Study characteristics and quality assessment.

* Number of patients available for analysis † 1) Recruitment at schools; 2) All schools or randomly selected; 3) Age groups 6–7 and 13–14 years; 4) Use of validated questionnaires; 5) questionnaires completed by parents (< 12 years old) or by adolescents themselves (≥ 12 years old); 6) Participation >90%; 7) N ≥3000 ‡ Only two centers were included (Benslimane, Morocco; Conakry, Guinea. Study characteristics and quality assessment.