Is heart rate variability a biomarker of the severity of bipolar disorder?

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Reduced heart rate variability (HRV) is associated with severity in patients with bipolar disorder (BD), in terms of individual and global measures of disease severity, suggest new research.

In a study that included 53 adult patients with BD I or II, the researchers used the Disease Load Index (IBI), a new measure developed by the research team to assess patients. The results showed that the greater the severity of BD disease, the lower the HRV.

The new IBI is “an important component of this study, because by integrating several different indicators of disease burden into bipolar disorder … we were able to create a unique measure that was associated with VHR,” he said. investigated the study Abigail Ortiz, MD, Center for Addiction & Mental Health, Toronto, Canada, said during a presentation at the 2021 virtual congress of the European Psychiatric Association (EPA).

“We wanted to compress a lot of clinical information into a single number [in order to] make it very suitable for doctors, ”Ortiz said Medscape Medical News. “We are aware that this result needs to be replicated in a larger sample, but the IBI could be a clinically useful index to assess clinical trajectories in bipolar disorder,” he added.

The findings were also published online March 30 al Journal of Psychosomatic Research.

HRV and morbidity, mortality

BD is associated with premature death and ischemic cardiopathy it is the leading cause of excess mortality, Ortiz noted. HRV is an indicator of autonomic cardiac function and has previously been shown to be a predictor of morbidity and mortality in patients with and without cardiovascular disease.

Specifically, healthy people have a high degree of HRV, which reflects their ability to adapt quickly to the physical or psychological demands of their environment. On the other hand, reduced VHR, which is found in many diseases, “is associated with fatal arrhythmias, myocardial infarction, and sudden death, “Ortiz said.

The researchers examined the link between HRV and disease burden in patients with BD because previous studies examining that association have yielded conflicting results, he added.

The current study included 53 patients with bipolar I and II disorder. They were all issued a portable device – a sports shirt that incorporated a EKG (Zephyr, Medtronic) and carried him for 24 hours.

The researchers collected baseline clinical and demographic characteristics and patients completed several scales to assess functional cardiovascular capacity and disease burden factors, including disease duration, number and type of previous episodes, and history. familiar.

From these data, the researchers developed the IBI. They integrated 10 disease factors using a weighted geometric mean that emphasized information such as the number of previous episodes, a history of psychosis, and the past. suicide suicide attempts and family history.

The majority (66%) of the participants were women and the mean age was 44 years. In addition, 90% were white and the average body mass index was 29.3 kg / m2.

Just over half (55%) of patients had bipolar II disorder and 60% were euthymic at study entry. The mean age of onset of the disease was 20.8 years and the mean life episodes were 11.6. 36% of participants reported a family history of bipolar disorder, 39% had a family history of major depressive disorder (MDD), and 36% had a family history of suicide.

Reverse relationship

“There were four main clinical variables that correlated with HRV reduction,” Ortiz said. These include the duration of the illness, the number of lifelong depressive episodes, the duration of the most severe manic or hypomanic episode, and a family history of suicide.

The results showed that the higher the severity of BD, the lower the HRV, which was significant for two HRV measurements, Oriz said.

The first measure was the mean square root of successive differences (RMSSD), which estimates the short-term components of HRV. The second measure was the standard deviation from normal to normal intervals (SNDD), which calculates the overall HRV.

RMSSD was also significantly associated with individual measures of disease burden, specifically age at onset (Pg = .009), comorbid anxiety (Pg = .006), and a family history of suicide (Pg = .01).

SNDD was significantly associated with the vital number of depressive episodes (Pg = .02), number of depressive and manic / hypomanic episodesPg = .01), start age (Pg = 0.05), and a family history of suicide (Pg = 0.02).

“In addition, in participants experiencing a depressive episode, the score in Montgomery – Åsberg Depression The scoring scale was negatively correlated with HRV, ”Ortiz told meeting attendees.

Ortiz said Medscape Medical News his team plans to use IBI in future studies to assess, for example, the association between disease burden on the index and cognitive function.

They would also like to determine if those with a very high score of 3.5 or 4 could be “better responders to litigation or antipsychotics “or combination therapy. They also plan to examine whether there is a relationship between IBI scores and the common genetic variants associated with DB.

Links Mental and physical health

Commenting on the findings of Medscape Medical News, Andrew Kemp, PhD, professor of psychology at Swansea University, Swansea, UK, described the study as “an important work that shows associations with several different clinical variables”.

“I agree with the overall conclusion that heart rate variability can be used as a clinical index to assess the trajectories of these patients,” said Kemp, who did not participate in the study.

In fact, the findings fit with theirs previous research showing that mania is associated with an increase in heart rate and a decrease in HRV compared with euthymia. They also found that, compared to their healthy peers, patients with BD have highly sympathetic cardiac modulation, reduced vagal modulation and lower HRV complexity.

One of the main questions has been whether VHR reductions are motivated by the disorder or the treatment of the disorder, “Kemp said. His research in MDD and generalized anxiety disorder has shown that “antidepressants have adverse effects, but the disorder itself is also associated with reduced heart rate variability,” he added.

BD is included in the list of mental health disorders associated with reduced VHR, suggesting that VHR is a “transdiagnostic marker of mental disorder“associated with emotion and its regulation, and the sense of meaning, purpose of life, and longevity of the individual,” Kemp said.

As such, HRV can be considered as a structural link between mental and physical health, and provides a “psycho-physiological index of well-being. [that supports our] ability to connect with ourselves, others and nature “- and to manage environmental stressors,” Kemp concluded.

The study was funded by a grant from the University of Ottawa’s Department of Psychiatry Research Funds and was supported in part by the University of Toronto’s Department of Psychiatry Academic Awards and the Labatt Family Chair in Biology of Depression in Late Adults at the University of Toronto. The study authors and Kemp have not revealed any relevant financial relationship.

Congress of the European Psychiatric Association (EPA) 2021: Abstract O006. Filed April 10, 2021.

J Psychosom Res. Published online March 30, 2021. Summary

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