I think it would depend on the probabilities and payoffs: if surviving to the Singularity is sufficiently worthless, or taking care of your health is sufficiently expensive, or the Singularity is near with extreme confidence, then you might conclude that you can neglect your health, stop brushing your teeth, etc. But very few people expect any singularity to be near or sooner than a decade or two, or with extreme confidence, so I think for any plausible values you'd wind up wanting to pay attention to your health. Cancer can strike at any time, among other threats.