CHAPTER 14 Analyzing Incidence and Prevalence Rates in Epidemiologic Data 191

Chapter 14

Analyzing Incidence and

Prevalence Rates in

Epidemiologic Data

E

pidemiology is the study of the causes of health and disease in human

populations. It is sometimes defined as characterizing the three Ds — the

distribution and determinants of human disease (although epidemiology

technically also concerns more positive outcomes, such as human health and

wellness). This chapter describes two concepts central to epidemiology: ­prevalence

and incidence. Prevalence and incidence are also frequently encountered in other

areas of human research as well. We describe how to calculate incidence rates and

prevalence proportions. Then we concentrate on the analysis of incidence. (For an

introduction to prevalence and to learn how to calculate prevalence ratios, see

Chapter 13.) Later in this chapter, we describe how to calculate confidence inter-

vals around incidence rates and rate ratios, and how to compare incidence rates

between two populations.

IN THIS CHAPTER»

» ^{Determining and expressing the}

prevalence of a condition»

» ^{Calculating incidence rates and rate}

ratios, along with their standard

errors»

» ^{Comparing incidence rates between}

two populations»

» ^{Estimating sample size needed to}

compare incidence rates