Older patients with bipolar I disorder appear to have lower serum levels of brain-deprived neurotrophic factor than similarly aged adults without bipolar I, a study showed.

At the beginning of the study, Aline T. Soares, MD, and her colleagues recruited 118 patients from clinics in the United States and Canada with bipolar disorder who were aged 50 and over and a similar control group of 76 healthy patients. Twenty-seven of the 118 patients had type II bipolar disorder, and 91 had type I bipolar disorder; all had been clinically euthymic for at least 4 weeks when they were evaluated, reported Dr. Soares of the department of internal medicine at the University of São Paulo (Brazil).

The results showed that patients positively identified with bipolar I disorder had lowered brain-deprived neurotrophic factor (BDNF) levels, compared with their control group counterparts. Lower levels of BDNF were not detected in those with bipolar II disorder, the investigators reported (Am J Geriatr Psychiatry. 2016 Aug;24[8]:596-601).

“Our study represents a continuation of the [bipolar disorder] and BDNF story: Prolonged bipolar illness appears to lead to decreased BDNF, even in the euthymic state,” Dr. Soares and her colleagues wrote. “This reduces the brain’s capacity for neurogenesis and neuroplasticity and theoretically increases the risk of hippocampal shrinkage, cognitive deficits, and dementia.”

Future studies are needed to look into how BDNF levels affect mood, cognitive abilities, and other areas of life related to bipolar disorder, they said.

Dr. Soares and her colleagues reported that they had no conflicts to disclose.

To read more about the study, click here .