Measures

There were two outcome measures: 1) current cigarette smoking, and 2) current smoking of other tobacco products. We defined current cigarette smoking as use on one or more days within past 30 days. Current smoking of other tobacco products (cigars, pipes, shisha, bidis) was defined as any use within past 30 days.

Sociodemographic characteristics included age group (10–12, 13–15 and 16–19 years); sex (male/female); grade (JS2/JS3/SS1); students’ status (day student/boarder); possession of weekly spending money (none, ≤100 NGN or about 0.27 US$, >100 NGN); parents’ work status (initially measured in four categories of neither/father only/mother only/both parents, but father only and mother only were combined into one parent); parents living together (yes/no); and SES, which was measured using parental education (low SES for parental education of secondary or lower/high SES for tertiary parental education). SES was determined for each parent, and was treated as both an exposure variable and an effect modifier. School characteristics included geographical location (urban/rural) and school type (public/private). A rate of 1 US$ to 360 NGN was used for currency conversion.

Environmental factors included exposure to secondhand tobacco smoke (SHS) (‘yes’ if exposed at home, indoor or outdoor public places in last 7 days, ‘no’ if unexposed); exposure to pro-tobacco advertisements (‘yes’ if exposed to tobacco promotions/advertisements at points-of-sale or watching use of tobacco on TV in past 30 days or possess an item with tobacco logo on it or offered a free tobacco product, ‘no’ if unexposed); exposure to anti-tobacco messages on media, at events/gatherings, at home, or by health warnings on cigarette packages in past 30 days (yes/no); inclusion of tobacco in school curriculum (‘yes’, if within past 12 months, the student was taught in class about dangers of tobacco, read about health effects of tobacco in school books, or discussed in class the reasons why adolescents smoke, ‘no’ if student did not receive any tobacco teaching in school); sale of cigarettes near school (‘yes/no/don’t know’ but ‘don’t know’ was combined with ‘no’) was used to measure tobacco access and availability; peer tobacco use was assessed with friends’ smoking and classmates’ smoking, each categorized as none/some/most/all; and parental smoking (none/one parent/both parents).