LECTURE 5 Basics Of Epi Research Part 2 V2
Basics of Epidemiology
Research
PA R T 2
Measuring Disease
Occurrence
I N C I D E N C E A N D P R E VA L E N C E
Measuring Disease Occurrence
What do you think you need to quantify
(measure) disease occurrence?
The number of people affected
The total number of people in the population that the affected people came from
The length of time that population is followed
Basic Measures
Incidence
Prevalence
Incidence
Cumulative incidence =
Number of new cases occurring over a specified time period x 10n
Population at risk at the beginning of the time period
Incidence density =
Number of new cases occurring over a specified time period x 10n
Total person time at risk
Incidence Example
San Carlos County Health Department
reported 17 new cases of TB at the beginning of 2001. The population of the county was
204,500 at the beginning of the year and
215,000 at the end of the year. What is the cumulative incidence per 10,000 people?
Incidence Example
Imagine that, in January 1996, a team of
epidemiologists identified a sample of 4,500 men,
65-74 years of age, in Cedar Rapids, IA, for a study of prostate cancer. Tests indicated that 7% of the men already had prostate cancer and, therefore, were not at risk. The rest of the men were followed prospectively for 5 years to determine the cumulative incidence rate of prostate cancer in the sample. By the end of the 5 years of follow up, 156 of the men had developed prostate cancer. What was the 5-year cumulative incidence rate of prostate cancer in this group per 100 men?
Prevalence
Point prevalence rate =
Number of new + existing cases occurring at a specific time x 10n
Population at that time
Point Prevalence Example
Assume 3,465 women, 60-74 years of age,
were screened for the presence of osteoporosis at a major women’s health fair held January 3-10, 2002, in Phoenix, AZ. A total of 974 cases were identified. What was the prevalence of osteoporosis in this group per 100 women?
Point
Research
PA R T 2
Measuring Disease
Occurrence
I N C I D E N C E A N D P R E VA L E N C E
Measuring Disease Occurrence
What do you think you need to quantify
(measure) disease occurrence?
The number of people affected
The total number of people in the population that the affected people came from
The length of time that population is followed
Basic Measures
Incidence
Prevalence
Incidence
Cumulative incidence =
Number of new cases occurring over a specified time period x 10n
Population at risk at the beginning of the time period
Incidence density =
Number of new cases occurring over a specified time period x 10n
Total person time at risk
Incidence Example
San Carlos County Health Department
reported 17 new cases of TB at the beginning of 2001. The population of the county was
204,500 at the beginning of the year and
215,000 at the end of the year. What is the cumulative incidence per 10,000 people?
Incidence Example
Imagine that, in January 1996, a team of
epidemiologists identified a sample of 4,500 men,
65-74 years of age, in Cedar Rapids, IA, for a study of prostate cancer. Tests indicated that 7% of the men already had prostate cancer and, therefore, were not at risk. The rest of the men were followed prospectively for 5 years to determine the cumulative incidence rate of prostate cancer in the sample. By the end of the 5 years of follow up, 156 of the men had developed prostate cancer. What was the 5-year cumulative incidence rate of prostate cancer in this group per 100 men?
Prevalence
Point prevalence rate =
Number of new + existing cases occurring at a specific time x 10n
Population at that time
Point Prevalence Example
Assume 3,465 women, 60-74 years of age,
were screened for the presence of osteoporosis at a major women’s health fair held January 3-10, 2002, in Phoenix, AZ. A total of 974 cases were identified. What was the prevalence of osteoporosis in this group per 100 women?
Point