statistical difficulties

[miriam_e]

In a couple of places recently I've read the uncritical statement that caffeine and nicotine have some apparent protective effect against alzheimers. I find this difficult to believe. I have seen spurious statistical effects before and have to wonder if this is another. Did study control for the number of people killed by cigarettes and coffee? If people die earlier from cigarettes then a younger, intrinsically more resilient group will remain, who may well be less likely to get alzheimers, but not because nicotine protects; it would be simply that the cigarettes had already killed the most susceptible.

I know people are fond of saying that caffeine is safe, but I frankly don't believe it (to my shame I do drink caffeine). When I was a kid I embarked on an experiment with a friend at school to mutate fruit flies by feeding caffeine to them. Doesn't sound like a safe substance to me. Doesn't it strike anybody else as odd that caffeine producing plants are rendered fairly safe from pests. Why would that be do you suppose? Perhaps the insects are, in a sense, smarter than we are. I am almost willing to bet that some day in the future we will find that caffeine has been afflicting society with massive health problems that we have been studiously ignoring, just as we did for so long with cigarettes, and still do to some degree with alcohol.