CRP is a protein that helps you fight infections. However, it is also a marker of low-grade inflammation and a predictor of your heart disease risk. It links stress, emotional, and socioeconomic cues to physiological ones. Keep reading to find out about the symptoms and causes of high CRP.
Why is High C Reactive Protein (CRP) Bad?
Signals Chronic Inflammation and Stress
Apart from acute infection or injury, CRP points to chronic or systemic inflammation. Its levels rise in response to chronic stress .
CRP is not only a marker of inflammation, it also worsens any underlying inflammation. In the lining of blood vessels, CRP lowers nitric oxide and prostacyclin release, which improve blood flow, while increasing the inflammatory compounds (monocyte chemoattractant protein-1 (MCP-1), interleukin-8 (IL-8), and plasminogen activator inhibitor-1 (PAI-1)) .
Symptoms & Health Risks of High C Reactive Protein (CRP)
High CRP levels do not cause symptoms directly. You will only show symptoms related to the cause of your high CRP levels, such as infections or chronic inflammation.
Thus, you may have symptoms of any of the diseases CRP increases your risk for.
1) Cardiovascular Disease
CRP increases inflammation in blood vessels and hardens the arteries, which can eventually lead to heart disease. Plus, it can activate cells that line the interior of blood vessels and can cause their dysfunction [6, 7, 8].
Additionally, CRP reduces nitric oxide release from arteries and veins, depriving tissues of adequate blood flow . Nitric oxide is good for the cardiovascular system because it relaxes blood vessels, increasing oxygen and blood flow throughout the body .
To make matters worse, plaques in arteries can also release CRP into the bloodstream, perpetuating the cycle in people who already suffer from heart disease or who are at high risk .
When should you be concerned? CRP levels <1 mg/L are considered low-risk, 1 to 3 mg/L as average risk, and >3 mg/L as high risk for cardiovascular disease .
High LDL and High CRP: A Deadly Combination
Increased levels of LDL cholesterol in at-risk patients cause blood vessels to increase CRP, which may, in turn, makes more LDL enter blood vessel cells .
Similarly, CRP was additive to LDL cholesterol (and the Framingham 10-year risk score) in predicting future cardiovascular disease in healthy American women in the Women’s Health Study .
The American Heart Association and Centers for Disease Control and Prevention recommended using CRP as a risk marker for cardiovascular diseases in people with a Framingham risk score between 10% and 20%. This subgroup of patients may benefit from high-sensitivity (hs)-CRP testing, mainly because physicians are often undecided about the treatment for a patient who is considered at intermediate risk .
A controversial trial named JUPITER, healthy people with high-normal CRP levels (> 2 mg/L) given statins experienced a 44% reduction in their risk of heart attacks, stroke, hospital admissions for unstable angina, or death from heart disease . This study has, however, received a lot of critiques and should be taken with a grain of salt .
High Blood Pressure
CRP may turn on a pro-inflammatory switch in blood vessels, making them narrow and stiff–resulting in high blood pressure (hypertension) .
Elevated CRP preceded new-onset hypertension at an early stage in an elderly healthy population. People with the highest CRP levels had a twofold greater risk of high blood pressure compared to those with the lowest CRP levels .
2) Metabolic Syndrome
People with metabolic syndrome have high inflammation and CRP levels. The more features of metabolic syndrome a person has, the more their CRP levels increase (linearly so). It additionally increases the risk of heart complications in people with the syndrome [8, 8, 8].
School children who were overweight/obese had higher levels of CRP and IL-6, whereas children with more belly fat and total body fat only had higher levels of CRP. CRP levels can even predict BMI changes during childhood [12, 13].
High CRP levels are associated with a great risk of strokes, stroke complications, and death. Levels over 3 mg/ml were linked with a 40% increased risk, compared with CRP<1 mg/l over a 15-year follow-up period, especially in men with high blood pressure [14, 14, 14].
5) Obstructive Sleep Apnea
Sleep apnea treatment with CPAP (continuous positive airway pressure) reduced the effect of the disease on CRP levels .
6) Systemic Lupus Erythematosus (SLE)
Low CRP levels may contribute to the development of systemic lupus erythematosus (SLE). This is because CRP may protect against autoimmunity by binding to cellular waste and autoantigens, which helps clear dying cells [18, 19, 20].
If damaged and dying cells aren’t cleared away by macrophages, their waste products build up in various tissues. Animals that can’t clear these dying cells develop autoimmunity. In fact, CRP injections can delay the onset of lupus and the resulting kidney inflammation in mice[20, 20].
People with systemic lupus have don’t produce enough CRP when the body acutely needs it, possibly due to genetic reasons. A mutation in the CRP gene that lowers CRP blood levels has been detected in patients with systemic lupus [20, 20].
Low CRP could also be caused by IgG antibodies, which are found in up to 78% of patients with systemic lupus. IgGbinds CRP, lowering its levels in the blood .
The link between CRP and SLE is not that straightforward because people with higher CRP had greater lupus disease activity in a number of other studies .
7) Rheumatoid Arthritis
CRP is found in the joint cavity fluid of rheumatoid arthritis (RA) patients and can bind to white blood cells and other inflammatory cells .
Inflammation in RA is closely related to the production of CRP and pro-inflammatory cytokines. In patients with rheumatoid arthritis, high CRP is directly linked with worse symptoms .
Levels of CRP correlate with changes in inflammation, disease activity, tissue damage, and disability. High CRP is also linked with hardening of the arteries and osteoporosis in people with rheumatoid arthritis [24, 20].
CRP is one of the best predictive markers of joint destruction and disease progression in early rheumatoid artritis and is a strong predictor of fractures .
Additionally, CRP changes within the ﬁrst 2 weeks of therapy with an anti-TNF agent can determine treatment success .
8) Gum Disease
CRP levels are higher in people with gum disease .
9) Inflammatory Bowel Disease (IBD)
In one study, higher CRP before diagnosis was associated with a greater risk of Crohn’s disease and ulcerative colitis .
In another study, CRP levels at diagnosis were related to disease severity in patients with ulcerative colitis but had not in patients with Crohn’s disease .
One study failed to find a link between CRP and colonic inflammation .
Low-grade inflammation is linked to depression. Several studies found a significant association between increased CRP and depressive symptoms. High levels were more frequent in patients with recurrent depression, especially in people who are overweight and have low HDL [33, 34, 35, 36].
Hostility was also associated with increased levels of CRP .
Macular degeneration is a medical condition that may result in blurred vision or vision loss.
Several studies suggest a close association between CRP and eye blood vessel disorders. People with higher CRP levels are more likley to get age-related macular degeneration, especially if their CRP levels are over 3 mg/L .
High CRP levels (> 3 mg/L) are associated with a two-fold increased risk of late-onset macular degeneration, compared to low levels (< 1 mg/L). Women with levels exceeding 5 mg/L may be at a threefold increased risk [40, 40].
In the oldest-old, high CRP levels are associated with increased odds of all-cause dementia (memory decline), particularly in women .
Scientists think the link between high CRP and cancer could be due to three reasons. First of all, high CRP may directly cause cancer. If so, it could be extremely useful in prevention .
Secondly, it’s possible that cancer increases CRP, even in the early stages. If this is true, CRP may be used as an early cancer marker, even when a person has no symptoms. And lastly, high CRP may point to another underlying cause of cancer, such as inflammation, high stress, and chronic disease .
Higher CRP levels have also been associated with the progression of skin, ovarian, and lung cancer. For this reason, CRP is used to detect cancer recurrence after surgery .
This post is the second in a four-part series about CRP. Read the other parts to learn about:
- The hidden causes of high CRP
- Ways to lower your CRP levels naturally
- The CRP test, why you should get the high sensitivity CRP test (hs-CRP), and what the normal range is.
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