VITAL STATISTICS A branch of statistics that deals with the changes and most basic events of human populations: e.g., natality (birth); mortality (death); morbidity (illness and disease); injuries; marriage . . . Vital statistics are indispensable in studying social and health trends, and making important legislative, commercial (marketing) and health decisions Statistics are gathered from census and registrars’ reports, physicians’ records, medical examiners’/coroners’ records, funeral directors, and a variety of other health professionals

VITAL STATISTICS In the United States, national statistics are compiled and published by the Public Health Service of the Department of Health and Human Services The most important element in vital statistics is the rate, which customarily represents the average of births or deaths (incidents) for a unit of 10 during a given period of time (usually a year). General rates are called crude rates; when subdivided into sex, race, age, occupation, locality, etc., these are known as specific (refined) rates

RATES: DENOMINATORS AND NUMERATORS Rates or ratios are used to measure most health problems They consist of numerators and denominators: a count of events divided by the number of possible events Numerators and denominators used in public health statistics are of three types: Survival data (births, deaths, and a count of the population Health and socioeconomic status data Data based on health resources and utilization

THE DENOMINATORS The most important information on which activities in public health must be predicated is a count of the population to bee served The decennial census is an important and the most widely used information as the denominator May include intercensal estimates, based on projects or sample surveys Other sources of information may also be used, depending on the phenomenon of interest; for example -- School enrollment records Employer records of numbers of workers

THE DENOMINATOR Airline carriers for numbers of passengers carried during a given time Numerator data stem from administrative registration and reporting procedures Most significant of activities relate to the vital events of birth, mortality (death), and morbidity (disease, illness, and injury

INCIDENCE AND PREVALENCE Incidence Rate Number of new events occurring during a reporting period (such as cases of measles), divided by the population at risk of the events Incidence may be calculated for a week, a month, a year, or any period that is helpful in explaining the phenomenon Prevalence Rate Number of cases existing at a particular time, divided by the population at risk of the event Prevalence is typically referred to as point prevalence, since it calculated at a particular point in time

In both incidence and prevalence rates, a constant has to be selected, based on the frequency of the event E.g., for very rare diseases or conditions, such as leukemia, the constant may be 100,000, whereas it might be 1,000 or 100 for more common conditions, such as live births