The body’s protective response to infection and injury. When a sentinel white blood cell detects a foreign substance in the body, it sends out chemicals that make nearby blood vessels dilate (widen) and become more permeable. The widened blood vessels bring more blood and heat to the area, while the increased leakiness of the vessels allows fluid (that can cause swelling) and other infection-fighting white blood cells (that release antibacterial chemicals that can cause pain) into the area. Redness, heat, swelling, and pain are all hallmarks of inflammation.
While short-term inflammation may protect the body, chronic inflammation is thought to play a harmful role in many diseases, including periodontal disease, lupus, rheumatoid arthritis, Alzheimer disease, cancer, heart disease, stroke, and diabetes.
Although medical researchers have traditionally focused on cholesterol and blood pressure as risk factors for heart attack and stroke, they are now increasingly turning their attention to inflammation, using a blood marker for inflammation known as C-reactive protein, or CRP. Using a subset of people from the Physicians’ Health Study, researchers analyzed records of CRP levels from men who had had heart attacks or strokes within eight years of the end of the study and compared them with those of men similar in age and weight who had not had heart attacks or strokes. It turned out that men who had had heart attacks or strokes had higher levels of CRP during the study than those who didn’t. In fact, those with the highest levels of CRP had a threefold higher risk of heart attack and a twofold higher risk of stroke than men with the lowest levels.
The Women’s Health Study showed similar findings in women: Women with the highest levels of CRP were 4.5 times more likely to have a heart attack or stroke over an eight-year period than women who had the lowest. In this study, CRP levels were a better predictor of heart attack or stroke than LDL cholesterol levels.
Some medical researchers believe that inflammation promotes the buildup of atherosclerotic plaque on blood vessel walls. It may especially promote the so-called “vulnerable” plaque, which produces blood clots that block arteries, causing heart attacks and strokes.
Research has uncovered a link between inflammation and diabetes as well. In the Cardiovascular Health Study, the quartile of people with the highest CRP levels were three to four times more likely to develop diabetes within three to four years of the study than the quartile of people with the lowest levels of CRP. Some researchers speculate that Type 2 diabetes and atherosclerosis may be caused by some of the same underlying mechanisms — and that one of these mechanisms may be inflammation.
What does all this mean in terms of preventing heart disease and stroke? The same prevention strategies still apply. Exercise, controlling diet, stopping smoking, and losing weight if you are overweight can all lower CRP levels — and are already proven lifestyle measures for reducing the risk of heart attack and stroke. Statin drugs, which are used to lower cholesterol, may also help lower CRP levels. There is some evidence that aspirin may work to reduce inflammation, so the daily aspirin recommended for many people with diabetes may be of some help in fighting chronic inflammation.