This study found a nearly five-fold age-, race-, and sex-adjusted increased risk of CVD and a greater than two-fold increased risk of HTN among adults with BD-I versus controls. Even compared to subjects with MDD, those with BD-I have significantly greater prevalence of CVD and HTN. Moreover, controlling for obesity, smoking, anxiety disorders, and SUD did not substantially alter these findings. The mean age of BD-I subjects with CVD was approximately 14 years younger than that of controls and 6 years younger than that of MDD subjects with CVD. Similarly, the mean age of BD-I subjects with HTN was approximately 13 years younger than that of controls and 6.5 years younger than that of MDD subjects with HTN. These findings, from a representative population sample, suggest that the excessive cardiovascular mortality in BD-I cannot be explained solely by disparities in medical care (28
), but rather that there is markedly elevated prevalence of cardiovascular illnesses in BD-I.
These findings must be considered in the context of the methodologic limitations of this study. First, CVD and HTN were ascertained by asking NESARC respondents whether they had ever been diagnosed with these conditions. Medical examination was not undertaken to corroborate these reports, nor was examination of health records. Using this methodology would not detect undiagnosed CVD and HTN. Second, this study employed a cross-sectional retrospective methodology. As such, the direction of the associations between the variables cannot be determined. Third, the NESARC study did not include information regarding specific medications. Such data would have allowed us to examine the logical question of whether commonly used medications in BD-I, such as lithium and second-generation antipsychotics, are differentially associated with CVD and HTN. Previous findings suggest the possibility that lithium mitigates the impact of BD on excess cardiovascular mortality (29
), whereas second-generation antipsychotics are known to exacerbate cardiovascular risk (30
). Fourth, this study cannot address specific putative pathophysiological or behavioral underpinnings of these associations, because information regarding physical activity, dietary intake, glucose, lipids, and other biological factors was not collected in the NESARC. Fifth, this study examined BD-I specifically and not bipolar II disorder because evidence of the reliability of this diagnosis in NESARC is lacking. Therefore, present findings may not generalize to bipolar II disorder, cyclothymia, or bipolar disorder not otherwise specified. Finally, as with any large-scale epidemiologic study, this study is limited by its reliance on lay interviewer-administered structured interviews to determine psychiatric diagnoses.
In the present study, 22.1% of BD-I subjects reported being diagnosed with HTN. Previous estimates for HTN prevalence are generally 25–45%, although higher (8
) and lower (31
) rates have been reported as well. Most previous studies have found increased prevalence of HTN in BD compared to healthy or psychiatric controls (7
), although others have reported no significant differences (32
). In the present study, 10.1% of BDI subjects reported being diagnosed with CVD, which is similar to previous estimates (5
). Previous findings regarding the association between CVD and BD have yielded heterogeneous findings (5
). One study found lower prevalence of CVD among BD subjects versus controls, but the analyses did not control for age (5
). An underpowered population-based study that included 42 subjects with BD found a trend toward an association of BD with CVD (23
). Similarly, a prospective administrative database study found greater incidence of myocardial infarction (MI) among BD subjects (2.24%) compared to appendectomy subjects (1.72%); however, this difference did not achieve statistical significance (13
). To our knowledge, previous studies have not compared the prevalence of CVD among subjects with BD and MDD; however, a Veterans Affairs (VA) study found that males with BD were 44% more likely to have CVD compared to those with schizophrenia (21
The mean age of BD-I subjects with CVD and HTN was approximately 14 and 13 years younger, respectively, than controls with CVD and HTN. These discrepancies are in the same direction and of larger magnitude than previously reported. For example, Kilbourne and colleagues (5
) found that BD subjects with HTN were 7 years younger and those with CVD were 4 years younger compared to non-BD subjects. Similarly, Lin and colleagues (13
) found that BD subjects with MI were 5 years younger than appendectomy subjects with MI.
Despite its limitations, this study confirms and extends previous findings on this subject. CVD and HTN are highly prevalent among adults with BD-I at comparatively young ages. Given the complexity of BD-I itself, compounded by the high rates of psychiatric comorbidity, integration of medical care with psychiatric care is need in order to optimize medical and psychiatric outcomes and minimize costs. Preliminary evidence indicates that such integration may yield improvements in both psychiatric and medical health as well as reduce both forms of service utilization (33
). Longitudinal studies are needed to parse the contribution of various genetic, physiologic, pharmacologic, behavioral, and psychiatric factors to CVD and HTN risk in BD-I. These studies should be conducted at the earliest possible stage, and examination of this topic among youth may provide an excellent opportunity. Perhaps most importantly, preventive strategies are needed to reduce the excessive cardiovascular burden among people with BD-I.