epidemiology Flashcards
what is the discrepancy between mortality and incidence *
some cancers - eg skin - have low mortality, so incidence is much higher than mortality
some cancers eg pancreatic, are effectively acute - they are very lethal so mortality is very similar to incidence
what are the leading causes of death - global - 2012 *
non-communicable diseases are responsible for 70% of the deaths in HIC and previously LIC eg China
IHD is the largest cause of death
lung cancer is the highest cause of cancer mortality
after CVD cancer is next leading cause of death
this is because of the epidemiological transition
in india there is a mix of communicable ad non-communicable diseases
describe the change in death rate of heart disease over time
decrease
prevention and therapy are more effective - prevention reduces incidence, therapy reduces mortality
this is seen in the US and in other countries - things happen in US first
what is the epidemiological transition that is happening in US now
reduced life expectancy of poor white americans
because of drugs, alcohol and abuse of pharmaceutical drugs
describe the changes in death rates from cancer in US over time*
stayed stable
describe the cancer incidence rates in different countries *
3 fold difference in incidecne between ireland (higher incidence) and saudi arabia
this is after age adjustion - because cancer is a disease of the elderly
convergance is happening - poor/traditional countries are moving towards a western culture - lifestyle and exposure = more disease - the epidemiological transition
describe the international variation in different types of cancer’s incidence - 2002 *
depends on the cancer
for melanoma - 200x higher incidence in australia (Queensland) than china - because in queensland there is higher exposure to sunlight/UV which causes mutation in skin - also population has fair skin because they came from UK so genetically suseptibility to sunlight
is the data on cancer credible
yes - all cancer registries are verified by WHO
describe how migrant studies allow us to determine if cancer is genetic or environmental *
if migrants move from low risk to high risk area - and the risk of cancer is unchanged it is genetic, if the risk increases the cancer is environmental because it is the changed exposure that has increased the risk eg diet/environment pollution/smoking
in hereditory cancers (rare) migration doesnt affect the risk
teh extent and rate of change is what is important - a rapid change implies lifestyle/env factors act late in carcinogenesis, a slow change suggests that exposures early in life are most relevant, persistance of rates between generations suggests genetic suseptibility is important in determining risk
describe the stomach cancer in japanese migrant study *
stomach cancer was the 1st type of cancer in Japan - high incidence in Japan and low in US - this was the opposite for colon cancer
in japanese who migrated to US - incidence dropped to near US level
suggests the stomach cancer is env not inherited - a change in alleles in pop takes 100s of yrs so wouldnt happen this fast
environmental contributions - diet and H pylori infection
since then stomach cancer has reduced in Japan
increase in colon cancer - due to change to western diet of red meat and alcohol
describe cancer death rates over time for lung and stomach cancers * us
rapid change in frequency over time
increase in lung cancer from 40s - 20yrs after the increase in smoking
stomach decreased - better food preservation - less contaminated bacteria
describe the trends in incidence of cancer in western countries *
overall cancer has increased
now plateu in US, canada, australia
this is because there has been a reduction in exposure - eg in smoking = plateau in lung cancer
there are more physicians - cancer found earlier
increased sensitivity of diagnositic tests - screening identify earlier stages eg PSA for prostate or mamogram for breast has increased incidence in cancer
describe the trends in mortality in western countries *
survival increases so mortality decreases even though there is a higher incidence
the survival increases because there is earlier diagnosis and better therapies - smaller more curable cancer is detected
summary of the change in mortality and incidence in low and high income countries *
incidence increasing in both
mortality is decreasing in HIC but not LIC - because LIC like bangladesh are still in epidemiological transition so have cancers of affulence eg breast, colorectal, prostate and cancers of infection eg stomach and cervical; also have less access to screening and therapy
eg childhood leukaemia which is v treatable here still has high mortality in africa and south america
what are the 2 things that can be meant when we say that something is genetic *
that it is hereditory - this is 5/10% of cancers
that it is due to a genetic mutation/epigenetic change - ie the mutations are acquired eg sun causes p53 mutation (environmental) but some people dont have the enzyme to repair damage - therefore get a lot of skin cancer - here there is a genetic and environmental cause
90-95% cancers are environmental or env and genetic suseptibility
what are inherited conditions that increase the risk of cancer *
hereditory retinoblastoma - retina cancer - mutation in RB1 gene - inherit 1 gene and the other is mutated
xeroderma pigmentosum - skin cancer - dont have gene that can repaire DNA
Wilm;s tumour - kidney cancer
li-Fraumeni syndrome - sarcomas, brain, breast, leukaemia
familial adenomatous polyposis - colon, rectum
paget’s disease of bone - bone
fanconi’s aplastic anaemia - leukaemia, liver, skin
what are the main risk factors for cancer *
smoking, diet, alcohol, infection, occupation, reproductive hormone
pollution risk very minor
<5fruit/veg, too much salt. high bmi, less than 30mins exercise 5 days a week
45% cancers could be preventable if these risk factors were avoided
easy to determine smoking as a cause because do a questionaire and look at risk between the exposed and unexposed
this is un uk, france, italy, canada and australia
however to see contribution of pollution - difficult to compare exposed and unexposed, have to look at PCVs in blood - require biological specimens - so effect of air pollution might currently be underestimated
now trying to study the exposome
effect of smoking on cancer *
accounts for at least 30% of all cancer deaths
smoking is associated with increased risk of at least 15 types of cancer
smoking causes 90% of lung cancer deaths in men and 80% in women
effect of diet on cancer *
increase in intake of fibre from fruit/veg decreaes the risk of cancer - colon cancer decreases as fivre increases
red meat increases the risk of colon cancer
effect of alcohol on cancer *
associated with oral cavity, pharynx, liver, oesophagus, larynx cancer
all types of alcohol contribute
mechanisms poorly understood
synergism with tabacco - increase oesophageal/laryngeal cancer if do both
balance with preventative effect of CHD
describe obesity and cancer *
associated with post menopausal breast, colon, pancreatic, endometrial
this is because cancer is inflammatory - it causes an increase in the inflammatory cytokines = chronic inflammation - this is a hallmark for cancer = increased risk of cancer - inflammaton leads to the selection of mutated cells
what are the guidelines for dietry prevention of cancer
be as lean as possible - w/o underweight
be physically active for at least 30mins a day
avoid sugary drinks. energy dense foods
eat more variety if veg, fruit, wholegrains, pulses - plant based diets
limit consumption of red meats
klimit alcohol intake
limit salt intake ]
dont take vitamin supplements to reduce risk of cancer - wongt work or increase risk
what is the western lifestyle and what is the effect of it *
energy dense diet, rich in fat, refined carbs, animal protein; low physical activity, smoking and drinking
consequences - greater adult height, early start of period (menarch), obesity, dm, cvs, hypertension
describe infectious causes and cancer *(
16% cancer world wide is likely to be caused by infectious agents - more in africa than europe for eg
hpv = cervix, head and neck
ebv - hodgkin’s lymphoma, brukitts
hcv and hbv - liver
h pylori - stomach
important factors in carcinogenesis *
chemical carcinogens
radiation
onchogenic viruses
what does epidemiology tell us that cancer incidence is related to *
age
env causes
geographical variation and secular trends
