Lecture 15 - Tobacco As A Cause Of Disease Flashcards Preview

Block 3 - Resp > Lecture 15 - Tobacco As A Cause Of Disease > Flashcards

Flashcards in Lecture 15 - Tobacco As A Cause Of Disease Deck (17):
1

Which cancers does tobacco have sufficient evidence of causing?

- lung cancer
- nasal cavity and nasal sinus cancers
- oropharyngeal canceer
- laryngeal cancer
- oesophageal cancer
- stomach cancer
- cervical cancer
- liver cancer
- pancreatic cancer
- urinary tract cancer
- bladder cancer
- myeloid leukemia

2

Diseases that have sufficient evidence to be caused by smoking: CV disease and resp disease

1) CV disease
- abdominal aortic aneurysm
- atherosclerosis
- cerebrovascular disease
- coronary heart disease

2) Respiratory disease
- COPD
- pneumonia
- asthma
- impaired lung function

3

Sufficient evidence that smoking causes Repriductive diseases + other diseases

- reduced fertility
- foetal death
- pregnancy complication
- pre-term delivery
- low birthweight
- SIDS

- cataract
- low bone density
- hip fracture
- peptic ulcer disease

4

4 steps for establishing causality

- the exposure precedes the outcome
- the association is unlikely to be due to chance
- the association is unlikely to be due to bias
- the association is unlikely to be due to confounding

5

Other criteria for causality

- the association is strong
- there is a dose-response relationship
- the association is consistent
- the association is coherent with other epidemiological data
- the association is specific
- the association is biologically plausible

6

Evidence that smoking precedes outcome

- cigarette smoking is generally in early adult life
- lung cancer is rare under 40 years of age and peaks in frequency very late in life
- association demonstrated in a number of large, long lasting cohort studies
- lung cancer rare before 40-50

7

Studies: smoking and life years

- men who smoked only cigarettes and continued smoking died on average 10 years younger than lifelong smokers
- cessation at age 60, 50, 40 or 30 years gained about 3, 6, 9, 10 years of life expectancy

8

Why is the smoking and lung cancer association unlikely to be due to bias

- very strong association
- case-control studies and cohort studies have given similar results

9

What are possible confounding factors that could alter the assocation

- demographics
- occupation
- age
- pollution
- alcohol

- those are controlled by statistical models

10

Smoking and lung cancer : dose-response

- the longer you've been smoking, the higher your chances of cancer
- if you stop, kind of goes back to baseline

11

The associatin is coherent with other information

- prevalence of smoking in men began to rise around the turn of the century, lung cancer mortality began to rise in the 1940s
- women started smoking much later than men, lung cancer mortality rise began later

- 20 years delay between smoking and cancer

12

The association is biological;y plausible

- cigarette smoke contains over 200 different chemical compounds that can increase the incidence of cancer in experimental studies
- condensates of tobacco smoke painted on mouse skin cause skin cancer
- respiratory tract tumours caused in dogs, rats and hamsters forced to inhale tobacco smoke

13

The association is reversible

- cessation at 30 avoids almost all of adverse effects on survival compared with continuing smokers

- if you stop you can gain some of your years of life expectancy back

14

Attributable risk

= Iexposed - Iunexposed

15

Attributable fraction

= (Iexposed - Iunexposed)/ I exposed x 100

- the proportion of the disease in an exposed group that is due to exposur

- x% of lung cancer among smokers is attributable to smoking

16

Attributable fraction of smoking in Australia

- up to 2/3 in current smokers can be attributed to smoking
- cessation reduces mortality compared with continuing to smoke, with cessation earlier in lige resulting in greater reductions

17

Population attributable fraction

- multiply by the proportion of the population which is exposed to that exposure to get an estimate of impact in population as a whole
- x% of disease in australia is attributable to smoking and therefore preventable by reducing smoking prevalence

- will depend on prevalence of smokers, whereas attributable fraction doesnt

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