Epidemiology and risk factors for AMD

Question 1

what is the odds ratio of smokers and non-smokers with regard to the presence of AMD

Answer 1

(10/40) / (5/45) = 2.25

people who smoke are 2.25x more likely to get AMD than the ones who don’t smoke

Question 2

what 3 categories can the outcome of a relative risk be put in and define each one

Answer 2

1 = no difference between the groups

<1 = event is less likely in exposed group (compared to control group)

> 1 = event is more likely in the exposed group (compared to control group)

Question 3

what is the calculation of a relative risk study

Answer 3

diseased & exposed / diseased & exposed + healthy & exposed
/
diseased & non exposed / diseased & non exposed + healthy & non exposed

AMD
positive and smoker = 5
negative and smoker = 75

positive and non smoker = 3
negative and non smoker = 237

RR = (5/80)/(3/240) = 5.0

The probability of developing AMD is 5x higher in smokers in this (hypothetical) study

Question 4

If CI spans 1, then the difference in risk between groups is…

Answer 4

not statistically significant

e.g. relative risk 1.2 (CI 0.9-1.5) – we can’t be sure that there is an increased risk associated with the variable

Question 5

name 4 non modifiable risk factors for AMD

Answer 5

Age
Sex
Ethnicity
Family history/genetics

Question 6

how is sex associated with a risk factor for AMD

Answer 6

Female sex may be associated with increased risk early and late AMD but evidence is mixed

Question 7

list the 4 ethnic groups studied suggesting prevalence of AMD from low to high and explain why this be

Answer 7

2. 4% Africans
3. 2% Hispanics
4. 6% Chinese
5. 4% Caucasians

Maybe due to melanin offering protection, or due to difference in AMD susceptibility genes

Question 8

at what stage of AMD showed a lower rate in black people compared to white

Answer 8

early disease prevalence similar BUT reduced risk of late AMD in black people

Question 9

how many gene variants does the genomic heritability of AMD involve

Answer 9

variants in 34 genetic loci

Question 10

what 3 things are the 34 gene loci of AMD involved in

Answer 10

the complement system
extracellular matrix remodelling
and
lipid metabolism

Question 11

name a complement gene with 2 variants associated with the incidence of AMD and the property of each

Answer 11

complement factor H - two variants associated with incidence of AMD, and progression to nAMD

(one associated with increased risk and one protective)

Question 12

how are the lipid metabolism proteins gene associated with AMD

Answer 12

involved in drusen formation

Question 13

name 3 other complement genes associated with risk of AMD and what are the 2 main variants

Answer 13

C2/CFB
CFI
C3

the 2 main variants = one associated with increased risk and one protective

Question 14

list 7 other less common non modifiable risk factors for AMD listing the ones with the strongest evidence first

Answer 14

Cataract surgery
Hypertension
History cardiovascular disease
High plasma fibrinogen
Light iris colour?
History cerebrovascular disease? Diabetes?
Serum total and HDL cholesterol and triglyceride levels?

Question 15

name 3 modifiable risk factors for AMD

Answer 15

Cigarette smoking
Diet and nutrition
Light exposure

Question 16

what is the risk of smokers developing AMD compared to never smokers

Answer 16

2x-3x risk in current-smokers vs never-smokers

Question 17

which type of diet is thought to be protective against late AMD

Answer 17

Mediterranean diet

Question 18

which type of food is thought to have a higher risk of onset/progression to AMD

Answer 18

High glycemic food

Question 19

what can a high dietary intake of provide a protective factor for AMD

Answer 19

xanthophylls and other antioxidants

Question 20

how is someone with a high BMI associated with an increased risk of developing AMD

Answer 20

due to elevation of pro-inflammatory cytokines/ complement components, and absorption of carotenoids by adipose tissue

Question 21

how does regular exercise influence a decreased likelihood of developing AMD

Answer 21

increased antioxidant enzyme activity

Question 22

which type of light exposure is a risk factor for developing AMD and how

Answer 22

Blue light
thought to result in more oxidative stress in the retina, causing the increased risk

However, the quantification of the total amount of light exposure is difficult to determine and therefore not often found to be associated with disease progression

Question 23

when in life is it best to recommend sunglasses and why

Answer 23

from a young age

blue light affects starts at a younger age before the lens starts to become hazier

Question 24

what pathological feature is independently associated with increased risk progression to AMD

Answer 24

presence of reticular pseudodrusen (subretinal drusenoid deposits)

Question 25

where are hyperreflective foci on OCT located in the retina and what isit often associated with

Answer 25

located in the neuroretina, often above drusen, and are associated with hyperpigmentation

Question 26

how much % of risk is there of nAMD in second eye per annum when one eye is already affected

Answer 26

12.2%