Introduction: It has been commonly accepted that second-hand smoke (SHS) is associated with atherosclerosis and endothelial dysfunction. There is growing evidence that the changes might begin in childhood. Unfortunately, no study has focused on the early atherosclerosis of Tibetan adolescents exposed to SHS.
Aims: We aimed to investigate the endothelial function and carotid atherosclerosis in healthy school-aged Tibetan male adolescents.
Materials and methods: All passive smoking participants (SHS) were students were 16 years old and male, and were recruited through middle schools in Lhasa city. In total 624 subjects were accepted after excluding subjects who actively smoked. The adolescents were divided into three groups according to serum cotinine level: high cotinine group (High Group) with 205 boys, intermediate cotinine group (Intermediate Group) with 210 boys, and low cotinine group (Low Group) with 209 boys. Venous blood was sampled for the measurement of cotinine concentration, lipid profile and endothelin-1 (ET-1) quantitation. High-resolution B-mode ultrasonography was performed to evaluate carotid intima-media thickness (cIMT) and intima smoothness. The invasive vascular endothelial function was evaluated through the measurement of flow-mediated dilation (FMD) with B-mode ultrasound and ankle-brachial index (ABI) by using a blood pressure cuff and a Doppler instrument.
Results: No statistical significance was found between groups in total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, triglyceride, ApoA-I, systolic blood pressure, diastolic blood pressure, and heart rate (p>0.05). In the lipid profile, only apolipoprotein B (ApoB) values were different between groups: ApoB in the High Group was higher than in the Low Group (p=0.0164). Plasma ET-1 concentrations in the High Group were also much higher than in the Intermediate and Low Groups (p=0.0112, p<0.001). The cIMT and intima smoothness had deteriorated in the High Group compared with the Low Group (p<0.001 and p<0.05 respectively). FMD and ABI, which indicate vascular endothelial function, was decreased in the High Group compared with the Intermediate and Low Groups (FMD, p<0.001; ABI, p<0.001).
Conclusions: SHS was associated with sub-clinical carotid atherosclerosis and endothelial dysfunction in Tibetan school-aged male adolescents. Considering the widespread exposure to SHS and the clinical relevance of early atherosclerosis, this result is of public health importance in Tibet, where health education is not satisfactory. Data from our study emphasize the importance of endorsing smoke-free environments for adolescents.