Epidemiology in

„Sozialmedizin“Part 1

Based in part on a powerpoint presentation by Prof. Dr. med. Hans-Werner HenseInstitut für Epidemiologie und SozialmedizinUniversität MünsterTranslated, shortened and added to by Wirsing

Epidemiology is one the foundations Epidemiology is one the foundations of Health Sciencesof Health Sciences

Related concepts: What is an epidemic? What is a pandemic? What does it mean when a disease is said to be endemic?

What is epidemiology? It is the study of the distribution of diseases (morbidity), invalidity, and

death (mortality) among a population and the various factors associated

with these diseases.

Related concepts: What is an epidemic? What is a pandemic? What does it mean when a disease is said to be endemic?

What is epidemiology? It is the study of the distribution of diseases (morbidity), invalidity, and

death (mortality) among a population and the various factors associated

with these diseases.

Aims of Epidemiological ResearchAims of Epidemiological Research

• Frequencies (descriptive)

• causes (analytical, explaining)

• prognosis (analytical, explaining)

• prevention and intervention,

•Its goal (aim) – is description, explanation, prevention and intervention

• Frequencies (descriptive)

• causes (analytical, explaining)

• prognosis (analytical, explaining)

• prevention and intervention,

•Its goal (aim) – is description, explanation, prevention and intervention

Definition of Incidence rate (= Rate of newly diseased)

The incidence rate tells us how many new cases of a diseaseper time unit (e.g. per year) occur within a specific population in relation to all people „at risk“ – all those who theoretically could fall sick.

Number of Newly Diseased CasesI = ------------------------------------------------------------- per time

Number of people within population at risk

In general, the incidence rate is usually computed per year and per 100, 1 000, 10 000 oder 100 000 persons.

Graphical Distribution of Incidence ofBreast CancerAccording to ..

Persons(age, ethnicity)And Place (SF, Hawaii)

The Difference between Prevalence and Incidence The Difference between Prevalence and Incidence

What has an influence on prevalence?

The number of cases (people) with a given disease at a given time

New cases

Died

Cured Prevalence Pool

Definition of prevalence rate

The proportion of the population that is affected by a certain disease is the prevalence rate,

The prevalence rate P is computed:

Number of affected (sick) peopleP = ---------------------------------------------------

Number of all people in population

The prevalence of a certain disease is determined in a survey by first finding the number of all affected people in the study population.

Surveys or Prevalence Studies:

What else has an influence on prevalence

Besseres Überleben mit Krankheit

Zunahme der Neuerkrankungen

Zunahme der allg. Lebenserwartung

Zuwanderung Kranker

Abwanderung Gesunder

Verbesserung der Diagnostik

Increases Prevalence

Decreases Prevalence

Höhere Letalität

Abnahme der Neuerkrankungen

Abnahme der allg. Lebenserwartung

Abwanderung Kranker

Zuwanderung Gesunder

Vermehrte Heilung

Social Status und Prevalence of Being Sick

Quelle: Nationaler Gesundheitssurvey, Deutschland 1999

Men Women

Surveys or Prevalence Studies:Who is still sick?

0% 5% 10% 15% 20% 25% 30% 35% 40%

Coun

try

China

Australia

AlbaniaGreece

RussiaEthiopia

SingaporeSpain

Hong KongJapan

FranceGermany

KenyaFinland

South AfricaUSA

BrazilPeru

Canada

New ZealandUnited Kingdom

IndonesiaSource: The Lancet 1998

The 12-month prevalence (%) of asthma symptoms in 13–14 year olds (written questionnaire) for each centre by selected country

Surveys or Prevalence Studies: :Where is the disease rarer / more frequent?

Epidemiological conceptsmorbidity (can be incidence or prevalence) morbidity - the rate of illness and disease in a population; usually specified for a given

disease, such as tuberculosis or lung cancer or … Data are collected from insurances or the Mikrozensus

Mikrozensus has the meaning of "kleine Volkszählung". It is a legally mandated statistical survey which is done every year since 1957 of 1% of all households in Germany. It is one of the most important sources of health data

 With the rise of life expectancy and the aging of our society until 2050 we can expect a rise in the morbidity of the following diseases: diabetes, heart attack, stroke, cancer (esp. of breast and prostate), dementia, pneumonia, fracture of femur, osteoporosis, glaucoma, COPD

Epidemiological concepts: mortality mortality- the rate or occurrence of death in a population per unit time (e.g. one year);

usually specified for a given disease and a given year. The rate is usually given per 100.000 population size. Data are collected from death certificates and published by the Statistisches Bundesamt

Here: mortality rates of a a disease (breast cancer) according to country

Other mortality rates

Infant mortality rates in Germany4,03 infant deaths/1.000 life birthsboys: 4,46 deaths/1.000 life birthsgirls: 3,58 deaths/1000 life births

Infant mortality in Germany: regional and ethnic distributionThe infant mortality differs by region within Germany (2004):NRW: 5 infants dead per 1000 life births,Baden-Württemberg and Bavaria: 3,4 per 1000 life births

Even within the state of NRW there are differences:3,3 in Rhein-Sieg-Kreis up to 8,7 in GelsenkirchenNRW 2004: differences according to citizenshipInfants of German parents: 4,6 deaths per 1000 life births

Infants of parents with foreign citizenship: 11,1 per 1000 life births

FragenFragen

1. The prevalence of CHD increases, even though itsIncidence has been sinking for years. How can this be explained?

1. Screening for cancer lowers the incidence of cancer - is this correct?

2. The number of people in Germany who ever had cancer is rising continuously. Is this a sign of bad medical care?

Epidemiological concepts:Life expectancy at birth

Life expectancy - the average number of years of life remaining at a given age, usually at the time of birth. It is the average expected lifespan of an individual of a given birth cohort

The life expectancy shows different distributions according to person (sex, social status), region (country) and time (year) Since 1950 estimated life expectancy at birth of the world’s population has been increasing However, in the final 15 years of the 20th century, life expectancy declined in sub-Saharan Africa and the countries of Central and Eastern Europe (CEE), Russia and other parts of the former Soviet Union. In Western Europe, in contrast, life expectancy increased between 6-8 years since 1970

Epidemiological concepts:life expectancy at birth continued

The post-Soviet experience shows that abrupt political, economic and social change can also have serious adverse effects on population health. The stress and chaos induced in Russia and other Soviet countries by the collapse of the Soviet Union and the transition from communism brought in its wake a dramatic and relatively long-lasting decline in life expectancy. Was meinen Sie: what might have influenced the development of life expectancy over the years in Europe? What could explain the usual 6-7 year difference in life expectancy between men and women?http://web.hszg.de/~wirsing/ASH%20Sozialmedizin09/Questions%20to%20Life%20Expectancy.pdf

Global Changes of Life Expectancies since the 70http://www.guardian.co.uk/news/datablog/interactive/2012/dec/13/how-people-die-global-mortality-visualised

Since 1970 the LARGEST GAINS in life expectancy have taken place in the Maldives (27.3 years for men and 29.4 years for women) and improvements in life expectancy at birth in excess of 20 years were recorded in Bangladesh, Bhutan, Iran, and Peru. But life expectancy FELL by one to seven years in Zimbabwe and Lesotho, where populations were severely affected by HIV/Aids, and for men in Russia, Ukraine and Belarus, where an alcohol crisis took hold.

Since 1990, the LARGEST GAINS in life expectancy have been in sub-Saharan African countries, especially Angola, Ethiopia, Niger, and Rwanda, where life expectancy since 1990 has increased by 12-15 years for men and women, thanks to more widespread and effective strategies for HIV control and reduction of childhood diseases

GLOBAL DEATHS, CAUSEShttp://www.guardian.co.uk/news/datablog/interactive/2012/dec/13/how-people-die-global-mortality-visualised