Healthcare and Medicine Reference
frequencies. It describes the situation in a group of workers exposed over
a period of time to an industrial carcinogenic substance from which some
workers develop cancer and some die. Quantification in this example is
Morbidity rates are rates of disease cases in a community defined in time
and space. The two most important are as follows:
1. Prevalence rates , disease frequency (cases, spells, manifestations, indi-
viduals treated, etc.) at a given point in time (point prevalence) or over
a period of time (period prevalence), independent of the moment of its
occurrence as it appears in a population of interest (cases and noncases
confounded) give us an idea of the overall magnitude of the health
problem either at a given moment or over a defined period of time.
Very often, chronic disease, handicaps, and other health problems of
long duration are in focus.
2. In incidence rates , frequencies of new cases of disease or another event
in a defined period of time (hours, days, years) are related to a popula-
tion in which they occur (preferably subjects susceptible to get it). In
our case, A/A + B and C/C + D. From one period of time to another, the
speed of disease spread can be measured. New cases, incidence spells,
incidence of various manifestations, or incidence of newly diagnosed
cases may be of interest from one problem to another. Infectious disease,
injury, cancer, or cardiovascular diseases are often followed this way.
Deaths in communities or any other group of interest are studied through
mortality and case fatality rates:
◾ Mortality rates are rates of death in such a community for all individu-
als , healthy, diseased, or suffering from other health problems con-
founded (in the denominator of a rate). They may encompass general
mortality rates or specific rates, which may be specific to disease, age,
sex, and other demographic or social-specific elements.
◾ Case fatality rates are deaths occurring in a given number of cases of
disease toward a given moment (cumulative events) or over a certain
period of time. They are therefore an occurrence of deaths by a disease
between cases only ( those who suffer from it already ).
Rates reflect the absolute magnitude of a given health problem. To get an
idea of the relative magnitude, we need health event ratios, event odds, and
other ways to compare rates, risks, or deaths. The most important ones for