Introduction

Epidemiology is the study of the distribution and determinants of diseases and the application of the findings to the control of health problems. By studying the distribution of a disease we can learn about:

• How many people are affected.

• Who is at risk.

• Causes.

• Risk factors.

Epidemiology has various applications:

• Understanding the natural history of a disease.

• Planning and evaluating services.

• Disease prevention:

• — Primary: stopping the problem from arising.

• — Secondary: early detection and treatment.

• — Tertiary: minimising impairment and disability.

Epidemiological studies of pain

The first step in the study of a disease is to define the population group and develop a valid set of diagnostic criteria. This has been a major problem in studies both on the general problem of pain as a whole and of specific conditions.

• Prevalence is the number of cases of a given disease in a given population at a designated time (e.g. ‘point’, ‘period’ and ‘lifetime’ prevalence).

• Incidence is the number of new cases arising during a given period in a specified population.

There have been many studies published on the prevalence of chronic pain. The results of these studies vary widely, because they used different:

• Study populations.

• Diagnostic criteria.