La. Mcnutt et al., Logistic regression analysis: When the odds ratio does not work - An example using intimate partner violence data, J INTERP V, 15(10), 2000, pp. 1050-1059
The odds ratio is one of the most common measures used to assess the relati
onship between exposure to violence and adverse health outcomes, adjusting
for possible confounding factors. A reason for the odds ratio's popularity
is that it is relatively easy to calculate from the coefficients of a logis
tic regression model. For most etiologic studies of disease, the odds ratio
is a suitable estimate of risk because incidence or prevalence of disease
is rare (<10%). However; health outcomes studied in violence research are o
ften more prevalent (e.g., fatigue, insomnia, stomach pain, and shortness o
f breath). In these cases, the odds ratio usually overestimates the strengt
h of association, sometimes erroneously tripling the magnitude. Data from a
study measuring the health effects of intimate partner violence are used t
o illustrate the problem of incorrectly using odds ratios. Methods to calcu
late relative risks and prevalence ratios from logistic regression models a
re presented.