Epidemiology_ A Very Short Introduction - Rodolfo Saracci.pdf

Health is everybody's natural concern, and
an everyday theme in the media. Outbreaks
of disease such as the most recent influenza,
occurring in many countries at the same time,
make front-page news. Beyond epidemics,
novel findings on dangerous pollutants in the
environment, substances in food which
prevent cancer, genes predisposing to
disease or drugs promising to wipe them out,
are reported regularly. Their actual
relevance for human health depends crucially
on the accumulation of evidence from
studies, guided by the principles of
epidemiology, that directly observe and
evaluate what happens in human populations
and groups.
These studies combine two features. They
explore health and disease with the
instruments of medical research, ranging
from records of medical histories to
measures of height, weight, blood pressure to
a wide variety of diagnostic tests and
procedures. At the same time they involve
individuals living in society exposed to a
multitude of influences, and they cannot be
conducted in the isolated and fully controlled
conditions of laboratory experiments. Their
design, conduct and analysis require, instead,
the methods of statistics and of social
sciences such as demography, the
quantitative study of human populations.
Without a clear understanding of this
composite nature of epidemiology and of its
reasoning in terms of probability and
statistics it is hard to appreciate the strengths
and weaknesses of the scientific evidence
relevant to medicine and public health that
epidemiology keeps producing. It is not only
among the general public that a woolly
appreciation or even a frank misreading of
epidemiology often surfaces, for instance in
debates on risks or on the merit, real or
imagined, of a disease treatment. In my
experience the same may occur with
journalists, members of ethics committees,
health administrators, health policy makers
and even with experts in disciplines other
than epidemiology responsible for evaluating
and funding research projects.
This Very Short Introduction is intended to
give readers insight into what makes a
difference between an epidemiological tale,
be it about a magic pill or a fearful virus,
and scientifically sound epidemiological
evidence. The difference does not depend on
how exciting or practically important the pill
or the virus stories maybe but solely on how
well the epidemiological methods behind
them have been applied. The methods and
logic of epidemiology are a rather austere
matter but I have attempted to give a flavour
of the nature of the field with no
mathematical symbols and formulas and only
the simplest arithmetic. To set epidemiology
into perspective its methods, logic and uses
in medicine and public health are outlined
against the backdrop of today's concerns for
ethics and social justice in health.
My gratitude goes to the many colleagues and
students, continuing sources of learning, that
have made this book possible. My task has
been facilitated by the cooperation and
competence of the Oxford University Press
staff. I owe personal thanks to Latha Menon
for her sympathetic support and thoughtful
advice throughout all phases of the book
preparation and to Sharon Whelan who
patiently revised my English.