Part Two. The urgent need for action
Chapter One. Chronic diseases: causes and health impact
Terminology on chronic disease
Part of the confusion that surrounds chronic diseases is that they appear under different names in different contexts. Sometimes the term "noncommunicable diseases" is used to make the distinction from infectious or "communicable" diseases. Yet several chronic diseases have an infectious component to their cause, such as cervical cancer and liver cancer. "Lifestyle-related" diseases is a term sometimes used to emphasize the contribution of behaviour to the development of chronic diseases. In fact, these diseases are heavily influenced by environmental conditions and are not the result of individual choices alone; "lifestyles" are, of course, equally important for communicable diseases. For this report, the term "chronic diseases" is preferred because it suggests important shared features:
- the chronic disease epidemics take decades to become fully established - they have their origins at young ages;
- given their long duration, there are many opportunities for prevention;
- they require a long-term and systematic approach to treatment;
- health services must integrate the response to these diseases with the response to acute, infectious diseases.
HEART DISEASE There are many forms of heart disease. Coronary heart disease, also known as coronary artery disease or ischaemic heart disease, is the leading cause of death globally. This is the form of heart disease considered in this report and it will be referred to simply as heart disease. It is caused by disease of the blood vessels (atherosclerosis) of the heart, usually as part of the process which affects blood vessels more generally. Heart disease, although known for centuries, became common in the early decades of the 20th century in high income countries. The epidemics have now spread worldwide.
STROKE Stroke is a disease of the brain caused by interference to the blood supply. Stroke and heart disease are the main cardiovascular diseases. There are several types of strokes and the acute events are usually caused by the same long-term disease processes that lead to heart disease; a small proportion of acute events are caused by a blood vessel bursting. Stroke is the main cardiovascular disease in many east Asian countries.
CANCER Cancer describes a range of diseases in which abnormal cells proliferate and spread out of control. Other terms used are tumours and neoplasms. There are many types of cancer and all organs of the body can become cancerous. Tobacco is the main preventable cause of cancer. The causes of many other cancers are also known, including cervical cancer, skin cancer and oral cancer.
CHRONIC RESPIRATORY DISEASES Diseases of the lung take many forms. This report focuses on chronic obstructive pulmonary disease and asthma. Chronic obstructive pulmonary disease is caused by airflow limitation that is not fully reversible; asthma is caused by reversible obstruction of the airways.
DIABETES Diabetes is characterized by raised blood glucose (sugar) levels. This results from a lack of the hormone insulin, which controls blood glucose levels, and/or an inability of the body’s tissues to respond properly to insulin (a state called insulin resistance). The most common type of diabetes is type 2, which accounts for about 90% of all diabetes and is largely the result of excessive weight and physical inactivity. Until recently, this type of diabetes was seen only in adults but is now occurring in obese children. The usual childhood form of diabetes (type 1 diabetes) is caused by an absolute lack of insulin and not by obesity. Without insulin, type 1 diabetes is rapidly fatal.