Mortality rates from two communities can best be compared after calculating:

• A. The age-adjusted rates.
• B. The crude rates.
• C. The gender-specific rates.
• D. The prevalence rates.

Answer: (A)

Mortality varies with age, so comparing two communities with different age structures can be misleading if you use crude rates. Age-adjusted rates remove the influence of age distribution and reveal true differences in mortality risk. This is done by applying each community’s age-specific mortality rates to a common standard population (direct standardization), then summing to get a single rate that would occur if both communities had the same age makeup. The result lets you compare mortality on the basis of risk rather than how old the populations are. Other options either reflect the age mix (crude rates), divide by gender (gender-specific rates), or measure existing cases rather than deaths (prevalence), none of which provide the fair, overall comparison that age adjustment achieves.