Objective: To determine the association between metabolic syndrome as defined by the modified NCEP/ATP TTT criteria and
cigarette smoking among Thai smokers aged 50 years or older.

Materials and Methods: Cross-sectional data were collected from 679 smokers and former smokers in a lung cancer screening program in Thailand between 2015 and 2017. Participants were interviewed and examined for weight, height, blood pressure, lipid profile, and fasting glucose concentration. Logistic regression models were used to estimate odds ratios [ORs] and 95% confidence intervals [CT].

Results: Metabolic syndrome was found in 49.0% of participants. Smoking status was statistically significantly related to metabolic syndrome (p-value = 0.001). Among non-metabolic syndrome
participants, 46.5% were former smokers and 53.5% were current smokers, compared with 60.0% former smokers and 40.0% current smokers among participants with metabolic syndrome. Reduced odds of being current smokers (vs. former smokers) were found for those with metabolic syndrome, higher BMT, and high blood pressure. Metabolic syndrome and its components were associated with current smoking levels among active smokers, with statistically significant effects found for high fasting plasma glucose (OR = 1.66; 95% CT: 1.03 to 2.67; p-value = 0.039) and high triglycerides (OR = 1.75; 95% CT: 1.07 to 2.85; p-value = 0.026). After adjusting for possible confounders, those with high fasting plasma glucose were 1.73 times more likely (95% CT: 1.02 to 2.93, p-value = 0.042) and
those with high triglycerides were 2.97 times more likely (95% CT: 1.43 to 6.13, p-value = 0.003) to currently smoke more than 10 cigarettes per day, compared with currently smoking 10 or less
cigarettes per day. However, there was a significant negative relationship between low HDL cholesterol level and smoking more than 10 cigarettes per day (OR = 0.48; 95% CT: 0.24 to 0.97;
p-value = 0.041).

Conclusion: Current smokers could be at high risk for developing metabolic syndrome. Those smoking more than 10 cigarettes a day have higher level of fasting plasma glucose and triglyceride.
However, low HDL cholesterol levels are more common among those smoking 10 or less cigarettes per day.

Keywords: Metabolic syndrome, Cigarette smoking, Current smoking, Heavy smokers, Lung cancer screening