Lithium use and bone health in women with bipolar disorder: A cross-sectional study.

INTRODUCTION: Several psychiatric disorders and medications used to treat them appear to be independently associated with skeletal deficits. As there is increasing evidence that lithium possesses skeletal protective properties, we aimed to investigate the association between lithium use and bone health in a group of women with bipolar disorder.

METHOD: Women with bipolar disorder (n = 117, 20+ years) were recruited from south-eastern Australia. Bipolar disorder was confirmed using a clinical interview (SCID-I/NP). Bone mineral density (BMD; g/cm2 ) was measured at the spine, hip and total body using dual-energy x-ray absorptiometry and low bone mass determined by BMD T-score of <-1.0. Weight and height were measured, socioeconomic status (SES) determined and information on medication use and lifestyle factors self-reported. Linear and logistic regression were used to test associations between lithium and (i) BMD and (ii) low bone mass, respectively.

RESULTS: Thirty-five (29.9%) women reported current lithium use. Lithium users and non-users differed in regard to SES and BMD; otherwise, groups were similar. After adjustments, mean BMD among lithium users was 5.1% greater at the spine (1.275 [95% CI 1.229-1.321] vs. 1.214 [1.183-1.244] g/cm2 , p = 0.03), 4.2% greater at the total hip (0.979 [0.942-1.016] vs. 0.938 [0.910-0.966] g/cm2 , p = 0.03) and 2.2% greater at the total body (1.176 [1.148-1.205] vs. 1.150 [1.129-1.171] g/cm2 , p = 0.08) compared to participants not receiving lithium. Lithium users were also less likely to have low bone mass (22.9% vs. 43.9%, p = 0.031). Associations persisted after adjustment for confounders.

CONCLUSION: These data suggest lithium is associated with greater BMD and reduced risk of low bone mass in women with bipolar disorder. Research into the underlying mechanisms is warranted.