Renal function in geriatric psychiatry patients compared to non-psychiatric older adults: effects of lithium use and other factors

Abstract

Objectives: Chronic renal failure is very common, affecting 30%–40% of community-dwelling elderly. We wished to verify whether geriatric psychiatry patients are at increased risk of renal dysfunction compared to elderly controls, as well as whether lithium exposure and other factors are important predictors of risk.Method: This is a four-year retrospective cohort and nested case-control study at a Canadian tertiary-care hospital using data from March 2007 to March 2011. We compared 82 geriatric psychiatry outpatients and 200 psychotropic-naïve family medicine controls aged ≥65. Our main continuous measure of renal outcome was change in estimated glomerular filtration rate (eGFR). Multivariate analyses were performed to determine potential risk factors for renal dysfunction in geriatric psychiatry patients, including age, hypertension, diabetes mellitus, diuretics, and lithium duration.Results: Clinically important decreases in eGFR (>8 mL/min/1.73 m2) were found in 40.2% of geriatric psychiatry patients compared to 29.5% of controls (p = 0.040). Multivariate analyses found that lithium duration was independently associated with adverse renal outcome in patients with eGFR < 60 mL/min/1.73 m2. In this sub-population, lithium users had clinically important decreases in eGFR when compared to non-lithium users: 10.3 vs. 0.40 mL/min/1.73 m2 (p = 0.017).Conclusion: Geriatric psychiatry patients are at a greater risk for clinically important decreases of renal function than similarly aged controls. Lithium appears to be an important risk factor for renal dysfunction when eGFR is <60 mL/min/1.73 m2. However, in the majority of older adults who have normal kidney function, lithium use appears to be safe.