Epidemiology of Diabetes

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  Hi, I am Thorkild I. A. Sorensen and I amProfessor of Metabolic and ClinicalEpidemiology at the Faculty of Health andMedical Sciences at the University ofCopenhagen.I'm also head of an institute of preventive medicine based at one of the hospitals inCopenhagen.I'm trained as an MD and specialised inInternal Medicine.But since 1989 I have worked only inEpidemiological Research.In this introductory lecture, I will tellyouabout some basic aspects of the epidemiologyof diabetes.More specifically, I'll try to giveanswers to the following questions:What is epidemiology?How many suffer from diabetes?Why is diabetes such a serious disease?What are the biological mechanics of thedisease?How is diabetes defined?Which types of diabetes are there?How is the distribution of diabetes?By type?Geographical regions?By ethnicity?By gender?By age?What is the global diabetes epidemic?Which are the most important risk factors?I'll encourage you to visit thewebsite of the International DiabetesFederation, you may find a lot of useful andimportant information.And with regard to the epidemiology,especially the'Diabetes Atlas' which is very frequentlyupdated, is helpful,what you find here on this of what I'm showing you comes fromthis websitefrom the 2012 version and part of the 2013version.So, what is epidemiology?Epidemiology of a disease is about theoccurrence of the disease in thepopulations.About what determines the occurrence,and what the effects and impacts of thedisease are.How many and who are suffering from thedisease.What characterises them in comparison tothe rest of the population.  What are the possibilities for preventionof the disease.And what are the consequences of thedisease with respect to its prognosis.Including co-morbidities and mortality.These are the questions addressed inepidemiology.This, of course, overlapping with theclinical aspects of the disease,which is about how to diagnosis thedisease in the individual patients.And how to improve their prognosis bytreatment.Hence, these latter aspects, often calledclinical epidemiology.How many sufferers from diabetes?Let's make it clear, that there's no doubtthat diabetes is very common and veryserious disease.It now affects between 350 and 400 millionpeople worldwide and the numbers are stillincreasing,and are expected to increase even furtherin the future.Approximately one in ten adult peopleworldwide suffer from diabetes.Unfortunately, about half of them do notknow it.Why is diabetes such a serious disease?It is because it's a chronic conditionthatleads to a risk of several other diseases.Many of which are debilitating and alsofollowed by increased risk of dying.Damages of the blood vessels, both thebigger ones and the more peripheral,smaller arteries.And hence the organs and tissues receivingblood via these vessels are frequent.This may affect the eyes, the brain, theheart, the kidney and the foot.More recently it has become clear thatalsothe risk of getting cancer and dementia isincreased.Treatment of diabetes followed byreduction in the riskof these co-morbidities is feasible, butalso difficult, demanding and expensive.The many patients with diabetes who don'tknow they havethe disease may develop the co-morbiditiesas a first manifestation.You will hear more about this in subsequentlectures.But here I think we can make it clear thatwe, from aworldwide point of view, need to find outhow we best can prevent it.This will require detailed knowledge of  the epidemiology of the disease.What are the biological mechanisms of thedisease?How do we define diabetes?To do this properly and understand thedefinition, we needto know some basic biological mechanismsabout glucose and insulin.This figure shows that glucose is anessential energy of source for the body.And in parts of the body, it is a mainsource, for example the brain.Your body needs insulin to transformglucose into energy.What is insulin?It's a peptide hormone produced by andsecreted from theso called beta cells in the small isletsof the pancreas.Which you will learn much more aboutlater.As shown here, insulin is crucial to getthe wheels running.Insulin helps getting the glucose into thecells, where the transformation to energytakes place.Keeping the cell alive and functioning.Keeping the system running appropriatelyis called glucose homeostasis.If this is not working, youmay get diabetes.On this background, we can now define thedisease and justify the definitionby knowledge about the biology of glucosehomeostasis and the role of insulin.So, how is diabetes defined?So here is the IDF definition.Diabetes mellitus, or simply diabetes, isa chronicdisease that occurs when the pancreas isno longerable to make insulin, or when the bodycannot make good use of the insulin itproduces.Insulin is a hormone made by the pancreas,thatacts like a key to the glucose srcinatingfrom thefood that we eat pass from the bloodstream into the cells in the body toproduce energy.All carbohydrate foods are broken downinto glucose in the the blood.Insulin helps glucose get into the cells.Not being able to produce insulin or useit effectivelyleads to raised glucose levels in theblood, known as hyperglycemia.Over the long term high glucose levels areassociated with  damage to the body and failure of variousorgans and tissues.The measurements needed for making thediagnosis of diabetes inthe individual patients will be dealt within later lectures.Which types of diabetes are there?As indicated in the definition, there areseveral ways in which the system may fail.You see here three major ways ofmalfunctioningthat ends up in three different types ofdiabetes.Type one diabetes to the left.Type two diabetes to the right.And gestational diabetes at the bottom.In type one diabetes, the pancreas doesnot produce insulin.In type two diabetes, the pancreas doesnotproduce enough insulin or the insulincannot be processed.Gestational diabetes is specific topregnant women, occurswhen the insulin is less effective thanotherwise.However, these three main types can befurther subdivided in subtypes ofeach of them, which you will learn moreabout in later lectures.Moreover, the delineation made betweenthem here is not clear cut.For example, patients who eventuallydeveloptype one diabetes, may experienceintermittent secretionof insulin in the beginning of the diseaseuntil the secretion eventually stops.Type two diabetes is also in the very latestage like type one.With a respect to how much insulin isproduced.These type two patients are almost unableto produce insulin in the final stages.Several other rare types of diabetes aredefined by specific genetic defects.[MUSIC]
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