The Global Diet Quality Score (GDQS) is a comprehensive metric that covers both the risks of nutritional deficiency and the risk of diet-related noncommunicable diseases (NCD). Validation tests were previously performed using secondary data from various countries. However, the study of the application of the GDQS to the Thai population is still necessary. Because Thai food usually consists of a variety of components, the GDQS may reflect the risks of nutrient inadequacy and the risks of NCD differently from the previous studies. Objective: This study aimed to characterize the GDQS’s performance by estimating the associations between the GDQS and diverse outcomes reflective of undernutrition and diet-related NCD risks. Methods: A cross-sectional study was conducted in Thai adults aged 40-60 years. GDQS was calculated from dietary data collected using a 24-hr dietary recall (24HR), a semi-quantitative food frequency questionnaire (FFQ), and the GDQS-Assessment System (GDQS-AS). Additional metrics were also calculated, including the Minimum Dietary Diversity for Women (MDD-W) and the Alternative Healthy Eating Index-2010 (AHEI-2010). Nutritional status was determined through anthropometric, body composition, blood pressure, and biochemical marker assessments. Spearman rank correlations and multivariable adjusted regression models were performed to evaluate the associations between GDQS and diverse outcomes reflective of undernutrition and diet-related NCD risks. Wolfe test and Wald test were used to compare the strength and trend of the correlations of the GDQS and outcomes between different dietary data collection methods and different metrics. Results: The prevalence of overweight to obesity (Body mass index ≥25 kg/m2) was 47.5%. Anemia was reported in 8.9% of men and 23.8% of women, hypertension in 54.1% of men and 39.4% of women, and metabolic syndrome in 42.5% of men and 35.9% of women. Mean urinary sodium excretion was 3,397 mg/day (147.7 mmol/day). The GDQS calculated by GDQS-AS and FFQ were relatively similar, while the GDQS-24HR was lower. Multivariable adjusted regression analysis found that GDQS-AS performed better in reflecting nutrient intakes, nutrient adequacy, and nutritional outcomes than GDQS computed from 24HR and FFQ. GDQS, MDD-W, and AHEI-2010 similarly performed in indicating nutrient adequacy and risks of NCD. Nevertheless, GDQS computed from FFQ better reflected nutrient adequacy. Conclusion: Overall, GDQS-AS had a relatively stronger performance in capturing both nutrient intakes and nutritional outcomes compared with GDQS computed from other methods, whereas GDQS scored from FFQ was outperformed
in capturing nutrient adequacy. Findings from this study only reflected a cross-sectional correlation between GDQS and nutrient adequacy and NCD risks. Thus, further study to longitudinally explore the correlations between GDQS and NCD risks is required.