Bone health in bipolar disorder: a study protocol for a case-control study in Australia

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.

Falls in community-dwelling women with bipolar disorder: a case-control study

BACKGROUND

Falls are a common occurrence in psychiatric hospital settings, however population-based research among individuals with psychiatric disorders, in particular bipolar disorder (BD) is scant. Thus, we aimed to investigate falls risk in community-dwelling women diagnosed with BD.

METHODS

Women with BD (cases, n = 119) were recruited from health care settings located in southeast Victoria, Australia. Age-matched controls (n = 357, ratio 3:1) without BD were participants in the Geelong Osteoporosis Study drawn from the same geographical region. Lifetime history of BD was identified by semi-structured clinical interview (SCID-IV/NP). Previous 12-month falls data were obtained via questionnaire. Information on mobility, alcohol use, general health, medication use, blood pressure, body mass index, socioeconomic status and use of a walking aid was collected. Generalised Estimating Equations, binary and ordinal logistic regression were used to determine the odds ratio (OR) and 95% confidence interval (CI) for falls following adjustment for confounders.

RESULTS

During the 12-month period, 34 (28.6%, median age 48.4 yr) cases and 70 (19.6%, median age 49.1 yr) controls reported one fall; 22 (18.5%) cases and 18 (5.0%) controls reported ≥ two falls (p < 0.001). Cases had 2.5-fold increased odds of at least one fall and 2.9-fold increased likelihood of increasing falls categories (0 vs. 1 vs. 2 +), compared to controls [adjOR 2.5, 95%CI (1.8, 3.4), adjOR OR 2.9, 95%CI (2.0, 4.1)].

CONCLUSION

Risk of falls was greater among women with BD. Balance training could be a research and clinical focus for falls prevention programs among women with bipolar disorder to prevent the detrimental outcomes associated with falling.

Bipolar disorder and bone health: A case-control study

BACKGROUND

Bipolar disorder (BD) is associated with significant psychological and physical comorbidity. Yet little is known about the bone health of individuals with BD. Thus, we aimed to investigate the association between BD and bone health in a population-based sample of women.

METHODS

Women with a history of BD (cases; n = 117) were recruited from public and private health care settings and controls, without BD, were drawn from the Geelong Osteoporosis Study (n = 909). BD was identified using a semi-structured clinical interview (SCID-I/NP). Bone mineral density (BMD) was measured at the spine, femoral neck and total body using dual energy x-ray absorptiometry, and bone quality by quantitative heel ultrasound and included the following parameters: Speed of Sound (SOS), Broadband Ultrasound Attenuation (BUA) and Stiffness Index (SI). Weight and height were measured and information on medication use and lifestyle was obtained.

RESULTS

Adjusted mean BMD among the cases was 4.3% lower at the hip and 1.6% lower at the total body compared to controls. Age was an effect modifier at the spine. Among women <50 years, mean spine BMD for cases was 3.5% lower than controls. No differences in spine BMD for those ≥50 years were detected. Cases also had a 1.0%, 3.2% and 7.8% lower adjusted mean SOS, BUA and SI compared to controls, respectively.

LIMITATIONS

Course, chronicity and recovery of BD were not explored in relation to bone health.

CONCLUSION

These data suggest BD is associated with low bone quantity and quality in women. Replication and research into underlying mechanisms is warranted.

Age-related changes in physiology in individuals with bipolar disorder

BACKGROUND

Individuals with bipolar disorder have a reduced life expectancy and may experience accelerated biological ageing. In individuals with bipolar disorder and healthy controls, we examined differences in age-related changes in physiology.

METHODS

UK Biobank recruited more than 500,000 participants, aged 37-73, between 2006 and 2010. Generalised additive models were used to examine associations between age and grip strength, cardiovascular function, body composition, lung function and heel bone mineral density.

RESULTS

The main dataset included 271,118 adults (mean age = 56.04 years; 49.60% females). We found statistically significant differences between cases and controls for grip strength, blood pressure, pulse rate and body composition, with standardised mean differences of up to -0.24 (95% CI -0.28 to -0.19). Evidence of differences in lung function, heel bone mineral density or arterial stiffness was limited. Case-control differences were most evident for age-related changes in cardiovascular function (both sexes) and body composition (females). Differences did not uniformly narrow or widen with age and differed by sex. For example, the difference in systolic blood pressure between male cases and controls was -1.3 mmHg at age 50 and widened to -4.7 mmHg at age 65. Diastolic blood pressure in female cases was 1.2 mmHg higher at age 40 and -1.2 mmHg lower at age 65.

LIMITATIONS

Analyses did not distinguish between bipolar disorder subtypes. Results may not generalise to other age groups.

CONCLUSIONS

Differences between bipolar disorder cases and controls were most evident for cardiovascular and body composition measures. Targeted screening for cardiovascular and metabolic health in middle age is warranted to potentially mitigate excess mortality.