Inflammation is part of the body's defense mechanism. It is the process by which the immune system recognizes and removes harmful stimuli and begins the healing process. There are generally two types of inflammation: acute and chronic inflammation.
Tissue damage due to trauma, microbial invasion, or noxious compounds all induce acute inflammation. It starts rapidly, becomes severe in a short time and symptoms may last for a few days for example cellulitis or acute pneumonia. Subacute inflammation is the period between acute and chronic inflammation and may last 2 to 6 weeks.
Chronic inflammation is also referred to as slow, long-term inflammation lasting for prolonged periods of several months to years. Generally, the extent and effects of chronic inflammation vary with the cause of the injury and the ability of the body to repair and overcome the damage. This article reviews chronic inflammation.
Chronic inflammation can result from the following:
Chronic inflammatory diseases are the most significant cause of death in the world. The World Health Organization (WHO) ranks chronic diseases as the greatest threat to human health. The prevalence of diseases associated with chronic inflammation is anticipated to increase persistently for the next 30 years in the United States. in 2000, nearly 125 million Americans were living with chronic conditions and 61 million (21%) had more than one. In recent estimates by Rand Corporation, in 2014 nearly 60% of Americans had at least one chronic condition, 42% had more than one and 12% of adults had 5 or more chronic conditions. Worldwide, 3 of 5 people die due to chronic inflammatory diseases like stroke, chronic respiratory diseases, heart disorders, cancer, obesity, and diabetes. The prevalence of some specific chronic inflammation-mediated diseases are as follows:
Most of the features of acute inflammation continue as the inflammation becomes chronic, including expansion of blood vessels (vasodilation), increase in blood flow, capillary permeability and migration of neutrophils into the infected tissue through the capillary wall (diapedesis). However, the composition of the white blood cells changes soon and the macrophages and lymphocytes begin to replace short-lived neutrophils. Thus the hallmarks of chronic inflammation are the infiltration of the primary inflammatory cells such as macrophages, lymphocytes, and plasma cells in the tissue site, producing inflammatory cytokines, growth factors, enzymes and hence contributing to the progression of tissue damage and secondary repair including fibrosis and granuloma formation, etc.
Types of Chronic Inflammation
Risk Factors Associated with Chronic Inflammation
Several risk factors promote low-level inflammatory response. These include:
Symptoms of Chronic Inflammation
Some of the common signs and symptoms that develop during chronic inflammation are listed below.
Tests for Chronic Inflammation
Unfortunately, there are no highly effective laboratory measures to assess patients for chronic inflammation and diagnoses are only undertaken when the inflammation occurs in association with another medical condition.
Many dietary and lifestyle changes may be helpful in removing inflammation triggers and reducing chronic inflammation as listed below. The most effective is weight loss.
In human clinical trials, it is shown that energy expenditure through exercise lowers multiple pro-inflammatory molecules and cytokines independently of weight loss.
Conventional Drugs to Combat Chronic Inflammation
Metformin is commonly used in the treatment of type II diabetic patients with dyslipidemia and low-grade inflammation. The anti-inflammatory activity of Metformin is evident by reductions in circulating TNF-alpha, IL-1beta, CRP, and fibrinogen in these patients.
Non-steroidal anti-inflammatory drugs (NSAIDs) like naproxen, ibuprofen, and aspirin acts by inhibiting an enzyme cyclooxygenase (COX) that contributes to inflammation and are mostly used to alleviate the pain caused by inflammation in patients with arthritis.
Statins are anti-inflammatory as they reduce multiple circulating and cellular biomediators of inflammation. This pleiotropic effect appears to contribute in part to the reduction in cardiovascular events.
Corticosteroids also prevent several mechanisms involved in inflammation. Glucocorticoids are prescribed for inflammatory conditions including inflammatory arthritis, systemic lupus, sarcoidosis, and asthma.
Herbal supplements like ginger, turmeric, cannabis, hyssop, and Harpagophytum procumbens are shown to have anti-inflammatory properties however one should always consult with a doctor before their use and caution should be taken for using some herbs like hyssop and cannabis.
It is important to realize that chronic inflammation is not a specific disease but a mechanistic process. The diseases associated with chronic inflammation are multiple and include CVD, diabetes, malignancy, auto-immune disease, chronic hepatic and renal disease, etc. Hence a good history, physical examination, and routine laboratory tests (glucose, creatinine, liver function, rheumatoid factor, complete blood count, antinuclear antibodies) can confirm or rule out most of the differential diagnoses. Also, pertinent imaging studies will be helpful in certain circumstances, e.g., Inflammatory bowel disease or serum protein electrophoresis for polyclonal gammopathy.
Although chronic inflammation progresses silently, it is the cause of most chronic diseases and presents a major threat to the health and longevity of individuals. Inflammation is considered a major contributor to several diseases.
Chronic inflammation can have a deleterious effect on the body and is a key factor causing almost all chronic degenerative diseases. The following are some of the most effective ways to prevent chronic inflammation.