HMB342 Lecture 9 Genetics & Environmental Factors

What study designs can we use to determine whether genetic or environmental factors are contributing?

if there are genetic factors: family members of cases are at higher risk than family members of controls

family information/history can be treated as a risk factor- however be cautious because familial aggregation may also be explained by shared environmental factors such as diet, pollution, second hand smoke

What are concordant pairs?

Twin study where both twins have the disease

What are discordant pairs?

twin study where one has the disease and other does not

What does concordance tell us?

potential genetic factors, potential environmental factors in how they were raised/in utero exposures

What does discordance tell us?

Environmental actors at least play a part in the disease

For diseases that we can model as a binary outcome (ie has disease, doesn't have disease), what is the calculation for concordance rate?

a/a+b+c (#twins where both have disease/#of twins who both have disease + twin 1 has disease twin 2 doesn't + twin 2 has disease twin 1 doesn't)

What is the calculation for discordance rate?

B+c /a + b + c

What would we expect in terms of concordance for fraternal vs identical twins?

lower rates of concordance for identical twins if there is a genetic factor of the disease, this is assuming that twins share environmental factors to the same degree

What would a higher concordance rate for monozygotic twins than dizygotic twins suggest?

would suggests a genetic component for the disease

What is the sample correlation coefficient?

describes the direction and strength of the linear association between two quantitative variables ; - or + sign indicates the direction of association and magnitude of r indicates strength

What do time trends imply?

implies that there are environmental factors influencing disease; genetic factors do not change nearly as quickly as environmental factors

What are migrant studies used for?

used to assess environmental factors; compare risk for migrants with risk for the population they migrated from, and the population they migrated to ;

if a disease has primarily environmental causes then over time the risk for migrants becomes closer to the risk of the adopting country

What happens if a disease has primarily genetic causes (case of migrant study)?

the risk stays the same for the migrant group even after migrating

What are some considerations for migrant studies?

age of the individual at immigration

how much of original environment (culture, lifestyle, diet etc) is kept after immigrating

individuals who immigrate are not representative of the average person (ie older individuals, sicker individuals may be less likely to move)

What are some considerations for adoption studies?

age at adoption, open vs closed adoptions (contact with biologic parents)

information about biological parents is not always available

characteristics that make individuals less/more likely too be adopted can be associated with the disease

What is an interaction effect?

when the effect of one factor depends on the value of another factor; the effect of the two factors together is different than what you would expect if you just added or multiplied their effects together

What is precision medicine/personalized care/dynamic treatment?

where an individuals genetic profile and other subject level data (age, gender, prior treatment) to make decisions for prevention, diagnosis and treatment

idea is to move away from the "one size fits all" idea that the best treatment is the same for everyone