The temporal gradient of intoxication in the night-time economy

It's pretty clear to most people who have been out late in the CBD of a city on a Friday or Saturday night that there are a lot of very intoxicated people about. But how intoxicated are people out and about on the streets at night? In a new journal article in the latest issue of the Journal of Studies on Alcohol and Drugs (sorry there isn't an ungated version, but you can email me for an offprint), Matthew Roskruge (Massey University), Nic Droste and Peter Miller (both Deakin University) and I set out to find out.

Essentially, we (along with some willing research assistants) spent five nights in November and December 2014 surveying every seventh person on the street, and taking a breathalyser reading from every one of them that was willing (which was almost all of them). The following diagram neatly summarises the results. The solid line is the moving average breath alcohol content (BrAC) at each point in time throughout the night. You can clearly see that it is pretty flat until about 9:30pm (the dinner crowd), then upward sloping until around midnight (the slow part of the night), then flattens out again when things start to get busy. We referred to those changes in the average level of intoxication as the temporal gradient of intoxication. The other thing to note from the diagram is the difference between those who were pre-drinkers (those who had something to drink before coming out to the CBD that night) and non-pre-drinkers. Pre-drinkers in the CBD at night are clearly more intoxicated, but their average BrAC levels out from about midnight, whereas the non-pre-drinkers continue to increase in intoxication throughout the night.

There's also an interesting difference between men and women, as shown in the second diagram below. Men continue to get more intoxicated (on average) throughout the night, but women's BrAC levels off from sometime around midnight. We don't have any firm details on why, but we can speculate that men are more likely to continue drinking at high levels when they are out on the town, but women are less likely to.

This research tells us a lot about what is happening in the CBD at night, and the most surprising thing was the levelling off of average BrAC from about midnight, which from our observations was when the majority of pre-drinkers really started to arrive. There's clearly more work for us to do on this, especially around understanding the factors associated with pre-drinking, which we hope to look at more in-depth in a follow-up study. We also have another paper also out this week using the same dataset as this one, and I'll blog about that one in the next couple of days.