becomes red and painful because your immune system is battling the infection, preventing it from spreading. Dr. Moshe Arditi, a pediatrician at Cedars-Sinai Medical Center, calls this "acute inflammation," and he notes that a limited immune response during this stage is beneficial.

The term "inflammation" was first coined by the Roman encyclopedist Aulus Cornelius Celcus, who defined the core signs as rubor (redness), tumor (swelling), calor (heat), and dolor (pain)—terms still used today. At a microscopic level, acute inflammation involves the body sending fluid, proteins, and white blood cells to infection or injury sites to fight pathogens and promote healing.

However, while acute inflammation is life-saving, chronic inflammation can be damaging over time. Chronic inflammation is often linked to several risk factors, including obesity, smoking, and poor diet. Dr. Thaddeus Stappenbeck, chair of inflammation and immunity at the Cleveland Clinic, suspects that the modern American diet—rich in processed foods, refined sugars, and trans fats—may be a major contributor to chronic inflammation. In fact, trans fats were banned in 2015 and removed from many food products by 2018.

Lifestyle factors such as lack of exercise, sleep deprivation, and stress also promote inflammation, according to Dr. Shmerling. The signs of chronic inflammation can vary but may include joint pain, fatigue, constipation, and depression.

Reducing inflammation can be achieved through weight loss, regular exercise, and avoiding highly processed foods. Following a Mediterranean diet—rich in whole fruits, vegetables, and plant-based foods—has been shown to reduce inflammation. “It’s often not an on/off kind of switch,” Dr. Shmerling said. “Inflammatory markers can improve with lifestyle changes.”

Chronic disease rates have increased significantly. The Centers for Disease Control and Prevention (CDC) estimates that 129 million Americans have at least one chronic disease. The prevalence of chronic diseases has been rising steadily, with an estimated 7 million more people affected every five years, according to Stanford University. Experts believe inflammation plays a key role in this trend.

Dr. Shmerling added, “There’s a fair amount of consensus that a lot of the chronic diseases we see now in higher prevalence than in the past could well be related to chronic inflammation.”

When inflammation persists, it can damage organs and blood vessels. "Ongoing inflammation may lead to heart disease and the buildup of plaque in blood vessels, which can cause heart attacks and strokes,” explained Dr. Arditi. Chronic inflammation can also contribute to neurodegenerative diseases by damaging neurons in the brain.

Conditions like lupus and multiple sclerosis are also linked to chronic inflammation, where the immune system mistakenly attacks the body’s own tissues. “There’s chronic inflammation that’s ongoing and quite damaging,” Dr. Shmerling noted.

Due to inflammation’s connection to many diseases, patients are increasingly asking to be tested for it. While there are blood tests to measure inflammation, they are not perfect. Tests like the erythrocyte sedimentation rate and C-reactive protein (CRP) tests assess the level of certain proteins that correlate with inflammation in the body. However, these tests have limitations, including false positives, and must be interpreted alongside symptoms.

Dr. Shmerling warned against routine screening for inflammation in healthy individuals without symptoms, saying, “There can be normal inflammation tests even when inflammation is present, and sometimes the tests are abnormal even when it doesn’t seem there is any inflammation present.”

One promising test is hs-CRP, a more sensitive test that detects smaller increases in CRP levels. High CRP levels have been linked to heart attacks and strokes. Some experts suggest that hs-CRP testing should be routine, similar to cholesterol testing, to help assess risk for heart disease and stroke. However, the evidence remains mixed, which is why the test isn't widely adopted.

“There are people who are so low-risk or so high-risk that it’s very unlikely the CRP is going to help you,” Dr. Shmerling said. “There are subsets of people, maybe at moderate risk, where a CRP for cardiac risk could be helpful.”

In conclusion, while inflammation is necessary for the body’s defense against illness and injury, chronic inflammation is a serious health concern linked to numerous diseases. Lifestyle changes, including improved diet and exercise, are crucial for managing inflammation and reducing the risk of chronic health conditions.