The Association Between Metabolic Syndrome and Lung Cancer: A Systematic Review and Meta-analyses

Lung cancer has a 29% survival rate, with nearly half detected at Stage 4. Survival increases to 65% with early-stage diagnosis, yet only 28.1% are diagnosed early. Cardiovascular and respiratory comorbidities coexist with LC and may affect detection and prognosis. Metabolic syndrome (MetS), characterized by central adiposity, hypertension, dysglycemia, hypertriglyceridemia, and low high-density lipoprotein cholesterol, has been associated with LC incidence and mortality. We estimated associations between MetS and LC incidence and mortality and examined study-level heterogeneity. Following PRISMA 2020, we searched CINAHL, Web of Science, and PubMed (2000-March 2025) for adult (≥18 years) studies reporting quantitative associations between MetS and LC outcomes. Two reviewers independently screened studies and extracted design, population, MetS definitions, outcomes, effect estimates, and covariates. Random-effects meta-analyses and sensitivity analyses were conducted. Study quality was assessed using NHLBI tools; funnel plots and Egger's test evaluated small-study effects. Of 163 full-text articles, 11 contributed to the incidence analysis and four to the mortality analysis. MetS was associated with higher LC incidence (pooled hazard ratio [HR] = 1.18; 95% CI: 1.04-1.33; p = .010). Among good-quality studies with thorough smoking adjustment, the HR was 1.15 (95% CI: 1.04-1.28). LC mortality was not significantly associated with MetS. Although pooled findings indicate higher LC incidence among individuals with MetS, variation in smoking adjustment precludes causal inference. Future prospective cohorts across diverse populations and settings should use standardized MetS definitions and detailed smoking histories and assess whether MetS can provide a meaningful window for LC screening and early intervention.