It is unclear whether physical activity and sedentary behavior are associated with economic development in low- and middle-income countries (LMICs). We aimed to assess the association between these two behaviors and country economic development among young adolescents in LMICs. Data came from the Global School-based Student Health Survey (GSHS) conducted between 2009 and 2016 in 68 LMICs. A total of 180,298 adolescents aged 12–15 years were included; 15.3% of young adolescents achieved the recommended level for sufficient physical activity (≥60 min/day of physical activity of any kind per week according to WHO) and 64.6% achieved a low sedentary behavior (≤2 h of sitting activities/day according to some guidelines, not accounting for sitting time at school or for doing homework). However, only 9.1% of young adolescents met the recommended levels of both behaviors. Comparing the lowest to the highest quintiles of a country’s purchasing power parity per capita (PPP), mean values of both physical activity (boys: 2.55 to 2.96 days/week; girls: 2.10 to 2.31 days/week) and sedentary behavior(boys: 1.86 to 3.13 h/day; girls: 1.83 to 3.53 h/day) increased. The prevalence of having both recommended behaviors decreased among boys (12.0% to 10.0%) and girls (9.6% to 4.9%) (p < 0.001). Although there might be an ecological fallacy, the findings emphasize the need for interventions to increase physical activity and reduce sedentary behavior among children and young adolescents.

Sexual behaviors, particularly risky sexual behavior, has become a serious public health concern among adolescents worldwide, presenting a substantial obstacle to the prevention of sexually transmitted infections, including human immunodeficiency virus (HIV). However, there is limited research using consistent and standardized methodology to examine associations between tobacco and alcohol use frequency and both total and risky sexual behaviors among adolescents. We aimed to examine the association between tobacco and/or alcohol use with both total and risky sexual behaviors among adolescents worldwide. Data were collected from the Global School-based Student Health Survey, which comprised 211,847 adolescents aged 12–17 years from 59 countries. The frequency of tobacco or alcohol use during the past 30 days was categorized as 0, 1–2, 3–5, 6–9, or ≥ 10 days. Tobacco and alcohol use were also categorized as non-use, tobacco use alone, alcohol use alone, and combined use. Multi-variable logistic regression analysis was used to examine both the independent and combined associations of tobacco and alcohol use with total and risky sexual behaviors. Compared with no tobacco use, the odds ratio of engaging in sexual intercourse increased with the frequency of tobacco use from 1 to 2 days to ≥ 10 days (total: 2.03 [95% confidence interval 1.47–2.81] to 3.98[2.63–6.03]; risky: 2.43[1.75–3.38] to 4.21[3.26–5.42]), as well as with the frequency of alcohol use. Overall, combined users had greater likelihood of both total and risky sexual behaviors than tobacco users alone, alcohol users alone, and non-users. Similarly, the association between risky sexual behaviors and tobacco use alone was more pronounced among adolescent girls (vs. adolescent boys), as were those of risky sexual behaviors with alcohol use alone among younger adolescents aged 12–14 years (vs. aged 15–17 years) and with tobacco and/or alcohol use among adolescents in the Western Pacific region (vs. Regions of Africa and Americas). Our findings suggest independent and combined associations between tobacco and/or alcohol use with sexual behaviors among adolescents, with variations across age, sex, and WHO region.