Objectives
Waterpipe tobacco smoking has received little epidemiological and policy attention in the UK despite reports of increasing prevalence alongside an anecdotally non-compliant industry. This study aimed to determine how waterpipe tobacco smoking is changing among young people in the UK, both in terms of prevalence and sociodemographic correlates of use, and to quantify the extent of illegal underage use in waterpipe-serving premises in the UK.

Study design
Repeat cross-sectional.

Methods
A secondary analysis of two cross-sectional surveys (total N = 3376), conducted in 2013 and 2015 among secondary school students aged 11–16 years in Stoke-on-Trent, measured lifetime (both surveys) and regular (at least monthly; 2015 survey only) waterpipe tobacco prevalence and location of usual use. Logistic regression models measured the association between independent variables (age, sex, ethnicity, presence of free school meals, cigarette smoking status) with lifetime and regular waterpipe tobacco use, and with illegal underage use; the latter defined as usually smoking waterpipe tobacco in a waterpipe-serving premise.

Results
Lifetime waterpipe tobacco prevalence remained similar in 2013 (13.7%, 95% confidence interval [CI] 12.0–15.4%) and 2015 (14.6%, 95% CI 12.8–16.4%), whereas regular use was measured at 2.9% (95% CI 2.1–3.8%) in 2015. Older, non-white, males who concurrently used cigarettes had higher odds of lifetime waterpipe tobacco use. Illegal underage use was reported among 27.1% of all regular users, correlates of which included increasing age and South Asian ethnicity. The presence of free school meals was not associated with lifetime or regular waterpipe tobacco prevalence, nor illegal underage use.

Conclusions
Increased monitoring of waterpipe tobacco prevalence and patterns, including the underage policy compliance of waterpipe-serving premises, is needed to help inform policy decisions to control waterpipe tobacco use.