3.2 Diabetes as a risk factor
One risk factor – diabetes – requires special attention with regard to cardiovascular diseases. Diabetes mellitus is a condition in which the blood glucose level is higher than it should be for a healthy individual. If it remains that way, over time, it will cause numerous medical problems, including cardiovascular diseases. Cardiovascular diseases are responsible for up to four-fifths of the deaths of people with diabetes. The risk factors you are becoming familiar with are greater for people with diabetes; they have a two- to three-fold increased risk of atherosclerosis and a three- to five-fold increased risk of heart failure. As well as a doubling of cardiovascular disease risk, the risk of death from coronary heart disease for people with diabetes is two to four times higher than average.
The word ‘diabetes’ comes from the Greek for ‘siphon’. A siphon removes liquid, and diabetes is used to describe disorders that remove liquid from the body, as the ‘external’ symptoms include excessive thirst and the production of large amounts of urine. The word ‘mellitus’ is Latin for ‘honeyed’. Diabetes mellitus, therefore, describes a condition that produces ‘sweet urine’. This production of sweet urine occurs as the end result of a high blood glucose level. Diabetes mellitus has been known for thousands of years, but it is rapidly increasing in occurrence in modern times. From now on, throughout the course, the term diabetes will be used to describe diabetes mellitus.
There are several types of diabetes, but we are only interested in the two most common: Type 1 and Type 2. Worldwide, about 90 per cent of people with diabetes have Type 2 and about 10 per cent have Type 1. Type 2 diabetes was previously called non-insulin-dependent diabetes. People with Type 2 diabetes produce insulin (unlike Type 1), but it may be in insufficient amounts and/or their cells may be resistant to the action of insulin (insulin resistance). Because insulin directs glucose into cells from the bloodstream, glucose will be left to build up in the blood if there is not enough insulin or if cells are resistant to its actions. In people without diabetes, blood glucose levels are kept tightly controlled. Type 2 diabetes may be present for many years before a clinical diagnosis is made. This is because some people may have few obvious symptoms, and others do not see their thirst or getting up at night to pass urine as a problem. Having diabetes for several years before a diagnosis is made can mean that complications of diabetes, including cardiovascular diseases that take years to develop, may therefore already be present at the time of diagnosis. Obesity and lack of exercise are two particularly important environmental factors thought to be contributing to the rapidly increasing numbers of people worldwide with Type 2 diabetes. Although it has previously been considered to be a condition of adults, particularly those over 40 years old, it is now occurring with increasing frequency in younger people, including adolescents.
This section has introduced you to the concept of risk factors and the possibility that they can be altered through either lifestyle modification or medical intervention.