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Uncover the fundamentals of epidemiology, from its historical roots with John Snow to modern-day frameworks like incidence and relative risk. Learn about the importance of confidence intervals and temporal relationships, with a focus on controlling health problems in populations.
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Epidemiology: a very basic start…. Gavin Shaddick Department of Mathematical Sciences University of Bath UBC, September 2008
What is epidemiology? • “The study of skin diseases?”
What is epidemiology? • “The study of skin diseases?” • “The study of the distribution and determinants of health-related states in specified populations, and the application of this study to control health problems."
Overview of epidemiological framework • Incidence • Proportion of people who develop the disease during specified period • Risk • Probability of developing disease within a specified time interval (between 0 and 1) • Relative Risk • The ratio of risks under two exposure distributions
Relative risks and confidence intervals • RR is a ratio • Values ‘significantly’ >1 indicate increase in risk with increased exposure • Values ‘significantly’ <1 indicate protective effect of exposure • Values ‘close’ to 1 indicate no significant effect • 95% confidence interval • Gives a range of values within which we are ‘confident’ the true relative risk lies • Interest in values with the lower limit greater than one
RR = 1.3 1.5 1.1 0.9 1.7 Confidence intervals • 95% confidence interval • Gives a range of values within which we are ‘confident’ the true relative risk lies • Interest in values with the lower limit greater than one 1
Temporal relationships between exposure and effect Latent Acute Lead time Latency Time Time Exposure and Effect Chronic Endemic Time Time
SIRs for (a) lung and (b) brain cancer in North-West England, 1991-91