Background: Lithium has been used as the corner stone treatment for Bipolar Affective Disorder, depression and mania over the past 40 years1. It remains today as the first choice maintenance treatment for these conditions. However, research on long term lithium use and renal function has yielded mixed results with evidence suggesting it worsens kidney function over time and other findings indicating there is no relationship. In light of such conflicting results this study aimed to investigate the trajectory of Estimated Glomerular Filtration Rate (eGFR) over time in patients treated with lithium therapy2,3,4.
Methods: This longitudinal cohort-based linkage study examined 381 patients on lithium therapy. The cohort was identified as patients having being first dispensed lithium by a major NSW Local Health District (LHD) spanning regional and rural areas from 2005 – 2015. Data obtained from the LHD was linked with pathology test results from Southern IML, a community pathology provider for the LHD. eGFR levels were assessed at each patients first reported dispensing of lithium date (baseline) and then at yearly increments for up to 10 years. The closest eGFR value within a month (30 days) of each timepoint was used for analysis. If patients had fewer than 2 time-points of eGFR data they were excluded from analysis.
Results: An unconditional linear growth model with random slopes and intercepts was used to examine the trajectory of eGFR over
time. The model consisted of 202 patients and assumed an unstructured covariance structure. The effect of time on eGFR was found to be nonsignificant (ß = 0.07; 95% CI = -0.53 – 0.66; p = 0.807). Additionally, the intraclass correlation coefficient suggested that ~ 75% of the variability of eGFR result is explained between patients.
Conclusions: Despite the uncertainty surrounding the prolonged use of lithium and its adverse effects on renal function this study found no significant change in eGFR trajectories over time for patients on lithium treatment.