If one sleeps less than 6 hours a night, maybe there's other reasons for that, that lead to stroke, like anxiety over being deep in debt. So reducing such risk of stroke may not be as simple as getting more sleep.

Reminds me of the study that concluded that people living together (vs. married) leads to ~30% greater chance of alcholism. Maybe alcoholics just aren't as likely to get married?

Surely there's a Wiki on this type of logical fallacy somewhere. Anyone know what it's called?