Unaffected siblings of individuals with bipolar disorder had a higher prevalence of dyslipidemia and ischemic stroke compared with controls, according to study data published in the Journal of Affective Disorders.
Investigators conducted a longitudinal cohort study using data abstracted from the Taiwan National Health Insurance Research Database, which comprises comprehensive health information on >99% of the entire Taiwanese population. Individuals who had siblings with bipolar disorder but who had no major psychiatric diagnoses themselves were selected for inclusion. Study cases were then matched 1:4 by age, sex, income, level of urbanization, and birth date to controls without a sibling with bipolar disorder. As primary outcome measures, investigators captured all incidence of metabolic and cardiovascular disorders between 1996 and 2011 in the study and control cohorts. Logistic regression analyses were performed to calculate the odds of having cardiometabolic disease in unaffected siblings of patients with bipolar disorder.
A total of 7225 siblings and 28,900 controls were enrolled. The pooled cohort had a mean age of 32.37± 7.90 years. Individuals in the sibling cohort had a higher prevalence of dyslipidemia (5.4% vs 4.5%; P =.001), younger age at diagnosis of type 2 diabetes mellitus (34.81 vs 37.22 years; P =.024), and a slightly higher prevalence of any stroke (1.5% vs 1.1%; P =.007) and ischemic stroke (0.7% vs 0.4%; P =.001) compared with controls.
In the logistic regression model adjusted for demographic data, siblings of patients with bipolar disorder were more likely to have dyslipidemia (odds ratio [OR], 1.24; 95% CI, 1.10-1.40) in later life than controls. In a subanalysis stratified by sex, only male siblings of patients exhibited this increased risk for dyslipidemia (OR, 1.28; 95% CI, 1.10-1.48). Additionally, siblings had higher risk for any stroke (OR, 1.38; 95% CI, 1.10-1.74) and for ischemic stroke (OR, 1.86; 95% CI, 1.31-1.63) compared with controls. When stratified by sex, male siblings alone displayed this increased risk for any stroke (OR, 1.38; 95% CI, 1.02-1.85) and for ischemic stroke (OR, 2.43; 95% CI, 1.60-3.70).
The study could not account for the influence of stress, lifestyle, smoking, and education; did not look at other first-degree relatives (parents, children); and may not be generalizable to non-Taiwanese populations.
According to these analyses, siblings of patients with bipolar disorder, particularly brothers, had a significantly increased risk for dyslipidemia and ischemic stroke compared with controls. These data support a familial association between cardiometabolic diseases and bipolar disorder, although further research is necessary to identify the etiology of this association.
Tsao WY, Hsu JW, Huang KL, et al. Risk of cardiometabolic diseases among siblings of patients with bipolar disorder [published online April 22, 2019]. J Affect Disord. doi:10.1016/j.jad.2019.04.094