Does lower urine-specific gravity predict decline in renal function and hypernatremia in older adults exposed to psychotropic medications? An exploratory analysis.

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.

Predictors of psychiatric re-hospitalization in older adults with severe mental illness.

OBJECTIVE: Many patients with severe recurrent mental illness are approaching late life; however, little is known about psychiatric re-hospitalization in this population. Our objective was to identify predictors of psychiatric re-hospitalization. METHODS: This was a retrospective cohort study of all 226 geriatric patients (age ≥65 years) admitted to a tertiary care Canadian inpatient psychiatric unit between 2003 and 2008. The main outcome was psychiatric re-hospitalization in 5-year follow-up post-discharge (e.g. 2008-2013 if a patient had been first admitted in 2008). Multivariate Cox regression analyses were used to identify potential predictors of re-hospitalization. RESULTS: Over 5-year follow-up, 32.3% (73/226) required psychiatric re-hospitalization. Prior lifetime history of psychiatric admission, currently living in a supervised setting and bipolar disorder diagnosis all independently predicted a lower time to psychiatric re-hospitalization (HRs > 2.0, p < 0.05). CONCLUSIONS: The rate of psychiatric re-hospitalization is high in older adults admitted for severe mental illness. Clinicians should be aware of the especially high rates of re-hospitalization in geriatric psychiatric inpatients with bipolar disorder, previous psychiatric admissions, or those living in a supervised setting. Future research could investigate approaches to prevent psychiatric re-hospitalization in these vulnerable sub-populations.