Saw an article abstract in the February edition of Menopause about isoflavones, insomnia, and hot flashes in post-menopausal women. Researchers studied 38 post-menopausal women - admittedly a small number. The study was placebo-controlled and double-blinded.
The women participants took either a placebo or 80 mg of isoflavones (found in soybeans) daily for four months. They did sleep studies to determine how much they slept while in bed on the night of the study - called sleep efficiency. I use 85% or more as a cutoff for normal sleep efficiency. This means, that you are asleep 85% or more of the time you are in bed. For the isoflavone group, sleep efficiency went from 77.9% to 83.9%. For the placebo group, sleep efficiency went from 77.6% to 81.2%. The difference between the placebo and isoflavone group was deemed statistically significant. These numbers are very underwhelming and neither placebo nor isoflavone were able to get the sleep efficiency to what I consider the normal level.
Insomnia intensity went down over four months for both the placebo group and the isoflavone group, but the isoflavone group had a greater decrease. Specifically, 95% of the placebo group and 90% of the isoflavone group rated their insomnia as moderate or intense at the beginning of the study. After four months, 63% of the placebo group and 37% of the isoflavone group had moderate or intense insomnia.
Finally, the number of hot flashes experienced trended downward by two months and was statistically less by four months in the isoflavone group than the placebo group. Numbers were not given in the abstract so I don't know how much each group changed by themselves. Apparently, hot flash intensity also was significantly lower in the isoflavone than placebo group - again no numbers were given in the abstract to put this into perspective like for the sleep efficiency data above.