Measuring the frequency of disease

Question 1

what is point prevalence?

Answer 1

number of cases / number of people surveyed

Question 2

what is the period prevalence?

Answer 2

the number of people who have suffered from a problem within a specified time period

period prevalence = number of cases at any time in the study period / average number of people in the population over the period

Question 3

what is the prevalence?

Answer 3

burden of disease - useful in determining the need for health services

Question 4

what is the incidence?

Answer 4

the rate at which new cases are appearing = incidence

Question 5

what is the cumulative incidence?

Answer 5

the number of people who develop a disease in a defined period / average number of people in the population in that period

this is useful if you run a service that engages patients over long periods, but not as useful for conditions that may happpen repeatedly to the same person

Question 6

what is the incidence density?

Answer 6

total number of episodes / total number of person-years at risk

useful for diseases that recur - gives us an index of the total burden of illness

Question 7

cumulative incidence vs. incidence density - which do we use?

Answer 7

if the focus = how many people, then cumulative incidence is better

if the focus is how many events then incidence density is better

Question 8

short lasting diseases have a low… compared to their … ?

Answer 8

they have a low prevalence compared to their incidence

Question 9

long lasting diseases have a high… compared to their…

Answer 9

long lasting diseases will have high prevalences compared to their incidences

Question 10

preventing death without curing the patient will increase duration of disease therefore, increase…?

Answer 10

increase prevalence