Passage Summary: People usually blame women's longer lives for their higher rates of Alzheimer's, but new evidence suggests it might actually be due to differences in hormone levels between men and women.

Conclusion: The theory that women suffer more from Alzheimer's simply because they live longer may be incorrect.

Reasoning: Research suggests that estrogen levels play a role in preventing the disease; since men maintain stable levels of a hormone that converts to estrogen while women's estrogen drops after menopause, hormonal differences likely explain the discrepancy.

Analysis: To find the conclusion here, look for the claim the author is trying to prove rather than the background facts. The author introduces a common theory regarding lifespan only to pivot with the phrase 'this theory may be wrong,' which signals the main point. The subsequent information about estrogen and testosterone serves as evidence to support this skepticism of the traditional explanation.