Introduction to Epidemiology and Public Health
HNE-24806
Lecture 1
Cancer
Cancer: accumulation of epigenetic (omkeerbare erfelijke veranderingen in de genfunctie die optreden zonder
wijzigingen in de sequentie van het DNA in de celkern) and genetic changes
1/3 people in high-income countries
13 % of all deaths worldwide
31% of deaths is from communicable diseases (infections, etc.) and nutritional deficiencies
Incidence: occurrence of new cases; new patients diagnosed with a certain disease; 14.1 million new
patients/year (incomplete registries)
Lung > breast > colorectum (colon and rectum) > prostate > stomach
Prevalence: amount of people living with a disease at a certain time
Breast > prostate > colorectum > lung > cervix uteri (baarmoederhals)
Global cancer figures
WHO; World Health Organization
IARC: International Agency for Research on Cancer
In some countries poor quality and incomplete registries
The age-standardized mortality rate: weighted average of the age-specific mortality rates per 100,000 persons,
where the weights are the proportions of persons in the corresponding age groups of the WHO standard
population.
Cancer by age
> 55 years old (takes about 40 years for a tumour to grow)
Exceptions
Testicular cancer: piek bij 25-29 jaar oud
Hodgkin’s disease (cancer cells spreading between lymphe
nodes): pieken bij 20-24, 2e piek op oudere leeftijd
Cancer by gender
Men; lung > prostate > stomach
Women; breast > cervix (baarmoederhals) > bowel (GI-tract) 1 Increase of cancer diagnoses with age. Bigger increase for
men.
1. Age: most important determinant of cancer incidence and mortality → caused by accumulation of genetic
damage during life
2. Gender: second important determinant of site-specific cancer incidence and mortality → caused by
endogenous factors (sex hormones) and exogenous factors (smoking)
3. For a meaningful comparison between populations; both age and gender should be taken into account
Cancer by region estimated age-standardised incidence rates per 100.000
All cancers excl. non-melanoma skin cancer (niet uit moedervlek ontstaan); both sexes, all ages → highest in
high-income countries
Liver cancer; both sexes, all ages → highest in South-East Asia and North-West Africa, lowest in high-income
countries (caused by a virus)
Colorectum cancer; both sexes, all ages → highest in high-income countries
Stomach cancer; both sexes, all ages → highest in Asia and Russia (caused by Helicobacter pylori)
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, 2 Cancer incidence and level of prosperity
Geographic variation: The 5-10 fold differences in age-standardised & sex-specific cancer incidence between
populations suggest that genetic and/or environmental factors play an important role in cancer risk.
Migrant study; Japanese immigrants in Hawaii
Risk factors for cancer
5-10% inherited
Interplay of: inherited susceptibility vs environment & lifestyle vs bad luck
Main risks: smoking, radiation, toxic chemicals, viruses and bacteria, sunburns and hormones
Major causes: obesity, high energy intake and low energy expenditure
Positive associations between obesity and all kinds of cancer
Exception: obesity at an early age and pre-menopausal breast cancer
Physical activity reduces cancer risks: colorectal, breast (post-menopausal) and endometrium
(baarmoederslijmvlies)
20% of cancers due to chronic infections
Hepatitis B virus (liver)
Human Papilloma viruses (HPV); sexually transmitted
disease; causes cervix cancer
Human immunodeficiency virus (HIV); causes Kaposi
sarcoma (skin cancer) and lymphomas (vorming van
kwaadaardige lymfocyten in lymfestelsel)
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, Smoking and cancer: higher risk of lung, mouth, larynx (strottehoofd), pharynx (keelholte), stomach,
colorectum and breast cancer
Quit smoking helps!
X = continued smoking
Alcohol and cancer: increases risk of mouth, pharynx, larynx, oesophagus, stomach, colorectum, breast and
liver cancer ● = quit smoking
Combination of risk factors: effect of the combination of exposures exceeds multiplicativity of the separate
effects! O = lifelong non-smokers
30-40 % of all cancer cases could be avoided by healthy food habits and an increase in physical activity
How much can be prevented depends on the type of cancer
1.2 Introduction to epidemiology and public health
Knowledge clip
Epidemiology
Academic setting Public Health setting
How to be sure about exposure effects Prevention for a risk group/population
‘Crime prevention’ ‘Scientific detection’
Knowledge generation Knowledge application
Causal factors Prevention and health promotion
DISH
Determinants of diet and lifestyle → Epidemiology in Public Health setting
Intake of food and nutrients →
Status and function of the body → Epidemiology in academic stetting
Health and disease risk →
Book pp 1-9, 17-18
Epidemiology epi: upon demos: people logia: study
Measuring health, identifying the cause of ill-health and intervening to improve health
Providing a logic and structure for the analysis of health problems
Descriptive epidemiology: person, place and time
Public health: identifying health problems within a community, identifying the cause of the disease and then
test possible solutions to resolve the problem
Epidemiology: providing data to make public health judgements
Attack rate: amount of people who did something before they got sick; for example: 45% of people who ate cold
chicken became sick.
Relative risk: a measure of the risk of sickness relative to staying healthy; for example: 45% of people who ate
cold chicken became sick, 32% of people who didn’t eat hot chicken became sick. Relative risk = 45/32 = 1.4.
1.3 History of epidemiology and public health
John Snow and epidemiology
1854: John Snow finds out that cholera spreads via water.
Vibrio cholerae: causes severe diarrhoea which can lead to death
John Snow found out that all patients lived near the same water pump and he could also explain why some
people who also lived near the pump didn’t get sick;
People from the beer brewery didn’t drink the water
People in the workhouse had their own water reservoir
Some elderly who lived near other water pumps asked their relatives to get water from the ‘infected’ water
pump because they preferred the taste of that water
Evidence for causality: John Snow removed the handle from the ‘infected’ water pump and the amount of new
patients decreased.
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, Knowledge clip
Pre-formal epidemiology Early epidemiology Classical epidemiology Modern epidemiology
1662 – 1900 1900 – 1940 1940 – 1980 > 1980
Infectious diseases, Chronic diseases, non- All diseases; tuberculosis All aspects of human
nutritional deficiencies communicable diseases and the relation between health
(niet-overdraagbaar), tobacco smoking and
pellagra and other chronic diseases
vitamin deficiencies
States started counting Combination between Established academic First intervention trials
the amount of citizens social medicine and field in US and UK → prevention strategies
and the amount of deaths statistics is made. Large-scale Epidemiology as
→ no equal distribution First epidemiology epidemiological foundation for public
of deaths over the prof is appointed. studies started health
population → group New study designs;
thinking about infectious case-control, cohort,
diseases → focus on ecological studies
hygiene and sanitation
Graunt: ‘founder of Doll & Hill: British
descriptive doctors study;
epidemiology’: he prospective cohort study
studied parish which provided
christening registers convincing statistical
(doopboeken) and proof that tobacco
collected all data on birth smoking increases the
and deaths risk of lung cancer
Farr: studied levels of
mortality in different
occupations and
institutions
Snow: ‘founder of
epidemiology’; stopped
the cholera epidemic by
remove the handle of a
waterpump
Identification of water Identification of Identification of AIDS
as reservoir and cigarette smoking as a syndrome and that it’s
vehicle of major cause of lung caused by a sexually
communicable cancer, lung transmitted virus
diseases as cholera emphysema and
and typhoid fever cardiovascular disease
Identification of
mosquitos, flies, etc.
for diseases as
malaria, yellow fever
and sleeping sickness
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