When Stones Begin: Age of Onset Reveals the Systemic Metabolic Nature of Nephrolithiasis.

Background: Kidney stone disease is a common urological condition with a rising worldwide incidence. Although multiple metabolic and lifestyle risk factors have been identified, determinants influencing the age at which symptoms begin remain poorly defined. Understanding factors associated with earlier disease presentation may improve prevention strategies. Methods: This observational cohort study included 546 patients with confirmed nephrolithiasis. Participants were stratified into early-onset (<45 years) and late-onset (≥45 years) groups. Sociodemographic, lifestyle, clinical, urinalysis, and biochemical data were collected. Group comparisons were performed using the Chi-square test. Multivariable linear regression analyses evaluated independent associations between age of onset and clinical, laboratory, and hormonal variables. Statistical significance was set at Results: Early-onset disease accounted for 57.1% of cases. Higher body mass index, smoking, functional status, employment, and education level were significantly associated with age of onset ( Conclusion: Early-onset nephrolithiasis is strongly associated with metabolic and cardiovascular comorbidities and specific biochemical abnormalities. Age of onset may serve as a clinically meaningful marker for risk stratification and targeted preventive interventions.