Aucklanders don't drink or smoke as much as Kiwis in some other parts of the country, new research has found. But when the weekend comes, the taps in the big city start flowing.
Researchers collected wastewater samples from different locations around Auckland, Canterbury and the Bay of Plenty over the course of a week, and tested them for signs of alcohol and nicotine use.
They found while nicotine use was consistent over the course of a week, alcohol consumption peaked at the weekend - rising up to 171 percent over a typical weekday in some urban areas.
Whilst this might not surprise anyone, the pattern of alcohol use differed across the three regions. People in the Bay of Plenty drank the most overall, followed by Canterbury then Auckland.
People in the Tauranga urban area drank more than those in rural Bay of Plenty - the researchers citing tourism and the high number of bars - but in the super city it was the other way around.
Rural Aucklanders drink more overall than those in the city, and they keep it up right through the week with only a "negligible" increase at weekends - suggesting "habitual use may be more common there".
"Rural communities typically have less access to alcohol addiction resources and can experience higher levels of alcohol dependency," the study, published in journal Drug and Alcohol Review this week, said.
"Alternatively, given the popularity of central-Auckland's nightlife scene, it may be that individuals travel citywards to consume alcohol."
At the weekends, Aucklanders in the city more than double their consumption - overtaking those left in rural areas.
There wasn't any correlation between socio-economics and the amount of alcohol consumed in an area - previous data from the New Zealand Health Survey suggesting while people in poorer areas "tend to consume alcohol at higher intensities", those in richer areas are more likely to drink more frequently, balancing it out.
Nicotine on the other hand showed higher rates of use in poorer areas. Use was also more common in the urban Tauranga area than in rural Bay of Plenty, while the opposite was true for Auckland.
"This complicates attempts to generalise nicotine consumption as a simple function of urbanisation," the researchers said. "Clearly other factors influence consumption, for example local preference, income, access to treatment/cessation services and proximity to retail shops."
They noted Auckland Council implemented the country's "most comprehensive and strict outdoor smoking policy in 2013" which could be contributing to lower rates of use in the city.
"Pharmacy numbers in rural communities have declined substantially in the past 50 years . This reduces access to smoking cessation products like gum and patches."
The data was collected using 'wastewater-based epidemiology', which has also been used to look for undetected COVID-19 outbreaks. It's said to be more accurate than data collected in surveys, which suffer from "under-recruitment of certain demographics, including youth, homeless, institutionalised, incarcerated and physically isolated communities" with "distinct patterns of consumption"; and "high-use groups are less likely to participate in surveys".
"It is estimated that only 20-70 percent of population alcohol use is captured in survey responses when compared to other data sources like sales information."
The number of cigarettes smoked according to the wastewater testing - 1.5 a day per person on average - almost exactly matched sales data for 2018, when the testing was done; while the average number of standard drinks a day - 1.2 - was slightly lower than the total available for consumption.
"The difference might reflect the different metrics of the two datasets (ie availability vs actual consumption) or perhaps more is consumed outside of these regions," the researchers said.
"It could also reflect a minor discrepancy in the excretion rate of ethyl sulphate or degradation in the sewer."
Similar tests in 2017 revealed meth users indulged every day of the week, while cocaine and ecstasy use peaked at weekends.