Prevalence, Incidence, and Risk Factors for Tinnitus.

How many people are affected by tinnitus? Is the risk of developing tinnitus on the rise or has it been declining over time? What modifiable lifestyle factors could help to prevent tinnitus? These population-based questions can be addressed through epidemiological research. Epidemiology refers to the underlying and basic science of public health. It describes the study of the distribution and determinants of health-related states or events in specified populations and the application of this study to the control of health problems. There are two key concepts in epidemiology: (1) measures of frequency and (2) measures of effect. In this chapter, we introduce the two main measures of frequency, prevalence and incidence. We also introduce the notion of risk factors, critical for understanding measures of effect concerning the risk of developing a health condition. In both sections, we provide illustrative examples from the published literature on tinnitus. We end by offering a critical evaluation of the current status of epidemiological research on tinnitus and point to some promising future directions.