I think this analysis is incomplete. It's important to separate out longevity from cause of death. "The China Study"'s central premiss is that a vegan diet reduces the likelihood of dying of the "Western" diseases such as heart disease and cancer. A simple correlation between a vegan diet and longevity doesn't address this and also wouldn't take into account the high correlation between not being able to afford animal products and a lack of access to medical care. If you actually read the book the author goes into all this detail.