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
