Diabetes results from reduced production of the hormone insulin, resistance of body tissues to the effect of insulin, or both. The result is abnormally high levels of glucose (sugar) in the blood and widespread disturbances to metabolism. Type 1 diabetes is more common among younger people and usually needs treatment with insulin. Type 2 diabetes is the most common form (around 90% of cases) and is more common among older people and those who are overweight. Diabetes is an important cause of death and disability. It increases the risk of coronary heart disease, stroke, renal (kidney) failure, peripheral vascular disease (poor circulation, usually in the legs), neuropathy (damage to nerves) and visual problems, including blindness. The number of cases of type 2 diabetes is increasing rapidly in the UK and worldwide, probably because of increasing levels of obesity and ageing populations. Diabetes is a leading cause of blindness, renal failure and neuropathy in the UK. Life expectancy is reduced on average by 20 years in those with Type 1 diabetes and up to 10 years in Type 2 diabetes.