Dr Eva Batistatou

Outline of this presentation… What is epidemiology? The Fundamentals of Epidemiology course What is biostatistics? The Biostatistics course

What is Epidemiology? Origin of the term: epi (upon) + demos (people) + logy (study of)

What is Epidemiology? Definition: e.g. The study of the distribution and determinants of disease frequency in man MacMahon & Pugh (1970)

One of the pioneers of epidemiology due to his study of cholera in London in John Snow ( )

Importance of Epidemiology in Public Health Epidemiology provides the basis for describing and explaining disease occurrence in a community Examples of epidemiological questions: How many new cases of AIDS were reported among teenagers in USA last year? We might want to compare the number of reported cases to numbers in prior years to get a sense of whether AIDS is increasing or decreasing in this age group. The number of reported new cases of AIDS is almost three times higher in young adults, 20-24years of age, compared to teenagers. …seeking an explanation for the difference into behaviors/factors that differ between the age groups eg sexual activity, intravenous drug use.

Importance of Epidemiology in Public Health Also… Epidemiology provides a basis for developing, prioritizing, and evaluating public health programs Examples of epidemiological questions: What problems are present in the community? What problems have the greatest public health impact? Are adequate health services available and accessible? Is a specific public health program successful?

Risk The probability of disease developing in an individual in a specified time interval Association The relationship between an exposure or risk factor and an outcome Bias and confounding Systematic errors in the collection or interpretation of data that must be minimised Causation Establishing that the association between an exposure and an outcome is causal

Descriptive studies Describe the distribution of disease in relation to person, place and time Case-control studies What is the likelihood of exposure in people with disease compared with people without disease? Cohort studies What is the likelihood of developing disease for people who are exposed compared with people who are not exposed? Intervention studies What is difference in outcome among people who received the intervention compared to people who did not?

On completion of the FOE unit you should be able to: Calculate incidence and prevalence rates Outline the advantages and disadvantages of descriptive studies, case-control studies, cohort studies and interventional studies Calculate the appropriate effect measures within these study designs such as the OR and the RR Understand the types of bias that can occur in observational studies Understand the impact that bias, confounding and effect modification can have on observational studies Perform direct and indirect age standardisation Understand the principles of routine epidemiological surveillance and screening

What do we need to answer our epidemiological questions? Data!!! And then…what?

What is Biostatistics? It is the science which deals with development and application of the most appropriate methods for the: Collection of data Presentation of the collected data Analysis and interpretation of the results Making decisions on the basis of analysis

Collection of data Sources of data Records Surveys Experiments

Types of data Constant Variables

Types of Variables Qualitative e.g. favourite colour Quantitative Discrete e.g. shoe size Contin. e.g. height

Presentation of the collected data

Manchester Childrens Growth and Vascular Health Study data

On completion of the Biostats unit you should be familiar with: the concepts on which statistical methods are based different types of data and different types of statistical tests statistical analysis using a statistical package (e.g. Excel, StatsDirect, SPSS) focus on understanding and interpreting the output from a statistical package

And also… Descriptive statistics: mean, median, standard deviation, confidence intervals etc Hypothesis tests: z-test, t-test, Mann-Whitney, chi-square etc Sample size, correlation and simple linear regression Multiple linear regression and logistic regression Survival analysis

Assignments Assignment 1 - Week 5 (30% of final mark) Assignment 2 - Week 10 (70% of final mark) Overall score 0-40%Fail 40-50% Diploma pass 50-70%Masters pass %Distinction pass

Recommended reading Raj Bhopal (2002) Concepts of Epidemiology: an integrated introduction to the ideas, theories, principles and methods of epidemiology Kirkwood and Sterne (2003) Essential Medical Statistics