Bipolar disorder and bone health: a systematic review

BACKGROUND: Bipolar disorder is a chronic, episodic mental illness, affecting around 2.4% of the population worldwide. Psychological and/or physiological comorbidities are a common consequence, and osteoporosis is one such possible comorbidity. Thus, this systematic review aimed to collate, evaluate, and discuss the literature examining the link between bipolar disorder and bone health. METHODS: We conducted an e-search of PubMed/OVID/MEDLINE, PsychINFO and CINAHL to identify studies that investigated associations between bipolar disorder and bone in adults aged ≥18. Two reviewers determined eligibility according to pre-determined criteria, and methodological quality was assessed using a previously published methodological scoring system. Due to heterogeneity, a best-evidence synthesis was performed. RESULTS: Our search yielded 1409 articles, of which three (all cohorts) met predetermined criteria. The studies from Taiwan and the United States of America analysed administrative data, albeit spanning different years, and comprised a total of 344,497 participants. No studies investigating bone quantity or quality were identified. Bipolar disorder was associated with an increased risk of fracture (range 20-80%); and fracture-free survival time for those with bipolar disorder decreased substantially with advancing age, and for women (10-30% shorter than men). Fracture incidence per 1000 person years (py) was 21.4 and 10.8 in those with and without bipolar disorder, respectively. LIMITATIONS: Limited data and marked methodological heterogeneity prevented the pooling of these data for a numerical synthesis. CONCLUSIONS: Increased fracture risk was observed in individuals with bipolar disorder, independent of older age, sex, comorbidities and medication use. The operative mechanisms, risk and treatment factors warrant further enquiry.