Summary: Hnh Introduction To Epidemiology And Public Health

Read the summary and the most important questions on HNH Introduction to epidemiology and public health

• College 2

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• Explain and give an example of a cumulative incidence/incidence proportion calculation

  - Measures the proportion of people who develop the disease during a specified period (NEW cases)
  

  • Number of people who develop disease in a specified period / Number of people at risk of getting the disease at the start of the period

  - Estimate of the average risk of the persons in the cohort
  - Condition: complete follow-up, no competing mortality
  
  7 deaths
  5 nothing
  12 in total
  
  7/12 = 0.58 --> average risk in population is 58%       

• How do you calculate the incidence rate?

  - Incidence rate/mortality rate/incidence density
  

  • Number of people who develop disease / Number of person years when people were at risk of getting the disease

  --> time at risk instead of people at risk
  
  24.5 time at risk (calculate how many people where at risk at what time)
  2 deaths 
  
  
  2/24.5 = 0.082 person-year

• What is a proportion and what is a rate?

  - Proportion
  

  • Number of people in the denominator
  • One number / another number + one number = total number
  • Always a ratio, between 0 and 1

  - Rate
  

  • Has person-time in the denominator 
  • One number / another number
  • Not all ratios are proportions
    

• What is the case fatality ratio?

  - Proportion of people with a given disease who die from it in a given period (usually < 1 month)
  - Measure of the short term severity of an acute disease
  - Number of deaths from a disease in a specified period / Number of people diagnosed with the disease in same period

• In a community with a population of 50.000 people, 27 developed diabetes during a 2 year period. Calculate the measure of incidence and identify what type of measure it is.

  - Incidence rate
  

  • 27 / 50.000 * 2 = 27 / 100.000 person-years 
    

• When do you use incidence and prevalence?

  1. Incidence is generally used for acutely acquiered diseases, prevalence is used for more permanent states, conditions or attributes of ill-health
     
  2. Incidence is more important when thinking of etiology of the disorder, prevalence when thinking of societal burden of the disorder including the costs and resources consumed as a result of the disorder
     

• What was the prevalence of high blood pressure at age 55? (in %)What was the prevalence of high blood pressure at age 65? (in%)How many women were at risk of high blood pressure at the start of the 10 year period?What was the incidence of high blood pressure in these women? (% in 10 years)Is this an incidence proportion or an incidence rate?

  1. 100/2000=0.05 --> 5%
  2. 400/2000=0.2 --> 20%
  3. 2000-100 (already had it) = 1900
  4. 300/1900=0.16 --> 16% in 10 years
  5. IP: these same women have been followed for 10 years

• Assume that, on average, each of these women who developed high blood pressure did so half-way during the 10-year follow-up period.Calculate the total number of person-years at risk (of developing high blood pressure) during the 10 yearsWhat was the incidence rate of high blood pressure in these women? 

  1. 300 women developed HBP x 5 years = 1500
  1600 women without HBP x 10 years = 16.000
  In total: 17.500 person years
  
  2. 300/17.500 = 1714/100.000 = 17,1 per 1000 person-years

• Tell more on incidence, prevalence and the duration of the disease

  - Prevalence varies directly with both incidence and duration
  - If incidence is low, but duration is long (chronic), prevalence will be large in relation to incidence
  - If prevalence is low because of short duration (due to recovery, migration or death), prevalence will be small in relation to incidence
  
  Prevalence = incidence x duration
  
  What influences prevalence and incidence figures?
  

  • Risk factors, type of population, genetic background
  • Disease duration, medicale treatment, cure
  • Risk of dying from the disease, case fatality
  • Detection, diagnosis, awareness (patients & doctors)
  • Disease coding and registratrion systems
  • Contagiousness, transmission of disease, hygiene, population density       

• College 3

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• What influences COPD?

  Genetic susceptibility
  

  • Genetic variants associated with lung function

  DNA methylation
  

  • Epigenome is link between the inherited genome and environmental exposures
  • Exposure to cigarette smoke, air pollution and job-related exposures