Non-infectious disease

Non-infectious diseases (also called Non-communicable diseases [NCDs]) are those diseases that are not caused by a pathogen and cannot be shared from one person to another. In contrast, transmissible diseases caused by pathogenic organisms are infectious diseases. There are many kinds of non-infectious diseases. Some examples of are cancer, asthma, and heart diseases.

According to the General Director of WHO Dr. Margaret Chan in 2008 non-infectious diseases were the reason for more than 36 million deaths, representing 63% of the total death number - 57 million. 80% of these deaths, as reported, were in the low-and middle-income countries.

Non-infectious diseases may be caused by either the environment, nutritional deficiencies, lifestyle choices, or genetic inheritances. Unlike infectious diseases, non-infectious diseases are not communicable or contagious, although some kinds can be passed down genetically to the children of a carrier.

Historically, infectious diseases were the main cause of death in the world and, indeed, in some developing regions this may still be the case. With the development of antibiotics and vaccination programs, infectious disease is no longer the leading cause of death in the western world. Non-infectious disease is now responsible for the leading causes of death in both developed and some developing countries.

Some medical conditions are not infectious in nature, but are also not normally classified with non-infectious diseases. These include some types of physiological malfunction, some mental illnesses, and some conditions that are not classically considered "diseases", such as substance abuse, ageing and obesity.

Causes

Causes of non-infectious disease are categorized into genetically inherited diseases and environmental diseases. Non-infectious diseases that are not genetic disorders are environmental diseases, although many diseases are affected by both genetic and environmental factors.

Inherited diseases

Genetic disorders are caused by errors in genetic information that produce diseases in the affected people. These errors may include:

• A change in the chromosome numbers, such as Down syndrome
• A defect in a single gene caused by mutation.
• A rearrangement of genetic information

Cystic fibrosis is an example of an inherited disease that is caused by a mutation on a gene. The faulty gene impairs the normal movement of sodium chloride in and out of cells, which causes the mucus-secreting organs to produce abnormally thick mucus. The gene is recessive, meaning that a person must have two copies of the faulty gene for them to develop the disease.

Cystic fibrosis affects the respiratory, digestive and reproductive systems, as well as the sweat glands. The mucus secreted is very thick and blocks passageways in the lungs and digestive tracts. This mucus causes problems with breathing and with the digestion and absorption of nutrients.

Environmental diseases

Environmental disease is a very broad category. It includes avoidable and unavoidable conditions caused by external factors, such as sunlight, food, pollution, and lifestyle choices. The diseases of affluence are non-infectious diseases with environmental causes. Examples include:

• Many types of cardiovascular disease
• Chronic obstructive pulmonary disease caused by smoking tobacco
• Diabetes mellitus type 2
• Lower back pain caused by too little exercise
• Malnutrition caused by too little food, or eating the wrong kinds of food (e.g. scurvy from lack of Vitamin C)
• Skin cancer caused by radiation from the sun

Further reading

• Lower GM, Kanarek MS (1982). "The mutation theory of chronic, noninfectious disease: relevance to epidemiologic theory". Am. J. Epidemiol. 115 (6): 803–17. PMID 7046429. {{cite journal}}: Unknown parameter |month= ignored (help)