SO081LITHIUM EXPOSURE AND OCCURENCE OF CHRONIC KIDNEY DISEASE IN THE IRISH HEALTH SYSTEM: A COHORT STUDY

Abstract

Abstract Background and Aims Lithium is implicated as a causative factor in the development and progression of chronic kidney disease (CKD). Few studies have assessed the independent impact of plasma levels and duration of lithium therapy on CKD progression. We examined the influence of lithium on CKD progression in the Irish health system. Method We utilised data from the Irish Kidney Disease Surveillance System (IKDSS) to explore associations of lithium levels and duration of exposure with kidney function in a regional cohort. A retrospective cohort study was conducted between 1999 to 2014 from the Midwest Region. All adult patients with lithium levels were identified and followed longitudinally. Kidney function was assessed at baseline and longitudinally using serum creatinine and estimated glomerular filtration rate (eGFR) was calculated using the CKD-EPI. Patients with < 2 lithium values, missing data on creatinine were excluded. The index date was the date of the first lithium blood test. Toxicity from lithium was defined as levels >1.2mmol/L as per NICE guidelines while duration of treatment was calculated based on patient –years of exposure as determined by positive blood lithium levels. Relationships between baseline kidney function, lithium levels, duration of exposure and each patients most recent eGFR value on follow up were assessed using multiple linear regression Results We identified 1,978 patients exposed to lithium from 1999-2014, mean age was 47.4 (15.6), 45.1% were men, eGFR [median (IQR)] at baseline was 84.4 (32.1) ml/min1.73m and the median duration of exposure was 3.0 years (IQR=4 years). Frequency of lithium testing increased from 1.77 in 1999 to 2.66 in 2014. In multiple linear regression, the final eGFR on follow-up was significantly lower in older patients (-0.48 ml/min/1.73m per year increase in age), P<0.001; in patients with elevated baseline lithium levels (-2.18 ml/min1.73m lower per unit increase), P<0.05, with long duration of exposure (-1.42 ml/min/1.73m lower for each year on lithium), P<0.001, and for patients with low GFR at baseline (P<0.001). Together these variables explained 58% of the variation in the final model. Conclusion Both the magnitude of and the duration of lithium exposure are both independently associated with CKD progression among lithium users in the Irish health system. Higher baseline lithium values had a more deleterious impact on kidney function. Continued efforts should be expended in minimising the risks of lithium induced nephrotoxicity through switching to alternatives and dose reduction when over possible. Funding This study is funded by the Health Research Board and the Midwest Research and Education Foundation (MKid).