Humans are one of the few species in which females undergo menopause.

But the company is also testing the drug in women who undergo natural menopause.

That's important, because many women report problems with sleep while they're undergoing menopause.

The 541 women in the study were 42 to 50 years of age and had not undergone menopause when the study began.

The researchers used women who underwent menopause between 50 and 55 as their point of comparison.

Of the 537 who underwent menopause from the ages of 40 to 44, 105, or 20 percent, died.

Of the 1,532 who underwent menopause from the ages of 45 to 49, 230 or 15 percent died.

Of the 2,314 who underwent menopause from the ages of 50 to 54, 300, or just under 13 percent died.

Of the 778 women who underwent menopause at 55 or older, 103, or slightly more than 13 percent, died.

But the researchers cited earlier studies showing that women can usually remember when they underwent menopause within a year.