BMJ 1994;308:660 (5 March)

Letters

Osteoarthritis of weight bearing joints

EDITOR, - Urho M Kujala and colleagues report an analysis of the time to the first recorded episode of osteoarthritis of the leg, using the Cox proportional hazards model.1 They state that "by analogy with the logistic model, the hazard ratios estimated by Cox model are termed here odds ratios." The hazard ratio is the ratio of the instantaneous probabilities of the event (onset of osteoarthritis) for those with the risk factor and those without, not an odds ratio. Relative risk would be a better term. An odds ratio does not have the same numerical interpretation as the ratio of two probabilities. For example, for the probabilities 1/2 and 1/4 the ratio of probabilities is 2 but the odds are 1 and 1/3, so the odds ratio is 3. The abstract to this paper refers to "age adjusted odds ratios," with no suggestion as to how these were obtained. This . . . [Full text of this article]


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Relevant Article

Osteoarthritis of weight bearing joints of lower limbs in former elite male athletes
U M Kujala, J Kaprio, and S Sarno
BMJ 1994 308: 231-234. [Abstract] [Full Text]

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