**1. Introduction**

One of the oldest diseases of mankind is diabetes mellitus. It was only during the later part of the nineteenth and first half of the twentieth centuries that newer advances relating to the pathology, predisposing factors, management, course and complications of diabetes mellitus were discovered. Yet many more demanding solutions relating to the disease are still required. It has been seen that urbanisation and ageing of the population is definitely related to diabetes mellitus. But it is also true that diabetes mellitus affects all ages and all races. It has been estimated that around 400 million people will be affected by diabetes mellitus by 2030 AD. There are three principal forms of diabetes mellitus: type 1, type 2 and gestational diabetes mellitus (GDM). It has been seen that Finland has one of the highest incidence rates of type 1 diabetes mellitus. Type 1 diabetes is most likely a polygenic disease and has a number of potential risk factors. Type 2 diabetes is associated with the interaction of environmental factors and genetic factors. Impaired glucose tolerance (IGT), which has a great potential to be converted to diabetes mellitus, also carries cardiovascular and other risks. It has been seen that the important risk factors for the occurrence of diabetes are (i) changes in lifestyle due to urbanisation, (ii) hereditary, (iii) resistance to insulin, (iv) accumulation of fat around the waist rather than generalised obesity, (v) increasing age and (vi) ethnicity. It has been seen that long-standing diabetes mellitus is associated with an increased prevalence of macrovascular and microvascular diseases. Other chronic complications such as neuropathy and retinopathy are very common in diabetes mellitus.

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
