||BACKGROUND: The adverse renal effects of lithium have long been known, but glomerular insufficiency had been considered an unlikely event until recently, when new studies have raised concern regarding very long-term treatment. In this cross-sectional study, we examined glomerular function in a cohort of patients treated with lithium for up to 33 years and a control group of lithium-naive patients treated with other mood-stabilizers. METHODS: Patients with a diagnosis of recurrent or persistent affective disorders, examined between 1 October 2007 and 31 December 2009, were screened. Demographic and clinical data were extracted from clinical charts regarding two study groups: one for patients treated with lithium for at least 12 months and the other for patients never exposed to lithium. Multivariate regression analysis was applied: the dependent variable was the estimated glomerular filtration rate (eGFR) calculated from the last available serum creatinine value using the Modification of Diet in Renal Disease Study Group equation; the following independent variables, potentially associated with renal dysfunction, were included: gender, current age, duration of lithium treatment, cigarette smoking, hypertension, diabetes and dyslipidemia. RESULTS: eGFRs lower than 60 ml/min were significantly more frequent in the group treated with lithium (38/139 = 27.3%) compared to lithium-naive patients (4/70 = 5.7%) (P = 0.0002; Fisher's test). Regression analysis showed a significant effect on eGFR of age, gender and duration of lithium treatment but no effect of cigarette smoking, hypertension, diabetes or dyslipidemia. eGFR was estimated to decrease by 0.64 ml/min (95% confidence interval = 0.38 to 0.90; P = 0.00) for each year of lithium treatment. CONCLUSIONS: The duration of lithium treatment is a risk factor for glomerular failure, in addition to advancing age. For example, all patients aged 60 years or older may be estimated to undergo Stage 3 or more severe chronic kidney disease (namely an eGFR less than 60 ml/min) if treated with lithium for 30 years. These data may be added to the current debate on the balance between the protective effects of lithium on recurrent affective disorders and suicide and the risk of renal disease.