title: Does lower urine-specific gravity predict decline in renal function and hypernatremia in older adults exposed to psychotropic medications? An exploratory analysis.
abstract: BACKGROUND
  Exposure to psychotropic agents, including lithium, antipsychotics and antidepressants, has been associated with nephrogenic diabetes insipidus (NDI). This is especially concerning in older adults already at risk of developing chronic kidney disease (CKD) and hypernatremia with advanced aging. This study investigates whether commonly performed random urine-specific gravity (USG) tests can predict adverse NDI outcomes (CKD and hypernatremia) in psychotropic-exposed older adults.
  
  
  METHODS
  This was a retrospective longitudinal study of 173 geriatric psychiatry patients (age ≥65 years) exposed to psychotropic medications. Our main continuous outcome was 'decrease in estimated glomerular filtration rate (eGFR) >10 mL/min/1.73 m(2)' over 5-year follow-up. Hypernatremia and acute kidney injury (AKI) were secondary outcomes. Whether baseline USG <1.010 predicted outcomes was assessed in bivariate and multivariate analyses.
  
  
  RESULTS
  USG <1.010 predicted hypernatremia episodes (sodium concentration ≥150 mmol/L-28.1 versus 12%, χ(2) = 4.7, P = 0.03). USG <1.010 [odds ratio 2.36 (95% confidence interval 0.93-6.0), P = 0.07], baseline eGFR and typical antipsychotic use independently predicted decrease in eGFR >10 mL/min/1.73 m(2). Patients with a single baseline sodium concentration of ≥140 mmol/L and USG <1.010 have a 26.3% incidence of AKI and a 57.9% incidence of hypernatremia over the ensuing 5 years.
  
  
  CONCLUSIONS
  In psychotropic-exposed older adults, there appears to be a clinically important association between low USG and developing both hypernatremia and CKD. USG may be a useful surrogate measure for NDI-related outcomes in large administrative database studies, where ideal measures such as 24-h urine volume may not be available.
authors.affiliation: Geri-PARTy Research Group, Department of Psychiatry, Jewish General Hospital , McGill University , Montreal, QC , Canada.
authors.forename: Sahar
authors.initials: S
authors.lastname: Sajadi
authors.affiliation: Geri-PARTy Research Group, Department of Psychiatry, Jewish General Hospital , McGill University , Montreal, QC , Canada.
authors.forename: Ching
authors.initials: C
authors.lastname: Yu
authors.affiliation: Geri-PARTy Research Group, Department of Psychiatry, Jewish General Hospital , McGill University , Montreal, QC , Canada.
authors.forename: Jean-Daniel
authors.initials: JD
authors.lastname: Sylvestre
authors.affiliation: Geri-PARTy Research Group, Department of Psychiatry, Jewish General Hospital , McGill University , Montreal, QC , Canada.
authors.forename: Karl J
authors.initials: KJ
authors.lastname: Looper
authors.affiliation: Geri-PARTy Research Group, Department of Psychiatry, Jewish General Hospital , McGill University , Montreal, QC , Canada.
authors.forename: Marilyn
authors.initials: M
authors.lastname: Segal
authors.affiliation: Geri-PARTy Research Group, Department of Psychiatry, Jewish General Hospital, McGill University, Montreal, QC, Canada; Department of Psychiatry, University of Toronto, Toronto, ON, Canada.
authors.forename: Soham
authors.initials: S
authors.lastname: Rej
keywords: hypernatremia; nephrogenic diabetes insipidus; older adults; renal disease; urine specific gravity