In the context of an epidemiological study, a multinomial regression analysis was used to obtain odds ratios for an outcome variable with four different categories.
proc logistic data=ha8 descending;
class gp (ref='1')/ param=ref;
model gp = BMI_A2/link=glogit;
run;
For example we got results as follows (the values are fictional):
- 1.4 is the multinomial logit estimate for a one unit increase in BMI (continuous) for group 4 relative to group 1. If a subject were to increase his BMI by one point, the multinomial log-odds for group 4 relative to group 1 would be expected to increase by 40%.
- 1.3 is the multinomial logit estimate for a one unit increase in BMI (continuous) for group 3 relative to group 1. If a subject were to increase his BMI by one point, the multinomial log-odds for group 3 relative to group 1 would be expected to increase by 30%.
- 1.2 is the multinomial logit estimate for a one unit increase in BMI (continuous) for group 2 relative to group 1. If a subject were to increase his BMI by one point, the multinomial log-odds for group 2 relative to group 1 would be expected to increase by 20%.
Which conditions are necessary in order to interpret odds ratios obtained from this multinomial logistic regression, as relative risks?
Many thanks!