Events per person year—a dubious concept

In 1982 a new measure was introduced in research into osteoporosis and is now used everywhere in the literature. The so called "fracture rate" relates the number of fractures (single in some patients, multiple in others) to the cumulative time of observation of all patients. This concept,...

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Bibliographic Details
Published in:BMJ 1995-02, Vol.310 (6977), p.454-456
Main Authors: Windeler, Jurgen, Lange, Stefan
Format: Article
Language:English
Subjects:
Clinical trials
Education & Debate
Estimators
Estrogens
Estrogens - therapeutic use
Female
Fractures, Bone - prevention & control
Humans
Medical research
Observational research
Osteoporosis
Osteoporosis, Postmenopausal - drug therapy
Patient Dropouts
Placebos
Postmenopausal osteoporosis
Randomized Controlled Trials as Topic - methods
Sample size
Spine
Statistics as Topic - methods
Treatment Outcome
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Summary:In 1982 a new measure was introduced in research into osteoporosis and is now used everywhere in the literature. The so called "fracture rate" relates the number of fractures (single in some patients, multiple in others) to the cumulative time of observation of all patients. This concept, however, has no sound basis. Counting events instead of patients usually violates basic statistical assumptions and invalidates the use of common statistical tests and estimators. Its clinical interpretation is rather dubious. The use of such a measure impedes the search for valid and clinically meaningful outcome criteria and should be abandoned.
ISSN:0959-8138
1468-5833
1756-1833
DOI:10.1136/bmj.310.6977.454