Here you go.
"A review of more than 15 studies on the effects of alcohol on performance found that alcohol was involved in roughly 50 percent of all accidents in people of drinking age. In Diving and Subaquatic Medicine (Edmonds C, et al., 2002), the authors report that alcohol is associated with up to 80 percent of all drownings in adult males.
Somewhat of a necropost here, but the quote illustrates a problem with the statistics cited (the original article may clear it up, but the quote as given has some problems).
"Alcohol was involved in 50 percent of all accidents of people of drinking age." This statement is meaningless unless you know what percentage of the population was consuming alcohol. It's very different if 1% consume alcohol and result in half the accidents than if 90% consume alcohol, in which case it's those 10% teetotalers who are more dangerous.
Likewise, the quote from Edmonds about *up to* 80% of all drownings in adult males has some issues. Does that count people getting drunk in a hot tub or committing suicide in a bathtub? How about drunken beach goers? Or drivers who wind up in the river. Or ice fishermen who fall in and are unable to save themselves. These all in the "drownings" bucket, but none of them are necessarily representative of hung-over/drunken divers, so citing the statistic doesn't help with the original question.
The subsequent cite from Perrine is a much better one.. it's describing data from actual divers, but unfortunately, it's for "experienced divers". One could (not seriously) contend that with a bunch of mid experience "once a year" kind of divers (past the nervousness of the newly minted and more careful, but not had the near death experiences of the more experienced) that the danger from over confidence is small compared to alcohol induced bad judgement.
I'm also a bit leery of statements like "X may be reduced".. that's usually something the author puts in because it's sort of expected, but the data didn't show it, or there's no way to test for it. "may be" is a pretty weaselly way to say something. And I doubt anyone has quantified the safety implications of "protective inhibitions" with respect to dive safety. Sure, it seems common sense that protective inhibitions are the opposite of carelessness and carelessness is certainly a risk factor, but then, it's also common sense that showing up at the dock with a pounding hangover headache and alleviating it with some hair of the dog isn't the best plan.
The OP was looking for something objective: "hangovers are positively correlated with death and injury" that he could use to help dissuade customers who are unhappy with being unable to dive when they've paid in advance for it. This is a dicey area of customer relations and it's a very fine line you have to walk between being the dive *master* (implying that the DM gets to make the go/nogo decision) and selling an (expensive) service to a customer. And while it's a rationalization in most cases, it is also reality that you might be sending that customer on to someone less conscientious (Dude, you've only pounded half that sixer so far.. strap on the tanks and let's go diving, you're good to go.). You read the stories on forums like this and in the magazines, and hear them on the boats.. How many divers have gone in where the DM wasn't feeling real confident in the diver's abilities (whether due to alcohol, illness, or just plain inexperience/lack of training) and the DM says "They're here to have a good time, I think I can manage to keep them in safe territory, and they'll go home happy"
This is true in ALL activities where there's a service provider involved.. horseback riding, paragliding, ATV rentals, etc.
I think what the OP is looking for is something that is "neutral and objective" to use to help convince the customer, so it doesn't become a personal thing. (One could argue that it's also sort of passive aggressive, but hey, nothing is clearcut). Sort of like the sign at the auto shop that says "Insurance regulations prohibit customers in the shop".. when in reality it's nothing of the sort.
