Cardiovascular comorbidity increases the risk for renal failure during prophylactic lithium treatment.

Background: The development of lithium-associated kidney damage is still a matter of controversy. We have addressed this question by investigating the role of somatic comorbidity for developing kidney failure in lithium treated patients.

Methods: The study group comprised of 1741 adult patients with normal creatinine levels at the start of lithium treatment. Patients who developed severe renal failure (CKD stages 4-5, n = 109), were matched by sex, time on lithium and age at start of lithium, with 109 controls (CKD stages 1-2) that did not develop severe renal failure.

Results: Patients in CKD 4-5 did not differ significantly from controls (CKD 1-2) in sex (females/males were 76/33 in both groups), time on lithium (mean 9.8 years, SD 6.4; vs. 9.6, SD 6.2) or age at start of lithium (mean 61.6 years, SD 13.4; vs. 60.5 years, SD 12.3), respectively. However, comparisons between groups showed a significantly higher prevalence of somatic comorbidity (p < 0.001), especially cardiovascular diseases (p < 0.003), among patients in CKD 4-5.

Limitations: Patients in our study group were relatively old and the findings are therefore not generalizable to patients starting lithium at an early age. The retrospective design, relying on available charts, did not allow to grade severity of comorbid conditions other than need for hospitalisation or chronic drug treatment.

Conclusions: Our findings emphasize the role of somatic comorbidity for renal damage in lithium treated patients and especially the role of cardiovascular comorbidity. Monitoring of somatic comorbidity should be taken into account in treatment recommendations and safety routines in long-term prophylactic lithium treatment.