3.1.5—Health problem prevalence
- Syllabus
- First assessment 2027
- Objective
- 3.1.5
- Level
- HL
Prevalence describes how common a health problem is in a defined population
Prevalence is the proportion of a population with a condition at a specified time or period. Incidence counts new cases over time. Both need a numerator, denominator, case definition and date before comparisons are meaningful.
Prevalence rises when incidence increases or when people live longer with the condition, and falls when recovery or death removes cases. Survey method, diagnosis and access can change the measured rate without changing underlying health.
If 80 of 2,000 adults meet a defined criterion on a survey date, point prevalence is 4%. Comparing that with another country requires aligned age groups, instruments, sampling and dates.
Prevalence is not automatically risk or cause. A high value can reflect better detection or longer survival, so interpret the denominator and time window.