Association of triglyceride-glucose index with presence and development of impaired spirometry: results from Austrian LEAD cohort

BACKGROUND: The triglyceride-glucose (TyG) index is a marker of metabolic dysfunction. However, evidence regarding its association with lung function (LF) impairment, particularly from longitudinal studies, are scarce. This study aimed to evaluate the association between TyG and both the presence and development of LF impairments. METHODS: Nine thousand six hundred sixty-eight participants (aged 25-82 yrs; 48% male) who participated in the baseline assessment of the Austrian LEAD cohort and 6,880 individuals with longitudinal follow-up data (mean interval:4.3 yrs) were included in the analysis. Fasting triglycerides and glucose levels were used to calculate the TyG index. Obstructive spirometry, restrictive spirometry, and preserved ratio impaired spirometry (PRISm) were defined using both fixed cut-off and lower limit of normal (LLN) criteria. Associations between the TyG index and lung function parameters, as well as the presence of spirometric impairments at baseline, were examined. In addition, the predictive ability of the TyG index for incident spirometric impairment was assessed. RESULTS: Higher TyG was significantly associated with lower FEV₁, FVC, MMEF₂₅-₇₅, TLC, and RV. Baseline TyG was associated with higher risk of fixed cut-off defined restrictive spirometry [odds ratio (OR): 1.26 (95% confidence interval (CI): 1.04-1.53)] and PRISm [OR (95% CI): 1.23 (1.00-1.53)], and showed borderline significance for predicting incident restrictive spirometry [risk ratio (RR) (95% CI): 1.50 (0.95-2.40)] over time. Its predictive ability (area under the curve = 0.63) was comparable to established metabolic syndrome indices, including the International Diabetes Federation, Adult Treatment Panel III, and American Heart Association criteria. Sensitivity analyses using LLN-defined spirometric impairment yielded similar results. CONCLUSIONS: TyG index is associated with the presence and development of restrictive pulmonary outcomes. However, its standalone predictive value is limited, and its utility may lie in being an easily accessible index rather than a definitive screening tool for impaired lung health.