just how uncommon is low sex drive with mirena? any statistics?

Well, I can tell you that I have the Mirena for 3 Years. I have been married for 4 years, I got pregnant really fast, with in 3 months I was expecting my second child from my second marriage. I had the regular IUD with out the hormones just the regular copper one, never had issues, or weight gain, or mood swings, and regular periods. - Once I had my second baby at 39, I asked my doctor for the same thing. He talked me in to try the Mirena, much better, bla, bla, bla, and that It will stop my menstrual cycle. So I was like YES! Amen! - This got to be the best thing ever invented. HA!
"Be Careful What You Wish For"
I haven't got any sexual desired in the last 3 years. NONE- I don't feel like it, I don't care for it... I have become very depressed and sometimes I get very angry for no good reason. My face has dark spots and all I cant think is that the mirena must have something to do with all this - During these past 3 years I have blame the lack of sex/desired to the new baby, having a baby and a teenager - moved to a new city, my husband had a job chance, the fact that I became a stay home mom, and then my husband develop Diabetes...so, all of this in my mind equal stress and off course who in the world wants to have sex. My life its pretty much back to normal...and NOTHING! so I started to read about the only thing that I have with in me, that I did not had before. BINGO! Mirena with all the hormones...it got to be it! I hope this is it. I am only 42 and I think I should be having a normal and healthy sexual life- ....Good Luck! Do your research. I think Mirena is not for everyone. Don't let this happened to you.
When you are not happy, you can not make your family happy.

Mirena does not contain estrogen (progestin-only), and this could be a factor in these women's experiences with low-sex drive (compared to the combination oral contraception, that contains both estrogen and progestin).

Unfortunately, there are no statistics that I have found regarding actual causes of low libido from Mirena.

I also responded to your other post regarding who Mirena is recommended for:

I believe Mirena IUD was primarily for women who already have had children. Have you talked with your health care provider about this? Here is some information from the Mirena website:
"Mirena (levonorgestrel-releasing intrauterine system) is recommended for women who have had at least one child. This is because most of the medical research conducted on Mirena for FDA approval was among women who had at least one child." source: http://www.mirena-us.com/mirena_right/index.jsp