Hi - I'm writing a short text on epidemiological study design, analysis and
critical appraisal and I'm describing prevalence and incidence.
I have stated that prevalence is a cross-sectional measure of frequency
(time is not included in the denominator, just "person") while incidence is
a longitudinal measure of frequency (with time in the denominator i.e."
person-time")
However I'm now trying to describe period prevalence. While time is not
explicitly in the denominator it seems to be not disimilar to some measures
of incidence. For example, the prevalence of symptomatic asthma, is often
estimated by asking study participants if they have had any asthma symptoms
in the last year. While this period prevalence measure does not consider
how often the participant has asthma symptoms, how does the period
prevalence of asthma symptoms in the last year differ from a measure of
incidence of symptomatic asthma measured over 1 year, where each person
with asthma symptoms is only counted once in the numerator?
any help would be great.
Rod Jackson
Rodney Jackson MBChB PhD FAFPHM
Professor of Epidemiology
Head of Department
Dpt of Community Health
Faculty of Medical & Health Sciences
University of Auckland
(Grafton Mews, 52-54 Grafton Rd)
Private Bag 92019
Auckland, New Zealand
Phone: +64 (0)9-3737599 ext 6343
Fax: +64 (0)9-3737494
e-mail: [log in to unmask]
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