Descriptive Epidemiology, Measures of Disease Frequency
Principles of Epidemiology
Homework Assignment #1
*Descriptive epidemiology, Measures of disease frequency*
NOTE: Assignment is due (hard-copy and typed) at the start of the discussion group.
- Create a summary table of formulas that will be helpful for you from this week’s lectures.
CI= | Number of new cases of disease during a specified time period | |
Number in at-risk population at beginning of time period | ||
AR= | Number of new cases of disease | |
Total population at risk for a ‘limited’ period of observation | ||
Case-fatality rate= | Number of deaths from disease | |
Number of cases of that disease | ||
IR= | Number of new cases of disease during a specified time period | |
Total at-risk person time of obervation | ||
MR= | Total number of deaths | |
Total person-time of follow-up | ||
P= | Number of existing cases of disease at a specified time | |
Total of people in population at that time | ||
Birth defect rate= | Number of children born with defects | |
Total number of births |
- A total of 2,121,323 deaths were recorded in the US in 1987. The mid-year population was estimated to be 243,401,000. HIV-related mortality and population data by age for all residents and for black males are shown in the table below, also for 1987. Use these data to calculate the following:
- Crude mortality rate for the US population
MR=2,121,323/243,401,000=871.5 per 100,000 PY
- Express this crude mortality rate (your answer to part a.) in a different way. What is this measure called?
One-year Cumulative Incidence of death=0.87%
- HIV-specific mortality rate for entire population
MR=13,465/243,401,000=5.5 per 100,000 PY
- HIV-specific mortality rate among all 35-44 year olds
MR=4794/34,305,000=14.0 per 100,000 PY
- HIV-specific mortality rate among 35-44 year old black males
MR=1212/1,663,000=72.9 per 100,000 PY
- Summarize your results in a couple of sentences.
HIV mortality rate for entire population of US in 1987 was 5.5 per 100,000PY. Important differences were observed, with black males among 35-44 years of age suffering higher HIV deaths than that of others
All races | Black males | |||
Age group | HIV deaths | Population | HIV deaths | Population |
0-4 | 191 | 18,252,000 | 47 | 1,393,000 |
5-14 | 47 | 34,146,000 | 7 | 2,697,000 |
15-24 | 492 | 38,252,000 | 145 | 2,740,000 |
25-34 | 5026 | 43,315,000 | 1326 | 2,549,000 |
35-44 | 4794 | 34,305,000 | 1212 | 1,663,000 |
45-54 | 1838 | 23,276,000 | 395 | 1,117,000 |
55+ | 1077 | 51,855,000 | 168 | 1,945,000 |
- The following 8 elderly women were residents of an assisted living facility and were followed by the same doctor for 12 years. The table below describes events that occurred during the 12-year period.
Patient | Outcome |
A | Followed for the full 12 years. At the end of year 5, she was diagnosed with Alzheimer’s disease. |
B | Died at the end of year 2 and never had Alzheimer’s disease. |
C | Died at the end of year 8 and never had Alzheimer’s disease. |
D | Diagnosed with Alzheimer’s disease at the end of year 2 and died at the end of year 8. |
E | Lost to follow-up at the end of year 7 and never had Alzheimer’s disease. |
F | Died at the end of year 4. At the start of the study, she had already had Alzheimer’s disease for 2 years. |
G | Lost to follow up at the end of year 9. At the end of year 3, she was diagnosed with Alzheimer’s disease. |
H | Followed for the full 12 years, and never had Alzheimer’s disease. |