A woman that hits menopause and doesn't have children is a dead end from an evolutionary perspective. What potential there was for propagating her genes is gone.
Men have a much larger window, and can produce offspring at any age from the first pre-teen ejaculation until death.
Back to the poll, it means that there isn't a single good answer for what 40 means. If you're a childless woman who feels the imperative drive to reproduce, it might mean you're way past middle age and really need to hurry. But if you're a free man, you might still have a good part of your reproductive years ahead of you.
And if you have children, regardless of gender, whether it's middle aged or old might depend on how old those children are.
There is no good answer, but I think overall, chances are that a woman will feel older at 40 than a man does. And even more so at 50.