EPIDEMIOLOGY 371
CENSUSESApart from censuses of Roman and biblical times, the fi rst
modern census was taken in Sweden in 1751. The fi rst in the
United States was in 1790, and the fi rst in England was in- Censuses traditionally were taken for two main purposes,
military and fi scal. Their epidemiological value in supplying
denominators for the construction of rates of mortality was very
much an incidental usage. Just as the concern about the plague
gave a new impetus to the regular production of the London
Bills of Mortality, so the anxiety about attacks by cholera was
an important factor in setting up national registration of deaths
in England and Wales in 1837. But from that time onward, mor-
tality rates were published annually in England and Wales, and
their implications, medical, social, geographical, and occupa-
tional, were very effectively analyzed and discussed by William
Farr, the fi rst medical statistician appointed to advise the regis-
ter general, which collected information on Mortality.
CAUSES OF DEATH AND THE ICDWith the advent of routine death registrations and censuses
throughout Europe and North America, the publication of
mortality rates in successively increasing detail stimulated
comparison, and demanded at the same time an agreed basis
for terminology. This led to the setting up in the middle of
the nineteenth century of international Statistical Congresses
to produce a classifi cation of causes of death. Gradually
these lists of causes became generally adopted by individual
countries, and in order to keep up with medical advances,
the list was required to be revised every 10 years. From a list
of causes of death it was extended to include diseases and
injuries not necessarily resulting in death, so that it could be
used for incidence by hospitals as a diagnostic index. The
ninth revision of the International Statistical Classifi cation
of Diseases, Injuries, and Causes of Death (ICD) came into
force in 1979 and has recently been replaced by the ICD-10,
on January 1, 1999. The ICD was originally formalized in
1893 as the Bertillon Classifi cation of International Causes
of Death. The ICD-10 is copyrighted by the World Health
Organization (WHO). The WHO publishes the classifi ca-
tion and makes it available to countries of the world. In
the United States, the U.S. government developed a clini-
cal modifi cation for purposes of recording data from death
certifi cates.
The degree of detail it is now possible to convey through
the use of the latest ICD code is very great, but of course
it is entirely dependent upon the subtlety of the informa-
tion available to the coder. However, the hierarchical design
of the code does permit expression of a rather less specifi c
diagnosis when the data are inadequate or vague. One of the
biggest problems with this type of system is that the data are
extracted from death certifi cates, which may not accurately
refl ect the true cause of death.
The WHO collects mortality data from its member states
and publishes mortality rates by cause, sex, and age group,
in the World Heath Statistics Annual. Individual countriesalso publish their own mortality data, often including more
detailed subdivisions, for instance of geographical areas.
The same offi ces in nearly all countries are responsible for
collecting and publishing statistics of births and marriages,
and probably also for the censuses, which recur at intervals
of 5, 7, or 10 years, according to the practice of the country.THE SEER PROGRAMAnother evaluator of specifi c mortality is the Surveillance,
Epidemiology, and End Results (SEER) Program of the
U.S. National Cancer Institute (NCI). This report provides
information on cancer incidence and survival using various
geographic locations of the United States. The concept of
these areas is to represent occurrence for the overall popu-
lation. SEER registries now include in its collection about
26 percent of the U.S. population. Information collected by
the SEER registries includes patient demographics, primary
tumor site, morphology, stage at diagnosis, fi rst course of
treatment, and follow-up status. Currently this is the only
source of population-based data on cancer that includes
its stage and diagnosis and survival rates for the stages of
cancer. This is also a Web-based source and is provided by
the National Center for Health Statistics. Analyses of SEER
data are commonly published in the literature, including for
determining trends of disease (Price and Ware, 2004).OTHER DATA SYSTEMSThere are other Internet-based data systems that provide
information on rates on deaths in the United States. This
includes the CDC Wonder system (CDC, 2004). This system
provides both crude and age-adjusted death rates as cat-
egorized by the ICD-9 and ICD-10 (specifi c causes or dis-
eases). Thus, by using this system, rates can be determined
by county and state and for the United States as a whole for
any year or group of years. Such systems allow evaluation of
varying rates over time and determination of trends. These
data can also be used in ecological epidemiological studies
to evaluate trends.COMPARISON OF MORTALITY RATES AND
STANDARDIZATIONWhen comparing the experience of two different countries
with respect to mortality from a specifi c disease, the rates
for each age group can be contrasted perhaps most easily in
graphical form. But comparing their crude rates of mortality
from the disease, in an endeavor to simplify the comparison,
is only legitimate in the unlikely event of their age struc-
tures being identical. Thus, in most studies there is an age
adjustment (Baris et al., 1996). This adjustment is based on
a large population, which is usually based on the national
or state population. Use of crude rates alone, without age
adjustment, may lead to inaccurate interpretation of the rateC005_011_r03.indd 371C005_011_r03.indd 371 11/18/2005 10:25:39 AM11/18/2005 10:25:39 AM