st: Interpretation of log transformed variables in logistic regression?

[Jason Davis <jason_davis@umail.ucsb.edu>]

I can use some help with this one. I have run a multivariate  
logistical regression with log transformed continuous variables,  
non-transformed continous variables, and some categorical variables.  
The DV is birth outcome in a given year (yes/no) and the IV of  
interest is income (log transformed). The results are in odds ratios.  
My confusion is how do I interpret the odds ratio of the log  
transformed continous variable. Specifically, the odds ratio of log  
income is 5.4. If I back transform this I get 1.68. This does not seem  
right, as a $1 increase in income would raise the odds of giving birth  
in a given year by 68%. This would mean $1,000 raise would increase  
the odds by 0.68*1000 or a 680% increase in the odds of giving birth.  
Any suggestions would be greatly appreciated.

Jason

*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/